Effect of supplemental energy source and frequency on growing calf performance.

Crossbred heifers (n = 120; 265 kg, SD = 37) were fed individually (84 d) to determine the effect of supplement type, concentration, and frequency on intake and performance and to estimate the energy value of dry distillers grains plus solubles (DDGS) in a high-forage diet. Treatments were arranged in a 3 x 2 x 2 factorial, with 3 supplements, 2 concentrations, and 2 frequencies of supplementation. Supplements including dry-rolled corn (DRC), DRC with corn gluten meal (DRC + CGM), and DDGS were fed at 0.21% (LOW) or 0.81% (HIGH) of BW daily and were provided daily (DAILY) or 3 times weekly (ALT). Heifers were fed to consume grass hay (8.7% CP) ad libitum. Individual DMI, diet composition, BW, and ADG were used to calculate energy values for DDGS and DRC. Supplement type, concentration, frequency, and interactions were tested using the MIXED procedure of SAS, with BW included as a covariate. Supplement x concentration interactions for gain (P = 0.01) and G:F (P < 0.01) were detected. At the LOW concentration, heifers supplemented with DDGS gained more and were more efficient (P </= 0.03) than those supplemented with DRC or DRC + CGM. No performance differences were observed (P >/= 0.22) between DDGS and DRC + CGM in HIGH treatments, although both improved (P </= 0.01) gain and G:F relative to DRC. Calculated TDN content of DDGS was 18 to 30% greater than DRC. Gain and G:F were improved (P < 0.01) in heifers fed HIGH vs. LOW. Total intake was greater (P < 0.01) for HIGH than LOW, but LOW heifers consumed more hay (P < 0.01) than HIGH. The DAILY heifers consumed more (P < 0.01) hay and total DM than the ALT heifers. The DAILY heifers gained more (P < 0.01) than ALT, but G:F was not affected (P = 0.85) by supplementation frequency. In a high-forage diet, DDGS has greater energy value than corn.