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

Authors: Lents, Clay; SUPAKORN, C - Iowa State University; DEDECKER, A - Smithfield Foods, Inc; PHILLIPS, C - Smithfield Foods, Inc; BOYD, R - North Carolina State University; Vallet, Jeff; Rohrer, Gary; FOXCROFT, G - University Of Alberta; FLOWERS, W - North Carolina State University; TROTTIER, N - Michigan State University; SALAK-JOHNSON, J - Oklahoma State University; BARTOL, F - Auburn University; STALDER, K - Iowa State University

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2020
Publication Date: 10/20/2020
Publication URL: https://handle.nal.usda.gov/10113/7151574
Citation: Lents, C.A., Supakorn, C., Dedecker, A.E., Phillips, C.E., Boyd, R.D., Vallet, J.L., Rohrer, G.A., Foxcroft, G.R., Flowers, W.L., Trottier, N.L., Salak-Johnson, J.L., Bartol, F.F., Stalder, K.J. 2020. Dietary lysine-to-energy ratios for managing growth and pubertal development in replacement gilts. Applied Animal Science. 36(5):701-714. https://doi.org/10.15232/aas.2020-02016.
DOI: https://doi.org/10.15232/aas.2020-02016

Interpretive Summary: In order to improve lifetime productivity of sows, managing replacement females, called gilts, to achieve optimum body composition as they enter the breeding herd is a priority for producers, but appropriate strategies to achieve this goal are heavily debated in the U.S. swine industry. The Sow Lifetime Productivity Research Consortium of the National Pork Board concluded that additional research was needed to characterize relationships among prebreeding growth rates and body composition of gilts with sow lifetime productivity. Scientists conducted a study within a large commercial production system with the objective to evaluate growth and pubertal attainment in replacement gilts fed diets with varying ratios of lysine to energy during development. Low, medium, and high lysine to energy ratios were used and differences in body composition and age at puberty were measured. Scientists found that body weights, growth rates, and amount of total back fat and muscle were increased when gilts were fed greater dietary lysine to energy ratios. Reducing the lysine to energy ratio in the diet increased the number of gilts within optimal bodyweight range at puberty, however gilts fed lower lysine to energy ratios reached puberty later with less total back fat, which may have negative consequences for sow productivity. These research results fill a critical need for commercial stakeholders by providing vital information about levels of dietary lysine and energy needed in gilt development diets. The next step will be to evaluate how these developmental responses impact gilt longevity and productivity from first through third parity.

Technical Abstract: Objective: Our objective was to determine growth rates, body composition, and pubertal development of replacement gilts fed diets with different ratios of standardized ileal digestible (SID) lysine to ME. Materials and Methods: Diets with low, medium, and high ratios of SID lysine to ME (grower: 2.3, 2.6, and 2.8; and, 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. Results and Discussion: 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). Implications and Applications: 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 2.1 g of SID lysine to megacalorie of ME in grower and finisher diets, respectively.