Impact of feeding reduced crude protein diets to lactating sows on nitrogen utilization1

Abstract

Forty lactating multiparous Yorkshire sows were used to test the hypothesis that reducing dietary CP and supplementing with crystalline amino acids (CAA) increases dietary N utilization for milk production during early and peak lactation. Sows were assigned to 1 of 4 diets: 1) 16.0% CP (as-fed; analyzed contents; HCP); 2) 15.7% CP (MHCP); 3) 14.3% CP (MLCP); 4) 13.2% CP (LCP); diet HCP was formulated using soybean meal and corn as the only Lys sources. The reduced CP diets contained CAA to meet requirements of the limiting AA. Sow and piglet BW were measured on d 1, 3, 7, 14, 18, and 21 of lactation. Nitrogen retention was measured on sows between d 3 and 7 (early) and d 14 and 18 (peak) of lactation. Milk true protein output was calculated from estimated milk yield and analyzed true protein concentration. Sow BW change (overall mean: -4.2 ± 3.37 kg over the 21-d lactation period) and average daily DM intake (overall mean: 4.05 ± 0.18 and 6.12 ± 0.20 kg/d, early and peak lactation, respectively) did not differ between diets. Nitrogen intake decreased as dietary CP concentration decreased (114.3, 106.0, 107.4, and 99.0 ± 5.29 g/d and 169.5, 168.3, 161.2, and 145.1 ± 5.29 g/d for HCP, MHCP, MLCP, and LCP in early and peak lactation, respectively; L: < 0.05). Sow loin eye area loss tended to increase as dietary CP concentration decreased (Linear (): = 0.082). Litter growth rate (LGR) over the 21-d lactation period tended to increase with decreasing dietary CP concentration (L: = 0.084). In early lactation, N retention (N intake- fecal and urinary N) and milk true protein and casein output were not affected by dietary treatment. In early lactation, as dietary CP decreased, N retained as percentage of N intake tended to increase (L: = 0.093) and estimated efficiency of using retained N for milk N output was not influenced by dietary CP concentration. In peak lactation, N retention (122.5, 123.8, 121.2, and 109.0 ± 4.88 g/d for HCP, MHCP, MLCP, and LCP, respectively) decreased (L: < 0.05), N retained as percentage of N absorbed (N intake - fecal N) increased (L: < 0.05), milk casein yield increased ( = 0.051), and estimated efficiency of using retained N for milk N output (44.5, 51.0, 54.9, and 62.9 ± 5.9% for HCP, MHCP, MLCP, and LCP, respectively) increased (L: < 0.05). Feeding lactating diets reduced in CP from 16.0% to 14.3% with CAA inclusion as partial replacement for limiting AA improved N retention and N utilization efficiency for milk protein production in peak lactation, while these effects were less pronounced in early lactation.

Reduced protein diet with near ideal amino acid profile improves energy efficiency and mitigate heat production associated with lactation in sows

“…It was reported that [18] the loss of BW in lactating sows fed diets containing CP from 146 to 186 g/kg was due to BL mobilization. On the other hand, Huber et al [6] reported that sows fed a similar low CP diet as this study lost BW over a 21-day lactation period, and indicated based on loin eye area measurements that the BW loss resulted from greater body protein as opposed to BL mobilization. The greater BP loss in that study may have been associated with feeding diets marginally deficient in Lys [6].…”

“…On the other hand, Huber et al [6] reported that sows fed a similar low CP diet as this study lost BW over a 21-day lactation period, and indicated based on loin eye area measurements that the BW loss resulted from greater body protein as opposed to BL mobilization. The greater BP loss in that study may have been associated with feeding diets marginally deficient in Lys [6]. In contrast, sows fed CON and OPTLEU lost a minimal amount of BW and were in a positive maternal N balance [8].…”

“…Total energy retained was similar across diets, but sows fed OPT retained less maternal energy, suggesting that OPT diet resulted in more energy partitioning for milk production. Huber et al [6] indicated that reduced protein diets favored partitioning of AA towards milk protein yield rather than maternal protein pool. This observation may be in part related to a reduced dietary Leu intake, because Leu stimulates maternal body protein gain [23,24].…”

“…The NIAA diet was designed by reducing soybean meal relative to corn to meet the minimum SID Leu requirement, which corresponded to a CP concentration of 137.5 g/kg. Then, supplemental crystalline source of Lhistidine (His), L-isoleucine (Ile), L-Lys, DL-Met, Lphenylalanine (Phe), L-threonine (Thr), L-tryptophan (Trp) and L-Val and were added to meet the minimum Based on nutrient concentrations in feed ingredients according to NRC [13] 5 SID: standardized ileal digestible 6 Methionine concentration in Optimal and Optimal + Leucine is higher than Control because methionine was added to meet requirement of (methionine + cysteine) 7 Additional calcium (1.0 g/kg) and phosphorus (1.5 g/kg) releases were accounted due to phytase from the premix 8 STTD: standard total tract digestible SID requirement for those AA in the NIAA diet. Crystalline DL-methionine was added to meet the requirement of Met + cysteine (Cys).…”

“…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 also appears to increase nutrient partitioning towards mammary metabolism [6,8]. However, the impact of feeding such diet on energy partitioning and efficiency still need further investigation.…”