Abstract
BackgroundThe study objective was to test the hypothesis that 1) lowering dietary crude protein (CP) increases dietary energetic efficiency and reduces metabolic heat associated with lactation, and 2) excessive dietary leucine (Leu) supplementation in a low CP diet decreases dietary energetic efficiency and increases metabolic heat associated with lactation.MethodsFifty-four lactating multiparous Yorkshire sows were allotted to 1 of 3 isocaloric diets (10.80 MJ/kg net energy): 1) control (CON; 18.75% CP), 2) reduced CP with a near ideal or optimal AA profile (OPT; 13.75% CP) and 3) diet OPT with excessive Leu (OPTLEU; 14.25% CP). Sow body weight and backfat were recorded on day 1 and 21 of lactation and piglets were weighed on day 1, 4, 8, 14, 18, and 21 of lactation. Energy balance was measured on sows during early (day 4 to 8) and peak (day 14 to18) lactation, and milk was sampled on day 8 and 18.ResultsOver 21-day lactation, sows fed OPT lost body weight and body lipid (P < 0.05). In peak lactation, sows fed OPT had higher milk energy output (P < 0.05) than CON. Sows fed OPTLEU tended (P = 0.07) to have less milk energy output than OPT and did not differ from CON. Maternal energy retention was lower (P < 0.05) in OPT and OPTLEU compared to CON sows, and did not differ between OPTLEU and OPT sows. Sows fed OPT had higher (P < 0.05) apparent energy efficiency for milk production compared to CON. Heat production associated with lactation was lower (P < 0.05) or tended to be lower (P = 0.082), respectively, in OPT and OPTLEU compared to CON sows.ConclusionThe OPT diet, in peak lactation, improved dietary energy utilization for lactation due to less urinary energy and metabolic heat loss, and triggered dietary energy deposition into milk at the expense of maternal lipid mobilization. Leucine supplementation above requirement may reduce dietary energy utilization for lactation by decreasing the energy partitioning towards milk, partially explaining the effectiveness of OPT diet over CON diets.
Highlights
The study objective was to test the hypothesis that 1) lowering dietary crude protein (CP) increases dietary energetic efficiency and reduces metabolic heat associated with lactation, and 2) excessive dietary leucine (Leu) supplementation in a low CP diet decreases dietary energetic efficiency and increases metabolic heat associated with lactation
In a previous study conducted on lactating sows [8], we reported that reducing dietary protein to meet the minimum Standardized ileal digestibility (SID) Leu requirement increased utilization efficiency of N, arginine (Arg), His, Ile, Leu, Phe + tyrosine (Tyr) and Trp for milk yield while maintaining overall lactation performance
In the current work we aimed at determining dietary energetic efficiency, partitioning, and heat production associated with lactation in sows fed a reduced protein diet with a near ideal amino acid (NIAA) profile (OPT) and OPT diet with supplemental Leu (OPTLEU)
Summary
The study objective was to test the hypothesis that 1) lowering dietary crude protein (CP) increases dietary energetic efficiency and reduces metabolic heat associated with lactation, and 2) excessive dietary leucine (Leu) supplementation in a low CP diet decreases dietary energetic efficiency and increases metabolic heat associated with lactation. Lactation is an energetically costly process that depends on the sow’s ability to consume enough energy to sustain milk production. Lowering dietary crude protein (CP) in growingfinishing pigs improves energetic efficiency (i.e., retained tissue net energy:gross energy intake) due to reduced heat and urinary energy loss [4, 5]. Feeding diets with reduced CP concentrations and improved amino acid (AA) balance to lactating sows increases the efficiency of nitrogen (N) and indispensable amino acid (IDAA) utilization [6,7,8], and appears to increase nutrient partitioning towards. Near ideal amino acid (NIAA) profile may reduce heat production due to changes in metabolic demand resulting from less AA destined to oxidation
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