Summary In this study the reproductive performance of indigenous Ethiopian cows and their F1 crosses was evaluated and factors affecting reproductive performance were assessed, based on crossbreeding data collected from Asella Livestock Farm, Ethiopia. Age at first calving, number of services per conception, days open, gestation length and calving interval were considered in the evaluation of reproductive performance. Results obtained showed that genetic (breed) group was a significant source of variation for almost all of reproductive performance traits studied. First (F1) crosses were found to be better than the indigenous cows. Among the first crosses, Jersey crosses were the best. They had a lower age at first calving, required less number of services per conception, shorter days open and calving intervals than the rest of the genetic groups. Under the prevailing conditions (feeding, management, etc.), upgrading indigenous cows with Jersey inheritance would be recommendable provided that sound breeding programmes are established to maintain the merits of first crosses. Zusammenfassung Die Untersuchung wertet Daten über die Reproduktionsleistung äthiopischer Rassen und ihrer Kreuzungsnachkommen aus und schätzt genetische und nicht‐genetische Einflüsse auf die Fortpflanzung. Die Aufzeichnungen stammen von der Asella‐Livestock‐Farm, Arsi, Aüthiopien. Verwendet wurden die Fruchtbarkeitsmerkmale Erstkalbealter, Besamungsindex, Güstzeit, Trächtig‐keitsdauer und Zwischenkalbezeit. Die Ergebnisse zeigen die genetische Gruppe (Rasse) als signifikante Variationsursache für fast alle untersuchten Merkmale. F1‐Kreuzungstiere waren den einheimischen Rassen überlegen. Dabei hatten Jersey‐Kreuzungstiere bessere Leistungen als Holstein‐Kreuzungen. Bei ersteren war ein geringeres Erstkalbealter festzustellen, sie hatten einen niedrigeren Besamungsindex, und kürzere Güst‐ und Zwischenkalbezeiten als alle andern genetischen Gruppen. Unter den vorherrschenden Bedingungen hinsichtlich Futterangebot, Management usw. empfiehlt sich die Kreu‐zungzucht mit Jersey unter der Voraussetzung, daß fundierte Zuchtprogramme die überlegenheit der F1‐Tiere erhalten.

Data collected on number of services per conception (NSC), age at first calving (AFC), calving interval and calf pre-weaning mortality rate of Boran cattle and their Friesian crosses were evaluated. The NSC was 1.81, 1.61 and 1.69 for Boran, F1 Boran-Friesian and three-quarter Friesian heifers respectively. The AFC varied from 31.5 months in the F1 crosses to 46.8 months in the Boran heifers artificially inseminated with Friesian semen. The mean calving intervals were 465, 552, 525 and 487 days for Boran cows naturally mated to Boran and Friesian bulls, Boran and F1 cows artificially inseminated with Friesian semen respectively. The preweaning calf mortality rate was 3.4% and was significantly influenced by parity, sex and interaction of breed with year of birth. Year as well as season had in general significant effects on the traits considered. However, the variation between mating or breeding groups was also large and it was in favour of the F1 crosses.

Birth (4,197) and weaning (2,441) weight data on Boran, F1 Boran Friesian and three quarter Friesian calves as well as adjusted one-year (390), 2-year (177) and 3-year (364) weights on Boran cattle were analysed to estimate the influence of genetic and environmental factors. Boran, F1 and three quarter calves weighted 25.2, 25.4 and 25.7 kg at birth and 157.5, 176.7 and 179.9 kg at weaning, respectively. All factors included in the analysis and their interaction had significant effects on both traits with the exception of the effect of season of birth and its interaction with breed group on birth weight. Weight of Boran cattle at one-, 2- and 3-years of age were 179, 269 and 338 kg, respectively. Heritability values calculated on the basis of paternal half-sibs were 0.32, 0.24, 0.48, 0.29 and 0.24 for birth, weaning, one-year, 2-year and 3-year weights, respectively. The study indicated that F1 crosses were 12.2% heavier at weaning than Boran calves. Of the environmental factors considered, year of birth was found to be the major source of variation mainly due to variation in the amount of rainfall between years.

The objective of these studies were to investigate the digestibility of poultry litter of layers and to add poultry litter to grazing Boran Zebu bulls and Ogaden sheep in East Ethiopia. Two feeding experiments (132 and 102 days) with Boran Zebu bulls (10 and 16 bulls per trial) and one feeding experiment with female Ogaden sheep (30 ewes) were carried out. All animals were grazing all day long. During the night the animals of all trials were divided into two groups each. The animals of one group of each experiment obtained poultry litter ad libitum without any other feedstuffs. Apart from feeding trials digestion experiments were carried out in order to determine the digestibility of poultry litter in 4 Ogaden sheep. The apparent digestibility of organic matter and crude protein of poultry litter amounted to 69.8 and 82.8%, the net energy content was indicated with 474 EFUc per kg of dry matter. The daily weight gain of Boran Zebu bulls fed on poultry litter was by 40 and 91 g (6.5 and 13.6% in exp. 1 and 2) higher than that of control groups. Especially during the dry season (Feb./March 1982) bulls supplemented with poultry litter were highly superior in daily weight gain (84 and 310 g per day more in exp. 1 and 2) to unsupplemented groups. The daily weight gain of Ogaden sheep fed on poultry litter in a short-term experiment (56 days) under improved grazing conditions (April-June 1982) was by 13 g per day higher than that of control animals (weight gain: 18 and 31 g per animal and day).(ABSTRACT TRUNCATED AT 250 WORDS)