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Effects of Roughage Type and Texture on Milk Fat Secretion and Body Weight Recovery by Lactating Dairy Cows¹

Department of Animal Sciences, Washington State University, Western Washington Research and Extension Center, Puyallup 98371

ABSTRACT

Twenty-five lactating Holstein cows were fed five rations in which the roughage portions (dry matter) consisted of either 1) baled hay; 2) cubed hay; 3) cubed hay, 90% and corn silage, 10%; 4) cubed hay, 80% and corn silage, 20%; or 5) cubed hay, 60% and corn silage, 40%. Hays were third-cutting alfalfa. Rations were fed in a continuous test during the first 168 days of lactation to determine effects of ration on feed intake, production and composition of milk, and change in body weight.

Substituting corn silage for cubed hay depressed intake of roughage dry matter at 20 and 40% substitution and increased milk fat percent at 40%, but had no effect on solids-not-fat percent or production of fat-corrected milk. In early lactation mean milk fat percentages increased linearly as corn silage was substituted for cubed hay at 20 and 40%. Gross efficiencies of milk production of the 20 and 40% corn silage rations exceeded efficiencies of baled hay, cubed hay, or 10% corn silage rations. Rate of body weight recovery after parturition was slower for cows fed baled hay than for those fed cubed hay or mixed cubes and silage.

The interrelationships of milk fat tests and rumen volatile fatty acids of cows fed coarse textured hay (baled), fine textured hay (cubed), and cubes supplemented with corn silage indicate milk fat percentages are affected by type as well as texture of forage and that the potential metabolic mechanisms due to type and texture may differ.

¹ Scientific Paper No. 5179. College of Agriculture Research Center, Washington State University, Pullman 99164. Project No. 0045.