Optimal dietary energy and amino acids for gilt development: Growth, body composition, feed intake, and carcass composition traits

Authors: CALDERON DIAZ, J - Iowa State University; Vallet, Jeff; PRINCE, TERRY - Prince Nutrition Service Llc; PHILLIPS, CHRISTINA - Murphy Brown Llc; DEDECKER, ASHLEY - Murphy Brown Llc; STALDER, KENNETH - Iowa State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2015
Publication Date: 3/31/2015
Publication URL: http://handle.nal.usda.gov/10113/60857
Citation: Calderon Diaz, J.A., Vallet, J.L., Prince, T.J., Phillips, C.E., DeDecker, A.E., Stalder, K.J. 2015. Optimal dietary energy and amino acids for gilt development: Growth, body composition, feed intake, and carcass composition traits. Journal of Animal Science. 93(3):1187-1199.

Interpretive Summary: Female pigs need to remain in the breeding herd and produce at least three litters of piglets in order to cover the costs of their development; many are culled before they reach this threshold. Studies have shown that growth rates and body composition of female pigs before they reach puberty affects both puberty onset and retention in the breeding herd. This study was designed to develop diets that would manipulate growth rates and body composition of young female pigs as a prelude to testing dietary effects on retention of sows in the breeding herd. Six different diets were developed consisting of all combinations of three different metabolizable energy levels (ME; high, control, and low) and two different lysine levels (L; control and low) and were provided to female pigs without restriction from 100 days of age until 260 days of age. Female pigs were weighed and loin eye area and back fat were measured using ultrasound on day 100 of age at the beginning of the dietary treatments; these measures were repeated at 28-day intervals until 260 days of age. Feed intakes were measured at two-week intervals. At 260 days of age, female pigs were slaughtered and hot carcass weights and back fat measures were collected. Results indicated that neither growth rates nor loin eye area measures were affected by the dietary treatments. Back fat was approximately 10% greater in young females receiving diets with high ME levels, but this difference is unlikely to be biologically relevant. The lack of differences in growth were likely due to the fact that the females altered their feed intake according to ME levels in the diet such that their daily ME intake did not differ among diets over the course of the experiment. The lack of effect of L levels on growth suggest that the amount of L included in the diets exceeded requirements of the growing females, even for the low L diet. Thus, differences in ME levels in diets fed to growing female pigs do not alter growth rates or body composition due to compensatory adjustments in feed intake, and further experiments are needed to determine whether lower lysine levels in the diet will alter growth or body composition of growing female pigs.

Technical Abstract: The objective of this study was to manipulate the lean to fat ratio by feeding diets differing in lysine and metabolizable energy (ME) content to replacement gilts from 100 d to 260 d of age. A secondary objective was to evaluate lysine and caloric efficiency between dietary treatments fed to developing gilts from 100 d to 260 d of age. One-thousand-two-hundred-and-twenty-one crossbred Large White × Landrace gilts housed in groups of 17 to 18 were randomly allotted to 6 corn-soybean diets in a 2 × 3 factorial arrangement formulated to provided 2 standardized ileal digestible (SID) lysine levels [100% (high, HL) and 85%, (low, LL); the latter designed to reduce protein deposition] and 3 ME levels [90% (low, LME), 100% (medium, MME), 110% (high, HME)] at 100 d of age. The 100% lysine and 100% ME were based on an informal survey from the U.S. commercial swine industry to obtain average levels that are currently fed to developing gilts. Gilts were weighed and backfat thickness, and loin area were recorded at the beginning of the trial and then every 28 days. Feed intake (FI) was recorded as feed disappearance within the pen at 2-wk intervals. Biweekly and daily lysine (grams) and ME (Mcal) consumed on a pen basis were calculated based on diet formulations. Additionally, average daily gain, feed, lysine and ME intake per kg of body weight (BW) gain were also calculated on a pen basis. At approximately 260 d of age, gilts were slaughtered and warm carcass weight and fat thickness were recorded. From these, fat free lean meat content was calculated. Data were evaluated for normality and analyzed using mixed model equation methods. Pen was considered the experimental unit (12 pens per diet; 72 pens on trial). Models included lysine and ME content, data recording day, and their interactions as fixed effects. Pen within lysine × ME level within barn was included as a random effect. BW at 100 days of age was used as a linear covariate in the model. The interaction between lysine level and ME levels was not a significant source of variation for growth and body composition traits (P > 0.05). There were no differences between lysine levels or ME levels for growth and body composition, except for back fat, which was slightly greater for gilts fed a HME diet, although the difference (2 mm) is likely to be biologically irrelevant. Feed intake differed according to the ME in the diet. Gilts fed HME diets had a lower FI but a greater ME intake compared with gilts fed LME (P < 0.05). Additionally, gilts fed the HME diet had lower FI and lysine intake per kg of BW when compared to gilts fed LME or MME diets (P < 0.05). However, there was no difference in the Mcal consumed per kg of BW gain among treatments (P > 0.05). Gilts fed LL diets had lower lysine intakes compared with gilts fed HL diets (P < 0.05). Carcasses from gilts fed the HME diet were 3.3 kg and 2.5 kg heavier than those from gilts fed the LME or MME diets (P < 0.05). Despite significant differences in the lysine:ME ratio in the diets, no changes in growth or body composition traits occurred, likely due to compensatory changes in feed intake in response to dietary ME content. Caloric efficiency (Mcal to deposit 1 kg of BW) was similar among treatments. Carcass weight differences at slaughter were likely related to organ size and organ weight, which could have been affected by FI. Further research is necessary to identify the optimal lysine-to-energy ratio to manipulate growth and body composition in replacement gilts fed ad libitum.