Effect of dietary intake on somatotrophic axis–related gene expression and endocrine profile in Osmanabadi goats

This study was conducted to establish the effect of different dietary intake levels on the somatotrophic axis–related gene expression and endocrine profile in Osmanabadi goats. The study was conducted in 12 Osmanabadi goats, 6-8 months of age, for a period of 2 months during the summer season (April-May). The animals were randomly divided into 2 groups based on body weight: GI (n = 6; ad libitum feeding) and GII (n = 6; 40% less of ad libitum). The goats were fed with feed consisting of 50% roughage and 50% concentrate. Blood collection was done at fortnightly interval. Body weight, plasma growth hormone (GH), insulin-like growth factor 1 (IGF-1), and leptin were evaluated at fortnightly intervals. At the end of study period, all the 12 animals were slaughtered and different organs were collected for histopathological studies, as well as relative gene expression studies. The targeted gene expressions were GH, growth hormone receptor (GHR), leptin, and IGF-1. Results showed that body weight (P < 0.01), IGF-1 (P < 0.01), and leptin (P < 0.05) concentration was significantly lower in GII as compared to GI. However, plasma GH was significantly (P < 0.01) higher in GII as compared to GI. Hypothalamus GH and leptin mRNA transcript expression showed the opposite trend between the groups. Furthermore, pituitary GH mRNA transcript expression was found to be higher in GII (1.3 fold) as compared to GI (1 fold) goats. In addition, the corresponding GHR mRNA transcript expression in liver samples was also found to be higher in GII (7.9 fold) as compared to GI (1 fold) goats. Hepatic damage and burden on the liver to cope with the nutritional insufficiency in GII group showed that nutritional stress induced in this study caused changes at the cellular level. The significantly higher plasma GH and lower IGF-1 and leptin level in GII as compared to GI demonstrates that the GII goats were under severe nutritional stress. This study also established the effect of nutritional stress on GH expression in pituitary and GHR gene expression in liver, and these findings may be useful for assessing the impact of nutritional stress in goats.