**2. Machine milking of small ruminants: based on the results of a study by Olechnowicz (2006)**

## **2.1. Introduction**

196 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

Many observations conducted in France on different breeds of sheep showed that pulsation rate should not be less than 150 cycles per minute, while 180 cycles/min should be the pulsation rate applied for high-yielding ewes, such as the Lacaune breed. To improve the quality of machine milking in ewes of the Greek Boutsiko breed, the use of vacuum level of 38 kPa is better, wherein machine stripped milk % is low and irritation of teats is reduced, without affecting the health status of the udder (Sinapis et al., 2006). The results indicate that the low vacuum level of 16.5 kPa is required for the opening of the teat sphincter in ewes of this breed (Sinapis et al., 2007). However, low vacuum significantly modifies the kinetics of milk ejection. The vacuum level of 28 kPa causes an extended latency time for the first milk emission, reduces the average milk flow rate and peak flow rate, and prolongs by about 17% the milking time for milking of a single ewe (Caria et al., 2008). In small ruminants SCC is a good indicator of subclinical inflammation of the udder. Healthy mammary glands in ewes and goats in regular studies during lactation should produce less 500 x 103 cells/ml of milk (Bergonier & Berhelot, 2003). For Murciano-Granadina goats at such a physiological threshold only 62.3% of milk samples could be correctly classified. At the level of the flock (SCC above 1 million/ml) BTSCC was a good indicator detecting the degree of mammary gland infections (r2 =845). During the drying-off period in ewes and goats an antibiotic therapy effectively reduces the proportion of infected mammary glands (Bergonier & Berhelot, 2003). Regular maintenance and inspection carried out every year in terms of the technical parameters of milking machines significantly contribute to the health of the udder and hygienic quality of milk; however, in a survey of milking machine maintenance in different countries Billon et al. reported that only 40-60% of milking machine instalations are controlled every year (Billon et al., 2005). The etiological factor of infection in mammary glands in small ruminants is connected with staphylococci (Ameh & Tari, 2000; Bergonier et al., 2003). *Staphylococcus aureus* is the most common organism isolated from milk in cases of clinical *mastitis*, while in sub-clinical *mastitis* it is coagulase-negative staphylococci (CNS). According to Bergonier & Berhelot (2003), the proportion of clinical mastitis typically does not exceed 5% and it is associated with the start of the milking machine, whereas the percentage of subclinical inflammation ranges from 10% to 50%. The causes of damage to the end of the teat in small ruminants during lactation (apart from the overmilking time) include machine stripping and the period of suckling when lambs or kids try to suckle other females (Bergonier & Berhelot, 2003). Halves of udders with damaged teats are infected more frequently when compared with the halves with healthy teats (Ameh & Tari, 2000; Bergonier & Berhelot, 2003). In goats teat size and their distance from the floor do not influence the percentage of subclinical inflammation in the mammary glands (Ameh & Tari, 2000). Omission of machine stripping in the middle and late lactation decreases milk production by 14%; however, it eliminates the incidence of overmilking time. The elimination of machine stripping does not affect milk composition, length of lactation, or SCC in milk, while it increases the number of milked sheep from 15 to 28/h, at one or two milkers, respectively (McKusik et al., 2003). In Poll Dorset ewes omitted afternoon machine milking and machine stripping in the 8-week period of milking (Knight & Gosling, 1995). The consequence was a decrease of 19.4% (7.9 l/ewe) in milk production in that period. For Murciano-Granadina goats the reduction in the frequency of milkings from 2x to 1x daily

The rationale of this study is to determine the relationship between the organization and course of milking sheep and goats on the Zlotniki farm belonging to the University of Life Sciences in Poznan and qualitative and quantitative levels of milk production. In this farm one milker operates six milking clusters, which can have a significant impact on the course of milking, mainly through prolonged overmilking time. Such an organization of milking may result in an increased SCC in milk, infection of mammary glands, and teat-end damage in small ruminants. The results obtained can be used in practice, the recommendation for the milking milker to shorten or to eliminate overmilking time. On the other hand, the results will be used when selecting individuals to operate milking machines. The aim of the study was to evaluate milking of small ruminants and its effect on some characteristics of milk (SCC and composition). Additional objectives were to determine the influence of some factors on the course of milking, assess the degree of teat end damage and contamination of milk, evaluate dimensions of the udder and their relationship with the course of milking. Correlation coefficients between the phenotypic traits of the udder and milking characteristics were also calculated. Such ratios were also calculated between parameters of machine milking course and morphological traits of the udder and selected milk characteristics.

## **2.2. Material and methods**

The study was conducted at the Zlotniki farm (Poznan University of Life Sciences, Poland). On the farm machine milking is performed on dairy sheep of line 05 with the shares of East-Friesian genes in their genotype amounting to 50 – 75%, and 76 – 90% (13/16 East-Friesian sheep and 3/16 Polish Merino), a prolific ewe sheep 09 (25% of the Finnish sheep, 31% East-Friesian and 44% Polish Merino), white-headed and blackheaded sheep, and meat and dairy goats of the White Improved breed. In the years 2000 - 2002 a total of 755 sheep and 207 goats were analyzed. Ewes were milked for 16 weeks in two calendar seasons: spring - summer (March to June) and summer - autumn (July to October). Milking was performed on ewes with clinically healthy udders, after two months of lamb nursing. Milking performance of ewes was tested at monthly intervals and milk production was described from both morning and evening milkings (ml); additionally, milk samples were collected before the morning milking for laboratory testing. Nanny goats with clinically healthy udders were selected for milking after 70 days of rearing kids. Goats were milked from May till November. At monthly intervals each year six milking tests were carried out, with measurements of both morning and evening

