The study was executed to determine the effect of different dietary energy levels on attainment of age of puberty in Nili-Ravi buffalo heifers. The age and weight at puberty were determined through periodical (fortnightly) observations. Ovarian activity was monitored through rectal palpation and serum progesterone concentration. Eight Nili-Ravi buffalo heifers of 20 month age were divided into two groups viz, group A and group B (n=4). Two experimental rations providing dietary energy levels of 2 and 1 M.cal as per NRC (2001) were used and designated as ration No.1 and ration No.2.

In experimental heifers of groups A and B fed rations 1 and 2 having 2 and 1% M.E., only one heifer from group A and one heifer from group B reached puberty and exhibited estrus signs at an average age of 1274±20.63 and 1608±29.22 days, respectively. There was a significant (P <0.01) difference between the ages of two groups. The mean weight in groups A and B heifers at puberty was 318.9±34.07 and 289.2±40.43 kg, respectively. The average weight gain was 122.5±6.53 and 115.5±8.21 kg and average daily weight gain was 189±59.77 and 178 ±55.88 grams in the heifers of groups A and B, respectively; There was a significant difference (P < 0.01) between the weight gain of two groups (A and B). During the first 210 days of experiment there was non-significant difference between the average daily weight gain of both the groups and from 210 days till end of experiment, there was significant difference between the average daily weight gain. The biometry of genital organs were done & on weekly basis. There was a significant difference between the groups A and B for length, width and thickness of ovaries, diameter of uterine horns, length of cervix and length and width of the vulva. The average serum progesterone concentrations were 0.221±0.017 and 0.238±0.018 ng/ml in groups A and B, respectively. There was a non-significant difference between the progesterone concentrations in both the groups but a gradual increase in progesterone concentration was observed. It is concluded that concentrate/dry ration alone is not sufficient to bring about changes relevant to onset of puberty. It must be fed alongwith green fodder for better results.