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The determination of amount of feed grade lysine usage in lactating sows
Two studies were conducted to evaluate optimal levels of feed grade lysine usage in lactating sows. Data were analyzed with Proc Mixed and reported as LSMEANS. In Exp. 1, 290 PIC 1050 sows were blocked by parity and allotted to one of four experimental diets containing 20% dried distillers grain with solubles (DDGs) and different levels of L-Lys HCl (0.30, 0.40, 0.50, and 0.60%, respectively) replacing intact lysine from soybean meal. L-Thr and Met (Alimet™) were included in the diets as necessary. All diets contained 1.12 % SID lysine and 3.45 Mcal ME/kg. Each treatment was represented in a 4×2 factorial where sows were fed once or twice a day. Parity 1, 2, and 3+ sows were allowed a maximum ADFI of 5.2, 5.5, and 5.7 kg / d, respectively. Data were analyzed with lysine level, feeding time and parity as main effects along with two-factor interactions. There were no significant interactions. Percent sow weight loss did not differ between the two feeding treatments (-4.08 vs -4.72, respectively, P=0.71). Piglet litter gain (2.35, 2.50, 2.50, 2.41 kg, P=0.27) and sow weight loss (-2.82, -4.76, -3.07, -6.69 kg, P=0.31) were not affected by L-Lys.HCL level. However, sow backfat loss increased linearly as percent of L-Lys.HCL increased (-3.88, -4.55, -4.54, -5.68 mm, P<0.10). In Exp 1, the higher L-Lys.HCL diets had SID Trp:Lys levels below 16. A second study (Exp. 2) was conducted to evaluate increased levels of L-Lys.HCL when SID Trp:Lys was above 17. L-Lys.HCL was added in replacement of soybean meal at levels of 0.30, 0.45, and 0.60%. All 257 sows were allowed a maximum intake of 5.9 kg/d and water ad-libitum. Diets were formulated at 1.05% SID lysine. The study was designed as a randomized complete block design with the block being parity (P1, P2, and P3+). Data were analyzed as main effects and respective interactions of lysine level and parity with linear contrast and treatment comparisons. As L-Lys.HCL increased, piglet ADG did not change (0.230, 0.230, 0.230 kg, P=0.49), nor did sow weight loss (-2.35, -3.52, -2.74%, P=0.70) or wean to estrus interval (4.64, 5.43, 5.00 d, P=0.47). In conclusion, feeding 0.06% synthetic Lys does not appear to influence sow lactation criteria when the SID Trp:Lys level is above the minimum requirement.
Keywords: sow, lactation, lysine