Effect of supplemental light on growth, prolactin, progesterone and luteinizing hormone in water buffalo (Bubalus bubalis).

Fifty non-pregnant Surti buffalo heifers aged between 17 and 42 months (n = 24, less than 24 months; n = 26, greater than 24 months) were randomly assigned to groups subject to either natural daylight +4 h supplemental light (n = 25) or natural day light (n = 25), to study changes in growth, serum prolactin (Prl), progesterone (P4) and luteinizing hormone (LH) to supplemental lighting. Ambient temperatures (T) and relative humidity (RH) generally were greater than 27 degrees C and less than 70% during the daytime, respectively. Light-supplemented heifers had 16.2 kg net body weight (BW) gain at 9 weeks compared to 20.8 kg for controls, but higher mean Prl after 6.5 weeks (P less than 0.01), and higher P4 (0.41 vs 0.19 ng/ml; P less than 0.06) than control heifers. Older heifers had 39.7% greater BW (P less than 0.01), but a net 4.3% BW gain compared to a 10.1% gain for younger heifers at 10 weeks. Older, light-supplemented heifers had higher mean P4 (0.63 vs 0.19 ng/ml; P less than 0.07) than the other groups. These weight and hormonal changes suggest that 4 h supplemental light can alter growth and endocrine function in buffaloes under similar planes of nutrition. While light supplementation did not have a positive effect on body weight during the 10 week study, body weight and endocrine changes due to supplemental light may be important factors for initiation of reproductive cyclicity.