Supplementing cows and heifers on pasture

Dairy Pipeline: August/September 2005

Robert E. James
Extension Dairy Scientist,
Dairy Nutrition
(540) 231-4770 email: jamesre@vt.edu

This year pasture for grazing has been extremely variable. May was very cool, followed by a very dry June. In some regions of the state the drought has persisted, while in others heavy rains have encouraged lush growth. These variable conditions make a "one size fits all recommendation" for pasture supplementation an untenable option for meeting the nutritional needs of growing heifers. Here are five recommendations for the pasture reared dairy heifer.

1. It's not uncommon for grazers in more temperate climates to move heifer calves into pasture systems when they are 3 months old. There are two risks that must be considered. First, heifers should be included in parasite control programs shortly after entering the pasture systems with the advice of your veterinarian. The second risk is of low intake and variable quality. Typically intake is lower on pasture than confinement system rations. This is especially important when demand for nutrients is high. Typically young calves (< 6 months of age) will require continued, significant concentrate intake (5 lb./ head/ day).

2. Inclusion of an ionophore will probably yield as much return as any additive available today. Ionophores are best included in the diet by including them in even a limited amount of a concentrate mixture. Lasalocid (Bovatec) may be fed in free choice mineral supplements, but Monensin (Rumensin) is most successful when included as a component of a concentrate mixture that is fed daily.

3. Nutrient levels of pasture are highly variable in much of the U.S. During the cooler months of the year it's not uncommon for pastures to contain in excess of 16% protein and 70% TDN, which is more than adequate to support excellent rates of growth (>1.8 lb. / day) in older heifers without too much additional supplementation. Vitamins and most minerals are also adequate in high quality pasture. However, during drought and the hotter months of the summer, protein may decline to less than 12% and energy to less than 60% TDN, which is not adequate. During these months supplemental concentrate feeding is necessary.

4. How much concentrate to feed/day? I hear many dairy producers and heifer growers' state that they feed 5 lb. / heifer / day regardless of the pasture quality or availability. If one assumes that a 16% protein mixture cost $175/ton, this could represent an extra $.40/head/day in unnecessary added costs if heifers are consuming a high quality pasture mixture.

5. Most progressive dairy producers or heifer growers have weight tapes or have purchased electronic or mechanical scales to evaluate heifer growth during routine handling procedures such as vaccination, parasite control or breeding. This provides an opportunity to objectively evaluate growth of heifers and make more timely adjustments in supplemental concentrate feeding if growth is outside of the desired ranges of gain. Documented weights can reveal the existence of management or nutritional deficiencies that might go unnoticed if the manager relies solely on the "eyeball method".

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