*Calf-Sex Influence in Bovine Milk Production DOI: http://dx.doi.org/10.5772/intechopen.93966*

*Animal Reproduction in Veterinary Medicine*

**214**

**Country**

USA

1995-1999

2,390,000

Holstein

**Years analyzed**

**N (lactations)**

**Breed**

**Main results** Cows favor daughters, producing significantly more milk

for daughters across lactation.

Effects of fetal sex interact dynamically across parities,

whereby the sex of the fetus being gestated can enhance

or diminish the production of milk during an established

lactation.

Sex of the fetus gestated on the first parity has persistent

consequences for milk synthesis on the subsequent parity.

Specifically, gestation of a daughter on the first parity

increases milk production by, 445 kg over the first two

lactations

The effect of the calf sex hardly affected milk production.

[53]

A small effect in favor of males was observed in parity 2

and 3 and was similar across breeds.

The estimated effect of the sex of the calf in gestation on

the simultaneous lactation was also very small.

Cows with female calves had higher milk and fat yield,

[40]

persistency of milk and fat yield and longer lactation

length, while cows that gave birth to male calves had

shorter calving interval and longer productive life.

Also, cows with female calves had higher milk yield per

day of lactation in the first two parities, but there was no

difference in milk yield per day of lactation for parities ≥3.

Cows produced higher volumes of milk if they had a bull

[32]

calf, with a significantly higher milk production of 0.28%

in the first lactation period for cows giving birth to a bull

calf.

Such difference was even higher when cows gave birth to

another bull calf, so having two bull calves resulted in a

difference of 0.52% in milk production compared to any

other combination of sex of the offspring.

France

Iran Denmark

till 2013

71,088

Holstein

1992-2008

402,716

Holstein

2000-2008

8,901,000

Montbéliarde and Holstein

**Study** 

**(chronologically)**

[1]

during the second lactation. Calving a female on the first parity, increases milk production by 445 kg over the first two lactations, identifying a dramatic and sustained programming of mammary function by the offspring in utero. On the other side, cows calving a male son on their first parity produced less milk on their second lactation (P < 0.001), particularly if they also gestated a male calf on the second pregnancy (**Table 2**). According to the same study, the milk composition was similar whether the gestation produced a gestation of a son or daughter; the fat concentration was 3.61% after gestation of a daughter and 3.62% after gestation of a son; protein concentrations were the same (3.17%) [1].

Gillespie et al. [57] also showed that, in the UK, calving a heifer was associated with a 1% milk yield advantage in first lactation heifers, but calving a bull calf conferred a 0.5% advantage in second lactation. Heifer calves were also associated with a 0.66 kg reduction in saturated fatty acid content of milk in first lactation, even though there was no significant difference between genders in the second lactation. Interestingly, the effects of calf gender observed on both the yield and saturated fatty acid content were considered minor compared to the nutritional and genetic influences. Aspects that affect milk production, such as mastitis [58] or lameness [59], seem to have a deeper impact on milk production than calf gender.

An Iranian study, using 402,716 Holstein milk records from 1991 to 2008, report that cows calving a female offspring present a higher milk and fat yield and longer persistency of milk and fat yield, as well as a longer lactation length [41]. Cows calving a male offspring presented shorter calving interval and an overall longer reproductive life. The observed higher daily milk yield after calving a female in the first two parities was not maintained for the next parities [60]. However, a higher occurrence of dystocia in male calving was not taken into consideration and was most likely a factor for the higher milk production observed after calving a female calf [41]. In contrast, both a French [54] and a Danish [33] studies found a small increase in milk yield in both Holstein and Montbéliarde dams calving a male offspring. On the French study, the sex-bias favoring males effect reached 40 kg milk (0.5% of the mean), 0.6 kg fat, 0.6 kg protein. A small difference was also noticed for fat and protein contents (from 0.01 to 0.02%) in parity 2 and 3. Similarly, the estimated effect of the sex of the calf in gestation on the simultaneous lactation is very small [54].

Græsbøll et al. [33] also reported significantly higher milk productions (0.28%) in first lactating cows producing a bull calf. This difference was even higher when cows calved another bull calf, with a difference of 0.52% in milk production compared to any other possible combinations of offspring sex. The same study pointed that dams would favor a bull fetus by decreasing milk production during the second pregnancy if the calf born in the first parity was a heifer, which diluted the positive effect on milk production of calving a male in the first pregnancy. Being pregnant with a bull fetus may reduce milk production to possibly increase the energy spent


**Table 2.**

*Effect of the calf gender combination at the first and second lactation (305d) according to Hinde et al. [1].*

**217**

*Calf-Sex Influence in Bovine Milk Production DOI: http://dx.doi.org/10.5772/intechopen.93966*

cantly different from each other [40].

tion in their own adulthood [48, 64].

with a higher milk production [67].

and by consequence a lower incidence of dystocia [41].

percentage was associated with the birth of a male calf [34].

on the bull fetus. Also, cows seem to favor living bull offspring over unborn bull