milking production (ml). Milk samples were collected for laboratory analyses before the morning milking. The technical condition of the milking machine was tested annually in accordance with the Polish Standards. The measurements of pulsation frequency and pulsator coefficients were taken with the use of a Milko Test 2000 electronic pulsograph (Bilgery). Ewes and goats were milked in 14 and 11 stands, respectively, of a milking parlor (Westfallen). The ewes were milked at milking vacuum of 41 kPa, the pulsation rate of individual clusters ranged from 121.7 to 126.7 pulses/min and pulsation ratio was 50±5%. Milking of goats was conducted at a vacuum level of 41 kPa, pulsation rate of 69.9 to 76.7 pulses/min and pulsation ratio of 60 ± 5%. During three or four sheep milking performance tests, as well as two and five goat milking performance tests, milk samples of approximately 15 ml each were collected for bacteriological tests under sterile conditions. Directly after the samples had been collected they were cooled down to the temperature of 4o, and next, after freezing (- 20oC), they were delivered to the microbiological laboratory of the State Veterinary Institute in Pulawy (Branch in Bydgoszcz). Microbiological determination was carried out according to the laboratory diagnostics of *mastitis*. At each milk test day before the morning milking, after fore-stripping, washing and drying of the teats, approximately 50 ml of milk (preserved with a CC preparation) were collected from ewes and nanny goats from their udder halves in order to determine the percentage contents of fat, total protein and lactose, as well as SCC. Analyses of milk samples were carried out at the Laboratory of Milk Evaluation in Krotoszyn. The basic milk composition was determined with the use of a MilkoScan apparatus, while SCC was analyzed with Fossomatic appliances. All parameters were measured to monitor the course of milking in seconds. Measurements of activities related to milking were taken every month for 3 days (milk test day ± 1 day) during the morning milking. Measurements of the duration of individual milking tasks (the time of milk flow from udder halves, the time of overmilking of udder halves, the time of machine stripping, and the total milking time) were recorded using electronic timers for the same three-person team. One person supervised milking time simultaneously in two sheep/goats. Udder zoometric measurements were carried out on sheep and goats on milk test days accurate to 0.1 cm applying both zoometric callipers and a measurement tape. The following parameters were measured in ewes and nanny goats: length, width, depth and circumference of udder, teats dimensions and teat length. Additionally, in goats the distance of teats from the floor was measured and teats were evaluated in terms of their morphology, distinguishing the following types: cylindrical, funnel-shaped, pear-shaped and bottle-shaped. Directly after milking the clinical condition of the teat ends was examined, adopting the following criteria: teats without injuries – canal of teat impalpable, flabby and thin, teat end injuries of the first group – livedo or white ring in the region of escape of teat canal; the teat canal lightly pachynsic and perceptible, teat end injuries of the second group – escape of teat canal enclosed with grommet pachyepidermi, hypertrophy of the epidermis and the circular muscular layer; the canal of teat more perceptible. Winter feeding of ewes was based on haylage, maize silage, mangolds, meadow hay, and all-mash, while the basis for summer feeding of sheep was green fodder from lucerne and cereal grain. The estimated nutritive value of the ration for milked ewes was 11 MJ energy and 320 g crude protein in 2.3 kg DM. During lactation goats were fed green lucerne forage (7-8 kg), concentrate (0.8 kg), meadow hay (0.3 – 0.5 kg) and fodder straw (0.4 kg). The study used mathematical models, applying the statistical package by SAS, Version 8 (2000).

#### **2.3. Results**

198 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

milking production (ml). Milk samples were collected for laboratory analyses before the morning milking. The technical condition of the milking machine was tested annually in accordance with the Polish Standards. The measurements of pulsation frequency and pulsator coefficients were taken with the use of a Milko Test 2000 electronic pulsograph (Bilgery). Ewes and goats were milked in 14 and 11 stands, respectively, of a milking parlor (Westfallen). The ewes were milked at milking vacuum of 41 kPa, the pulsation rate of individual clusters ranged from 121.7 to 126.7 pulses/min and pulsation ratio was 50±5%. Milking of goats was conducted at a vacuum level of 41 kPa, pulsation rate of 69.9 to 76.7 pulses/min and pulsation ratio of 60 ± 5%. During three or four sheep milking performance tests, as well as two and five goat milking performance tests, milk samples of approximately 15 ml each were collected for bacteriological tests under sterile conditions. Directly after the samples had been collected they were cooled down to the temperature of 4o, and next, after freezing (- 20oC), they were delivered to the microbiological laboratory of the State Veterinary Institute in Pulawy (Branch in Bydgoszcz). Microbiological determination was carried out according to the laboratory diagnostics of *mastitis*. At each milk test day before the morning milking, after fore-stripping, washing and drying of the teats, approximately 50 ml of milk (preserved with a CC preparation) were collected from ewes and nanny goats from their udder halves in order to determine the percentage contents of fat, total protein and lactose, as well as SCC. Analyses of milk samples were carried out at the Laboratory of Milk Evaluation in Krotoszyn. The basic milk composition was determined with the use of a MilkoScan apparatus, while SCC was analyzed with Fossomatic appliances. All parameters were measured to monitor the course of milking in seconds. Measurements of activities related to milking were taken every month for 3 days (milk test day ± 1 day) during the morning milking. Measurements of the duration of individual milking tasks (the time of milk flow from udder halves, the time of overmilking of udder halves, the time of machine stripping, and the total milking time) were recorded using electronic timers for the same three-person team. One person supervised milking time simultaneously in two sheep/goats. Udder zoometric measurements were carried out on sheep and goats on milk test days accurate to 0.1 cm applying both zoometric callipers and a measurement tape. The following parameters were measured in ewes and nanny goats: length, width, depth and circumference of udder, teats dimensions and teat length. Additionally, in goats the distance of teats from the floor was measured and teats were evaluated in terms of their morphology, distinguishing the following types: cylindrical, funnel-shaped, pear-shaped and bottle-shaped. Directly after milking the clinical condition of the teat ends was examined, adopting the following criteria: teats without injuries – canal of teat impalpable, flabby and thin, teat end injuries of the first group – livedo or white ring in the region of escape of teat canal; the teat canal lightly pachynsic and perceptible, teat end injuries of the second group – escape of teat canal enclosed with grommet pachyepidermi, hypertrophy of the epidermis and the circular muscular layer; the canal of teat more perceptible. Winter feeding of ewes was based on haylage, maize silage, mangolds, meadow hay, and all-mash, while the basis for summer feeding of sheep was green fodder from lucerne and cereal grain. The estimated nutritive value of the ration for milked ewes

#### *2.3.1. Parameters of the course of milking*

The results of measurements of the course of machine milking in ewes and goats are shown in Table 1. In the groups of ewes with a greater number of somatic cells (over 250 000 in 1 ml), shorter times of milk flow from both halves of the udder were reported, overmilking time was the longest in the groups of sheep with injuries to the end of the teat. In these ewes longer milking times were also observed. In the course of machine milking in ewes observed high variability of the studied traits, which indicates the necessity of improving the ewes (by selection) towards better milkiness.

