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Effect of altered dietary Lysine: energy ratio in gestation on gilt performance and piglet survivability
Based on the new NRC (2012) model, the increase in protein requirement in late gestation is to a greater extent than the increase in energy requirement suggesting a need for phase-feeding. To determine the effects of phase feeding Lysine: energy to gilts on piglet birth weight and survivability, 27 gilts were randomly assigned to 1 of 3 gestation feeding regimens: Control, 2.21 kg/d from breeding to d112 (0.46g Lys /MJ ME); Bump feeding (BF), the control diet at 2.21 kg/d from breeding to d89 and 2.61 kg/d from d90 to 112; Phase feed (PF), 2.21 kg/d (0.43g Lys/MJ ME from breeding to d89) and 2.61 kg/d (0.59g Lys/MJ ME from d90 to 112). All diets contained 13.5 MJ ME/kg. Gilt weights and back fat were monitored regularly. Cord blood was collected at birth for cortisol determination, birth weights were recorded and weekly piglet growth was monitored. Piglets were assigned to three weight categories according to birth weight (light weight <1.2, average 1.21-1.6, heavy >1.61kg).
Data were analyzed using the MIXED procedure in SAS. Litter birth weight variation was assessed using a Chi-squared test. During gestation and lactation, there were no differences in mean body weight or mean back fat between the treatment groups , but there was a tendency (P = 0.07) for higher feed intake during lactation in the Control sows compared to BF and PF gilts (4.35, 3.25 and 3.53 ± 0.3 kg/d, respectively).Pigs born alive was higher (P = 0.03) in Control sows than the BF or PF sows 13.5, 10.5, and 11.9 ± 0.9, respectively ).There was no difference in mean birth weight (1.43 ± 0.07 kg) but more PF piglets (P = 0.04; χ2=6.6) had birth weights in the average category and a trend to more bump piglets (P = 0.09; χ2=4.9) in the heavy category. PF piglets had higher (P = 0.05) cord blood cortisol than Control and BF piglets (88.2, 56.3, and 64.1 ± 9.3 ng/mL, respectively). There was no difference in piglet body weight from birth to weaning; however, body weight change from birth to d 7 showed a positive correlation with cord cortisol (r = 0.30, P = 0.003)
Phase feeding Lysine: energy and bump feeding resulted in more piglets born at a desirable birth weight; however, only phase feeding resulted in higher levels of cord cortisol, which are associated with a higher probability for survival.
Keywords: phase-feeding, late gestation, piglet survival