Effect of substituting alfalfa hay with beet pulp, treated and untreated wheat straw on performance of 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 (P < 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.