عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The objective of this study was to evaluate the effects of sources of four starch on milk production and composition, nutrients digestibility and blood metabolites of lactating Holstein cows. Eight multiparous Holstein cows (683±31 kg of body weight; 83±9 DIM) were used in a replicated 4×4 Latin square design with 21-d periods. The exprimental diets contained wheat, barley, corn, or potato as the primary source of starch and contained 25.4, 31, 22, and 23 percent of diet DM respectively. Dry matter intake was similar among treatments. Raw, fat, and energy corrected milk production was lower (P<0.05) in cows fed the potato-based diet compared with other diets. Cows fed the corn-based diet had higher (P<0.05) milk fat content, but milk protein content was unaffected by the source of dietary starch. Milk production and lactuting net energy efficiency, milk nitrogen and feed nitrogen efficiency was lowes in cows received potato based diet (P<0.05). Total tract apparent digestibility of dry and organic matter, crude protein and ether extract were higher (P<0.05) in cows fed the wheat or corn-based diets compared with those fed barley or potato-based diets. Plasma glucose, total cholesterol, HLD-cholesterol and LDL-cholesterol concentrations were similar among experimental diets, but triglycerides concentration was higher (P<0.05) in cows fed potato-based diet compared with other diets. These results showed that corn and wheat based diets improved the nutrient digestihilty, feed energy and nitrogen efficiency, and milk production compare to potato based diet.