Abstract
The objective was to estimate essential AA (EAA) utilization efficiency for milk production in sows (n = 24) fed control (19.6% CP) or reduced CP (RCP; 14.2% CP) diets under thermoneutral (TN; 21±1.5°C) or cycling heat stress (HS; 32±1.5°C daytime and 24±1.5°C nighttime) conditions. We hypothesized that RCP fed lactating sows with supplemental AA have increased EAA efficiency for milk production under TN and HS conditions. Diets contained 0.90% SID Lys and 2,580 kcal/kg. Sow BW and backfat were recorded on d 1 and 21 to estimate body protein mobilization (BPM). Piglet BW was recorded on d 1 and 21 to estimate milk yield. Amino acid efficiencies were calculated based on milk AA output relative to SID AA intake corrected for AA contribution from BPM. During HS, N, Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Trp, and Val efficiency for milk production did not differ between sows fed control (42, 26, 44, 36, 39, 49, 52, 32, 50, 43 and 44%, respectively) and RCP (56, 39, 51, 49, 56, 47, 42, 39, 50, 59 and 41%, respectively) diets. Compared to control sows, RCP sows had greater (P < 0.05) efficiency of Arg (30% vs. 61%) under TN condition. Efficiencies of His, Ile, Leu, Phe, and Trp tended to be greater (P = 0.07, 0.06, 0.06, 0.07 and 0.06, respectively) in RCP compared to control sows (50, 41, 44, 36, and 50% vs. 74, 67, 75, 54 and 78%, respectively). Efficiencies of Lys, Met, Thr, Trp and Val did not differ between control and RCP sows (56, 59, 57, and 50% vs. 67, 59, 69 and 57%, respectively). In summary, an RCP diet improved efficiency of N, Arg, His, Ile, Leu, Phe, and Trp for milk production in lactating sows under TN but not HS conditions.
A cathepsin F-like peptidase involved in barley grain protein mobilization, HvPap-1, is modulated by its own propeptide and by cystatins
