Simple SummaryThe decision to provide energy and protein sources to beef cows, offering low- or medium-quality forages, is critical to producers in terms of economics and animal production, particularly during gestation and lactation stages. While corn has been the predominant energy supplement, co-products of corn have increasingly been incorporated as energy supplements in forage-based diets because of lower cost. The objective of this study was to determine the effect of level of hominy feed supplementation on intake, digestibility, ruminal fermentation characteristics, and in situ dry matter disappearance of bermudagrass hay in lactating beef cows. Treatments were low hominy feed fed at 0.25% of body weight, medium hominy feed fed at 0.50% of body weight, low ground corn fed at 0.25% of body weight, medium ground corn fed at 0.50% of body weight, and no supplement (control). Hay dry-matter intake was not affected by supplementation and total dry-matter intake was greater with medium rates of supplementation. Supplementation did not affect ruminal parameters and did not affect dry matter disappearance of forages. Therefore, hominy feed can be used as an alternative feed to corn as an energy supplement without causing negative effects on measurements that are potential indicators of animal performance.AbstractHominy feed (HF) has been evaluated in feedlot and dairy rations but has not been evaluated as a supplemental energy source for lactating beef cows. The objective of this study was to determine the effect of level of HF supplementation on intake, digestibility, ruminal fermentation characteristics, and in situ dry matter (DM) disappearance of bermudagrass hay. Five ruminally cannulated lactating beef cows (body weight (BW) = 596 kg, SE = 13.9) were used in an experiment with a 5 × 5 Latin square design. Treatments were a bermudagrass hay-basal diet with low HF (LH; 0.25% BW), medium HF (MH; 0.50% BW), low ground corn (LC; 0.25% BW), medium ground corn (MC; 0.50% BW) and no supplement (CON). Cows were housed individually, and supplements were offered at 0800 daily. Hay was offered to maintain 10% refusal. Periods were 16–d, with 10 d for adaptation. Ruminal fluid was sampled on d 14 of each period for measurement of pH, volatile fatty acids, and rumen ammonia-N. An in situ degradation experiment for bermudagrass hay was completed for each diet. Hay dry-matter intake (DMI % BW) was not affected (p= 0.14) by supplement, but total DMI (DMI % BW) was greater (p≤ 0.05) in MH and MC compared to LH and CON. Digestible DMI % BW was greater (p= 0.05) in MH compared to LC, MC was intermediate, and LH and CON were lesser (p≤ 0.01) than all other diets. Dry-matter fill, passage rate, and retention time did not differ by diet (p≥ 0.31). A diet × time interaction was observed for ammonia-N (p= 0.0002), and propionate (p= 0.02) time effects were observed for other parameters, but no diet effects. Bermudagrass hay’s potentially degradable fraction was greater (p≤ 0.05) in LH than MH and CON, but effective DM degradability was not different (p= 0.39) among diets. Overall, no diets reduced hay intake or disappearance compared to CON; therefore, no negative associative effects were observed from any of the supplements at the levels offered in this study.