Digestibility, Mineral Balance, and Rumen Fermentation by Steers of Rations Containing Large Amounts of Lactose or Dried Whey

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Abstract
Nine Holstein steers in 3 ration groups were in a series of 5 digestion trials during 10 wk to measure digestibilities of rations containing lactose fed as either lactose or dried whole whey. All steers received a control ration of corn, soybean meal and corn silage during period 1. Three steers also received the control ration during periods 2-5. Steers fed lactose received 10, 20, 30 and 40% of their dry matter as lactose during periods 2-5, respectively. Steers fed dried whole whey received the same amount of lactose as the lactose-fed steers but from dried whole whey (15, 30, 45 and 60% dried whole whey) during periods 2-5. Digestibilities of energy and dry matter were highest for the dried whey rations and lowest for the control ration. Within the dried whey rations, 15% dried whey was most digestible. Digestibility of ration fiber was similar for all groups. Dry matter content of feces was reduced when rations contained 30% or more lactose as lactose or dried whey. Urine output increased slightly with increasing amounts of lactose fed as lactose but increased nearly 300% when steers were fed 45 and 60% dried whey because of the high salt intake. Ca and P absorption and retention were not affected by lactose or dried whey. Molar percentages of butyrate increased and propionate decreased in rumen contents of steers fed lactose or dried whey. Rumen NH3 tended to be lowest in steers fed dried whey rations. Steers can be fed large amounts of lactose or dried whole whey without adversely affecting ration digestibility or animal health.
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