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Title: Comparison of Alfalfa and Orchardgrass Hay as Replacements for Grain in Lactating Dairy Cow Diets

Author
item Jung, Hans Joachim
item RAETH-KNIGHT, M - University Of Minnesota
item LINN, J - University Of Minnesota
item PETERSON, PAUL - University Of Minnesota

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2010
Publication Date: 1/26/2010
Citation: Jung, H.G., Raeth-Knight, M.L., Linn, J.G., Peterson, P.R. 2010. Comparison of Alfalfa and Orchardgrass Hay as Replacements for Grain in Lactating Dairy Cow Diets [abstract]. Midwest Forage Association Annual Meeting, January 25-27, 2010, Wisconsin Dells, Wisconsin. CDROM.

Interpretive Summary:

Technical Abstract: While alfalfa has been the predominant perennial forage fed to dairy cows in the Midwest, there has been recent interest to increase use of perennial grasses. This interest is because alfalfa can be expensive to produce (short stand life), the perception that manure cannot be applied to alfalfa, and the belief that grass fiber digestibility is better. High corn grain price has also contributed to an interest in the ability of forages to support economical milk production. When forage replaces grain, the largest impact is replacement of starch with fiber. We conducted a study to compare the ability of fiber in alfalfa and orchardgrass hays to replace corn grain in a total mixed ration (TMR) that included 35% corn silage as the base ingredient. Five inclusion levels of alfalfa (15, 20, 25, 30, and 35% of the TMR) and orchardgrass (10, 15, 20, 25, and 30% of the TMR) were tested. Inclusion levels were off-set in range because of the differences in fiber (NDF) concentration of the alfalfa (41% NDF) and orchardgrass (60% NDF). Fifty cows (five cows/treatment) were allotted to the 10 treatments based on sire breed (Holstein, Montbeliarde, and Jersey) and days in milk (average 86 days). All cows began the experiment simultaneously and the experiment lasted 8 weeks. Feed intake, feed refusal, and milk production were recorded daily, and milk composition was determined weekly. During weeks four and eight, cow activity (eating, ruminating, and resting) was monitored every 15 minutes for 24 hours and fecal grab samples were collected for determination of in vivo TMR digestibility. In vitro rumen NDF digestibility (IVNDFD) was determined on alfalfa, orchardgrass, corn silage, and TMR samples collected during the experiment. Sample and data analysis for the experiment are not yet complete; therefore, this report is preliminary and conclusions may change as more data are acquired. Rate of IVNDFD was equal (4.6 vs. 5.2%/hr) and extent of IVNDFD was greater (79 vs. 56%) for orchardgrass compared to alfalfa. Although there was a general trend towards both reduced feed intake and milk production with increasing forage in the TMR, feed intake and milk production were not correlated. On average, milk production was similar with the two forages and declined with increasing forage inclusion rate. Milk fat (3.8%) and protein (3.0%) did not differ among the diets. Because NDF from corn silage was held constant, the percentage of TMR NDF that was contributed by the hays was a better predictor of milk production than overall NDF of the TMR. The alfalfa and orchardgrass hays appeared to support similar levels of milk production from their fiber; however, additional experiments should be conducted with other hay lots before concluding that alfalfa and orchardgrass fiber are equivalent for milk production.