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Evaluation of high-quality alfalfa silage in a high-forage diet for lactating dairy cows.

C. M. Engel



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Evaluation of high-quality alfalfa silage in a high-forage diet for lactating dairy cows.
C. M. Engel*1, D. K. Combs1, K. F. Kalscheur2. 1University of Wisconsin, Madison Madison, WI, 2US Dairy Forage Research Center, USDA-ARS Madison, WI.

High quality forages improve nutrient digestibility, reduce gut fill, and allow greater intake of protein and forage NDF in dairy cow diets. An experiment was conducted to determine how much high-quality alfalfa silage (AS) could be utilized in a high-producing dairy cow diet to replace concentrate feedstuffs without lowering milk production. Forty-eight lactating Holstein cows (24 multiparous, 24 primiparous, 141 � 22 DIM) were randomly assigned to 4 treatments in a randomized complete block design. The experiment had a 2-wk covariate period followed by an 8-wk treatment period. Diets consisted of 40% BMR corn silage, 10% conventional AS and either 0, 6, 12, or 18% AS (0AS, 6AS, 12AS, 18AS, respectively) on a DM basis. Diets were formulated to contain about 30% NDF, 26.4% starch, and 17.4% CP on a DM basis. Animals were housed in a tie-stall barn, milked 3 times a day and fed once daily. Data were analyzed using PROC MIXED of SAS. The model included covariate, treatment, parity, and week as the repeated measure. Increasing high quality AS in the diets linearly decreased DMI (P < 0.05). Because milk production was unaffected (P > 0.10) by diet, feed efficiency (FE = energy-corrected milk/DMI) increased linearly from 1.63 to 1.83 when high quality AS incrementally increased in the diets (Table 1). Milk fat % and yield increased linearly as AS replaced concentrate feedstuffs. Percent and yield of both milk protein and lactose did not differ among the treatments. Milk fat % and yield, lactose %, and FE were greater for primiparous cows than multiparous cows. Substitution of protein and non-forage fiber feedstuffs up to 18% of the diet (DM basis) with high quality AS did not reduce milk production and increased milk fat yield, milk fat % and FE.Table 1.

DMI, kg/d26.326.525.424.90.37L
Milk, kg/d43.743.043.342.60.74NS
Fat, %3.353.763.723.900.07L, C
Protein, %
Lactose, %
1L = linear effect (P < 0.05); Q = quadratic effect (P < 0.05); C = cubic effect (P < 0.05); NS = not significant (P > 0.05).

Keywords: high-quality alfalfa, forage, milk.

Biography: Graduate student at the University of Wisconsin, Madsion, studying ruminant nutrition in the department of dairy science with a Bachelor of Science degree in animal science from Southern Illinois University, Carbondale.