High-yielding lactating sows maintained a high litter growth when fed reduced crude protein, crystalline amino acid-supplemented diets

Abstract

The study was conducted to determine the optimal standardized ileal digestible (SID) CP level to maximize litter gain in high-yielding lactating sows when feeding reduced CP, crystalline amino acid-supplemented diets. In total, 520 Landrace × Yorkshire sows (parity 1 to 5) were allocated to 1 of 6 diets from day 2 post-partum when litters were standardized to 14 piglets. All diets were formulated to meet or slightly exceed Danish recommendations for Lys, Met, Met + Cys, Thr and Trp using crystalline amino acids. Diets contained 116, 126, 132, 138, 144, and 153 g SID CP per kg (as-fed). Sow body weight, back fat thickness, and litter weight were recorded at litter standardization and at weaning. On a subsample of 72 sows (parity 2 to 4), milk samples were collected at day 3, 10 and 17 post-partum, and blood was sampled at day 10 and 17 post-partum. All data were subjected to ANOVA using the MIXED procedure in SAS. Litter size at weaning was not affected by the dietary CP content (13.0 ± 0.06; P = 0.40), nor was litter ADG (3.13 ± 0.03 kg/d; P = 0.52), nor milk contents of fat and lactose (P > 0.05). Likewise, the daily changes in sow body weight (−0.58 ± 0.04 kg/d, P = 0.44) and back fat thickness (−0.15 ± 0.004 mm/d, P = 0.20) were similar across dietary treatments. Milk protein (P < 0.01), milk Lys (P < 0.05), and other essential amino acids in milk protein were reduced at a SID CP concentration of 116 g/kg. Plasma concentrations of NEFA and creatinine were not affected by dietary treatment (P > 0.05), but concentrations of plasma urea nitrogen were elevated (P < 0.001) as dietary CP content increased. In conclusion, sows were able to maintain a high litter growth when fed reduced CP, crystalline amino acid-supplemented diets. Though, it is not recommended to feed the lactating sows less than 126 g SID CP/kg (as-fed).