The time of milk flow and time of overmilking depend on a calendar year, and indicate a variety of external environmental conditions in particular years. The level of nutrition of ewes, as well as the quality of feed were also likely to vary in subsequent years. Ewes' milking season (March-June and July-October) had a significant effect on the time of milk flow from both halves of the udder, and the probable cause was the quality of feed used in the nutrition of ewes in both milking seasons. The month of lactation had a significant effect on all parameters of the course of machine milking. At the start of milking longer times of milk flow from udder halves, and longer times of overmilking from both halves were observed, which resulted in a simultaneous extension of stripping and milking times. It should be noted that the time of stripping was prolonged with the number of lambs reared, and was longer in the ewes with the number of somatic cells of less than 250 000 in 1 ml. This table contains also the values of these parameters in the groups of goats evaluated for the degree of teat end injuries, the degree of milk contamination and the type of teats. The descriptive statistics of the parameters characterizing the average milking in goats show large standard deviations, indicating a lack of improvement towards milking performance. On the other hand, the long and variable time of overmilking for the halves of the udder depends on the organization of machine milking (one milker operates 5 clusters), and the fact that nanny goats occupy different positions during subsequent milkings. Variability in assigning milking stations to the animals and the sequence of goat milking results in an increase or decrease in overmilking time. The time of milk flow, stripping time and milking time were significantly different in both years of the study (2001 and 2002). External environmental conditions affect the course of milking in goats, mainly through the variable forage base resulting from weather conditions. In the successive months of lactation there were no statistically significant differences in milk flow time, overmilking time, stripping time, and milking time. Nursing a greater number of kids by nanny goats had a considerable effect on the prolonged milk flow time and extended the milking time.



**Table 1.** Descriptive statistics of ewes' and goats milking course parameters (arithmetic averages in seconds ± standard deviation)

The results of the effect of selected factors, including injuries to the teat end of milked ewes and goats are given in Table 2. The degree of injury to the end of the teats in ewes in the group with the number of somatic cells below 250 000 in 1 ml had no effect on the course of milking; however, longer times can be seen trailing the times of milk flow and overmilking of teat end injuries. In the second group of ewes (SCC above 250 000/ml) a significant difference was found in the time of overmilking in right halves between the ewes with teat injuries from the first and second groups, amounting to 172.5 and 359.0 s, respectively. The long time of overmilking was associated with a significantly longer time of milking in ewes. In all the groups of sheep longer times of milk flow were recorded in halves with teat end injuries (especially with injuries of the second group) when compared with halves of the udder, which teats sustained no injuries. At the same time shorter times of machine stripping were found for halves with teat end injuries. The longer times of milk flow from halves with teat injuries may indicate disturbances in the milk flow, which may be due to internal damage of the teat canal. The long times of overmilking are caused by injuries of teat ends.

200 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

Milk flow from udder half

> 55.6±23.7 51.7±28.6 54.2±26.1

> 47.3±21.9 36.3±15.7 43.7±20.4

> 52.9±38.6 49.2±34.9 51.6±30.2

56.7±23.2 53.9±26.8 55.0±24.7

49.9±21.5 37.1±16.2 45.7±20.2

59.2±32.8 46.1±26.7 54.8±31.8

Somatic cell count in 1ml

≤ 250 000 > 250 000 Total

≤ 250 000 > 250 000 Total

≤ 250 000 > 250 000 Total

Number of udder halves

> 474 281 755

168 81 249

120 60 180

seconds ± standard deviation)

Milking parameters in ewes (s)

left right left right

Case–sensitive degree of teats end injuries

Case-sensitive degree of milk infection

Milking parameters in goats (s)

**Table 1.** Descriptive statistics of ewes' and goats milking course parameters (arithmetic averages in

The results of the effect of selected factors, including injuries to the teat end of milked ewes and goats are given in Table 2. The degree of injury to the end of the teats in ewes in the group with the number of somatic cells below 250 000 in 1 ml had no effect on the course of milking; however, longer times can be seen trailing the times of milk flow and overmilking of teat end injuries. In the second group of ewes (SCC above 250 000/ml) a significant difference was found in the time of overmilking in right halves between the ewes with teat injuries from the first and second groups, amounting to 172.5 and 359.0 s, respectively. The long time of overmilking was associated with a significantly longer time of milking in ewes. In all the groups of sheep longer times of milk flow were recorded in halves with teat end injuries (especially with injuries of the second group) when compared with halves of the udder, which teats sustained no injuries. At the same time shorter times of machine stripping were found for halves with teat end injuries. The longer times of milk flow from halves with teat injuries may indicate disturbances in the milk flow, which may be due to

147.4±110.2 131.1±111.0 141.4±110.6

204.6±149.1 211.7±114.6 206.9±136.5

143.3±118.2 151.4±97.4 146.0±110.9

207 129.2±46.7 116.3±48.2 95.9±98.7 107.9±101.4 33.3±24.6 258.5±99.3 414 122.7±47.1 101.9±97.3 33.3±23.7 258.5±99.3 Case-sensitive degree of teat end injuries 92 106.8±49.7 96.0±46.3 100.3±87.2 109.3±93.0 26.7±20.2 234.3±106.0 184 101.4±47.3 104.8±88.3 26.7±19.9 243.3±103.3 Case-sensitive degree of teat end injuries 67 126.3±53.4 107.3±45.8 102.2±113.8 121.2±117.3 32.4±23.4 261.0±122.3 134 115.9±50.3 110.9±114.1 32.4±22.5 261.0±119.9 Case-sensitive types of teats 184 101.4±47.3 104.8±88.3 26.7±19.9 243.3±103.3

Overmilking of udder

half Stripping

145.9±111.5 133.2±110.8 141.2±111.1

196.3±113.0 212.3±106.9 201.5±110.2

145.3±122.9 148.4±93.6 146.3±113.8 of udder Milking

235.1±116.2 215.3±117.8 228.0±118.1

228.0±132.6 283.6±120.9 286.6±126.8

236.4±182.3 224.9±100.4 231.8±118.3

33.7±18.9 30.0±16.1 32.3±18.1

37.2±22.8 33.6±30.2 36.0±25.7

32.5±18.5 27.0±12.7 30.7±17.0


**Table 2.** The effect of teat end injuries on the course of milking in ewes' and goats. Means in columns designated with identical capital letters differ significantly at P≤0.01, \*P≥0.05, ns – non-significant difference

Despite the small number of udder halves with teat end injuries of the second group (n = 2), the overmilking time for those halves was doubled when compared with halves of the udder and teats without injuries. No statistically significant impact of injuries to the teat end on the course of machine milking could be explained by large standard deviations and the small number of half exchange with teat end damage.

