AGE AND BODY WEIGHT AT PUBERTY IN MUTURU HEIFERS UNDER DIFFERENT FEEDING REGIMES

Abstract

Age and body weight at puberty were studied in two groups of Mutun helfen aged 4 to 7 months and comprising 13 heifers in each group. Group 1 heifers received nutritional supplementation et lating of a mixture of dry brewer's spent porin and palm kernel cake in a ratio of 1:1 addition to normal grazing. Group 1 theifers 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 Vacutabner tubes. Samples were centrifuged within 30 minutes of collection and the plasma stored frozen until assayed for progesterone using coat-2-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 i mg/ml. Results showed that Group 1 heifers were significantly younger (P< 0.01) at puberty than Group II heifers (12.25 + 0.20 months vs. 14.60+1.67 months) but their body weights did not differ significantly (90.50+ 1.82 kg & 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. the first oestrus in the young female, is due to ovarian changes which are in turn controlled by complex endocrinological events. In the Mutury bull, Ezekwe (1992) observed that under improved husbandry and nutritional conditions, puberty was attained at an early age of 11 months and a body weight of 87 kg. The study also revealed that Muturu bulls could be used for breeding from the age of 15 months. Studies on female reproduction of indigenous Nigerian Cattle breed have concentrated largely on zebu (Bos indicus) cattle (Johnson and Gambo, 1979, Zakari et al., 1981; Oyedipe et al., 1982; Dawuda et al., 1989). There is thus a dearth of inforination on the reproductive characteristics such as puberty of indigenous Nigerian non-zebu cattle like the Muturu. The Muturu, which is the most widely distributed indigenous non-zebu cattle in the southeastern states of Nigeria, has a population of 42,000 out of an estimated total national population of 177,000. The Mutunu is highly tolerant to trypanosomiasis and is also well adapted to the hot humid conditions prevalent in the southern rainforest areas. Despite these obvious advantages, the Muturu is considered an endangered breed because of its rapidly declining numbers (Adeniyi, 1984). The need to document important aspects of its reproductive characteristics is therefore impelling. This study was thus undertaken to determine the age and body weight at which Muturu heifers attain puberty under improved husbandry and management conditions.