20 Nutritional strategies to manage gilt growth and optimize lifetime productivity

Abstract

Abstract Improving gilt development is key to maximizing sow longevity. How to best manage and feed gilts during development is heavily debated. A series of studies were conducted to determine the optimal feeding program for gilts during development. The hypothesis was that metabolizable energy (ME) and standard ileal digestible lysine could be varied under commercial conditions (ad libitum feeding) to optimize body weight gain and composition, age at puberty, and mammary gland development to support increased productivity of gilts. Studies were conducted in commercial production facilities in Iowa and Utah using large numbers of maternal-line gilts that were monitored, under various dietary treatments from 100 to 200 d of age, for growth, body composition, age at puberty and development of reproductive organs and mammary glands. Varying the dietary Lysine:ME ratio (g:mcal) had modest effects on growth and body composition of gilts. Likewise, development of reproductive organs was minimally affected by diet, but slower growth delayed development of terminal lobular ductal units in mammary glands. Growth rates were slowed by reducing dietary lysine:ME ratio below the requirement and increasing fiber. Gilts still had adequate growth (> 600 g/d) and body composition (≥ 15 mm backfat) for good reproductive performance. Although dietary treatments did not affect the average age of puberty (205 d) or the total number of gilts that reached puberty, a greater percentage of gilts fed higher lysine diets exhibited puberty during the first 40 days of boar exposure. Gilts lost 2 to 3 mm backfat once moved from the development unit to the breeding farms, but pregnancy rates were ≥ 95%. Culling of gilts before first breeding did not vary with diet but was considerably higher than expected. Investigation of how these developmental traits affect productivity through subsequent parities is ongoing.