Dietary manipulation of gilt growth and development

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.J. 2018. Dietary manipulation of gilt growth and development. University of Alberta-University of Minnesota Reproduction Workshop: Improving Sow Lifetime Productivity. September 15, 2018, St. Paul, MN. PowerPoint.

Interpretive Summary:

Technical Abstract: The goal of the National Pork Board (NPB) research in sow lifetime productivity is to increase the number of quality weaned piglets produced per sow lifetime in the breeding herd by 30% over 7 years. The objective of this 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 to optimize the 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) and SID (standard ileal digestible) lysine were varied by approximately 15% in a 3 x 2 factorial arrangement. There were small but significant differences between diets in backfat and body composition at slaughter as well as age at puberty; however, daily gain or the proportion of gilts failing to reach puberty were unaffected by diet. Most gilts reached puberty at body weight that was well above optimal thresholds. Gilts consumed more feed to maximize genetic potential for body weight gain when ME and lysine were reduced. A larger study (n = 3,024 maternal line crossbred gilts) was conducted with three dietary treatments in a completely randomized block design with litter of origin being the blocking factor. 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. Here we report how diet affected growth rates, body composition, and pubertal development. 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 and considered noncyclic. The majority (88%) of these gilts were in-fact prepubertal at PG600 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.