Analyses were carried out on a range of performance traits and productivity estimates for indigenous Arsi and Zebu cattle and eight different grades of these with Jersey and Friesian, maintained for milk production. Data covered the period 1968 to 1981, and the animals were kept at Asela station and on surrounding smallholder farms in the Arsi Region of Ethiopia. Genetic and environmental effects relating to breed group, season and year of calving or birth, parturition number etc. were evaluated as appropriate for each performance trait.
Overall at Asela station, for the different breed groups, age at first calving ranged from 31.3 to 35.7 months, calving interval from 12.9 to 17.2 months, breeding efficiency index from 91 to 107%, postpartum cow weight from 236 to 336 kg, female calf birth weight from 21.9 to 28.4 kg, lactation milk yield from 809 to 2374 kg, lactation length from 272 to 411 days, milk yield per day of lactation from 2.7 to 6.3 kg, dry period from 76 to 165 days, butterfat percentage from 4.1 to 5.5%, total fat per lactation from 35 to 98 kg, fat-corrected milk yield per lactation from 803 to 2367 kg, fat-corrected milk yield per day of lactation from 2.8 to 6.5 kg, annual milk yield from 694 to 2044 kg, annual fat-corrected milk yield from 689 to 1973 kg and annual fat-corrected milk yield per unit metabolic weight of cow from 11.0 to 26.0 kg.
The major points to emerge concerning the final productivity index were the clear superiority of all crossbreds over the indigenous breed groups (105%), the similarity in performance of the 75% Bos taurus and the 50% Bos taurus, the lack of superiority of the Friesian cross over the Jersey cross, the similarity in performance between the indigenous Arsi and Zebu, and the major advantages of calving in the June -September wet season compared with the rest of the year.
Production levels on smallholder farms were rather similar to those on Asela station, and based on annual milk yield the rankings of the four crossbred groups kept on smallholder farms were the same as their rankings on Asela station.
