Effect of Extended Photoperiod on Age at Puberty and Growth in Hassan Sheep

Abstract

Nutrition and reproductive efficiency are closely linked in small ruminant farming, with inadequate nutrition negatively impacting female reproduction. Factors like photoperiod, growth rate, and nutrition influence age at puberty in ewe lambs, a key indicator of reproductive efficiency, making it essential to optimize these factors for improved productivity. The present study evaluated the effect of extended photoperiod on age at puberty and growth performance of Hassan ewe lambs under intensive rearing. Twelve healthy ewe lambs aged 5–6 months and two rams were randomly allotted into two groups. Group I (G-I) was maintained under normal photoperiod, while Group II (G-II) received an extended photoperiod with four additional hours of light (100 lux) daily from 6:00–10:00 pm over a five-month period. Age at puberty was determined by recording the first oestrus, and growth was assessed through fortnightly body weights and average daily gain (ADG). Results revealed that extended photoperiod significantly delayed puberty, with G-I lambs attaining puberty at 273.2 ± 6.50 days compared to 293.3 ± 5.70 days in G-II (p<0.05), indicating a delay of approximately 20 days. Growth performance showed no significant overall differences between groups. Mean ADG was 86.20 ± 1.65 g/day in G-I and 83.01 ± 3.16 g/day in G-II, reflecting broadly comparable long-term growth rates. However, fortnightly analyses highlighted significant variations, with G-I lambs maintaining higher ADG during the later stages of the trial. These findings demonstrate that extended photoperiod delays reproductive maturity without exerting a measurable influence on cumulative growth in Hassan ewe lambs.