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Supplementation for the grazing cow

Brad Heins
Assistant Professor - Organic dairy production
December 7, 2013

The challenge of managing a grazing system for dairy cattle is quite different than managing a confinement dairy. Currently, some grazing producers are moving towards 100% pasture because of increased feed costs, their personal philosophy to use less grain, or they may have a specific market demand for grass-fed products. We recently completed a study to develop practical strategies for organic dairy producers to enhance the profitability of their farm by evaluating organic grain supplementation levels and its effect on economics of organic dairy cows. I am presenting the first year results of a 2-year study in this article.

Organic dairy cows at the University of Minnesota's West Central Research and Outreach Center, Morris, MN, that calved during fall 2011 and spring 2012 calving seasons were used to evaluate production, reproduction, and grazing behavior of organic dairy cattle supplemented with three levels (no grain, low, and high) of organic grain. During the 2012 grazing season, 96 lactating Holstein and crossbred organic dairy cattle were assigned to a grain supplementation treatment (no grain, low grain, and high grain). Cows were fed the following dietary supplementation levels, 1) 'No grain" (100% pasture), 2) low grain (6 lb of grain supplementation per day), or 3) high grain (12 lb per day). Supplement was fed with a total mixed ration of an organic grain mix (corn and minerals). The TMR was 25 lb of organic corn silage, 20 lb of organic alfalfa silage, and 1.25 lb of organic minerals. Furthermore, at least 30% of their diet consisted of high-quality organic pasture during the grazing season. Supplemented cows were fed TMR in a compost barn after the morning milking and were allowed to graze during the afternoon and evening. The no grain cows were continually on pasture except during milking.

The no grain cows had lower milk, fat, and protein production than the low and high grain cows (see accompanying table). Surprisingly, there were no differences in production between the two supplemented groups of organic cows for milk production, but the high grain cows may have been partitioning the extra grain into body condition. As expected, the no grain cows had higher milk urea nitrogen than the low and high grain cows.

Across the grazing season, there were no differences for body weight for organic cows. For BCS across the grazing season, the no grain cows had lower body condition scores than the low and high grain cows. Potentially, the low and high grain cows in this study devoted more of the energy they consumed to maintain and restore BCS compared to the no grain cows and this, in turn, may have resulted in the enhanced reproductive cyclicity of the low and high grain cows.

Table 1. Supplementation results for cows fed no grain compared to higher levels of grain.

Measurement No grain Low grain High grain
Milk (lb) 32.2 40.4* 39.4*
Fat (lb) 1.23 1.53* 1.33
Fat (%) 3.82 3.78 3.38*
Protein (lb) 1.03 1.31* 1.26*
Protein (%) 3.20 3.24 3.20
Milk urea nitrogen (mg/dl) 14.25 10.06* 7.33*
Energy-corrected milk (lb) 32.2 37.2* 36.3*
Body weight (lb) 1,079 1.080 1,089
Body condition score 2.98 3.09 3.15*
TMR cost ($/cow/day) 0.0 3.18* 4.21*
Pasture cost ($/cow/day) 1.02 0.87* 0.86*
Production revenue ($/cow/day) 5.02 6.35* 5.53*
Income over feed cost ($/cow/day) 3.61 2.20* 0.38*
* = differences for low- and high-grain cows are significantly higher or lower compared to the no grain cows.

Total mixed ration costs were lower ($0.00 vs $3.18 vs $4.21), pasture costs were higher ($1.02 vs $0.86 vs $0.87), and production revenue from milk was lower ($5.02 vs $6.35 vs $5.53) for no grain, low grain, and high grain cows, respectively. Income over feeds costs ($/cow/day) was higher for the no grain and low grain cows. For profitability, grain costs were substantially higher for the high grain cows, and therefore, resulted in a reduced income over feed cost for high grain cows.

Pasture can be a cost effective source of feed and housing for dairy animals. During the first year of our organic grain supplementation project, cows that consumed 100% pasture had lower milk production, lower body condition scores, but higher income over feed cost. This information can be significant to organic dairy producers, as well as conventional producers, who are looking to reduce input costs during high grain prices. Producers who have a handle on their feed costs in an organic dairy production system can make informed decisions that reduce financial loss. The most important point for reducing inputs and increasing profits in organic dairy systems is to produce high quality forages and maximize dry matter intake on pasture.

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