Effect of Concentrate Level on Milk Production of Cattle Grazing High-Quality Pasture

Abstract

Over a six-year period milking cows grazed on pasture as a source of forage were given various levels of concentrates to determine effect on milk production. Several experimental designs were used. A 3 × 3 Latin-square design replicated three times was used in the first two years (modified between first and second years), after which continuous comparisons were made. In most instances the cows were past the peak of milk flow when comparisons started. In a limited way cows in full milk flow were tested for effects of variation in concentrate intake.While milk production was significantly affected by level of concentrate feeding in the first two trials, it would be very misleading to use mean values for economic analysis. The changes in milk production caused by increasing concentrate feeding levels over a given range were quite different in magnitude from results of decreasing levels. Furthermore, both responses, i.e., increases or decreases, were affected by how adequately the cow was meeting energy requirements at the time the change was made and her responsiveness to change. The changeover designs used the first two years were completely inadequate to derive data for meaningful economical analysis relating milk production to feeding levels.Results of continuous comparisons of different levels of concentrate intake indicated that most Holstein cows producing close to 23kg milk daily could be supported by good pasture alone. There were indications that high production (>23kg daily) would decline unless concentrates were provided. Higher levels of production appear to need supplementation with concentrates.