The degree of microbial contamination of milk in the first and second groups did not significantly influence the course of machine milking in ewes (Table 3). The degree of microbial contamination of milk by major and minor pathogens did not affect significantly the parameters of machine milking in ewes. However, longer times of milk flow from infected halves of the udder were reported when compared with the times of milk flow from healthy halves of the udder. The reason for the lack of significant differences in milking of ewes from these groups might have been connected with the small number of sheep, whose milk was contaminated by the major pathogens.


**Table 3.** The effect of degree of contamination in milk from udder halves on the course of milking in ewes. 1Staphylococcus aureus and Escherichia coli, 2Coagulase negative staphylococcus, Micrococcus, Corynebacterium and Bacillus.

Similarly, there was no significant effect of the contamination of milk on the course of milking in goats. Milk flow time and stripping time were found to be about 15 seconds longer in case of the halves infected by minor pathogens when compared to the healthy halves of the udder, but these differences are not statistically significant, probably due to the high variability of parameters that characterize milking.

## *2.3.2. Milk composition, somatic cell count and milk yield*

202 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

milk was contaminated by the major pathogens.

6 37 77

1 30 29

7 67 106

9 12 46

2 43 75

2 27 31

4 70 106

5 12 50 78.7 66.6 54.1

11.0 52.7 40.5

69.0 60.4 50.3

95.6 129.7 113.4

Number of udder halves

Milk contamination with microorganisms:





Corynebacterium and Bacillus.

growth

growth

growth

growth

The degree of microbial contamination of milk in the first and second groups did not significantly influence the course of machine milking in ewes (Table 3). The degree of microbial contamination of milk by major and minor pathogens did not affect significantly the parameters of machine milking in ewes. However, longer times of milk flow from infected halves of the udder were reported when compared with the times of milk flow from healthy halves of the udder. The reason for the lack of significant differences in milking of ewes from these groups might have been connected with the small number of sheep, whose

> Milk flow from udder half

Somatic cell count below 250 000 in 1 ml (n = 240)

Somatic cell count above 250 000 in 1 ml (n = 120)

Total (n = 360)

Milking parameters in goats (s) n = 67

120.4 126.3 101.5

**Table 3.** The effect of degree of contamination in milk from udder halves on the course of milking in ewes. 1Staphylococcus aureus and Escherichia coli, 2Coagulase negative staphylococcus, Micrococcus,

73.0 52,0 50.9

57.0 43.4 53.7 140.3 139.4 145.4

164.0 148.0 154.5

143.7 143.2 147.9

104.1 80.2 107.6

89.0 57.4 49.7 Milking parameters in ewes (s)

Stripping of udder halves

> 13.5 34.0 31.6

> 22.5 29.1 25.4

> 18.0 32.1 29.8

38.4 49.2 27.8

25.7 34.9 31.9

22.0 29.1 25.4

25.1 31.2 30.7

28.0 42.8 30.6

Milking of udder halves

> 262.5 237.6 233.5

> 244.5 224.1 224.3

> 253.5 232.4 230.8

> 292.2 307.0 246.8

244.7 241.9 231.4

197.0 227.4 223.2

237.9 235.4 229.2

228.3 252.7 269.5

Overmilkin g of udder half

left right left right left right left right left right

160.0 134.3 151.7

165.0 151.8 144.4

162.5 141.1 149.5

133.4 131.4 117.5 The results concerning the effect of overmilking time on the number of somatic cells in milk, milk composition and the level of small ruminants milkiness are shown in Table 4. Overmilking time for both halves of the udder of ewes did not have a significant effect on somatic cell counts. In early lactation of ewes (four to six weeks) longer overmilking times were associated on the one hand with longer stripping times, while on the other hand, with the organization adopted for the farm milking machine (one milker handled six milking clusters). With such an organization of machine milking the ewes, in which overmilking lasted longer, were characterized by both higher milk production and a lower percentage of fat and protein in milk. Ewes with somatic cell counts ≤ 250 000 w 1 ml a trend towards a higher lactose content and a higher milk production was observed. Evident differences in milk composition (with an increase in overmilking time) are visible in the group of ewes with lower somatic cell counts in milk (below 250 000 ml/ml). In the group of ewes with high somatic cell counts (above 250 000/ml), and including the two above mentioned groups of sheep such differences were not reported. Overmilking time of halves of the goats udder had no effect on daily milk yield, composition and SCC. Goats with a higher daily milk production were characterized by a longer milk flow and longer stripping time, as well as lower somatic cell counts in milk. In these goats, however, overmilking time was slightly longer.

In the milk of goats from udders halves with short milk flow times (up to 1.5 minutes) somatic cell count was twice as high (1 153 000/ml) when compared with milk of goats with a longer milk flow times (91-180 and 181 - 317s, 615 000 and 572 000 cells/ml, respectively). Shorter milk flow times were significantly associated with a lower daily milk production, a greater percentage of fat and protein in milk, and lower lactose content (P ≤0.01). Stripping time for halves of the udders was associated with daily milk production. The results indicate the need for improvement in terms of raising goats, obtaining large quantities of milk from milking, and a lower machine stripping yield. The selection should be aimed at increasing the capacity of the cisterns.




**Table 4.** The effect of overmilking time on milk somatic cell count and composition, and small ruminants milkiness level. Means in rows designated with the same capital letters differ significantly at P≤0.01.

## *2.3.3. Teat end injuries and milk infection*

Damage to teats of ewes during machine milking can affect the degree of milk contamination. The use of machine stripping is associated with a significant increase of overmilking time. A long overmilking time with an inadequate vacuum level and pulsation ratio may influence teat ends causing injuries. Damaged teats contribute to the penetration of the mammary gland by microorganisms, that cause inflammation of the mammary glands, and milk microbial contamination. Table 5 shows the results of the effect of selected factors, depending on teat end injuries, on milk somatic cell count, composition and production.

