For Grazing Dairy Cattle & Other Ruminants
Fay Benson 1 and Melanie Soberon 2
Feeding Recommendations:

Sulfur-containing volatiles and glucosinates derived from Brassica plants may contribute negatively to the flavor and odor of milk and meat of animals grazing Brassicas.
Therefore, it is advisable for lactating cattle to graze Brassicas immediately after milking to allow at least 4 hours to pass between Brassica consumption and the subsequent milking. To avoid milk taint, it is also recommended that the Brassica crop not constitute more than one third of the animals’ diet throughout the day. Meat animals should be removed from a Brassica crop 3-7 days prior to slaughter to minimize the risk of tainting the meat.

It is important to graze only mature Brassica crops as various health problems are associated with cattle grazing immature Brassica plants. Check with your seed distributor to determine the expected time after planting for a specific Brassica crop to reach expected maturity.

Introduce cattle to the crop slowly over an adjustment period of 1-2 weeks to allow rumen microbes to adjust to the change in diet. This can be done by restricting grazing to
1-2 hours per day and slowly increasing to unrestricted access over 7-10 days. Strip grazing with an electric fence can be used to restrict grazing during the adjustment period, while also encouraging uniform utilization and reducing trampling.

Strip Grazing is also recommended after the animals have adjusted to the Brassicas to insure efficient use of the plants. If the Brassica is designed for multiple grazing, be sure to remove the animals from them so as not to damage the regrowth portion of the plants.

Due to the low fiber content of Brassicas, it is recommended to provide additional roughage. During adjustment periods, it is best to offer additional roughage prior to the grazing of Brassicas to reduce the likelihood of problems associated with overeating.

When estimating the nutrient availability in Brassica crops, their high nutritional value must be considered o 1.22-1.52 MegaCalories Metabolizable Energy/lb Dry Matter o 15-25% protein in leaves, 9-16% in turnips and swede bulbs

Reported livestock weight gains while grazing Brassicas o 0.33-0.55 lb/head/day for lambs o 1.76-2.64 lb/d for growing cattle
1

Associated Animal Health Problems and their Treatments/Preventions

Brassica Poisoning o Glucosinolates and sulfur-containing amino acids in Brassicacae plants can cause signs of poisoning ranging from goiter, hyperthyroidism, blindness, diarrhea, redcolored urine, hemolytic anemia and pulmonary emphysema o These compounds are found in highest concentration in young plants and in the seeds o Rehydrating severely affected animals with large volumes of oral fluids and providing a good quality grass/alfalfa hay is beneficial in treating animals with
Brassica poisoning o Most health problems associated with Brassicas can be prevented by grazing plants at their maturity and allowing proper adjustment periods when transitioning into Brassica crops. In addition, waiting to graze until after a hard freeze can markedly reduce the risk of acute pulmonary emphysema.

Choking o Although rare, it is possible for a cow to choke on a turnip bulb. One can reduce choking by using slightly lighter sowing rates so the bulbs can grow larger and aren’t as likely to be swallowed whole.
The following sources were used in developing this fact sheet.
Ayres, L. and B. Clements. 2002. Forage brassicas – quality crops for livestock production.
Agfacts NSW Agriculture, The State of New South Wales.
Knight, A.P. and R.G. Walter. 2003. Plants affecting the blood: a guide to plant poisoning of animals in North America. Teton NewMedia, Jackson, WY.
For more Brassica information go to the Organic Dairy Initiative Website: http://www.organic.cornell.edu/cals/cuaes/organic/projects/dairy/dairy-initiative/index.cfm
1 Cornell Cooperative Extension-Cortland County Small Dairy Extension Support Specialist
2 Grad-Student Cornell University Animal Science
This project was funded by: “Towards Sustainable Farming Foundation,” And
2