Soybean hulls as a replacement of forage neutral detergent fiber in total mixed rations of lactating cows

Abstract

The potential of soybean hulls (SH) to replace forage neutral detergent fiber (NDF) in total mixed rations (TMR) of lactating cows was examined. Forty lactating cows were divided into two groups and individually fed ad libitum one of two experimental diets for 8 weeks: (I) a TMR containing 18% forage NDF, corn silage (CS TMR); and (II) a similar TMR in which the corn silage component (16.5% of dry matter, DM) was replaced by SH (SH TMR), containing only 12% forage NDF. Total NDF content was 39 and 36% in the SH TMR and CS TMR, respectively. The SH group tended ( P=0.09) to eat more NDF than the CS group, but DM intake was not influenced. Average milk fat yield was higher ( P=0.04) in the SH group. Findings were supported by the extent of in vitro digestibility data showing higher digestibility ( P<0.05) of organic matter (OM), NDF, hemicellulose and cellulose components in the SH TMR compared to the CS diet. Although the extent of digestibility of OM and fiber components was higher in the SH TMR, than in the CS TMR, milk fatty acid (FA) profiles, including conjugated linoleic acid (CLA), were similar between treatments. NRC (2001) recommendations regarding minimal forage NDF inclusion in TMR of high-producing cows, can be extended to diets containing as low as 12% forage NDF under conditions similar to that of the SH TMR.