Digestibility by Dairy Cows of Monosaccharide Constituents in Total Mixed Rations Containing Citrus Pulp

Abstract

Ten lactating cows were divided into two groups and individually fed ad libitum one of two experimental total mixed rations (TMR) as follows: 1) a TMR containing 20% corn grain and 10% dry citrus pulp (high corn); and 2) a TMR containing 21% citrus pulp and 9% corn grain (high citrus pulp). Both TMR also contained corn silage (28%), legume haylage (19.5%), extruded full fat soybeans (13.5 to 14%), soybean meal (6.5%), and minerals and vitamins. Voluntary dry matter intake of cows consuming the high corn ration tended to be higher than for cows in the high citrus pulp group (22.2 vs. 20.7±1.0 kg/cow per day, respectively). Digestibility of NDF was higher for the TMR with high citrus pulp compared with the TMR with higher corn. Across treatments, neutral detergent fiber (NDF) glucose was more digestible than NDF xylose and uronic acids and less digestible than NDF arabinose, galactose, and mannose. Digestibility of total neutral detergent soluble carbohydrates was also higher in the high citrus pulp group (86.8, high citrus pulp vs. 80.3±1.7%, high corn); with glucose and uronic acids accounting for most of that difference. Consequently, higher total carbohydrate digestibility was obtained in the TMR containing higher citrus pulp compared with the TMR with a higher percentage of corn (77.1 and 72.5±1.0%, respectively). Slightly lower carbohydrate intake in cows fed higher citrus pulp was compensated by higher digestibility of carbohydrates and protein. Thereby, partial replacement of corn by citrus pulp in TMR of high producing dairy cows improved feed efficiency.