Periódicos Brasileiros em Medicina Veterinária e Zootecnia

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Insulin resistance in different physiological states of high producing Holstein dairy cows

Chalmeh, AliasgharPourjafar, MehrdadNazifi, SaeedMomenifar, ForooghMohamadi, Mahboobeh

Background: Alterations in energy demands during different physiological states of dairy cows predispose them to metabolic disorders. Insulin as a main metabolic hormone has a key role to maintain homeorhesis in dairy cows. Insulin resistance phenomenon can expose these animals to metabolic dysfunctions. Information regarding insulin resistance at each physiological state of high producing dairy cows can assist veterinarians to control and prevent the metabolic disorders at herd levels.Materials, Methods & Results: This research was carried out at winter 2014 on 25 multiparous Holstein dairy cows from a high producing industrial dairy farm. The total mixed rations were formulated and prepared for all animals according to National Research Council (NRC) requirements. At this farm, a dry period of 60 days has been considered. Milk production was about 10,000 kg for year, an average of 3.6 of milk fat %, and 3.3 of milk protein %. All the animals were clinically healthy and body condition score (BCS) was estimated based on 0 to 5 system. Cattle were divided into 5 equal groups containing early, mid and late lactations, far-off and close-up dry periods. A blood sample was taken immediately after catheterization, and dextrose 50% was administered at 500 mg/kg, 10 mL/kg/h, subsequently. Blood samples were collected from all cows through the fixed catheter prior to and 1, 2, 3 and 4 h after dextrose 50% infusion in plain tubes. After sera separation, glucose and insulin were detected in all samples. Significant and rapid elevation of serum glucose and insulin concentrations were seen in all studied animals at 1st h after dextrose administration (P < 0.05). Decreasing the glucose level near to base line levels was seen at h 4 in late lactation and far-off dry cows. The glucose level at this time was remained significantly higher than h zero in other groups (P < 0.05).[...](AU)

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