In the group of ewes, which were characterized by a smaller number of somatic cell count (SCC≤ 250 000/ml) teat end injuries did not differentiate significantly the number of somatic cells, milk composition or production levels. A greater percentage of fat and protein content in milk was observed in the milk of both halves of the udder with healthy teats. The halves of the udder from the first group of teat injuries (SCC> 250 000/ml) yielded a higher percentage of milk fat, probably resulting from lower milk production. A comprehensive comparison of the results showed no effects of teat end injuries on milk somatic cell count,


5.11A 983.7AB

155 6.10 6.12 6.55A 4.54 799,0A

455 5.18 5.52 6.28 4.92 920.8

183 5.94 3.01 3.00 4.21 2 850.8

5.02CE 963.8DE

121 6.06 6.20 6.48B 4.45 754.9B

Somatic cell count above in 1 ml (n = 522)

Total (n = 1510)

Goats

**Table 4.** The effect of overmilking time on milk somatic cell count and composition, and small

ruminants milkiness level. Means in rows designated with the same capital letters differ significantly at

Damage to teats of ewes during machine milking can affect the degree of milk contamination. The use of machine stripping is associated with a significant increase of overmilking time. A long overmilking time with an inadequate vacuum level and pulsation ratio may influence teat ends causing injuries. Damaged teats contribute to the penetration of the mammary gland by microorganisms, that cause inflammation of the mammary glands, and milk microbial contamination. Table 5 shows the results of the effect of selected factors, depending on teat end

In the group of ewes, which were characterized by a smaller number of somatic cell count (SCC≤ 250 000/ml) teat end injuries did not differentiate significantly the number of somatic cells, milk composition or production levels. A greater percentage of fat and protein content in milk was observed in the milk of both halves of the udder with healthy teats. The halves of the udder from the first group of teat injuries (SCC> 250 000/ml) yielded a higher percentage of milk fat, probably resulting from lower milk production. A comprehensive comparison of the results showed no effects of teat end injuries on milk somatic cell count,

95 5.85 3.16 3.13A 4.31 2 988.4

297 5.26 5.84 6.35 4.79 878.7

5.07BD 1 059.6C

> 109 6.13 6.35 6.43B 4.41 767.2C

276 5.31 5.60 6.18 4.82 944.1

61 5.81 2.84A 2.88A 4.23 2 928.7

5.24ABC 1 105.3BE

> 56 6.15 6.43A 6.30 4.57 804.5D

188 5.11 5.22 5.86 5.04 1 015.7

34 5.83 3.19A 2.99 4.20 3 135.3

5.21DE 1 218.7ACD

81 6.14 5.49A 6.0ABC 4.65 1 042.0ABCD

> 294 5.08 4.93 5.75 5.06 1 170.0

> 41 5.80 3.09 2.99 4.28 3 104.1

Lactose content (%) Milk production (ml)

Fat content (%) Protein content (%) Lactose content (%) Milk production (ml)

Fat content (%) Protein content (%) Lactose content (%) Milk production (ml)

Fat content (%) Protein content (%) Lactose content (%) Milk production (ml)

P≤0.01.

Number of udder halves Somatic cell count (log SCC)

Number of udder halves Somatic cell count (log SCC)

Number of udder halves Somatic cell count (log SCC)

*2.3.3. Teat end injuries and milk infection* 

injuries, on milk somatic cell count, composition and production.

**Table 5.** The effect of selected factors in terms of teat end injuries on milk somatic cell count and composition, and ewes' milkiness level. Means in columns designated with the same capital letters differ significantly at P≤0.01.\*P≤0.05,\*\*P≤0.01,ns – non-significant difference.

composition and the level of milk production; however, a marked reduction in milk yield was observed in ewes with teat end injuries in the group with higher somatic cell counts (SCC> 250 000/ml). The result is a greater concentration of fat and less protein and lactose in milk. The results of the impact of teat end injuries on somatic cell count, composition and production of goats milk are given in Table 6.

Injuries to the teat end do not differentiate the log SCC, the composition and level of milk production in goats. At the same time it needs to be stressed that significant differences were found in the percentage of milk fat, at higher fat content in the right halves of the udder, while in the left it was lower (P <0.01). The volume of daily milk production in goats with damaged and healthy teats was similar. Month of lactation had an effect on contents of fat and protein in milk, as well as milk production; however, no such effect was observed on somatic cell count and lactose content in milk. Table 7 presents the results concerning the effect of the degree of contamination of ewe and goats milk on somatic cell count, composition and milk production.



**Table 6.** The effect of teat end injuries on somatic cell count in milk, basic milk composition and goats' milkiness levels.

Means in columns designated with the same capital letters differ significantly at P ≤ 0.01, ns – nonsignificant difference.

Microbial infections of mammary glands cause great economic losses in dairy sheep farms due to reduced milk production and adverse changes in its composition. The incidence of clinical inflammatory conditions generally does not exceed 5%, and most micro-organisms isolated from milk are *Staphylococcus aureus* bacteria. The etiological agents in subclinical inflammation of mammary glands in most cases are *Coagulase negative staphylococci*, and especially *Staphylococcus epidermidis.* The above-mentioned results do not indicate an association between milk contamination and milk composition and productivity levels, probably due to the low number of milk samples with increased contents of major pathogens. In ewes which are characterized by a smaller number of somatic cells (< 250 000/ml) infection caused by minor pathogens were associated with a smaller increase in somatic cell counts, whereas in ewes with greater numbers of somatic cells in milk (> 250 000/ml) this increase was larger. In the milk of ewes with infected mammary glands the concentration of fat and lactose was lower, at a higher concentration of protein when compared with milk from healthy mammary glands. These ewes produced also less milk.

No significant effect of microbial milk contamination by major and minor pathogens was found on the number of somatic cells (log SCC), milk composition and daily milk production in dairy goats. Somatic cell count in milk from both halves of the udder contaminated by major pathogens was greater (log 5.93, i.e. 858 000 cells/ml and log 6.21 i.e. 1 628 000 cells/ml) than that from both halves of the udder contaminated by minor pathogens (log 5.74 i.e. 548 000 cells/ml and log 5.72 i.e. 522 000 cells/ml). In milk from healthy halves of the udder somatic cell count was similar to that in milk from udder halves infected by minor pathogens (log 5.75 i.e. 561 000 cells/ml and log 5.85 i.e. 705 000 cells/ml). Less fat, protein and lactose was found in milk from infected halves of the udder when compared with the percentage of these components in milk from healthy halves of the udder, but these differences were not statistically significant. The daily milk yield from infected and healthy halves of the udder was similar in goats.


