Impact of dietary protein to energy ratio and two different energy levels fed during late gestation on plasma metabolites and colostrum production in sows

Factorial calculations indicate that energy requirement of sows in late gestation is relatively constant, while there is a marked increase in protein requirement. Thus, the objective was to investigate plasma nutrient metabolites and determine the yield and composition of colostrum in sows fed different energy levels and proportions of standardized ileal digestible protein relative to metabolizable energy for two weeks prior to parturition. A total of 28 sows were either fed a high energy level and a fixed protein supply (HE-FP); a high energy level with a daily increase in the proportion of protein (HE-IP); a low energy level and a fixed protein supply (LE-FP) or a low energy level with a daily increase in the proportion of protein (LE-IP) from day 101 in gestation to day 2 in lactation. Sows were fed combinations of: (1) a basic diet, formulated to match recommendations for gestating sows, and (2) a supplement diet, high in protein, to fulfill requirements for colostrum, mammary growth, fetuses, placenta and uterus. Blood was collected on day 105 and 112 of gestation by jugular vein venipuncture four hours after feeding. Colostrum was collected at 0, 12, and 24 h relative to birth of the first piglet. Colostrum yield was estimated based on piglets’ birth weight, weight gain, and the duration the individual piglet had access to the udder. A daily increase in the protein to energy ratio, increased plasma urea and glucose concentrations on day 112 of gestation in sows fed a low energy level (P < 0.05). A positive relationship between glucose and urea in plasma and the dietary protein to energy ratio was observed (P < 0.05). Colostrum fat concentration at 0 h tended to be greater in sows fed LE-IP than in sows fed LE-FP with HE-IP and HE-FP being intermediate (P = 0.06). Moreover, a positive relationship between plasma glucose on day 112 of gestation and colostrum fat at 0 h was observed (P = 0.01), suggesting that an increase in plasma glucose was used by the mammary gland for fat synthesis of the colostrum synthesized pre-partum. No evidence of impact of dietary energy or protein to energy ratio was found for sow colostrum yield (P > 0.10). In conclusion, except for sow BW gain, no direct effects of energy or protein supply on farrowing length, birth interval and litter gain were observed, whereas dietary protein to energy ratio influenced energy and protein metabolism and tended to increase colostrum fat synthesized pre-partum.