Co-Authors:
Barash, H., Institute of Animal Science, Agricultural Research Organization, Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Peri, I., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel
Gertler, A., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel
Bruckental, I., Institute of Animal Science, Agricultural Research Organization, Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Abstract:
Twenty-one 6-month-old Israeli Holstein heifers were used to determine the effect of three 6-month feeding regimes on growth, blood concentration of insulin, prolactin and insulin-like growth factor-1 (IGF-1), attainment of puberty and milk production during first lactation. Feeding regimes were as follows. (1) Restricted: the heifers were given food during months 1, 2 and 4, 5 of an experimental period, to support live-weight (LW) gain of 0·35 and 0·50 kg/day, respectively and during months 3 and 6 the heifers were given food to support compensatory growth. (2) Control: the heifers were given food to support LW gain of 1·0 kg/day. (3) Control + C: the heifers were given the same as the control, with a daily supplement of 0·05 mg/kg LW cimaterol (C) for 4 months. The total LW gain of the restricted heifers during the 6 months of the trial was significantly lower than that of the control heifers. Cimaterol improved growth rate only during the first 2 months of its application and its withdrawal was associated with severe LW gain retardation. The feeding regime employed in the restricted treatment was associated with a significant reduction in serum concentrations of insulin, prolactin and IGF-1 during the first restricted phase, followed by an elevation in the first compensatory phase. During the second restriction-compensation cycle, only the serum concentration of prolactin was significantly reduced. Cimaterol addition was also associated with a reduced blood concentration of the hormones. The animals in the restricted, control and control + C groups attained puberty at LW of 249·2, 277·6 and 304·9 kg (P <0·05), respectively. No effect of the treatments on milk yield was observed. The effect of the feeding regimes on skeletal growth and on metubolizable energy efficiency for growth is discussed. © 1994, British Society of Animal Science. All rights reserved.
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