**Table 7.** The effect of the degree of milk contamination on milk somatic cell count and composition, and the level of milk production. Means in columns designated with identical capital letters differ significantly at P≤0.01. *1Staphylococcus aureus and Escherichia coli, 2Coagulase negative staphylococcus, Micrococcus, Corynebacterium and Bacillus.* \*P≤0.05,\*\*P≤0.01,ns – non-significant difference.

#### *2.3.4. Phenotypic correlations*

206 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

ns 5.84 5.77 6.05

ns 6.06 6.08 6.14

Somatic cell count in milk from udder half (log SCC)

Percentage content in milk from udder half

left right left right left right

ns 3.22 3.47 2.87

ns 3.32 3.53 2.99

left right left right left right left right left right left right

\*\* 3.55A 4.14 3.98A

\*\* 3.40A 4.09 3.02A

Month of lactation 92 92 ns ns \*\* \*\* \*\* \*\* ns ns \*\* \*\* **Table 6.** The effect of teat end injuries on somatic cell count in milk, basic milk composition and goats'

Means in columns designated with the same capital letters differ significantly at P ≤ 0.01, ns – non-

Microbial infections of mammary glands cause great economic losses in dairy sheep farms due to reduced milk production and adverse changes in its composition. The incidence of clinical inflammatory conditions generally does not exceed 5%, and most micro-organisms isolated from milk are *Staphylococcus aureus* bacteria. The etiological agents in subclinical inflammation of mammary glands in most cases are *Coagulase negative staphylococci*, and especially *Staphylococcus epidermidis.* The above-mentioned results do not indicate an association between milk contamination and milk composition and productivity levels, probably due to the low number of milk samples with increased contents of major pathogens. In ewes which are characterized by a smaller number of somatic cells (< 250 000/ml) infection caused by minor pathogens were associated with a smaller increase in somatic cell counts, whereas in ewes with greater numbers of somatic cells in milk (> 250 000/ml) this increase was larger. In the milk of ewes with infected mammary glands the concentration of fat and lactose was lower, at a higher concentration of protein when compared with milk from healthy mammary glands. These ewes produced also less milk.

No significant effect of microbial milk contamination by major and minor pathogens was found on the number of somatic cells (log SCC), milk composition and daily milk production in dairy goats. Somatic cell count in milk from both halves of the udder contaminated by major pathogens was greater (log 5.93, i.e. 858 000 cells/ml and log 6.21 i.e. 1 628 000 cells/ml) than that from both halves of the udder contaminated by minor pathogens (log 5.74 i.e. 548 000 cells/ml and log 5.72 i.e. 522 000 cells/ml). In milk from healthy halves of the udder somatic cell count was similar to that in milk from udder halves infected by minor pathogens (log 5.75 i.e. 561 000 cells/ml and log 5.85 i.e. 705 000 cells/ml). Less fat, protein and lactose was found in milk from infected halves of the udder when compared with the percentage of these components in milk from healthy halves of the udder, but these differences were not statistically significant. The daily milk yield from

infected and healthy halves of the udder was similar in goats.

fat protein lactose (ml)

ns 4.38 4.39 3.95

ns 4.05 4.19 3.77

ns 2 794.3 3 250.0 2 607.3

ns 2 835.9 3 250.0 2 560.8

Milk production

Factor Number of

Teat end injuries

The first group The second group Teats without injuries

milkiness levels.

significant difference.

of:

udder halves

> Table 8 presents the correlation coefficients between the phenotypic characteristics of udders and the parameters of machine milking in ewes and in goats.

> Ewes with greater udder dimensions were characterized by a longer time of milk flow. Similarly, a longer time of milk flow was recorded in ewes with a greater distance between the teats. Correlation coefficients between the overmilking time for both halves of the udder and the udder dimensions were small, but significant. Ewes with a greater depth and circumference of udders were characterized by a longer stripping time. Milking time was significantly correlated with traits of the udder and distance of the teats. Teat length was not related with the course of machine milking.



**Table 8.** Coefficients of phenotypic correlations between udder traits and parameters of the course of milking in ewes (n = 747) and in goats (n = 621), \*P≤0.05, \*\*P≤0.01.

There were significant and positive correlation coefficients between milk flow times from both halves of the goats udders and the width, depth and circumference of udders (rp from 0.29 to 0.44). Statistically significant correlation coefficients were also calculated between the milk flow time and distance between teats (rp =0.46 and rp =0.37). Goat teat length was not related to the milk flow time. Longer milk flow times were recorded for udder halves with a shorter distance from the teat end to the floor. Overmilking time was slightly dependent on the circumference of the udder and distance between teats. Stripping time of the udder was positively and significantly correlated with the length, depth and circumference of the udder. Milking time was significantly dependent on all udder dimensions, with the exception of teat length. The calculated correlation coefficients indicate a slight relationship to the udder dimensions on overmilking time. The probable cause for the long overmilking time was the use of stripping of the udder, often in excess of 30 s, and milking organization adopted on the farm (one milker operating six clusters). Table 9 shows correlation coefficients between udder dimensions and ewes' milkiness parameters.

The number of somatic cells in case of both halves of the udder (log SCC) was negatively correlated with udder dimensions and the distance between the teats, but the calculated values of correlation coefficients were small. Similarly, negative and significant correlation coefficients were calculated between the percentage of fat and protein in the milk and all the dimensions of the udder. Ewes with a large circumference of the udder have less fat and protein in milk, and this trait was also associated with a higher milk production and lower concentrations of these components in milk. Lower contents of these components in milk were also found in ewes with longer teats. The lactose content in milk from both halves of the udder was positively correlated with all dimensions of the udder. The calculated values of correlation coefficients between the dimensions of the udder, teat length and the amount of milk produced were positive and statistically significant. Table 10 shows the correlation coefficients between phenotypic traits of the udder and the traits of goats' milkiness. Phenotypic correlation coefficients between all the dimensions of the udder and the number of somatic cells in milk from both halves of the udder were negative and statistically significant. A similar interdependence was found between the distance between the teats and log SCC for both halves of the udder. The greater distance from the teats end from the floor was associated with higher somatic cell counts in milk. The dimensions of the udder and the distance and the length of the teats were negatively and significantly correlated with percentage contents of fat and protein in milk (P≤0.05).

