Physical Form and Composition of Hay on Lactation, Rumen Development and Digestibility

Twenty-four lactating first-calf heifers were fed in dry lot for 126 days on various treatments of Coastal bermudagrass hay (ad libitum) supplemented with defluorinated phosphate and trace mineralized salt. The treatments were: hay fertilized with 100 lb. nitrogen per acre and fed in long form (100N-L); hay fertilized with 200 lb. nitrogen per acre and fed in long form (200N-L) and finely ground form (200N-G). Digestion trials were conducted on these hays plus 200N-G hay in ⅜-in. pellets (200N-P). Lactating cows fed these hays had average weight losses of 0.6 to 0.7 lb per day; however, calves nursing these cows gained from 0.7 to 1.0 lb. per day. Lactating cows fed hay ground through a ¼ in. mesh screen (200N-G) lost less weight, produced heavier calves and consumed slightly more dry matter than cows fed long hay (200N-L). Although not statistically significant, rumen total volatile fatty acid concentrations were higher for ground than long hay. A narrower acetic to propionic acid ratio was observed with ground hay. Moisture and fat-free epithelium per 100 lb. empty body weight was heaviest in cows fed ground hay. Digestion trials with steers and wethers showed higher digestibility of protein (P<.01) for 200N-L over 100N-L hay and 200N-L over 200N-P hay (P<.05). Crude fiber digestibility was lower (P<.01) in ground and pelleted hays but N-free extract and ether extract digestion coefficients were higher (P<.01).