Relationship of some metabolic Hormones with Increased Live Body Weight of Male and Female of Karakul and Awassi Lambs

This study was conducted in the animal field of the Al-Kafeel Company from November 2019 till May 2020 to investigate the possible association between growth hormone (GH) and thyroxine (T4) with the growth traits in Awassi and Karakul sheep. The total number of animals which used in the study was 60 lambs, 28 (13 males and 15 females) from Karakul and 32 (18 males and 14 females) from Awassi. Blood samples were collected at birth, weaning, and six months of age, and both GH and T4 concentrations were measured. Results showed higher values of T4 for Karakul as compared with Awassi at birth and weaning. Karakul breed was also exhibited significantly higher values of GH over Awassi breed only at weaning, while, no significant differences were observed at birth and six months of age. Karakul lambs showed higher weights as compared with Awassi lambs at all studied periods. A highly significant (p < 0.01) positive correlation was observed between T4 concentration and the weight of lambs at most studied periods. Whereas, GH did not exhibit any correlation with growth traits measured in both breeds. The elevated T4 might be one of the reasons for superiority of Karakul over Awassi breed in live body weights. This high correlation between T4 and growth traits could be used in the early selection of lambs to improve the weights of sheep at marketing.