208 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

0.356\*\* 0.331\*\* 0.114\*\* 0.094\*\* 0.046 0.158\*\*

0.107 0.116\* 0.076 0.076 0.169\*\* 0.181\*\*

coefficients between udder dimensions and ewes' milkiness parameters.

milking in ewes (n = 747) and in goats (n = 621), \*P≤0.05, \*\*P≤0.01.

Milk flow from the left udder half Milk flow from the right udder half Overmilking of the left udder half Overmilking of the right udder half

Milk flow from the left udder half Milk flow from the right udder half Overmilking of the left udder half Overmilking of the right udder half

Stripping of udder

Stripping of the udder

Milking

Milking

Ewes

Goats

**Table 8.** Coefficients of phenotypic correlations between udder traits and parameters of the course of

There were significant and positive correlation coefficients between milk flow times from both halves of the goats udders and the width, depth and circumference of udders (rp from 0.29 to 0.44). Statistically significant correlation coefficients were also calculated between the milk flow time and distance between teats (rp =0.46 and rp =0.37). Goat teat length was not related to the milk flow time. Longer milk flow times were recorded for udder halves with a shorter distance from the teat end to the floor. Overmilking time was slightly dependent on the circumference of the udder and distance between teats. Stripping time of the udder was positively and significantly correlated with the length, depth and circumference of the udder. Milking time was significantly dependent on all udder dimensions, with the exception of teat length. The calculated correlation coefficients indicate a slight relationship to the udder dimensions on overmilking time. The probable cause for the long overmilking time was the use of stripping of the udder, often in excess of 30 s, and milking organization adopted on the farm (one milker operating six clusters). Table 9 shows correlation

The number of somatic cells in case of both halves of the udder (log SCC) was negatively correlated with udder dimensions and the distance between the teats, but the calculated values of correlation coefficients were small. Similarly, negative and significant correlation coefficients were calculated between the percentage of fat and protein in the milk and all the dimensions of the udder. Ewes with a large circumference of the udder have less fat and protein in milk, and this trait was also associated with a higher milk production and lower concentrations of these components in milk. Lower contents of these components in milk were also found in ewes with longer teats. The lactose content in milk from both halves of the udder was positively correlated with all dimensions of the udder. The calculated values of correlation coefficients between the dimensions of the udder, teat length and the amount of milk produced were positive and statistically significant. Table 10 shows the correlation

0.405\*\* 0.444\*\* 0.022 0.020 0.146\*\* 0.259\*\*

0.115\*\* 0.171\*\* 0.093\*\* 0.090\*\* 0.118\*\* 0.119\*\*

0.297\*\* 0.287\*\* - 0.004 0.007 0.014 0.131\*

Parameter (s) Udder dimensions (cm) Teats dimensions (cm)

0.121\*\* 0.179\*\* 0.165\*\* 0.164\*\* 0.250\*\* 0.224\*\*

Length Width Depth Circumference Distance Teat length

0.415\*\* 0.414\*\* 0.118\*\* 0.108\*\* 0.146\*\* 0.188\*

0.433\*\* 0.390\*\* 0.115\* 0.146\*\* 0.259\*\* 0.362\*\* 0.177\*\* 0.194\*\* 0.167\*\* 0.157\*\* 0.194\*\* 0.188\*

0.460\*\* 0.370\*\* 0.117\* 0.172\*\* 0.157\*\* 0.363\*\* left right


0.076 0.231\*\* - 0.043 - 0.104 - 0.142 - 0.045

0.019 - - 0.007 - 0.053 0.002

0.072 0.105 - 0.095 - 0.098 - 0.097 - 0.073


**Table 9.** Coefficients of phenotypic correlations between udder traits and ewes' (n = 747) and milkiness parameters, \*P≤0.05, \*\*P≤0.01.


**Table 10.** Coefficients of phenotypic correlation between udder traits and goats' milkiness parameters (n = 621). \*\*P ≤ 0.01, P ≤ 0.05.

The width and circumference of the udder and the distance between teats were significantly positively correlated with the percentage of lactose in milk (P≤0.05). Teat length was not related to the content of lactose in milk. All dimensions of the goats' udder, mainly circumference, were positively correlated with daily milk production. The greater distance from the teat end to the floor was associated with lower milk production.

## **2.4. Conclusion**

A long overmilking time of udder halves in ewes is closely connected with teat end injuries. The injuries bring about a certain reduction of ewe milk production and an increased fat content, while protein and lactose contents are lower. In order to reduce the overmilking time or to eliminate it from the milking process the author suggests employing two milkers in the milking process. Injuries of goat teats do not influence milk yield, SCC or milk composition. The degree of milk infection in small ruminants does not influence the levels of production either in qualitative or quantitative terms. In future studies on the course of machine milking in small ruminants and its implications for quantitative and qualitative levels of milk production it is proposed to investigate the milking schedule and increase the overmilking time at different stages of lactation.

## **Author details**

Jan Olechnowicz *Poznan University of Life Sciences, Faculty of Animal Breeding and Biology, Department of Veterinary Medicine, Poznan, Poland* 

## **3. References**


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210 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

from the teat end to the floor was associated with lower milk production.

*Poznan University of Life Sciences, Faculty of Animal Breeding and Biology,* 

overmilking time at different stages of lactation.

*Department of Veterinary Medicine, Poznan, Poland* 

Vol. 62, No. 1-2,pp. 27-31, ISSN 0921-4488

**2.4. Conclusion** 

**Author details** 

Jan Olechnowicz

**3. References** 

ISSN 0921-4488

The width and circumference of the udder and the distance between teats were significantly positively correlated with the percentage of lactose in milk (P≤0.05). Teat length was not related to the content of lactose in milk. All dimensions of the goats' udder, mainly circumference, were positively correlated with daily milk production. The greater distance

A long overmilking time of udder halves in ewes is closely connected with teat end injuries. The injuries bring about a certain reduction of ewe milk production and an increased fat content, while protein and lactose contents are lower. In order to reduce the overmilking time or to eliminate it from the milking process the author suggests employing two milkers in the milking process. Injuries of goat teats do not influence milk yield, SCC or milk composition. The degree of milk infection in small ruminants does not influence the levels of production either in qualitative or quantitative terms. In future studies on the course of machine milking in small ruminants and its implications for quantitative and qualitative levels of milk production it is proposed to investigate the milking schedule and increase the

