Dairy Pipeline: May 2003
Charles C. Stallings
Extension Dairy Scientist, Nutrition
A review of published literature in the January 2003 Journal of Dairy Science (Volume 86:1-42) by researchers from Penn State University and New Zealand presented some interesting observations. They state that low dry matter intake of pasture fed, high producing dairy cows limits milk production and is a function of grazing time, biting rate, and bite mass. Supplementing concentrate reduced grazing time 5 _ minutes/day per pound of concentrate fed but did not affect biting rate or bite mass. The lower the substitution of concentrate for pasture the higher the response in milk, indicating you get more bang for your buck at lower inclusion rates. Overall the response of milk was one pound per one pound of concentrate supplemented. Compared with pasture only diets increasing the amount of concentrate up to 22 pounds/cow/day increased dry matter intake 24%, milk production 22%, and milk protein 4%, but reduced milk fat 6%. Feeding more rumen resistant protein sources did not consistently affect milk, perhaps indicating the high concentration of protein in pasture overcomes the fact it is highly rumen degradable. Fat supplementation increased milk by 6% without affecting milk protein or fat percent, indicating fat is desirable for high producing cows on pasture. Using high moisture corn, steam flaked corn, or barley in place of dry corn did not affect milk production or composition but did change some digestion characteristics. This excellent review gives us some idea what to expect when feeding pasture to high producing dairy cows. Concentrate supplementation is warranted but perhaps at a lower rate than with confinement fed cows. Rumen resistant protein sources can be used but milk production response may be limited. Fat supplementation is warranted to supply higher energy levels but the type of grain used might not be critical. Pasture certainly can be used successfully with high producing dairy cows when included in a comprehensive management program accommodating plant agronomic and animal nutrition concepts.