اثر دو سطح كربوهيدراتهاي غير فيبري همراه با چربي و بدون چربي بر عملكرد گاوهاي شيري هلشتاين

Effect of two levels of nonfiber carbohydrates with and without supplemental fat on performance of Holstein dairy cows

The effect of inclusion different levels of nonfiber carbohydrates(NFC) with and without supplemental fat on performance of Holstein dairy cows was investigated using a change over design with four treatments and four periods.Eight multiparous Holstein dairy cows were used with mean milk production and days in milking of 36±5 kg and 46±8 days.The experimental diets were 1) high nonfiber carbohydrates, no added fat; 2) high nonfibe carbohydrates, 2.5% fat; 3) low nonfiber carbohydrates, no added fat and 4) low nonfiber carbohydrates,2.5% added fat. The DMI, milk production and composition were not affected by supplemental fat or nonfiber carbohydrates. The digestibility of fiber components were higher (P<0.05) for diets with low nonfiber carbohydrates. Ruminal pH values were not affected by the experimental diets, but ruminal ammonia-N, BUN and MUN was significantly increased (P<0.05) by decreasing the level of nonfiber carbohydrates.Glucose and cholestrol of plasma were significantly increased (P<0.05) by increasing nonfiber carbohydrates and adding fat respectively. Chewing activity were not affected by nonfibe carbohydrates or fat. It appeared that response of dairy cows to adding fat was better in low fermentable carbohydrate diets.