Optimal dietary energy and protein for the development of gilts - NPB #12-209

Authors: Vallet, Jeff; CALDERON, JULIA - Iowa State University; STALDER, KENNETH - Iowa State University; PHILLIPS, CHRISTINA - Murphy Brown Llc; BRADLEY, GARY - Murphy Brown Llc; Miles, Jeremy; Rempel, Lea; Lents, Clay; Freking, Bradley - Brad; Rohrer, Gary; Nonneman, Danny - Dan; Cushman, Robert - Bob

Submitted to: National Pork Board Web Site <www.porkboard.org>
Publication Type: Research Technical Update
Publication Acceptance Date: 7/22/2014
Publication Date: 9/30/2014
Citation: Vallet, J., Calderon, J., Stalder, K., Phillips, C., Bradley, G., Miles, J., Rempel, L., Lents, C., Freking, B., Rohrer, G., Nonneman, D., Cushman, R. 2014. Optimal dietary energy and protein for the development of gilts - NPB #12-209. National Pork Board. Available: http://research.pork.org/FileLibrary/ResearchDocuments/12-209-Vallet-USDA.pdf.

Interpretive Summary: Sow longevity is a key component for efficient and profitable pig farming and efforts to improve it should start with the adequate management of replacement females. A key factor in the management of young females is to provide them with adequate feeding that supplies the right amount of amino acids and energy for their maintenance and growth to allow them to reach puberty at an early age and build up fat reserves to help support milk production to feed their first litter of piglets. Therefore, six different diets, consisting of 2 levels (85% and 100%) of dietary protein and 3 levels (85%, 100%, and 115%) of dietary energy were used in this study to try to manipulate the lean-to-fat ratio in replacement females by creating a protein and/or energy imbalance in the diet. The 100% protein, 100% energy diet was based on an informal survey of the swine industry to obtain average levels that are currently fed to young females. Female pigs had free access to diets from 100 days of age until approximately 260 days of age, when they were slaughtered. Data on litter of origin of the females, growth, body composition, feed intake, feed efficiency, age at puberty, measurements of the reproductive tract at the time of slaughter, and carcass composition were collected for this study. We found no difference in growth and minor differences in body composition traits among the six diets. However, females fed a low energy diet consumed almost 15 kg more feed than gilts fed a high energy diet, indicating that gilts adjusted their feed intake according to the energy in the diet. Thus, regardless of the diet, gilts used the same amount of dietary energy to deposit 1 kg of body weight. Also, even in the low protein diets, protein consumption was higher than the recommended lysine intake for young females. Therefore, despite considerable differences in the ratios of energy and protein in the diets, they had very little effect on measures of growth or body composition. We also did not observe a difference in the age at puberty or in the measurements taken of the reproductive tract between diets. Ovulation rate, uterus length, and ovary length and width were a function of age, stage of the estrous cycle, and the number estrous cycles rather than feed provided or body condition. Carcasses from females fed a high energy diet were almost 3 kg heavier than carcasses from females fed a low energy diet, most likely due to a larger organ size and heavier organ weight for females fed the low energy diets. More research is necessary in order to find an ‘ideal’ development diet that would create a protein and/or energy imbalance and decrease lean deposition and increase fat reserves in replacement females with free access to feed.

Technical Abstract: The main objective of this study was to determine three diets for use in a National Pork Board primary trial of dietary effects on gilt development and retention of sows in the breeding herd to fourth parity. A second objective was to examine the influence of litter of origin traits on gilt development. At birth, gilts were weighed, a blood sample was collected for immunocrit measurement, and litter details (born alive, stillborn, mummies) were recorded. Gilt weights were also recorded at weaning. One-thousand-two-hundred-and-twenty-one crossbred Large White × Landrace gilts housed in groups of 17 to 18 were randomly allotted 6 corn-soybean diets formulated using a 2 × 3 factorial arrangement that provided 2 levels of standardized ileal digestible (SID) lysine [100% (high, HL) and 85% (low, LL); the latter designed to restrict protein deposition] and 3 levels of metabolizable energy [ME; 85% (low, LME), 100% (medium, MME), 115% (high, HME)] at 100 d of age. Gilts were weighed and back fat thickness and loin area muscle were recorded every 28 d beginning when diets were applied. Fat free lean meat content was also calculated for every 28-d period. Feed intake was recorded as feed disappearance within the pen at 2-week intervals. Grams of lysine and Mcal consumed for every 2-week period and grams of lysine and Mcal consumed daily were calculated based on diet formulation on a pen basis. Average daily gain, feed, lysine, and ME intake per kg of BW gain were also calculated. Starting at 160 d of age, gilts were exposed daily to vasectomized boars and observed for behavioral estrous. At approximately 260 d of age, gilts were slaughtered and their reproductive tract was collected. Whether the gilt was cycling, stage of cycle, ovulation rate, uterine length, and ovary length and width were recorded. Warm and chilled carcass weight and carcass fat thickness were also recorded. Fat free lean meat content and dressing percentage were calculated. Data were tested for normality and analyzed using mixed model equation methods. There were no differences between lysine levels or ME levels main effect growth and body composition differences. Additionally, the interaction between lysine level and ME levels was not a significant source of variation for the growth and body composition traits (P > 0.05) except for back fat thickness, which was slightly higher for gilts fed a HME diet although this result is biologically questionable. Gilts fed the LL diet had a lower lysine intake compared with gilts fed the HL diet (P < 0.05). Gilts fed HME diets had a lower feed intake but a higher ME intake compared with gilts fed LME or MME diets (P < 0.05). Additionally, gilts fed the HME had lower feed and lysine intake per kg of BW compared with gilts fed LME or MME diets (P < 0.05). However, there was no difference in the Mcal consumed per kg of BW among treatments (P > 0.05). There was no difference in age at puberty or any of the reproductive tract measurements (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), respectively. Additionally, carcasses from gilts fed the HME diet had a higher dressing percentage than carcasses from gilts fed the LME or MME diets (P < 0.05). Despite significant differences in the ratio of lysine and energy in the diets, no changes in growth or reproductive traits occurred, likely due to compensatory feed intake in response to the energy content of the diet. Caloric efficiency (Mcal to deposit 1 kg of BW) was similar among treatments. The higher carcass weight and dressing percentage of gilts fed the HME diets is likely related to their lower feed intake and possible reduced organ weight compared with gilts fed LME or MME diets. Further research is required to identify the optimal lysine-to-energy ratio to manipulate growth and body composi