Authors: ZENNURE DEMİR, DEVRİM SARIPINAR AKSU
Abstract: The present study was conducted to investigate the physiological changes in leptin, adiponectin, and ghrelin hormones, which are effective in the regulation of energy metabolism, and the galactopoietic hormones including growth hormone (GH), insulin, insulin-like growth factor-I (IGF-I), cortisol, thyroid stimulating hormone (TSH) and thyroxine (T4 ) levels, which are also effective in the regulation of metabolic activities and their correlation with milk yield levels in Holstein and Simmental cows with low, medium, and high milk yield. Holstein (n = 30) and Simmental cows (n = 30) with low, medium, and high milk yield were used. Cows were divided into 6 groups with 10 animals in each group, and body condition scores (BCS) were determined. Serum GH, insulin, IGF-I, cortisol, TSH, T4 , leptin, adiponectin, and ghrelin levels were measured. GH level increased in both breeds (p < 0.05). As a result, in cases when the energy requirement increases during lactation without reaching a critical point, the GH, cortisol, and ghrelin hormone levels increase, while the plasma T4 level decreases and insulin, IGF-I, TSH, leptin, and adiponectin levels remain unchanged. An interaction between leptin, adiponectin, and ghrelin and galactopoietic hormones was noted.
Keywords: Adiponectin, growth hormone, ghrelin, leptin, milk yield
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