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Dietary lysine-to-energy ratios for managing growth and pubertal development in replacement gilts

Lents C.A., C. Supakorn, A.E. DeDecker, C.E. Phillips, R.D. Boyd, J.L. Vallet, G.A. Rohrer, G.R. Foxcroft, W.L. Flowers, N.L. Trottier, J.L. Salak-Johnson, F.F. Bartol, K.J. Stalder
Applied animal science 2020 v.36 no.5 pp. 701-714
animal development, animal growth, backfat, boars, body composition, body weight, digestible protein, estrus, estrus detection, feed supplements, feeds, gilts, grower diets, herd replacement rate, ileum, lysine, protein energy ratio, puberty, sows, swine feeding, swine finishing
Our objectives were to determine growth rates, body composition, and pubertal development in replacement gilts fed diets with different ratios of standardized ileal digestible (SID) lysine to ME.Diets with low, medium, and high ratios of SID lysine to ME (grower: 2.3, 2.6, and 2.8; finisher; 1.7, 1.9, and 2.1 g/Mcal) were fed from 100 to 200 d of age, after which gilts were moved from the gilt development unit to sow farms. Boar exposure and estrus detection began at 160 d of age and continued until first detected estrus. Estimates of BW and body composition were determined at 100, 142, 160, and 200 d of age and at puberty.Body weights and growth rates were reduced (P < 0.05) as dietary SID lysine–to–ME ratio decreased. Greater SID lysine–to–ME ratios increased the number of gilts that exhibited estrus upon boar exposure, increased the number of gilts with a spontaneous first estrus, reduced the number of gilts requiring P.G.600 (Merck Animal Health, Kenilworth, NJ), and decreased age at first estrus (P < 0.05). Slower growing gilts that weighed less with less backfat were more likely to require P.G.600 to induce puberty (P < 0.05).Reducing SID lysine–to–ME ratios in gilt diets can increase the number of gilts within optimal BW range at first estrus, but overall pubertal development is delayed if ratios are reduced below 2.8 and 2.1g of SID lysine to megacalorie of ME in grower and finisher diets, respectively.