The Utilization of Molasses and Urea in the Rations of Growing Dairy Cattle

Abstract

Growth studies have been conducted with 80 dairy heifers over a 2-year period to determine the value of molasses when fed at high levels of supplementation and to study more adequately the utilization of urea with molasses as the source of carbohydrate supplement when fed with low quality hay to growing dairy animals. Digestion and balance studies were also conducted with eight bull calves in two replicates of a 4 × 4 Latin square design. All the animals with one exception were fed about as much low-quality mixed hay, predominantly timothy, as they would consume, and this was supplemented as follows: Ration 1, molasses and urea; Ration 2, corn and soybean oil meal; Ration 3, molasses and soybean oil meal; Ration 4, molasses, corn and urea. In every trial but one, the animals that received the soybean oil meal rations with either corn or molasses gained significantly more than the urea-supplemented animals. Molasses apparently was not an adequate carbohydrate for the utilization of urea by the rumen microflora when fed with little or no starchy carbohydrate. When a small amount of corn was fed with urea and molasses, an increase in daily gain was noted which was not statistically significant. The nitrogen balance data have shown that adequate synthesis of protein from urea did not occur in these rations. Molasses and soybean oil meal did not produce as rapid gains as did corn and soybean oil meal. This may be attributed to the low digestibility of the protein in the molasses rations which were carefully adjusted to supply adequate, but no surplus, protein for a normal ration. Molasses also depressed the digestibility of dry matter, organic matter, ether extract, and crude fiber. When good quality legume hay replaced the poor quality timothy hay in a molasses-urea ration, excellent gains were obtained, showing that high levels of molasses can produce satisfactory gains when sufficient or excess protein supplied by the hay is available. © 1954, American Dairy Science Association. All rights reserved.