Authors : H.A. Zain El Abdein and S.A. Makkawi
Abstract: This study was conducted in the farm of the airy unit of the Arab Company for Agricultural Production an Processing (ACAPP), about 45 km south of Khartoum City near the northern boarder of the Gezira State. Pure Holstein-Friesian heifers an cows were raise in this farm unerd intensive system of management in a semi-ari zone, in the Sudan. Age at puperty was determine in 130 heifers, an the effect of season of birth on age an weight at first conception was invetigate in 63 locally bre heifers. Age at puberty was determine by using Ra ioimmunoassay (RIA) for detection of serum progesterone concentration, rectal palpation to check the presence of corpora lutea an visual observation of oestrous signs. The correlation between Bodyweight (BW), Heart Girth circumference (HG) an progesterone (P4) concentration were compute. The age of 18 months was considere as the age of puberty where more than 50% of heifers (61.5%) were recording progesterone concentration of >1 ng/mL an this was confirme by visual observation of oestrous signs an presence of corpora lutea on the ovaries. The effect of season of birth on age an bodyweight at first conception was not significant. The winter born heifers conceive at 21.3±4.2 months with a BW of 317.9±26.3 kg, summer born heifers at 24.3±6.9 months with BW of 323.6±46.9 kg an autumn born heifers at 24.5±4.4 months of age an 304.7±33.6 kg bodyweight.
H.A. Zain El Abdein and S.A. Makkawi , 2006. Age at Puberty an the Effect of Season of Birth on Age an Bodyweight at First Conception in Holstein-Friesian Heifers Born in the Su An. . Journal of Animal and Veterinary Advances, 5: 418-422.