DIETARY ENERGY DENSITY REGULATES GROWTH PERFORMANCE, LEPTIN CONCENTRATION, AND PUBERTY ATTAINMENT IN AWASSI EWE LAMBS
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Awassi ewe lambs, dietary energy density, leptin, behavioral estrus, luteal activity, right-censoring
Abstract
This study evaluated the effects of graded dietary energy density on growth performance, serum leptin concentration, and puberty attainment in Awassi ewe lambs. After a 30-day acclimation period, 27 Awassi ewe lambs aged approximately 195 ± 5 days were randomly allocated to three dietary treatments providing 9.5, 10.5, or 11.5 MJ metabolizable energy/kg dry matter (n = 9/group). The 120-day experiment comprised 30 days of acclimation, 60 days of controlled individual feeding, 15 days of exposure to two rams, and 15 days of post-exposure reproductive monitoring. Puberty was assessed from standing estrus or external estrus signs, followed 10 days later by serum progesterone measurement; concentrations ≥1.0 ng/mL supported luteal activity consistent with ovulation. Average daily gain was 69.7 ± 2.4, 112.5 ± 1.7, and 146.4 ± 1.4 g/day in the low-, medium-, and high-energy groups, respectively (P < 0.001). Dietary energy, time, and their interaction affected serum leptin (P < 0.001), with Day-75 concentrations of 0.79 ± 0.02, 1.58 ± 0.02, and 1.93 ± 0.02 ng/mL. Puberty attainment was 22.2%, 44.4%, and 66.7%, and time-to-event distributions differed among groups (log-rank χ² = 6.42, df = 2, P = 0.041). Higher dietary energy improved growth, leptin response, and earlier puberty attainment.
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References
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