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 age1

Abstract

The objective of this study was to determine the effect of ad libitum feeding diets differing in standard ileal digestible (SID) lysine and ME concentrations that bracket those fed to developing gilts in U.S. commercial settings. Average SID lysine and ME concentrations in diets currently fed to developing gilts were obtained from a poll of the U.S. commercial swine industry. Crossbred Large White × Landrace gilts (n = 1,221), housed in groups, were randomly allotted to 6 corn-soybean diets in a 2 × 3 factorial arrangement formulated to provided 2 SID lysine and 3 ME concentrations. Gilts received grower diets formulated to provide 1.02% (control = survey average) or 0.86% (control minus 15%) SID lysine and 2.94, 3.25, or 3.57 (survey average ME ± 10%) Mcal of ME/kg from 100 d of age until approximately 90 kg BW. Then, gilts were fed finisher diet containing 0.85% (control = survey average) or 0.73% (control minus 15%) SID lysine and 2.94, 3.26, or 3.59 (control ± 10%) Mcal of ME/kg until 260 d of age. 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, the stage of estrus cycle, ovulation rate, and uterine length. 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 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. Differences between dietary treatments on age at puberty or measurements of the reproductive tract were not detected. Growth rates to 160 d were not limiting for attainment of puberty in response to daily boar stimulation from 160 d.

Dietary lysine-to-energy ratios for managing growth and pubertal development in replacement gilts

“…It should be noted that overall LGR of gilts in the current study would be considered low growth when compared with typical studies with commercial gilts (Amaral Filha et al, 2009;Bortolozzo et al, 2009). This is reflective of the fact that SID lysine contents in current diets are 15 to 30% less (high and low SID lysine-to-ME ratio diet, respectively) than in typical diets fed to gilts in finishing (Calderón Díaz et al, 2015b). Lents et al (2013) showed that gilts with greater LGR at 21 wk of age reached puberty earlier and that this was independent of backfat, which is consistent with previous research (Patterson et al, 2002).…”

“…The frequency distribution for first estrus in the current study (Figure 1) clearly shows this was not the case. When approximately 1,200 commercial gilts in Iowa were subjected to direct boar contact beginning at 160 d of age, a wide range in age at first estrus (160 to 265 d of age) was observed (Calderón Díaz et al, 2015b) with 3 distinct subpopulations of gilts defined as early responders, midresponders, and late responders (Vallet, 2015). Gilt stimulation programs often involve remixing gilts every 2 wk to stimulate the onset of estrus in these mid and late responders (Levis, 2000;Soede et al, 2006).…”

“…A single boar entered up to 4 pens per day with up to 24 gilts per pen and was rotated daily among pens so that gilts were stimulated by different boars on consecutive days. Each gilt was assigned a daily estrus score (0 to 3) as described previously (Calderón Díaz et al, 2015b;Calderón Díaz et al, 2017). Scores were based on daily vulva changes and gilt behavior in the presence of the boar.…”

Effect of feeding three lysine to energy diets on growth, body composition and age at puberty in replacement gilts

“…The initial study was conducted with six diets fed ad libitum that contained two SID lysine and three metabolizable energy (ME) concentrations that bracketed those currently used by commercial swine herds in the USA. Growth rates, body composition and age at puberty did not differ (Calderón Díaz et al, 2015a, 2015b. Results indicated that gilts compensated for differences in ME between diets by altering feed intake.…”

“…The feeding model used in the present study recognized that intake is highly regulated for energy and nutrient input (NRC Swine, 2012). Energy density is a key modifying dietary intake factor in pigs, however, amino acid dietary content that is less than that recommended by the NRC (NRC, 2012) can also be partially compensated for by increasing intake (Calderón Díaz et al, 2015a, 2015b). The diet model of the present study involved increasing diet total NDF to ultimately result in a maximum dietary intake.…”