Growth Performance of Dorper and its F1 Crossbreds at Debre-Birhan Agricultural Research Center

Abstract

The current work was conducted at Debre-Birhan Agricultural Research Center to evaluate the growth performance of pure Dorper sheep and their F₁ crosses from Menz and Afar indigenous sheep.  A total of 527 lambs (233 pure Dorper, 294 Dorper X Menz 50% and 30 Dorper X Afar 50%) were born at Debre-Birhan Research Center between 2011 and 2014. The overall birth weight in the current study was 3.04+0.04 kg ranging between 1.00 and 5.60 kg. In the present study pure Dorper lambs were heavier at birth than the F₁ crosses (P<0.05) with Afar and Menz breeds with the mean birth weight of 3.39 vs 2.57 and 2.77 kg, respectively. Pure Dorper lambs were 32 and 22% heavier than the Afar x Dorper 50% and Menz x Dorper 50% lambs, respectively, at birth. Single born lambs were significantly (P<0.0001) heavier at birth compared to their twin counterparts; they had 29% more weight at birth than twins. Parity had also significant effect (P<0.0001) on the lambs birth weight. There was a trend of improvement in birth weight as parity advances. It was noticed that lambs born from the first parity were 16.77 % and 15.13% lighter in birth weight than lambs born from 2^nd and 3^rd parities, respectively. Lambs born in main rainy season and cold dry season had the higher birth weight compared to those born in the dry season and short rainy season. This tells us the difference in pasture availability in terms of quality and quantity among the different seasons of the year. Weaning weight at 90 days of age had significant (P<0.001) effect on most variables considered. Pure Dorper lambs were significantly (P<0.0001) heavier at 90 days compared to the Dorper x Afar 50% and Dorper x Menz 50% lambs. They were 71 and 31% heavier at this age compared to the F₁ crosses of Dorper x Afar and Dorper x Menz lamb, respectively. Lambs born in the dry season were 33 and 31% inferior in weaning weight compared to those born in the main and short rainy season, respectively. Breed/ genotype, sex, birth type, year and season of birth of the lambs had significant (<0.05) effect on the body weight of lambs at 6- months of age. Pure Dorper and Dorper x Afar 50% and Dorper x Menz 50% lambs weighed 24.30, 13.18 and 17.25 kg, respectively. Male lambs weighed 17.53 while females 16.33 kg at 6-months of age. More than one kg difference was observed on average between male and female lambs; this may be due to the effects of male hormone as age advances. Lambs born in the main rainy and short rainy seasons demonstrated to have good 6 month weight compared to those born in the cold dry and dry seasons. The adjusted yearling weight for the lambs from the current study was 32.43+0.46 kg. Comparable yearling weight (34.43 vs 31.33 kg) was obtained from Dorper x Menz 50% lambs to pure Dorper lambs. However, Dorper x Afar 50% lambs were 27.5 lighter (24.96 vs 34.43 kg) than the pure Dorper lambs at yearling age. There was significantly (P<0.0001) better pre-weaning growth pattern for the pure Dorper compared to the Dorper x Afar 50% and Dorper x Menz 50% lambs (142.93 vs 73.19 and 106.24 g/h/d, respectively), that accounted 95% and 35% more weight from pure Dorper compared to Dorper x Afar and Dorper x Menz 50% lambs at weaning age. This may be the dam effect since pure Dorper lambs were raised by the pure Dorper dam while the Dorper x Afar and Menz 50% lambs were reared by indigenous ewes. From the present study it can be concluded that both the pure Dorper and its f₁ crosses with the Menz sheep adapted very well and had higher body weight and better gain than indigenous sheep breeds. It is suggested to observe the performances of different blood levels of cross breeds with Dorper sheep and also investigate the finishing capacity of Dorper cross breeds at different age and feeding levels.     

Key words: Dorper, Menz and Afar sheep, cross breeding, year of birth, season of birth, and birth type