پردیس کشاورزی و منابع طبیعی دانشگاه تهران Iranian Journal of animal Science 2008-4773 49 1 2018 05 22 Effect of substituting alfalfa hay with beet pulp, treated and untreated wheat straw on performance of high-producing dairy cows Effect of substituting alfalfa hay with beet pulp, treated and untreated wheat straw on performance of high-producing dairy cows 159 170 67792 10.22059/ijas.2018.244268.653573 FA Mohammad Mehdi Hajmahmoodi M.Sc. Student, Department of Animal Science, Faculty of Agriculture, Isfahan University of Technology, Iran Ebrahim Ghasemi Assistant Professor, Department of Animal Science, Faculty of Agriculture, Isfahan University of Technology, Iran 0000-0002-5248-1980 Mohammad Khorvash Associate Professor, Department of Animal Science, Faculty of Agriculture, Isfahan University of Technology, Iran Journal Article 2017 10 28 In this study, the effectsof partial substitution of alfalfa hay (AH) with high fiber by-products (wheat straw: WS, beet pulp: BP) were evaluated on performance of high producing dairy cows. Eight high yielding cows (54±2.5 kg milk production) were used in a 4 × 4 Latin square design and fed 4 experimental diets. The 4 experimental diets contained constant level of corn silage (19.2%) with different proportions of 1) 19.2% alfalfa hay (CON), 2) 3.8% AH, 5.8% WS, 5.8% BP (WS-BP), 3) 3.8% AH, 8.5% WS (WS) and 4) 3.8% AH and 10.2% treated WS (TWS). Diets were similar in of NEL, CP, and NDF contents but WS-BP and TWS diets had lower undigested NDF (uNDF) level. Results indicated replacement of AH with high fiber sources increased nutrient digestibilities (<em>P</em> < 0.01). Moreover, cows received by-products substitutes showed greater dry matter intake than control cows (P<0.01). Milk yield and milk composition did not differ across treatments. Therefore, this resulted in a tendency for improved milk production efficiency (P=0.08) with feeding CON diet. Efficiency of 3.5% FCM was similar among different diets. Feeding different by-products diets had no effect on ruminal pH, total VFA concentration, and chewing behavior, but tended to increase acetate: propionate ratio (P=0.06). Substituting wheat straw with/without beet pulp for alfalfa hay resulted in improved DM and digestibility but reduced milk production efficiency in high-producing dairy cows. In this study, the effectsof partial substitution of alfalfa hay (AH) with high fiber by-products (wheat straw: WS, beet pulp: BP) were evaluated on performance of high producing dairy cows. Eight high yielding cows (54±2.5 kg milk production) were used in a 4 × 4 Latin square design and fed 4 experimental diets. The 4 experimental diets contained constant level of corn silage (19.2%) with different proportions of 1) 19.2% alfalfa hay (CON), 2) 3.8% AH, 5.8% WS, 5.8% BP (WS-BP), 3) 3.8% AH, 8.5% WS (WS) and 4) 3.8% AH and 10.2% treated WS (TWS). Diets were similar in of NEL, CP, and NDF contents but WS-BP and TWS diets had lower undigested NDF (uNDF) level. Results indicated replacement of AH with high fiber sources increased nutrient digestibilities (<em>P</em> < 0.01). Moreover, cows received by-products substitutes showed greater dry matter intake than control cows (P<0.01). Milk yield and milk composition did not differ across treatments. Therefore, this resulted in a tendency for improved milk production efficiency (P=0.08) with feeding CON diet. Efficiency of 3.5% FCM was similar among different diets. Feeding different by-products diets had no effect on ruminal pH, total VFA concentration, and chewing behavior, but tended to increase acetate: propionate ratio (P=0.06). Substituting wheat straw with/without beet pulp for alfalfa hay resulted in improved DM and digestibility but reduced milk production efficiency in high-producing dairy cows. https://ijas.ut.ac.ir/article_67792_7e6b446af2958943b8b8769bd5247c44.pdf