Nutritional evaluation of wheat bran from abrasion milling in backgrounding diets for cattle

Abstract

Two trials were conducted to evaluate the nutritional value of abrasion milled wheat bran (WB). In Trial 1, 312 Angus steers (303 ± 65kg) were randomly assigned to 1 of 24 pens and fed 1 of 6 diets in a 2x3 factorial design. Treatments included 2 levels of condensed liquid whey (CLW) (0 and 4.6%) and 3 levels of WB (0, 14 and 28%). Diet 1 consisted of 31.8% rolled barley, 40.6% brome grass hay, 13.5% barley silage, 7.3% corn/wheat blend DDGS and 6.9% supplement (DM basis). Diet 2 was identical to diet 1 except 4.6% of the barley was replaced with CLW. In the remaining diets, at each level of CLW, WB replaced barley at 14 and 28% (DM basis). No (P>0.05) No influence (P>0.05) of CLW or any WB by CLW interaction was seen on any parameter. Dry matter intake (DMI) was increased (P<0.01) in diets containing WB. Average daily gain was not (P>0.05) affected by WB inclusion, however gain:feed was reduced (P<0.01). Trial 2 used 5 Angus heifers (584 ± 40kg) in a Latin square design to evaluate the effects of WB on rumen fermentation and nutrient digestibility. The control diet consisted of 36% barley silage, 24% grass hay, 8% supplement and 32% rolled barley (DM basis). Wheat bran replaced barley at 8, 16, 24 and 32% of the diet (DM basis). There was no (P>0.05) effect of treatment on DMI, rumen pH, ammonia-N levels or fluid and particulate passage rate. Feeding WB caused a linear increase (p<0.05) in acetate concentration and decreased (P<0.05) DM, OM and GE digestibility in a linear fashion. Digestibility of NDF and ADF decreased (P<0.05) quadratically as WB inclusion increased. Diet digestible energy content tended (P=0.06) to decrease quadratically as WB increased. Digestibility of CP, total nitrogen (N) excretion and urinary N were not affected (P>0.05), but fecal N was increased (P<0.05) in a linear fashion. The results indicate that the energy value of WB is lower than barley grain which leads to decreased feed efficiency and diet digestibility in backgrounding rations, which indicates that inclusion of WB will be price dependent.