caa a22 4500 388059672 CHVBK 20180307125117.0 cr unu---uuuuu 161130e199806 xx s 000 0 eng 10.1017/S1357729800009164 doi S1357729800009164 pii (NATIONALLICENCE)cambridge-10.1017/S1357729800009164 The production parameters influencing the composition and structure of pastoral cattle herds in a semi-arid area of Kenya [Elektronische Daten] The size and composition of three herds belonging to Maasai pastoralists were monitored for more than 5 years (1990 to 1996). Animals were categorized as either suckling calves, weaned heifers, weaned males or breeding females. The dates of entries and exits were used to estimate the total number of observed animal days for each category. Fertility rates of breeding females and mortality and disposal rates for each category were estimated using animal days as the denominator. Herd differences were tested using contingency tables. Age to first calving and calving intervals were estimated and examined using analysis of variance tests. The patterns of births and deaths were seasonally influenced. The mean annual calving rate of all breeding females was 65·6% and for females excluding first calvers was 46·9%. No herd effects were observed. The mean observed interval between calvings was 609 days and the calving interval, calculated from the parturition rate, was 649 days with no herd differences. Mean age at first calving was approximately 4 years with no herd differences. Mean annual mortality rates were 8·9% for breeding cows, 7·8% for weaned males, 6·7% for weaned heifers and 22·1% for calves. The mean annual culling rate of cows was 10·8% and the sale rate of heifers and weaned males was 12·9% and 41·5% respectively. The mean age at disposal of heifers was 655 days and of steers was 801 days. Herd sizes were shown to fluctuate annually with no obvious trend between herds. The main determinants of production identified were the effect of seasonally poor nutrition on the rate of reproduction and the effect of season, herd mobility and disease on mortality. The study describes production levels that can be used to predict future changes to the system. The results are discussed in terms of the factors influencing and their relevance to pastoral development. The findings are compared with those observed in other, similar areas. Copyright © British Society of Animal Science 1998 cattle nationallicence Kenya nationallicence pastoralism nationallicence production nationallicence semi-arid zones nationallicence Roderick S. Veterinary Epidemiology and Economics Research Unit, Department of Agriculture, Earley Gate, University of Reading, Reading RG6 6 AT Stevenson P. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS Ndungu J. Kenya Trypanosomiasis Research Institute, Box 362, Kikuyu, Kenya Animal Science Cambridge University Press 66/3(1998-06), 585-594 1357-7298 66:3<585 1998 66 ASC https://doi.org/10.1017/S1357729800009164 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S1357729800009164 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Roderick S. Veterinary Epidemiology and Economics Research Unit, Department of Agriculture, Earley Gate, University of Reading, Reading RG6 6 AT NATIONALLICENCE 700 1- Stevenson P. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS NATIONALLICENCE 700 1- Ndungu J. Kenya Trypanosomiasis Research Institute, Box 362, Kikuyu, Kenya NATIONALLICENCE 773 0- Animal Science Cambridge University Press 66/3(1998-06), 585-594 1357-7298 66:3<585 1998 66 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge