اثر پوسته پنبه دانه و اندازه قطعات يونجه خشك بر عملكرد گاوهاي شيرده هلشتاين

Effects of Cottonseed Hulls and Alfalfa Hay Particle Size on Performance of Holstein Dairy Cows

The objective of this study was to evaluate the effects of Alfalfa hay Particle Size (APS) and Cottonseed Hulls (CSH) on the performance of Holstein dairy cows. Twelve dairy cows in midlactation were assigned to four treatments in a change-over design three periods and 2x2 factorial arrangement. During each of 28-d periods, cows were offered one of four total mixed rations that differed in particle size and cottonseed hulls substituted for AH (0 and 9.63% DM). Dietary treatments were: long AH no CSH (treatment 1), long AH with CSH (treatment 2), short AH no CSH (treatment 3) and finally short AH with CSH (treatment 4). Total physically effective NDF content, measured as percentage of NDF > 1.18 mm, decreased with reducing APS and increased with substitution of CSH (P<0.05). Mean particle size decreased with reducing APS (P<0.05), but was not affected by the CSH substitution. Dry matter intake, milk production and milk composition were not significantly affected by alfalfa hay particle size and the substitution of CSH. Total chewing activity expressed as minutes per day was unaffected by APS and by the substitution of CSH but when expressed as minutes per kilogram neutral detergent fiber intake or minutes per kilogram dry matter intake increased with increasing APS and decreased with the substitution of CSH(P<0.05). Results finally indicated that cottonseed hulls can be partly substituted for alfalfa hay.