The effect of sward type and fertilizer rate on milk production of spring calving, grazing dairy cows

Abstract

International audienceGrazed grass is considered the cheapest feed available for dairy cows in temperate regions. The objective of this study was to quantify the effect of sward type (perennial ryegrass (Lolium perenne L.; PRG)) sown with and without white clover (Trifolium repens L.; WC) and nitrogen (N) fertilizer rate (150 and 250 kg N ha-1) on milk production of grazing dairy cows. 120 cows were randomly divided to each of the four grazing treatments (PRG-only receiving either 150 or 250 kg N ha-1 and PRG-WC receiving either 150 or 250 kg N ha-1) as they calved, and swards were rotationally grazed at stocking rate of 2.75 cows ha-1. There was a significant effect of sward type on milk production (P>0.001). Over the three-year study, cows grazing the PRG-WC treatments had greater milk yield (+222 kg) and milk solids (kg fat + protein) yield (+27 kg) than cows grazing the PRG-only treatments. Nitrogen fertilizer rate did not affect milk production but did affect herbage production. This significant increase in milk production suggests the inclusion of white clover in grazing systems can be used effectively to increase milk production and reduce nitrogen use