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چکیده
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Two fattening trials were conducted to investigate the impact of concentrate energy levels and presentation form on the growth performance and feeding behavior of two dairy breed calves under an intensive fattening system. In the first trial, 86 Holstein bull calves were used, while the second trial involved 86 Montbeliarde bull calves. Different concentrate types with varying energy levels (low, medium, high) and forms (pellet, mash) were examined over a fattening period of 150 days growing and 60 days finishing. The Montbeliarde calves exhibited significantly higher average daily gain (ADG) and feed conversion ratio (FCR) than the Holstein calves throughout the fattening period (P ≤ 0.05). During the growing phase, no significant effect of the energy level was observed in Montbeliarde calves, while the Holstein calves on the medium level of energy showed greater ADG than low energy groups (P = 0.046). In the finishing phase, Holstein calves showed no significant response to energy levels, while Montbeliarde calves tended to demonstrate improved ADG and FCR with medium and high energy concentrates compared to the low energy. Feeding behavior in Holstein calves were slightly affected by the energy level, except for feeding rate. In contrast, significant differences in feeding behavior were observed among the experimental groups for Montbeliarde calves, particularly on days 14 and 84 of the trial (P < 0.01). Compared to the mash form, pelleting improved ADG (P < 0.01) in Holstein calves during the finishing phase. In Montbeliarde calves, pelleting enhanced ADG (P < 0.01) and FCR (P = 0.033) during the growing phase, but negatively affected these parameters in the finishing phase. The results indicated distinct growth performances and breed-specific responses to concentrate energy levels and presentation forms in Holstein and Montbeliarde calves.
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