Lysine Requirement of the Gestating Sow Determined by Using Plasma Urea Nitrogen as a Rapid Response Criterion

Lysine requirements at two stages of gestation were estimated in adult sows who had been fed either low (LL) or high lysine (HL) diets in the previous lactation period. Sows fed LL lost more weight during lactation that sows fed HL. Also, sows fed LL diet had more days of anestrus than sows fed HL. There were no differences, however, in litter weight gain of sows fed LL and HL. Estimates of gestation lysine requirements for sows fed LL were 9.6 ± 1.5 and 12.2 ± 1.7 g/d for early gestation and late gestation, respectively. The plasma urea nitrigen (PUN) technique did not accurately or precisely estimate the lysine requirement of the sows fed the HL diet in lactation