Utilization of ensiled corn crop residues by Holstein heifers

Corn crop residues were harvested 1 to 2 d after harvest of high moisture corn. Half the harvested residues were treated with an aqueous solution of ammonia before ensiling to give 34 g of ammonia/kg of residue DM. The untreated half was the control silage. Both silages were ensiled in bunker silos. More residues were harvested 2.5 wk later from the same field and combined with Brassica napus L. before ensiling in a bag, and this constituted the third forage treatment. Three diets containing 48.8, 46.5, and 63.8% residue silage (DM basis), with the latter containing corn crop residue and brassica in a 3:1 ratio, were designated as control, ammoniated, and brassica, respectively. The other ingredients of the diet were alfalfa silage, cracked corn, and urea. The diets were fed to Holstein heifers averaging 186 kg (light BW) and 372 kg (heavy BW). Weight gains were similar at 84 d for heifers fed the control and the ammoniated residue diets. Light and heavy heifers gained 619 and 631 g/d with the control diet and 678 and 631 g/d with the ammoniated residue diets. At 70 d, the heavy heifers fed control, ammoniated, and brassica diets had weight gains of 629, 671, and 786 g/d, respectively. Digestion coefficients were similar between the control and ammoniated residue diets: DM (62.6 and 58.7%), NDF (56.7 and 56.2%), and ADF (56.3 and 55.8%). Ammonia treatment of corn crop residue silage had no effect on animal performance or digestibility. Brassica appeared to improve animal performance when it was mixed with corn crop residue silage.