Supplementing grazing dairy cows: economics

Grazing cows
December 5, 2016

By Tamara Scully  Originally appeared in Country Folks

Grazing cows is a requirement for organic milk producers. Organic milk must come from cows that receive no less than 30 percent of their dry matter intake (DMI) from pasture forage during the grazing season, and are actively grazing on pasture for at least 120 days, or as long as possible in the region. Feeding grain is allowed.

Certified organic grain has become increasingly expensive, however, and little research is available on the results of grain supplementation levels and the subsequent impacts on the economics of milk production. Grain supplementation may also impact pest control management decisions. Fly concerns may be influenced by any feed supplementation.

Dr. Bradley Heins, West Central Research and Outreach Center, and Department of Animal Science, University of Minnesota, recently presented his research findings on the effects of various levels of organic grain supplementation in a certified organic grazing dairy herd. Heins’ presentation “Production, Economics, and Pest Management Strategies of Organic Grain Supplementation for Organic Dairy Cows” was offered during the recent Penn State Dairy Nutrition Workshop.

“If you don’t have enough feed, you will have to buy it and that may become very expensive,” Heins said in a follow-up interview. “For 100-percent grazing producers, you would need enough land to grow the grass and store it as silage or baleage for the winter. Producers need to make sure they have enough feed produced for all kinds of grazing dairies.”

By looking at the various implications of several levels of grain supplementation in comparison to 100-percent grass-fed herds, Heins’s objective was to offer producers practical strategies for enhancing dairy profitability.

Trial Design

Cows were divided into three groups, and provided either no, low or high levels of organic grain supplementation to complement their pasture grazing. The low supplementation cows received six pounds of grain per day, while the high group received double that amount. Grain was supplements via a total mixed ration (TMR) consisting of corn silage, alfalfa silage and a corn-grain mixture with minerals.

The herds were a mix of pure Holsteins, along with cross breeds of Jersey, Normande, Holstein, Montbeliarde, and Scandinavian Red. All except the Holsteins are known for grazing abilities. The groups were controlled for breed, lactation number, and previous lactation milk production.

Cows received any TMR in the barn after being milked each morning, and then allowed to graze on pasture each afternoon and evening. The 100-percent grass-fed cows remained on pasture except during milking times.

The groups grazed next to each other in the same pasture, and measurements of pasture composition were taken. Records of all feed consumption were kept. Animal behavior was monitored via neck tags, recording rumination and activity levels. Dung from the pastures was analyzed for insect levels.


All groups of cows maintained body weight across the grazing season. The all-grass group did experience some loss of body weight during the last two weeks of the grazing season, in September, due to lack of quality pasture. Pasture forages at this time had low digestibility (NDFD), and therefore cows could not consume enough quality DMI at this time, losing body condition score.

High supplementation cows had higher body condition scores than did lower supplementation cows, but milk production remained the same between high and low groups, and milk composition showed no differences. Heins has suggested that high supplementation cows were diverting energy into body condition.

Overall the 100-percent grass-fed cows had lower milk outputs. This group also had milk higher in beneficial fatty acids. The fatty acid profiles of 100-percent grass-fed milk were conducive to human health benefits. Because this group had no supplemental feed costs, and the price of organic corn was relatively high, profitability was greatest for 100-percent grass-fed cows despite the decrease in milk production.

The 100-percent grass-fed cows also consumed the most pasture, and had higher rumination levels. They remained active during the hottest parts of the day, and were active during all months of the study, which ran from June through September. Researchers had expected that these cows would rest during the hottest part of the day, and graze at night, which did not occur. Instead, the grass-fed cows were active during the day, and ruminated at night, as were the other two groups.

Activity rates for the grazing cows were slightly higher, and the high supplementation cows slightly lower, than the low supplementation group. Cows with the highest level of supplementation grazed the least, as expected, and had lower activity and rumination rates than cows in the low supplementation group. Within each group, activity and ruminations levels varied month to month, possibly due to weather, feed availability and insect pressures.

Heins suggests that activity monitoring could assist farmers in detecting health events or heat faster in grazing herds, increasing profitability on pasture through precision monitoring.

Fly Control

High supplementation cows had dung samples with larger amounts of horn, face and non-pest flies. The differences were not statistically significant. Non-pest flies cause no harm, but do aid in recycling the dung. Dung beetles did not seem to be impacted by feed changes.

Increased dung quality, leading to an increase in available nutrients for the face flies, is thought to be a reason for the higher number of flies present. Adding six pounds of grain to the diet allowed more face flies to survive in comparison to 100-percent grass. Fly increases were less significant when increasing from six to 12 pounds of grain. The adding of small amounts of grain to a grass-based diet is thought to cause changes involving nitrogen content and bacterial populations of the dung.


Cows on a 100-percent grass-fed diet had the highest income over feed costs (IOFC). As grain prices change, the IOFC for the low and high supplement groups would change, however, so the overall costs benefits of 100-percent grass would differ. Researchers hypothesized that a low supplementation level of grains in an organic dairy herd may be a manner of keeping feed costs down without sacrificing overall profit.

“Producers who have a handle on their feed costs in an organic dairy production system can make informed decisions that reduce financial lost,” Heins concluded in his report. “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.”

Activity monitoring can assist farmers with detecting health issues faster in grazing herds