PARTIAL REPLACEMENT OF ALFALFA FIBER WITH FIBER FROM GROUND CORN COBSOR WHEAT MIDDLINGS

This trial examined the effect of using corn cobs or wheat middlings t o replace alfalfa partially as the dietary fiber source for lactating cows. Multiparous midlactation cows were used in three 4 x 4 Latin squ ares with 21-d periods. A low fiber, basal diet contained 26.8 g of to tal NDF, including 14.7 g of alfalfa NDF/100 g of dietary DM. Dietary fiber was increased by addition of more alfalfa, corn cobs, or wheat m iddlings to obtain 27.4, 28.9, and 27.9%, respectively, of total dieta ry NDF. Intake (24.9 kg of DM/d) and milk yield (31.6 kg/d) were not d ifferent among treatments. Nonforage fiber sources raised milk fat con centration above basal amounts (3.1% to 3.4% fat) and decreased rumina ting time below that of the high alfalfa diet (423 to 390 min/d). Fat test was raised approximately one-half as much per unit of NDF from th ese nonforage feeds as it was per unit of NDF from alfalfa. When addit ional dietary fiber came from nonforage sources, milk protein concentr ation (3.3%) was greater than when alfalfa provided the added fiber (3 .2%).