Day-to-day variation in forage and mixed diets in commercial dairy farms in New York

Abstract

We evaluated variation in sampling and analysis of forages and quantified day-to-day variation in silages and TMR in typical New York dairy farms. Alfalfa-grass haylage and corn silage samples were collected daily from 7 dairies, for a total of 24 wk for haylage, 22 wk for corn silage, and 16 wk for TMR samples. Multiple samples also were collected at 4 dairies to evaluate both sampling and subsampling variation. Based on SD, sampling for DM varied from actual DM by up to ±2 percentage units. Haylage was more variable than corn silage, likely due in part to variability of grass percentage within fields. The most practical parameter to measure for daily rebalancing of rations is DM, and DM had considerable day-to-day variability for haylage, with less variability for corn silage and TMR. Assuming a 7 percentage-unit threshold for a weekly range in DM is great enough to benefit from daily rebalancing, this threshold was exceeded 14% of weeks for corn silage, 25% of weeks for TMR, and 42% of weeks for haylage. A better understanding of day-to-day variability will help determine the accuracy required for on-farm silage moisture determinations. Nutrient composition of fed rations differs from formulated rations due to day-to-day variation in DM concentration and nutrient composition of forages. Although providing excess feed likely will mitigate the effects of day-to-day silage variability, it not only increases feed costs but also is less environmentally acceptable.