Genetic Influence on Embryo Production
Researchers at the University of Guelph recently set out to assess the genetic correlation between the number of embryos produced by Holstein donors using in vivo and in vitro techniques—and the number of donor embryos produced as a heifer and as a cow. The results were published in the September issue of the Journal of Dairy Science.
Results indicated that genetic correlations between records produced in vivo and in vitro were moderately high and positive. This suggests that donors with high genetic potential for in vivo superovulation tend also to have high potential to produce multiple embryos in vitro.
Similarly, the moderately high genetic correlations found between heifer and cow records indicate that a donor tends to produce a comparable number of embryos as a heifer or as a cow. The researchers also noted that the service sires seem not to play an important role on the total number of embryos produced by a donor.
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Milk Protein as an Indicator of Reproductive Performance
Milk protein concentration (percentage) has been positively associated with a range of measures of reproductive performance in dairy cows. This is likely due to factors affecting both milk protein concentration and reproductive performance possibly being mediated, in part, by energy balance during early lactation. However, it is likely that factors other than energy balance are also involved in these relationships.
A retrospective study was conducted by Australian researchers to learn more about this concept. The results were published online by the Journal of Dairy Science on September 21, 2016.
The researchers found:
- Higher milk protein concentration was associated with better reproductive performance. For the first 150 days of lactation, the positive associations were strongest from 31 to 60 days and only slightly lower for all periods up to 150 days of lactation.
- Estimated associations for protein concentration from 31 to 60 days were stronger than for 0 to 30 days.
- In addition, milk protein concentration during a cow’s breeding period was positively associated with the subsequent pregnancy rate, even after adjusting for milk protein concentration in the cow’s first or second month of lactation.
The researchers say these results indicate that the association between milk protein concentration and reproductive performance is partly due to factors other than the extent of negative energy balance in early lactation. However, it is possible that energy balance accounts for some of the relationship, since as the magnitude and direction of energy balance can vary within and between cows throughout lactation.
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Do you Monitor Transition Period Blood Glucose Levels?
Researchers at Cornell University recently investigated the association between the metabolic indicators non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA) and glucose during the transition period and the development of uterine diseases. The research was published online by the Journal of Theriogenology on September 30, 2016.
Results showed that plasma glucose concentration can be associated with the occurrence of metritis and clinical endometritis (purulent vaginal discharge). Moreover, cows with an increased calving to conception interval (greater than 150 days) presented higher plasma glucose concentrations than cows that became pregnant within the first 150 days.
Glucose at three days in milk was the best predictor for metritis and endometritis diagnosis. Additional analyses showed that cows with higher levels of glucose at day three had:
- 6.6 times higher odds of being diagnosed with metritis than cows with lower glucose levels
- 3.5 times higher odds of developing clinical endometritis than cows with lower glucose levels
The researchers also noted a negative correlation between daily milk yield in the first and second weeks of lactation and plasma glucose concentrations measured at days seven and 14, respectively.
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