Abstract #40

# 40
Twinning in dairy cattle.
M. Travis*1, C. Becker1, A. Stone1, 1Mississippi State University, Mississippi State, MS.

The dairy industry continues to push for greater milk production through greater reproductive performance in our animals. A negative effect of this is increased twinning rates. Factors that contribute to twinning in dairy cattle include double ovulation, genetics, season, and management. Cows that experience an extended period in a negative energy balance can have atypical ovarian activities, such as double ovulation and anovulatory repeated follicular waves that can lead to the occurrence of twins (Lopes et al., 2003). High producing dairy cattle are in a negative energy balance for a longer period compared with their lower producing counterparts (Fricke 2001). Twin pregnancies have a negative economic impact. Depending on the type of twin pregnancy, parity, and days in milk when the twin pregnancy occurs, the cost of the vet services per pregnancy increased from $97 to $225 per cow when compared with singletons. The overall negative economic impact of twinning on dairy farm profitability in the United States was estimated to be $96 million per year (Novales et al., 2018). Twinning poses a variety of pre- and postpartum health risks, including a decrease in the number of days on a transition diet, increased dystocia occurrences, decreased milk yield, and increased days to conception. In one study, monozygotic (same sex) twins made up 5.5% of all twin births in the population. Dizygotic twins (a male and female) have a 90% chance of the heifer calf being a freemartin, due to the exchange of hormones across the blood barrier from fetus to fetus (López-Gatius et al., 2017). Twins struggle to thrive in the first few days after birth, and lag in growth when compared with singleton calves. The dairy industry must be prepared for the challenges that come along with twins, whether it be early termination of the pregnancy or better management of the cow during the pregnancy. Dairy producers can help their cows throughout the pregnancy by giving moving cows to the transition group 3 weeks earlier and monitoring and maintaining the body condition score of the cow during the dry period (Frickle, 2001). Producers can achieve this by monitoring the ration of the group of cows and feeding them the appropriate ration for their stage in lactation.

Key Words: twinnings, high production, twin