Inhibition of ovulation in the postpartum cow and the lactating sow

Modern sows have been improved genetically for higher productivity including ovulation rate, litter size and milk production. Peak milk yield is achieved within 10 days after farrowing with consequent massive mobilization of body fat and protein mass. Conservation of body protein mass (< 12% loss) during the first lactation minimizes the weaning to estrus interval by advancing ovarian follicular development toward ovulation. The lysine requirement in early lactation is extraordinary. Plasma insulin and IGF-I concentrations seem unrelated to the observed differences in ovarian follicular development. Overall, NEBAL inhibits ovulation in both high producing cows and sows, but there are species differences in response to protein losses and hormonal interactions.