Following P1, a cyclical HS pattern was implemented for 21 d (P2) where daily ambient temperatures ranged from 29.1 to 39.7°C and the THL was ˃ 74 for 24h/d and ˃ 83 for at least 14 h/d. during P2, half of the HS calves (n=7) received a control diet (CON) and the other half received the control diet supplemented with a product (300 g/d) containing gluconeogenic precursors (GLU). Throughout each period respiration rate, rectal temperature and skin temperature at the shoulder and rump were recorded at 0600, 1100 and 1500 h daily. Blood samples were obtained prior and 4 h post the a.m. feeding during both periods. Although HS markedly reduced DMI (18%) and growth as expected, supplemental GLU did not affect body weight gain. Supplemental GLU decreased the shoulder temperature at 0600 and 1500 h (P˂ 0.01) , and decreased respiratory rate at 1500 h (P˂ 0.02). Feeding GLU did not affect blood urea nitrogen (BUN), glucose or nonesterified fatty acids (NEFA) concentrations, but increased circulating insulin prior to the a.m. feeding (P˂0.03) and this demonstrates that GLU was effective at enhancing the post- absorptive carbohydrate status. Our results suggest that feeding supplemental GLU improves some body temperature indices but did not enhance growth performance in Holstein bull calves during HS.
کد مقاله : GGR-002
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