7.6. Culling reasons and life span

respectively), which was in good concordance with results of another study [40]. In contrary to these reports, mothers of twins have been shown to be superior to mothers of single calves in

The reproductive health of the herd is a great indicator of how a management system is working, by highlighting the profit or losses seen financially. With dairy cattle, these results can be seen from the view point of reproduction (calving interval, dry period, and services per

Ideally, every farmer would like his herd increase every year, with each cow having at least one calf, and in turn increase the milk yield with every subsequent lactation. In reality, multiple births come with unwanted problems. Unfortunately, more calves per cow do not automati-

From higher incidence of abortions, reduced birth weight or higher numbers of stillbirths, mastitis, and problems related to dystocia, the increase in costs in the case of multiple births

There is a higher incidence of pregnancy loss, with number of fertile heifers' herd replacement [15]. Increase of calf mortality is 18% [30] and fertility of the cows was shown to deteriorate after multiple pregnancies, with the most unfavorable indicators of fertility found in triplet births [14]. Other studies show that twinning increases open days and services per conception on average and therefore decreases reproductive performance of the dam during subsequent lactations [21]. There is a longer regeneration time of the uterus and this in turn causes the elongation of the resting period after calving‑these were increasing with the number of lactations, relating to twin calving and shorter gestation. This was more evident with calving in the summer period. Cows with dead twins also had increased time to conception, compared with live twins. The natural incidence of multiple births in cattle is largely due to multiple ovulations and is around

Analysis of bovine pregnancy–associated glycoprotein (bPAG-1) can also be used to determine the nature of the pregnancy from about day 90 [66]. Dissemination of twin and singleton pregnancies is not possible before day 85, so prevention or early identification of twinning is not possible with this measurement. To achieve diagnostic test with both high sensitivity and

The double ovulation occurs when two mature follicles are released at the same time in one cycle of ovulation [21]. Adhesion of the outer layers of the amniotic sacs can occur in twin and multiple pregnancies because of their proximity. This may result in fusion of the chorion layers at which point an anastomosis of the vessels occurs in most cases leading to a union of the blood circulations of both embryo. In case of twins with different sex (bull and heifer), in 98%

terms of milk yield in a third investigation [30].

74 Ruminants - The Husbandry, Economic and Health Aspects

conception) and milk production (milk yield and fat and protein %).

1–5%, depending on breed, parity, and environmental conditions [65].

specificity, further studies such as ultrasound are required.

7.4. Fertility and reproduction

cally mean more profits seen.

adds up to 40% per cow [64].

7.5. Freemartinism

It has been shown [14] that multiple pregnancies considerably decreased the chance of survival until the next calving and increased the culling rate. When analyzing the reasons for culling cows from the herds, it was found that multiple births gave rise to a greater proportion of cows culled due to udder diseases, infertility, reproductive diseases, old age, metabolic and gastrointestinal diseases, and diseases of the locomotor system.

The lifespan of 3581 cows that had never had twins and 386 cows that had twins at least once was examined [38]. On average, the total lifespan was 68 months. Whether or not the cows had twins had a significant impact on their lifespan (p < 0.001). The cows that never had twins reached on average 60 months (roughly 5 and a half years old), and cows that had at least one set of twins reached on average 76 months old (roughly 6 and a half years). The difference in life expectancy between these two groups was 15.8 months (a year and 3 months approximately).
