3. Reproductive traits in twin- and single-calving cows before calving

period, 1281 (3.94%) twin births occurred. The ratio of twin deliveries on the farms varied

We see that food intake is reduced with the rise in temperature in the summer, along with the decline in reproductive performance and milk yields [29]. Better feed quality supplied in the autumn and optimum temperature (absence of heat stress) contribute to multiple ovulations in

Cows with high milk yield show a threefold higher frequency of double ovulation than cows with medium to low lactation performance. Flushing could potentially be given as the reason

Quality of feeding has a huge knock-on effect throughout the life of a cow: before fertilization, prepartum, and postpartum. Nutrition plays a great part with the aim of getting the maximum energy intake from the silage and feedstuff to optimize milk production and fertility performance of the herd. This goes hand in hand with good management and good farming practice. Good nutrition can also lower the risk of postpartum disorders like ketosis, mastitis, and milk

Milk production is the primary factor affecting the incidence of double ovulation in lactating

High milk production near the time of ovulation can increase the incidence of double ovulation, which would therefore subsequently result in an increase in twinning. Current dairy management strategies are aimed at maximizing the milk production of the cow. This intensive feeding strategy would in turn increase the incidence of double ovulation in the dairy cattle population in general. It is therefore not unexpected that given the annual increases in milk

It was found [31] that the rate of twinning increased with increases in milk production, incidence of cystic ovarian disease, and the use of common pharmaceuticals, including gonadotropin-releasing hormone (GnRH), prostaglandin (PGF2α), and antibiotics. For farmers and the milk industry, only a functional cow with regular and healthy offspring is profitable. Any kind of disorder in relation to the reproductive system will cause losses, by increasing the number of required inseminations and elongating the calving interval. To avoid or at least to reduce these issues, a hormonal treatment could help to reach a successful pregnancy [32, 33]. For the "OV-Synch method," the cows get two intramuscular injections of gonadotropinreleasing hormone (GnRH) as well as one prostaglandin (PGF2α) injection in a specific order to synchronize the ovulation of a herd [21]. Another benefit beside the synchronization is the use of this injection combination to treat cysts of the ovaries [34]. Due to the effect of hormones

fever, which were associated with high reduction in milk production [16].

production that there should be an overall increase in twinning rates as well.

between 3.43 and 4.35%.

64 Ruminants - The Husbandry, Economic and Health Aspects

2.4. Nutritional influences

cows [30].

for this [21].

2.5. Milk yield

dairy cows [21].

2.6. Hormonal influences

Data from 393,002 parturitions were recorded along with the cows' performance in the following production cycle [30]. Data were collected from 145,457 Polish Holstein Friesian cows. The animals initially calved between 2000 and 2012 and were either in use or culled by the end of 2013. Among the factors analyzed, the cow's age had the strongest effect on the rate of occurrence of multiple pregnancies, showing multiple pregnancies to be much more frequent in cows than in heifers. Each consecutive lactation raises the chance of multiple ovulations, and occurrence of twin births increases linearly with the frequency of double ovulation [21, 35]. The incidence of twin pregnancies goes from 1% in maiden heifers to about 10% in following lactations. The rate of twin pregnancies increases the most between the first and second lactation. After the second lactation, the incidence increases to a lesser extent [23]. It should also be noted that heifers have an increased mortality of one of the fetuses in multiple pregnancies, due to the high nutrient requirement of the growing body of the heifer coupled with the demands of the twin fetuses [36].

In an analysis [37] of 4000 cows calving between 2000 and 2010 in a herd in northern Hungary (Table 2), ages were compared at first breeding, at first conception, and at first calving of twinning and nontwinning cattle. The average age at first breeding at the farm was 17.9 months (544 days), and no significant difference was found between future twinning and nontwinning heifers. The average age of first conception was 18.3 months (557 days). There was no significant difference between nontwinning and twinning heifers. On average, heifers became


Table 2. Reproductive traits of cows with single and twin birth before (BF) and after calving (AF) [37, 38].

pregnant by the 13th day of service if the first or second insemination was successful. On analysis of age of first calving, it was demonstrated that on average the age of first calving in pregnant heifers was 27.5 months, and there was also no significant difference between twinning and nontwinning heifers. The lack of deviation is due to the management system and when the farmer chose to inseminate them.

between 2010 and 2012. This is thought to be linked to increased production levels of the active population, because the yield of cows in their first lactation in 2000 was 5969 kg compared to

Twin Calving and Its Connection to Other Economically Important Traits in Dairy Cattle

http://dx.doi.org/10.5772/intechopen.72905

67

Milk yield is positively correlated to frequency of multiple pregnancies [3, 4]. In an analysis of 91,008 calvings between 1974 and 1985, it was shown that twinning was much more frequent

In Table 2, reproductive characteristics after calving are also presented with respect to the time from the calving to the service period [38]. The average number of days in the resting period on the farm was 75.8. The number of the calves had a strong effect on the length of the studied period (p = 0.043). The cows that had single calves took 73.6 days compared to the cows that

The service period was analyzed in a separate study of the same herd data [40] and the average service period length was 44.6 for the herd overall (Figure 1). The single-calving cows had a shorter (44.4 days) service period than twin-calving cows (51.2 days), but this difference was not considered statistically significant (p = 0.111). It was found that roughly a third of the cows were put in calf by the very first insemination. Fifty percent of the cows that had single and twin calves were put in calf by the 40th and 48th day of service period, respectively. However, it was found that this 8-day difference was not a statistically proven difference (p = 0.653)

Figure 1. Cumulative proportion of cows that became pregnant on the course of insemination period [40].

5. Reproductive traits in twin- and single-calving cows after calving

8215 kg for cows in their first lactation that calved in 2012.

had calved twins 78.0 days to recover.

in Holstein Friesians compared to the Polish Black-and-White breed.

The calving to service period prior to a viable pregnancy was on average 73.9 days, showing no significant difference between twinning and nontwinning cows. The cows that were nontwinning took 73.6 days.

There is a statistically proven difference between twinning and nontwinning cows (p = 0.047) in the length of open period, which was 109.3 days for nontwinning and 104.6 for twin-calving cows, meaning that twin-calving cows required a shorter service period by 4–5 days than nontwinning cows, due to their better fertility and higher chance for conception.

Cows carrying twins had an average gestation length of 274.0 days, which was confirmed to be shorter than their herd mates carrying single calves for 278.7 days. There was a significant (p < 0.001) difference in this study of nearly 5 days due to the type of calving. The average length of gestation was 276.3 days. The significant contributing factors to the total variance were the following: type of calving, calf gender, and calving season, 64.22, 17.32, and 10.92%, respectively.

Calving interval of the herd was 398.2 days. A relevant difference was detected between the twin-calving and single-calving cows. The calving interval in twin-calving cows was 392.2 days, shorter than the calving interval in nontwinning cows, which was 404.2 days. A difference of 12 days is significant (p < 0.001).

This farm study assumed that cows that would carry twins have a better body condition, which leads to better fertility provided the housing and feeding all the cattle receive are the same. It was concluded that the beginning of the breeding phase for young animals is dependent on the decision of the farmer and it will be similar for every heifer on that farm. The first part of the investigation was concerned with events only occurring once in life of a heifer. However, later characteristics that occur repeatedly in life of a dairy cow were analyzed, and in all cases, the characteristics were taken into consideration before calving, demonstrating differences between the length of the calving interval, open days, and gestation during the herd's life. This shorter calving interval can be seen as advantageous in a dairy herd.
