Biased Milk Production Programmed by Fetal Sex Affects Sexed Semen Economics
Recent research has shown that Holstein dairy cows produce more milk per lactation after giving birth to female calves and when gestating female calves compared to male calves. The objective of this study was to evaluate how the economics of the use of sexed semen are affected by these differences in milk production. A herd budget simulation program was used that included separate daily cash flow projections for heifers and at least 4 parities of cows. Cash flows were based on lactation curves, feed intakes, reproductive parameters, culling and prices for milk, feed, calves, cull cows, semen, among other inputs. Based on the recent research, a first parity cow produced 185 kg per lactation more milk when she had given birth to a female calf and was gestating a female calf compared to giving birth to and gestating a male calf. A second parity cow produced 269 kg per lactation more milk when she had given birth to female calves in the current and first parity. Third and greater parity cows produced 100 kg more milk when giving birth to a female compared to a male. Other combinations of males and females resulted in smaller effects. Compared to conventional semen, sexed semen reduced the probability of conception by 20% and was $15 more expensive. Female calves were $100 more valuable than male calves. Cow pregnancy rates were 21% without sexed semen. Five sexed semen scenarios were evaluated, ranging from 1x sexed semen in heifers to 3x in heifers and 2x in first parity cows. Sexed semen break-even prices ranged from $3 to -$2 without the effects of fetal sex on milk production, compared to no use of sexed semen. Including the effects of fetal sex on milk production, sexed semen break-even prices ranged from $15 to $4. Break-even female calf prices, compared to male calf prices, were up to $29 lower when including the effects of fetal sex on milk production than when ignoring these effects. In conclusion, the effects of fetal sex on milk production make the use of sexed semen more economically feasible and should be included in economic calculations.
Keywords: Fetal sex, milk production, sexed semen, economics