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Comparison of efficiency of energy use in Holstein and Jersey dairy cows offered diets containing reduce fat distillers grains RFDDGS
Fifty six energy balances were completed with 8 Holstein (H) and 8 Jersey (J) multiparous lactating cows to examine the effect of breed on the efficiency of milk production and energy use. Two dietary treatments were fed in a repeated switch back design to compare breeds. Dietary treatments consisted of 24.5% corn silage, 18.4% alfalfa hay, 6.9% grass hay, with either 22.9% rolled corn and 14.8% soybean meal or 4.51% rolled corn, 0% SBM, and 14.5% RFDDGS (dry matter basis). Diets were offered ad libitum for a 28 d adaptation period and 95% ad libitum for a 4 d collection period. During the collection days, ration digestibility and energy use was measured, indirect calorimeter respiration head boxes were used to determine heat production. Across the two treatments, Holstein cows had a significantly higher intake of gross energy (GE) (30 ± 3.96 Mcal/d; P=< 0.01), and higher energy output in feces, urine, methane, heat production (HP), and milk energy (6.5 ± 1.24, 0.11 ± 0.11, 1.2 ± 0.15, 8.95 ± 0.74, and 8.54 ± 1.27 Mcal/d, respectively; P= < 0.01) than did Jersey cows. Jersey cows produced milk with higher fat content (4.96% versus 3.69% ± 0.19 for Jersey and Holstein, respectively; P=<0.01), protein (3.75% and 3.20% ± 0.1 for Jersey and Holstein, respectively; P< 0.01), and energy concentrations, compared with those of the Holstein cows. Metabolizable energy (ME) and digestible energy (DE) intake as a proportion of GE intake were significantly higher for Holstein cows (0.03 ± 0.01 and 0.03 ± 0.007, respectively; P =< 0.01 and 0.02). However, breed had no significant effects on ME/DE (0.88 ± .01), HP/ME (0.56 ± .02), DE/DMI (2.78 ± .06), ME/DMI (0.45 ± .06), methane energy/DE (0.08 ± .004), and urine energy/DE (0.04 ± .002). No significant interaction was found between breed and treatment for any of the ratios of energy use examined. In addition, no significant differences in energy partitioning between milk (milk energy/ME intake) (0.40 ± .18), and body tissue (retention energy/ME intake) (0.04 ± .0034) were found between Holstein and Jersey dairy cows. In conclusion, breed had no effect on the overall production efficiency of dairy cows in terms of efficiency of ME use for lactation, and energy partitioning between milk and body tissue.
Keywords: energy efficiency, Holstein, Jersey.