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3-4, pp. 253-274, ISSN 0301-6226

0022-0302

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ISNN 0022-0302

ISSN 0018-506X

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Gonzalo, C.; Carriedo, J. A.; Blanco, M. A.; Beneitez, E.; Juárez, M. T.; De La Fuente, L. F. & San Primitivo, F. (2005). Factors of variation influencing bulk tank somatic cell count in

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	- Olechnowicz, J. & Jaśkowski, J. M. (2004). Komórki somatyczne mleka koziego [Somatic cells in goat milk]. *Medycyna Weterynaryjna*, Vol. 60, No. 12, pp.1263-1266, ISSN 0025-8628
	- Olechnowicz, J. (2006). Przebieg doju maszynowego u małych przeżuwaczy oraz jego związek z wybranymi cechami mleka i wymienia (in Polish). [Machine milking course of small ruminants and its relationship with selected traits of milk and udder]. Wydawnictwo Akademii Rolniczej im. Augusta Cieszkowskiego w Poznaniu, Vol. 377, pp. 1-125, ISSN 1896-1894
	- Pengov, A. (2001) : The role of coagulase-negative *Staphylococcus* spp. and associated somatic cell counts in the ovine mammary gland*. Journal of Dairy Science*, Vol. 84, No. 3, pp. 572- 574, ISNN 0022-0302
	- Peris, C.; Caja, G. & Such X. (1999). Relationships between udder and milking traits in Murciano-Grandina dairy goats. *Small Ruminant Research*, Vol. 33, No. 2, pp. 171-179, ISSN 0921-4488
	- Peris, C.; Diaz, J. R.; Balasch, S. & Beltrán, M. C. (2003a). Influence of vacuum level and overmilking on udder health and teat thickness changes in dairy ewes. *Journal of Dairy Science*, Vol. 86, No. 12, pp. 3891-3898, ISNN 0022-0302

Peris, C.; Diaz, J. R.; Segura, C.; Marti, A. & Fernández, N. (2003b). Influence of pulsation rate on udder health and teat thickness changes in dairy ewes. *Journal of Dairy Science*, Vol. 86, No. 2, pp. 530-537, ISNN 0022-0302

214 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

*Archivos de Zootecnia*, Vol. 48, No. 182, pp.135-146, ISSN 0004-0592

Vol. 57, No. 4, pp.263-267, ISSN 0021-8634

Vol. 86, No. 12, 3849-3856, ISNN 0022-0302

pp.181-187, , ISSN 0921-4488

pp. 1-125, ISSN 1896-1894

574, ISNN 0022-0302

ISSN 0921-4488

Vol.7, No. 1,pp. 49-66, ISSN 1083-3021

Molina, C. A.; Fernández Martinez, C.; Vergara Pérez, H. & Gallego Martinez, L. (1999). Efecto de las condiciones de ordeño sobre la producción, fraccionamiento y composición de la leche, y estado sanitario de la ubre en ovejas de raza Manchega.

Mottram, T. T.; Smith, D. L. O. & Godwin, R. J. (1994). Monitoring milk flow as an aid to management in automatic milking systems. *Journal of Agricultural Engineering Research*,

Muehlherr, J. E.; Zweifel, C.; Corti, S.; Blanco, J. E. & Stephan, R. (2003). Microbiological quality of raw goat's and ewe's bulk-tank milk in Switzerland*. Journal of Dairy Science*,

Mueller, C. & Kaufmann, O. (2005). The influence of mechanical stimulation on the milking behaviour of dairy goats. *Proceedings of the International Conference held in Nitra*, pp. 277-

Murray, T.L.; Blache, D.B. & Bencini, R. (2009). The selection of dairy sheep on calm temperament before milking and its effect on management and milk production. *Small* 

Negrão, J. A.; Marnet, P. G. & Labussiére J. (2001).Effect of milking frequency on oxytocin release and milk production in dairy ewes. *Small Ruminant Research*, Vol. 39, No. 2,

Neville, M.C.; McFadden, T.B.; Forsyth, I. (2002). Hormonal Regulation of Mammary Differentiation and Milk Secretion. *Journal of Mammary Gland Biology and Neoplasia*,

Olechnowicz, J. & Jaśkowski, J. M. (2005). Komórki somatyczne mleka owczego [Somatic cells in sheep milk]. *Medycyna Weterynaryjna*, Vol. 61, No. 2, pp. 136-141, ISSN 0025-8628 Olechnowicz, J. & Jaśkowski, J. M. (2004). Komórki somatyczne mleka koziego [Somatic cells in goat milk]. *Medycyna Weterynaryjna*, Vol. 60, No. 12, pp.1263-1266, ISSN 0025-8628 Olechnowicz, J. (2006). Przebieg doju maszynowego u małych przeżuwaczy oraz jego związek z wybranymi cechami mleka i wymienia (in Polish). [Machine milking course of small ruminants and its relationship with selected traits of milk and udder]. Wydawnictwo Akademii Rolniczej im. Augusta Cieszkowskiego w Poznaniu, Vol. 377,

Pengov, A. (2001) : The role of coagulase-negative *Staphylococcus* spp. and associated somatic cell counts in the ovine mammary gland*. Journal of Dairy Science*, Vol. 84, No. 3, pp. 572-

Peris, C.; Caja, G. & Such X. (1999). Relationships between udder and milking traits in Murciano-Grandina dairy goats. *Small Ruminant Research*, Vol. 33, No. 2, pp. 171-179,

Peris, C.; Diaz, J. R.; Balasch, S. & Beltrán, M. C. (2003a). Influence of vacuum level and overmilking on udder health and teat thickness changes in dairy ewes. *Journal of Dairy* 

*Science*, Vol. 86, No. 12, pp. 3891-3898, ISNN 0022-0302

278, Vol. 10, ISBN 92-95014-07-03, Nitra, Slovak Republic, 26-28 April 2005

*Ruminant Research*, Vol. 87, No. 1-3, pp. 45-49, ISSN 0921-4488

	- Zweifel, C.; Muehlherr, J. E.; Ring, M. & Stephan, R. (2005). Influence of different factors in milk production on standard plate count of raw small ruminants bulk-tank milk in Switzerland. *Small Ruminant Research*, Vol. 58, No. 1, pp. 63-70, ISSN 0921-4488

**Chapter 11** 
