Nutritional strategies for managing growth and body composition in gilts

Authors: Lents, Clay; SUPRAKORN, C - Iowa State University; Vallet, Jeff; BOYD, R - Hanor Family Of Companies; DEDECKER, A - Smithfield Foods, Inc; STALDER, K - Iowa State University

Submitted to: Proceedings of Allen D Leman Swine Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2018
Publication Date: 10/9/2018
Citation: Lents, C.A., Suprakorn, C., Vallet, J.L., Boyd, R.D., DeDecker, A.E., Stalder, K.I. 2018. Nutritional strategies for managing growth and body composition in gilts. In: Proceedings of 2018 Allen D Leman Swine Conference, September 17, 2019, St. Paul, Minnesota. Proceedings available: https://sites.google.com/a/umn.edu/leman-swine-conference/2018-present.

Interpretive Summary:

Technical Abstract: The objective of this National Pork Board funded research is to determine the optimal feeding program for gilts during development that will best maximize their longevity and productivity. The hypothesis is that energy and protein can be varied under commercial conditions (ad libitum feeding) to optimize a gilt’s development of body weight, tissue composition, age at puberty, and mammary gland function to support increased productivity. In a preliminary study utilizing 1,200 maternal line crossbred gilts, dietary metabolizable energy (ME, 2900, 3270, and 3594 kcal/kg) and standard ileal digestible (SID) lysine (Lys; grower diet, 1.02 and 0.86%; finisher diet, 0.85 and 0.73%) were fed in a 3 x 2 factorial arrangement. There were significant differences between diets in backfat and body composition at slaughter as well as age at puberty but these differences were small. Average daily gain and the proportion of gilts reaching puberty were unaffected by diet. Gilts reached puberty at body weight that was well above optimal thresholds by consuming more feed to maximize genetic potential for body weight gain when ME and Lys in the diet were reduced. Histological analysis indicates that lower ME may delay development of the mammary gland secretory tissue. A larger study (n = 3,024 maternal line crossbred gilts) was conducted with three dietary treatments in a completely randomized block (litter of origin) design. Dietary treatments were defined as high, medium, and low lysine where the content of SID lysine for high, medium, and low diets was 0.90%, 0.79%, and 0.68% (Grower; 100-142 d of age) and 0.68%, 0.60%, and 0.52% (Finisher; 143-200 d of age), respectively. Diets contained standard levels of ME (approximately 3200 kcal/kg). Boar exposure began at 160 d of age and at 200 d of age gilts were moved to sow farms and managed according to standard procedures. Measures of body weight (including caliper and flank to flank) and ultrasound measures of backfat and loin depth were collected at 100, 142, 160 and 200 days of age, as well as at first estrus and first breeding. Gilts fed the medium and low lysine diet had progressively lower body weight gain, backfat thickness, loin depth and fat-free lean when compared to gilts fed the high lysine treatment. Gilts fed the low lysine diet were proportionately fatter (fat:lean ratio) when compared to gilts fed the medium or high lysine diets. Although dietary treatments did not affect the average age of puberty or the total number of gilts that reached puberty, a greater percentage of gilts fed the high lysine diet had a spontaneous pubertal estrus during the first 40 days of boar exposure. Gilts that failed to reach puberty by 220 d of age were injected with PG600. The majority (88%) of these gilts were prepubertal as determined by plasma concentrations of progesterone. Gilts that had a first estrus induced with PG600 were older and heavier than gilts that had a spontaneous first estrus, but they also had less backfat and loin depth, suggesting they were less physiologically mature. Overall, gilts fed the high lysine diet had greater body weight and mass of metabolic tissue than gilts fed the other diets and these differences persisted through first breeding. Gilts had less backfat at first breeding compared with first estrus, which probably reflects management of gilts in breeding barns. Nonetheless, pregnancy and farrowing rates were quite high. These results indicate that growth rate and body composition of gilts can be slowed and altered without negatively affected age at puberty or the total number of pigs that reach a first estrus spontaneously. How this affects productivity and longevity through subsequent parities is subject of ongoing investigation.