The magnitude of sex bias milk production, when observed in other species, seems to be stronger among first parity females [11, 26, 27, 30, 59]. The fetal sex effect may be disguised in multiparous females because of the cumulative effects of sequential gestations with fetuses of different sexes on the mammary gland architecture [1]. It is also possible that maternal investment tactics may change according to the residual reproductive value of the offspring [1, 61] or transmit a targeted effort during a critical window of mammary gland preparation for a new lactation [1, 62]. Interaction effects were observed between calf gender across the first three parities, with the lowest second parity milk yield observed when a cow gave birth to male calves in all three parities. First parity calf sex did not have a significant effect on the third lactation milk yield. Disparities between the effects for calf sex sequences that differed only by the calf gender in the first parity were not signifi-

In cows' populations were a daughter-biased milk production was observed, this may involve life-history tradeoffs for both cows and their daughters. High milk production in dairy cows has been associated with reduced fertility, health, and survival depending on environmental conditions [63]. It was also observed that cows gestated during lactation have moderately reduced survival and milk produc-

Some of the differences found across different studies could be partly explained

The effect of the calf gander can further interact with other factors, like parity or seasonality, making it difficult to evaluate it in a precise way. It was observed that after the third calving, the mother milk production was independent of the calf gender. This observation might be related to larger pelvic dimensions of older cows

A significant difference between the dairy industry in Azores [34] or New Zealand [40] compared with other populations is that both are primarily pasturebased. The production and calving in Azores are not, however, as seasonal as the one observed in New Zealand [34, 40]. In the non-seasonal pasture-based system no calf-sex bias in milk yield was observed, even though a slight increase in fat

In Denmark, the difference observed in milk production due to the sex of the offspring was generally smaller than the difference between farms. Other management related aspects are more important for the milk yield registered and the differences identified might be due to size of the offspring rather than the sex, but size and sex might also have separated effects [33]. So far, no relation was observed among mean somatic cells count and the sex of the calf born [41, 68, 69], even though this parameter is often associated with the cow body condition [70].

by differences in the datasets used; Hess et al. [40] used total lactational yield, calculated using the test interval method; Hinde et al. [1] and Barbat et al. [54] used the test day model rather than predicting 305 day milk yields; Graesboll et al. [33] adopted a farm-based approach using Wilmink curves to calculate 305 day milk yields and Gillespie et al. [47] used the Milkbot lactation model, that can be affected by environment and genetics [65]. Also, the use of sexed semen was not known in most of the studies and it can have a significant impact in the results obtained. Sexed semen is mainly used to breed heifers with higher genetic merit [54, 66] and this creates an obvious bias towards female calves. This can be aggravated by the fact that heifers inseminated with sexed semen tend to have lower fertility and become pregnant later, consequently calving in an older age, which is associated

offspring, but unborn bull offspring over living heifer offspring [33].

### *Calf-Sex Influence in Bovine Milk Production DOI: http://dx.doi.org/10.5772/intechopen.93966*

*Animal Reproduction in Veterinary Medicine*

son; protein concentrations were the same (3.17%) [1].

seem to have a deeper impact on milk production than calf gender.

**Female-female vs. male-male**

at first lactation 24 (0.3) 7 (0.1) 13 (0.2) at second lactation 52 (0.6) 5 (0.1) 53 (0.6) Cumulative effect 76 (0.9) 12 (0.2) 66 (0.8)

*Effect of the calf gender combination at the first and second lactation (305d) according to Hinde et al. [1].*

during the second lactation. Calving a female on the first parity, increases milk production by 445 kg over the first two lactations, identifying a dramatic and sustained programming of mammary function by the offspring in utero. On the other side, cows calving a male son on their first parity produced less milk on their second lactation (P < 0.001), particularly if they also gestated a male calf on the second pregnancy (**Table 2**). According to the same study, the milk composition was similar whether the gestation produced a gestation of a son or daughter; the fat concentration was 3.61% after gestation of a daughter and 3.62% after gestation of a

Gillespie et al. [57] also showed that, in the UK, calving a heifer was associated with a 1% milk yield advantage in first lactation heifers, but calving a bull calf conferred a 0.5% advantage in second lactation. Heifer calves were also associated with a 0.66 kg reduction in saturated fatty acid content of milk in first lactation, even though there was no significant difference between genders in the second lactation. Interestingly, the effects of calf gender observed on both the yield and saturated fatty acid content were considered minor compared to the nutritional and genetic influences. Aspects that affect milk production, such as mastitis [58] or lameness [59],

An Iranian study, using 402,716 Holstein milk records from 1991 to 2008, report that cows calving a female offspring present a higher milk and fat yield and longer persistency of milk and fat yield, as well as a longer lactation length [41]. Cows calving a male offspring presented shorter calving interval and an overall longer reproductive life. The observed higher daily milk yield after calving a female in the first two parities was not maintained for the next parities [60]. However, a higher occurrence of dystocia in male calving was not taken into consideration and was most likely a factor for the higher milk production observed after calving a female calf [41]. In contrast, both a French [54] and a Danish [33] studies found a small increase in milk yield in both Holstein and Montbéliarde dams calving a male offspring. On the French study, the sex-bias favoring males effect reached 40 kg milk (0.5% of the mean), 0.6 kg fat, 0.6 kg protein. A small difference was also noticed for fat and protein contents (from 0.01 to 0.02%) in parity 2 and 3. Similarly, the estimated effect of the sex of the calf in gestation on the simultaneous lactation is

