Daily variations of forage allowance, effects on milk production and quality

Objective. To determine the effects of daily forage allowance variations on production and milk quality. Materials and methods. This study took place in five commercial farms and included two periods of observation. The daily forage intake was estimated through agronomic difference, measuring the daily area of allowance with a GPS and using the Doubled Sampling Technique to estimate biomass yield and the remaining herbage after pasture defoliation. Variations for each parameter were estimated within and between farms in order to determine its magnitude, relationships between daily herbage allowance and forage intake, and its influence on milk yield and composition during both periods of observation. Results. There was an association between daily herbage allowance and variation on daily forage intake (r2=0.65) as for variation on daily milk yield (r2=0.45). Daily variation on milk fat showed no direct relationship with daily herbage allowance, but its values were associated with forage to supplement ratio (r2=0.52). Relation between daily variation of milk protein and daily herbage allowance was low (r2=0.17), but higher between protein concentration and forage dry matter intake (r2=0.34). Conclusions. The results suggest that variation on daily herbage allowance explained largely the variations on dry matter intake, leading to a direct effect on milk yield, but explain little the variations on milk fat and milk protein.