Relationship Between Endocrine Profile, Energy Balance and Milk Yield in Dairy Cows During Lactation

Abstract

The objective of the present study was to investigate relationship between endocrine profile with energy balance (EB) and milk yield (MY) in Simmental dairy cows during lactation. Fifteen late pregnant cows, 15 early lactation cows and 15 mid lactation cows were chosen for the analysis. Blood samples were collected to measure growth hormone (GH), insulin, triiodothyronine (T3) and thyroxine (T4). Early lactation cows were found to have higher blood serum concentrations of GH (p0.05), T3 (p0.05) compared to dry and mid lactation cows. Insulin and thyroid hormones were in positive correlation with EB (p<0.05), and in negative correlation with MY (nonsignificant). GH was in positive correlation with MY (p<0.05), but in negative correlation with EB (nonsignificant). Relationship between hormones showed significant positive correlation between insulin and thyroid hormones. These relations are not principaly determinated by EB or MY. Negative correlations between insulin or thyroid hormones with GH were observed. These relations are principaly determinated by EB or MY

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