Productive and reproductive performance of Dorper and its crossbreds under a Romanian semi-intensive management system

Abstract

The overall objectives of the research were to evaluate the effect of cross-breeding Dorper (DO) rams with Turcana (TA) ewes on growth and reproductive performances of F₁ DOxTA and R₁ DOx(DOxTA) crossbred lambs reared under a semi-intensive management system; to study the adaptability of the DO breed to Romanian farming conditions; and to evaluate the effects of melatonin implants outside the breeding season on reproductive performances in DO ewes. Animals were managed on cultivated pastures, with an average stocking rate of 12 head/ha. Additional 200 g concentrates/day were given for 90 days during the winter season and a three lambings per two years system was practised with the use melatonin implants for oestrous induction outside the natural breeding season. Dorper and F₁ crossbreds were found to be highly precocious when put to the ram as ewe lambs, with an average fertility rate of 84.2% and 79.3%, respectively, compared with 19.3% in the TA controls (CG). The litter size in adult DO ewes was 136.6% versus 118.8% for the TA (CG). Dorper-sired progeny had significantly higher body weights of lambs at weaning (90 days) compared with TA purebreds (23.8 kg, 23.5 kg, 21.5 kg, 19.4 kg for DO, R₁, F₁ and TA, respectively). At the age of 8 months, all three DO genotypes were significantly heavier (46.1 kg, 40.7 kg and 43.5 kg for DO, F₁ and R₁, respectively) compared with the TA females, who reached 32.3 kg. Average daily gain from birth to 28 days of age was significantly higher in DO purebreds and F₁ and R₁ crossbreds compared with TA lambs (266.4 g, 253.8 g, 223.4 g and 157.3 g, respectively). Lamb survival rates until weaning were not affected by the genotype. When using melatonin implants in the DO ewes, the fertility rate increased to 88%, compared with a fertility of 41.6% in non-treated DO ewes. Out-of-season prolificacy was not affected by melatonin treatment, with litter size being 127% and 120% in treated and non-treated DO ewes, respectively. The DO breed performed well under Romanian semi-intensive management, and proved to be a highly adaptable breed to the new rearing conditions.

Keywords: Sheep, heterosis, growth, fertility rates, melatonin implants