Use of Protein Supplements for Dairy Heifers Fed Fresh Grass

¹ Experimental Farm, Agriculture Canada, La Pocatière, PQ, Canada G0R 1Z0
² Ralston Purina, PO Box 250, Woodstock, ON, Canada N4S 7X5

One experiment was conducted to determine the influence of protein supplements on the growth of dairy heifers fed fresh grass. Thirty heifers between 100 and 200 kg of BW were fed fresh grass cut daily either without supplement or supplemented with molasses or low rumen-degradable protein blocks. Protein contents of the two blocks were similar. Heifers were weighed every 4 wk during the 12-wk experiment. The BW gains of protein-supplemented heifers were higher than those of unsupplemented heifers, but DMI of grass was not different among treatments. Average daily BW gains of heifers fed degradable or undegradable sources of protein were similar. Intake of total N was correlated highly with average daily BW gain, suggesting that intake of N could limit performance of dairy heifers between 100 and 200 kg of BW when they are fed fresh grass. The data suggest that light heifers gain more when supplemented with low or high rumen-degradable protein.

Key Words: growth • protein • degradability • heifers

Submitted on June 1, 1992
Accepted on November 3, 1992