INVESTIGATIONS INTO TRADITIONALLY MANAGED DJALLONKE-SHEEP PRODUCTION IN THE HUMID AND SUBHUMID ZONES OF ASANTE, GHANA .3. RELATIONSHIP BETWEEN BIRTH-WEIGHT, PREWEANING GROWTH, AND POSTWEANING GROWTH OF LAMBS

Birth weight, which is subject to differences in prenatal nutrition, i ncreased with parities to the fifth among the subhumid zone (SH=1.89 k g) dams and to the sixth among the humid zone (H=1.71 kg) darns. Seaso nal influence did not significantly affect birth weights in either zon e. Litter type had the greatest influence on birth weight, growth rate , and viability at 60 days of age, among lambs in both zones. The dual advantage of higher birth weight of lambs and higher postpartum weigh t of their dams, with the benefit of the maternal effect that supporte d optimal postnatal development lambs, resulted in higher body-weight gain at 60 days of age at sixth parity (H=6.17 kg; SH=6.99 kg). In bot h zones, viability was optimum at the fifth parity (H=95.0%; SH=95.6%) . For all weight traits, single lambs (H=7.73 kg; SH=8.48 kg) were sig nificantly (p<0.05) and consistently superior to twin lambs (H=6.68 kg ; SH=7.31 kg) at the natural weaning age of 105 days. At birth, female lambs were 6.4% behind male lambs in their subsequent growth up to na tural weaning, even when the birth weight of both sexes was similar. I n both zones, the viability showed an upward trend, with an increase i n percentage of lambs weaned up to the fifth parity (H=80.0%; SH=90.1% ) and a rapid decline after the sixth parity. The postpartum weight an d higher parity, together with the postnatal maternal effect of dams' performance on growth in the first 60 days, influenced lambs' weaning weight at 105 days. There was no significant seasonal pattern of growt h. At 210 days of age, the influence of litter type started to diminis h. Differences in body weight due to sex also became relatively less i mportant at this age. The ewes which had gained rapidly in weight appe ared heavily pregnant, and with full udder, at 210 days of age. These findings confirm the importance of the transient nature of growth betw een 90 and 105 days of age. The physiologically mature weight is reach ed at higher parity, between the fifth and sixth, antibody weights of 20.93 and 23.59 kg for the humid and subhumid zone ewes, respectively. The mean liveweight considered to be a measure of physiological matur ity was attained between 3.5 and 4.0 years of age.