AN ESTIMATION OF THE VARIABILITY IN THE COMPOSITION OF ORTS FROM FEEDING TRIALS WITH LACTATING COWS

Abstract

A total of 320 samples of feed refusals (orts) were obtained from 16 cows fed four different forage mixtures. These samples of orts were analyzed for dry matter, protein, acid detergent fiber and lignin. The observations on amount of orts expressed as kilograms of dry matter or percent of intake and the chemical composition of orts were statistically analyzed to determine differences between cows and rations. Regression analyses were run to determine the influence of amount of weighback on its chemical composition. Analyses of the data indicated that there were differences between rations in the degree of selection that cows exhibited for protein and for acid detergent fiber. These data indicated that there are substantial differences among cows in their ability to select components of a mixed silage ration. The results of this study demonstrated the need to obtain individual weighback samples for each cow on a feeding trial rather than obtaining a composite sample. It was suggested that the feeding of complete feeds to lactating cows may not necessarily result in a uniform consumption of nutrients.