|CALDERON DIAZ, J - Iowa State University|
|Nonneman, Danny - Dan|
|Cushman, Robert - Bob|
|Freking, Bradley - Brad|
|PHILLIPS, C - Murphy Brown Llc|
|DEDECKER, A - Murphy Brown Llc|
|FOXCROFT, G - University Of Alberta|
|STALDER, KENNETH - Iowa State University|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2015
Publication Date: 7/1/2015
Publication URL: https://handle.nal.usda.gov/10113/61145
Citation: Calderón Díaz, J.A., Vallet, J.L., Lents, C.A., Nonneman, D.J., Miles, J.R., Wright, E.C., Rempel, L.A., Cushman, R.A., Freking, B.A., Rohrer, G.A., Phillips, C., Dedecker, A., Foxcroft, G., Stalder, K.J. 2015. Age at puberty, ovulation rate, and uterine length of developing gilts fed two lysine and three metabolizable energy concentrations from 100 to 260 d of age. Journal of Animal Science. 93(7):3521-3527.
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 and determine their effects on age at puberty and reproductive tract development 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. Growth and body composition measures were made throughout this period. Female pigs were observed daily for receptivity to male pigs beginning at 160 days of age; pigs were slaughtered at 260 days of age and the reproductive tract was collected. Tracts were examined to confirm whether pigs had experienced reproductive cycles. Ovary dimensions and uterine lengths were measured for each pig. Finally, the numbers of eggs shed by each pig were counted. Growth, lean and fat deposition are described in a companion paper and few effects of the diets were found on these traits. Age at puberty, number of eggs shed, and ovarian and uterine measurements were unaffected by diets. However, puberty failure, confirmed at slaughter, occurred at low incidence but was increased in diets containing low protein levels despite having no effect on growth, lean and fat deposition. In summary, within the ranges tested, dietary energy or protein levels did not affect age at puberty or reproductive tract dimensions. Dietary energy levels did not affect the incidence of puberty failure and reduced dietary protein increased the rate of puberty failure.
Technical Abstract: The objectives of this study were to determine the effect of feeding different lysine and metabolizable energy (ME) levels to developing gilts on age at puberty and reproductive tract measurements, and to determine relationships between these traits and growth trajectories. Crossbred Large White × Landrace gilts (n = 1,221) housed in groups of 17 to 18 were randomly allotted to pens. Pens randomly assigned to 6 corn-soybean based diets formulated using a 2 × 3 factorial arrangement that provided 2 standardized ileal digestible (SID) lysine levels (100% [high, HL] and 85%, [low, LL]; the latter designed to restrict 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 of 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 muscle area were recorded at the beginning of the trial and then every 28 d. Starting at 160 d of age, gilts were exposed daily to vasectomized boars and observed for behavioral estrus. At approximately 260 d of age, gilts were slaughtered and their reproductive tract was collected. Each reproductive tract was examined to determine whether the gilt was cyclic, stage of estrous cycle, ovulation rate, uterine length and ovary length and width. Data were evaluated for normality and analyzed using mixed model methods. Average age at puberty was 193 d of age with a range from 160 d to 265 d. When all gilts on trial at 160 d of age were included in the analysis, 91.0% reached puberty as determine by observation of standing estrus; however, when gilts removed from trial before 220 d of age were excluded from the analysis, the percentage increased to 94.2%. There were no effects of the dietary treatments on age at puberty or any of the reproductive tract measurements. Gilts that reached puberty were 3 kg heavier (P < 0.01) at age of puberty than gilts that did not show puberty at the same age, but grew in parallel with those that failed to reach puberty. Ovulation rate and ovary length and width increased with every increase in 1 kg at 160 d of age. Despite significant differences in the lysine:energy ratio in the diets, the expected differences in reproductive traits were not observed. Other factors such as BW, backfat thickness and days of estrous cycle had a greater effect on the traits recorded than feed provided.