Age at Puberty and Some Biological Parameters of Awassi and its First Crosses with Charollais and Romanov Rams

Abstract

The aim of this experiment was to determine the age at puberty of both ram and ewe lambs of three genotypes: Awassi (A), Charollais x Awassi (CA), and Romanov x Awassi (RA) F1 crosses. Twenty, six-month old lambs (10 from each sex) from each genotype were used. Ram and ewe lambs were kept in separate groups from the beginning until the end of the experiment. Birth weight and weaning weight were recorded for all animals. Body weights and body condition scores were recorded at monthly intervals between 6.5 and 12 months of age. Blood samples were collected weekly from ewe lambs and fortnightly from ram lambs to monitor progesterone and testosterone profiles, respectively. Semen characteristics and scrotal circumferences (SC) were evaluated fortnightly. Weight at puberty in ewe and ram lambs were not significantly different among the three genotypes and ranged around 35 kg and 42 kg, respectively. In ewe lambs, age at puberty was significantly higher (P< 0.01) in A (280±11.5 d) than in RA (232±11 d) and CA (255±11.5 d). Age at puberty of ram lambs was also significantly different (P < 0.01) among the three genotypes being higher in A (243±5 d) than in CA (223±5 d) and RA (226±5 d) ram lambs. Semen parameters improved with age in all genotypes. The RA ram lambs had greater semen concentration and lower abnormal spermatozoa than the other two genotypes (P< 0.05). Results of the present study indicate that crossing Awassi ewes with either Charollais or Romanov sires tends to improve reproductive characteristics of the F1 crossbreds through advancing age at puberty in both ram and ewe lambs.