ANALYSIS OF AN OPEN NUCLEUS BREEDING PROGRAM FOR DJALLONKE SHEEP IN THE IVORY-COAST .1. EXAMINATION OF NONGENETIC FACTORS

Data on Djallonke sheep collected from 1983 through 1992 on 29 partici pating farms of an open nucleus improvement programme and from the nuc leus were analysed. Initial on-farm records on 14342 lambs and on-stat ion records on 2551 ram lambs were edited down to 6605 for birth weigh t (BWT), 5857 for pre-selection (birth to 80 days) average daily gain (PSADG), 10417 for 80-day weight (WT80), 13054 for lamb survival at pr eselection, 1978 for 180 (WT180) and 849 for 365 (WT365) day weights. Year of birth, sire line, flock, month and season of birth had signifi cant (at least P < 0.05) effects on both on-farm and on-station weight s and on lamb survival. Trait means were 2.2 (s.e. 0.02) kg for BWT, 6 9.6 (s.e. 1.26) g/day for PSADG, 9.1 (s.e. 0.05) kg for WT80, 19.7 (s. e. 0.24) kg for WT180 and 31.8 (s.e. 0.45) kg for WT365. Mean survival was 90 (s.e. 0.9) %. Single lambs were heavier at birth and at 80 day s of age, grew faster to 80 days and were about 200 and 500 g heavier at 180 and 365 days respectively than multiple lambs. There was a larg e variation between flocks: flock means for WT80 varied from 6.4 to 12 .0 kg (CV 0.21), with smaller flocks having generally the lowest means . Lambs born in the hot-rainy season had the heaviest birth and 80-day weights, whereas ram lambs born in the cool rainy and early hot-dry s easons had the heaviest 180- and 365-day weights. Lambs born during th e cool months of July to October had the lowest survival rate. Multipl icative factors were found to be more appropriate for adjusting on-far m records for type of birth, management level, birth date, season of b irth and ewe parity than additive adjustment factors.