Age and body weight at puberty in Muturu heifers under different feeding regimes
Age and body weight at puberty were studied in two groups of Muturu heifers aged 4 to 7 months and comprising 13 heifers in each group. Group I heifers received nutritional supplementation of a mixture of dry brewer's spent grain and palm kernel cake in a ratio of 3:1 in addition to normal grazing. Group II heifers were grazed without any supplementation. From the age of 10 months and tasting for a period of 6 months, blood samples were collected twice weekly from each heifer via the jugular vein into heparinized vacutainer tubes. Samples were centrifuged within 30 minutes of collection and the plasma stored frozen until assayed for progesterone using coat-a-count solid phase 125, radioimmunoassay kits. Body weights of all heifers were also recorded bi-weekly during the experimental period. Puberty was assumed to have occurred in any heifer when plasma progesterone values reached/exceeded 1 mg/ml. Results showed that Group I heifers were significantly younger (P< 0.01) at puberty than Group II heifers (12.25 ± 0.20 months vs. 14.60 ± 0.67 months) but their body weights did not differ significantly (90.50 ± 1.82kg & 85.20 ± 0.87 kg for Groups I and II heifers, respectively). These results show that under improved feeding, puberty in Muturu heifers could be attained relatively at an early age.
Keywords: Muturu, Heifers, Puberty, Nutritional supplementation, Radioimmunoassay, Progesterone.