Performance, carcass and ruminal fermentation characteristics of heifers fed concentrates differing in energy level and cereal type (corn vs. wheat)

A total of 144 beef heifers (218 ± 26.4 kg body weight) were housed in 24 pens (6 animals each) and used in a 168-day feedlot study to evaluate the influence of cereal type and energy level on performance, carcass quality and ruminal fermentation. Four concentrates were formulated according to a 2×2 factorial arrangement of treatments, with two energy levels (1,452 vs. 1,700 kcal net energy/kg) and two main cereals (wheat vs. corn). Concentrate and straw were offered ad libitum. Concentrate intake and body weight were recorded on days 42, 84, 126 and 168. Ruminal fluid was obtained by ruminocentesis from 3 heifers per pen on days 1, 84 and 168; and carcass weight, classification and yield, were determined in the same animals. Heifers fed high-energy diets had lower intake (6.97 vs. 7.29 kg fresh matter/d; p=0.011), and lower concentrate to gain ratio (5.15 vs. 5.66 kg/kg; p=0.002) than those fed low energy concentrates, and tended (p=0.069) to be heavier along the time. Neither carcass yield and classification, nor ruminal pH, volatile fatty acids nor NH3 -N concentrations were affected (p>0.050) by energy level. Total volatile fatty acids concentration tended (p=0.070) to be greater in heifers fed corn-based than wheat-based concentrates. No energy level x cereal type interactions were observed. These results indicate that high energy concentrates decreased feed intake and feed conversion but had minor effects on carcass performance. Cereal type had no effects on performance and ruminal fermentation and no interactions between cereal type and energy were detected