Partitioning of dietary protein during lactation in the Meishan synthetic and European White breeds of pig

Abstract

AbstractLitter size of commercial European sow lines can be increased by the introduction of genes from the highly prolific, but obese Meishan. The introduction of these genes into sow lines may necessitate different nutritional strategies for lactation. A 2 × 2 × 2 factorial experiment was used to investigate the influence of breed type (Meishan synthetic 50% (M) or purebred European Landrace and Large White (W)) and parity (1 or 3) on response to dietery protein level (H = 178 g crude protein (CP) per kg 8 g lysine per kg, L = 136 g CP per kg 5 g lysine per kg over a 5-week lactation. M were lighter and fatter at farrowing than W (P < 0·001), consumed more food (M = 7·33 v.W = 6·98 (s.e.d. 0·17) kg/day, P < 0·05) but had higher maternal weight loss (M = 16·2 v.W = 11·9 (s.e.d. 1·88) kg, P < 0·05) and higher fat loss (M = 6·5 v. W = 26 (s.e.d. 077) mm P2, P < 0·001) during lactation. Litter growth rate was higher for M than for W (P < 0·005) and for H than for L (P < 0·005). Differences were found between breeds in the partitioning of food protein. Overall, higher correlations between lysine intake and litter growth rates were found in M (r = 0·55, P < 0·001) than in W (r = 0·13, P > 0·05). Lysine intake and sow weight loss were more correlated in W(r = 0·66, P < 0·001) than in M (r = 0·15), P > 0·05). Fat loss was correlated with initial fat depth in M (r = 0·61, P < 0·001) but not in W. Weaning to conception intervals showed a breed × diet interaction (loge days: ML = 1·38, MH = 1·55, WL = 1·73, WH = 1·43, s.e.d. 0·14, P < 0·05). It is concluded that M, with greater initial fat reserves, catabolize more body fat to support greater milk output. This is facilitated by provision of a high protein diet. The W sows do not utilize the extra protein for milk production but instead use it to minimize weight loss (maintain protein status of their own body) which may help prevent an extended weaning to conception interval.