Few studies have been conducted in sub-Saharan Africa where multiple recordings of heart girth and body weight were made for the same cattle population. In this study, monthly measurements were taken of working oxen on 24 smallholder farms in the Ethiopian highlands for 1 year. The overall yearly mean body weight of oxen across working and nonworking periods was 281637 kg. No significant differences in mean monthly body weights were observed, except for December and January compared to August (297636 and 296637, and 271635 kg, respectively, P , 0.05) and December versus April 272635 kg (P , 0.05). Simple linear regression equations derived from body weight and heart girth measurements were significantly different between months. Nevertheless, separate monthly equations and a single equation for the year explained variation in body weight about the same. The monthly equations predicted 83 to 95% of oxen weights to within 610% of 2 weighbridge values, while the equation for the entire year predicted 87%. The R values for the monthly equations ranged 2 from 0.63 to 0.87 and the R value for the entire year was 0.75. The single equation for the year predicted body weight of oxen as a group to within 627 kg of mean monthly weighbridge values, whereas for a single animal the predicted body weight was 637 kg of the actual weight (C.I. 95%). The single equation can be used to monitor mean body weight of the oxen population equally well across working and nonworking periods of the year.

Reproductive performance, mortality, growth, and culling and replacement rates based on 20000 calving records were evaluated for grade Boran beef cattle maintained with trypanocidal drugs in an area of high trypanosomiasis risk in Tanzania. Under ranching conditions, over a 10-year period in this area of high Olossina morsitans morsitans, O. pallidipes and O. brevipalpis challenge, a calving interval of 15-9 months, pre-weaning mortality of 8%, annual cow mortality of 5-8% and 8-month weaning weight of 133-5 kg resulted in a herd productivity of 96 kg of weaner calf per cow per year. The proportion of heifers required as replacements (45%) and the generation interval (6-9 years) indicated scope for implementation of selection programmes on growth traits. The level of productivity achieved compared favourably with major data sets recently analysed from pure Boran cattle under trypanosomiasis-free ranching conditions in Kenya, and from trypanotolerant N'Dama cattle in West Africa. These results indicate the possibility of improving livestock production in tsetse-infested areas by the rational use of chemoprophylaxis as an integral part of management.Year, season, cow age, calf sex and location on ranch had significant effects on practically all the traits of calving interval, pre-weaning mortality and growth, and cow productivity. Superior performance where bush clearance and tsetse fly control had taken place suggests that economic evaluation of these interventions should be attempted. The season of calving had a major effect on productivity. Cows of 5-8 years of age were the most productive, as were animals producing male calves, features well recognized in beef cattle production.An average of 4-4 treatments with Samorin, a prophylactic, and 0-6 treatments with Berenil, a therapeutic, were required per year. The number of treatments varied from year to year and by area, being greater in the south of the ranch where the tsetse challenge was considered higher. However, the age and season of calving had little effect on the number of treatments required. Despite such extensive use of trypanocidal drugs, there was no indication that drug resistance had developed or evidence that repeated inoculation of Samorin had affected productivity.Grading-up of small East African Zebu cattle to Boran over an 8-year period allowed annual comparison of birth weights, pre-weaning growth and weaning weights of two groups of calves, one having a higher level of Boran genes (varying from 12 to 6% higher annually) than the other. Those with the higher level of Boran genes performed better by 3-3% for all attributes studied, but as the percentage difference in Boran genes decreased, so did this difference. In an environment improved through bush clearance and tsetse fly control, the calves with higher levels of Boran genes were superior, but this superiority was not expressed in the unimproved environment.

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Purebred cows were evaluated for reproductive performance and live weight, and for pre-weaning growth and viability of crossbred progeny sired by unrelated breeds. The cows comprised three indigenous breeds, Mashona, Nkone and Tuli and four exotic breeds Africander, Brahman, Sussex and Charolais. Over 3 years, the mean calving rates % (s.e.) were 55-5 (3-0), 76-0 (3-8), 63-1 (4-5), 69-6 (3-5), 70-0 (3-8), 60-0 (4-3) and 67-0 (5-0) for Africander, Mashona, Nkone, Tuli, Brahman, Sussex and Charolais cows, respectively. Bos taurus and Brahman cows were heavier at parturition and at calf weaning than indigenous cows. Mashona cows were lightest at both stages. Calves of Bos taurus cows were heaviest at birth and those of Mashona lightest. Calves of Brahman cows had the most rapid growth rate and at weaning (240 days) weighed in kg (s.e.) 207 (3-1), compared with 184 (2-1), 172 (2-2), 187 (2-6), 184 (2-1), 178 (2-7) and 186 (2-9) for progeny of Africander, Mashona, Nkone, Tuli, Sussex and Charolais, respectively. Pre-weaning survival rates of the breeds were not significantly different but viability was higher in progeny of indigenous than exotic breeds. The productivity estimates combining calving rate, cow weight, calf weaning weight and pre-weaning viability demonstrated the superiority of indigenous breeds and the Brahman over Africander and Bos taurus breeds. t Present address: Grasslands Research Station, Private Bag 3701, Marondera, Zimbabwe.

A comparison of productivity over a 4-year period from indigenous type beef cattle under two production systems in Botswana is reported. The two systems are: the traditional system on unenclosed communal grazing (cattle post) and ranching within fenced paddocks. Calving percentages, 7-month old calf weight, calf mortality and post-weaning growth to 18 months of age under cattle post conditions were 46.4 per cent, 122.5 kg, 10.2 percent and 88.5 kg respectively. Corresponding figures for cattle on the fenced ranches were 74.0 per cent, 177.4 kg, 8.5 per cent and 105.8 kg. These results indicate overall productivity estimates of 51 and 120 kg of weaner calf per cow per year and 86 and 188 kg of 18-month old calf per cow per year for the cattle post and fenced ranch respectively.