Journal of Animal Science

Effect of wheat forage maturity and preservation method on forage chemical composition and performance of growing calves fed mixed diets

P. A. Beck*, C. B. Stewart*, H. C. Gray*, J. L. Smith* and S. A. Gunter**

Abstarc :

Three 2.4-ha wheat (Triticum aestivum L.) fields were used totest the effects of maturity at harvest (boot vs. dough) andpreservation method (hay vs. silage) on forage yield, chemicalcomposition, and animal performance when fed in mixed diets.Forages were incorporated into 4 diets in a 2 x 2 factorialarrangement of treatments with hominy feed, soybean hulls, andcottonseed meal as the primary concentrate ingredients. In Exp.1 diets contained 20% wheat forage (DM basis) and were fed to96 beef calves (n = 48 steers and 48 heifers; initial BW 229± 6.0 kg) in 12 mixed-sex pens. In Exp. 2 diets contained40% wheat forage (DM basis) and were fed to beef steers (n =48; initial BW 198 ± 6.8 kg) in 12 pens. These dietswere also individually fed to 32 calves (Exp. 1, n = 16, BW= 187 ± 9.4 kg; Exp. 2, n = 16 calves, BW = 160 ±8.2 kg) to determine DM and NDF digestibility and gastrointestinaltract passage kinetics. Advanced maturity increased (P <0.01) DM yield, decreased (P < 0.01) CP concentrations, andtended (P = 0.10) to increase nonfiber carbohydrate concentrations,but did not affect (P >=0.22) NDF, ADF, or TDN concentrations.Maturity at harvest, preservation method, or their interactiondid not affect (P >=0.15) ADG when wheat forage was fed as 20or 40% of the diet. When calves were fed the 40% wheat foragediets, maturity at harvest did not affect (P >=0.27) DMI or G:F.Calves fed 40% hay diets consumed more (P = 0.04) feed DM asa percentage of BW than calves fed silage diets, but tended(P = 0.09) to be less efficient. With 20 or 40% wheat foragediets, there were no differences (P >=0.13) in passage rate,ruminal retention time, or fecal output due to maturity or preservationmethod. Digestibility of DM tended (P = 0.07) to be greaterfor silage than hay diets when fed in 20% wheat forage diets.Dry matter and NDF digestibility of 40% boot-stage wheat foragediets were greater (P < 0.01) than diets containing forageharvested in dough stage. Forty percent hay diets also tended(P = 0.07) to have greater DM digestibility, and NDF digestibilitywas greater (P < 0.01) compared with silage diets. Althoughdifferences in performance were not noted in the present experiments,increased maturity at harvest and preservation as silage cancause differences in DMI and digestibility of DM and NDF indiets containing 40% wheat forage.

Key Word :
cattle, forage quality, hay, silage, Triticum aestivum L

Volume 87, Number 12, December 2009