Græsbøll et al. [33] also reported significantly higher milk productions (0.28%) in first lactating cows producing a bull calf. This difference was even higher when cows calved another bull calf, with a difference of 0.52% in milk production compared to any other possible combinations of offspring sex. The same study pointed that dams would favor a bull fetus by decreasing milk production during the second pregnancy if the calf born in the first parity was a heifer, which diluted the positive effect on milk production of calving a male in the first pregnancy. Being pregnant with a bull fetus may reduce milk production to possibly increase the energy spent

**Calf gender combination at the first and second lactation**

**Female-male vs. male-male**

**Male-female vs. male-male**

**216**

**Table 2.**

very small [54].

**Differences Kg (%)**

on the bull fetus. Also, cows seem to favor living bull offspring over unborn bull offspring, but unborn bull offspring over living heifer offspring [33].

The magnitude of sex bias milk production, when observed in other species, seems to be stronger among first parity females [11, 26, 27, 30, 59]. The fetal sex effect may be disguised in multiparous females because of the cumulative effects of sequential gestations with fetuses of different sexes on the mammary gland architecture [1]. It is also possible that maternal investment tactics may change according to the residual reproductive value of the offspring [1, 61] or transmit a targeted effort during a critical window of mammary gland preparation for a new lactation [1, 62]. Interaction effects were observed between calf gender across the first three parities, with the lowest second parity milk yield observed when a cow gave birth to male calves in all three parities. First parity calf sex did not have a significant effect on the third lactation milk yield. Disparities between the effects for calf sex sequences that differed only by the calf gender in the first parity were not significantly different from each other [40].

In cows' populations were a daughter-biased milk production was observed, this may involve life-history tradeoffs for both cows and their daughters. High milk production in dairy cows has been associated with reduced fertility, health, and survival depending on environmental conditions [63]. It was also observed that cows gestated during lactation have moderately reduced survival and milk production in their own adulthood [48, 64].

Some of the differences found across different studies could be partly explained by differences in the datasets used; Hess et al. [40] used total lactational yield, calculated using the test interval method; Hinde et al. [1] and Barbat et al. [54] used the test day model rather than predicting 305 day milk yields; Graesboll et al. [33] adopted a farm-based approach using Wilmink curves to calculate 305 day milk yields and Gillespie et al. [47] used the Milkbot lactation model, that can be affected by environment and genetics [65]. Also, the use of sexed semen was not known in most of the studies and it can have a significant impact in the results obtained. Sexed semen is mainly used to breed heifers with higher genetic merit [54, 66] and this creates an obvious bias towards female calves. This can be aggravated by the fact that heifers inseminated with sexed semen tend to have lower fertility and become pregnant later, consequently calving in an older age, which is associated with a higher milk production [67].

The effect of the calf gander can further interact with other factors, like parity or seasonality, making it difficult to evaluate it in a precise way. It was observed that after the third calving, the mother milk production was independent of the calf gender. This observation might be related to larger pelvic dimensions of older cows and by consequence a lower incidence of dystocia [41].

A significant difference between the dairy industry in Azores [34] or New Zealand [40] compared with other populations is that both are primarily pasturebased. The production and calving in Azores are not, however, as seasonal as the one observed in New Zealand [34, 40]. In the non-seasonal pasture-based system no calf-sex bias in milk yield was observed, even though a slight increase in fat percentage was associated with the birth of a male calf [34].

In Denmark, the difference observed in milk production due to the sex of the offspring was generally smaller than the difference between farms. Other management related aspects are more important for the milk yield registered and the differences identified might be due to size of the offspring rather than the sex, but size and sex might also have separated effects [33]. So far, no relation was observed among mean somatic cells count and the sex of the calf born [41, 68, 69], even though this parameter is often associated with the cow body condition [70].

Modeling complex biological features, such as milk production, is challenging due to the number of inherent and environmental aspects that can influence them. Also, the statistical model used for analysis may influence to a certain point the results and data interpretation. One explanation for the differences of the several studies on calf-sex biased milk production can be related to the models used. For example, in one of the studies, Holstein Friesian cows calving males in the first three parities had significantly lower first lactation milk yield than cows calving two males followed by a female in the first three parities, but this observation is biased if models do not include lactation length. Also, there are no reasonable biological reasons why to test the effect of the gender of the third calf on the first lactation yield. In fact, the observed effect of calf gender on milk yield is due to an association between calf gender and milk yield rather than calf gender triggering a difference in milk yield. The alleged effect of the third parity calf gender on the first lactation milk yield was not apparent when lactation length was included in the models [40].

In beef cows, studies with limited samples led to different sex-biased milk production, pointing to either favors a son [71], or a daughter [72], or not show any sex-biases [73]. A study in the red Chittagong cattle found no effect of the calf-sex in milk production [74].
