Wheat Straw or Alfalfa Hay in Diets with 30% Neutral Detergent Fiber for Lactating Holstein Cows

¹ Department of Animal Science, University of Arizona, Tucson 85721

Twenty-four Holstein cows near peak lactation were fed diets formulated to contain 30% NDF with forage NDF from chopped wheat straw or chopped alfalfa hay in proportions of 0:3, 1:2, 2:1, and 3:O in an 8-wk trial to evaluate effects of fiber source on lactational performance. Concentrate was based on highly degradable carbohydrate in steam-flaked sorghum grain. Forage to concentrate ratio decreased from 49:51 to 28:72 when straw was substituted for alfalfa hay. Milk yield (38.4 kg/d) and DMI (23.1 kg/d) were not influenced by forage source. Milk fat percentage decreased and milk protein percentage increased linearly with increasing straw. Yields of 3.5% FCM and fat showed linear and quadratic responses, because they appeared to be reduced only on the 0:3 diet, and protein yield showed a quadratic response and was highest for the 1:2 diet. Digestibility of NDF averaged 43.5, 45.4, 40.7, and 31.2%. and acetate to propionate ratio was 3.0, 2.4, 2.2, and 1.9 with increasing dietary straw. Passage rates were not influenced by diet and averaged 9.3, 7.6, 6.1, and 4.7%/h for fluid, grain, alfalfa hay, and wheat straw, respectively. It is suggested that the ratio of forage NDF to ruminally degradable starch be maintained 1:1 when diets based on low quality forage are fed to cows in early lactation.

Key Words: wheat straw • alfalfa hay • fiber

Submitted on August 23, 1990
Accepted on April 19, 1991

This article has been cited by other articles:

				R. Z. Zhong, J. G. Li, Y. X. Gao, Z. L. Tan, and G. P. Ren Effects of Substitution of Different Levels of Steam-Flaked Corn for Finely Ground Corn on Lactation and Digestion in Early Lactation Dairy Cows J Dairy Sci, October 1, 2008; 91(10): 3931 - 3937. [Abstract] [Full Text] [PDF]