Utilization of wheat straw in rations for lactating dairy cows.

摘要

An experiment involving three feeding trials was conducted to study the effect of substituting chopped wheat straw for alfalfa in diets for lactating dairy cows. The results of these trials have shown that in complete mixed diets or diets containing long alfalfa hay, replacement of half of the alfalfa in rations containing 45% roughage for lactating dairy cows with chopped wheat straw does not adversely affect DM intake or milk yield and increase milk fat percentage. Replacing half of the long alfalfa with chopped alfalfa also apparently improved lactational performance although not as dramatically as that of chopped straw. Ammoniation of wheat straw did not improve the performance response by lactating cows. Inclusion of chopped straw in the diets seemed to enhance the efficiency of milk production. Higher ruminal acetate:propionate ratios and increased digestibility of ether extract resulted from feeding straw. Digestibility of other nutrients were generally either not affected or were depressed by straw feeding. Increasing the chopped wheat straw level to 75% of the roughage resulted in lower DM intake and milk yield and negative body weight gains but higher milk fat levels. It did not appear that maintenance of constant ADF level in a dairy ration regardless of roughage level was the solution to the maintenance of milk fat levels. Thus it has been indicated that under the conditions of this experiment a combination of chopped alfalfa and wheat straw can be used successfully in complete mixed rations for high producing dairy cows. For the most part all productive parameters measured were improved by the addition of straw and by the feeding of complete mixed diets. This was especially true for milk fat which, from a dairyman's viewpoint, is very important because of its impact on milk pricing. It would also have a direct bearing on management by reducing labor costs through elimination of labor intensive handling of long alfalfa. Mechanical handling of complete mixed rations is relatively easier and cheaper.