The indirect estimation of the digestibility of pasture herbage. IV. Regressions of digestibility on faecal nitrogen concentration: effects of different fractions of the herbage upon within- and between-period regressions

Abstract

1. In each of 6 digestibility trials, comprising a total of 21 measurement periods of 3-4 days, two steers were fed on herbage cut from the top of the sward, two on the remaining bottom growth and two on a mixture of equal parts of these fractions. Within each period the fractions were similar in digestibility although the top growth had a higher content of nitrogen.2. The trials were divided into three groups, according to time of year, for the purpose of calculating regressions of digestibility on faecal nitrogen concentration. Regressions calculated in the usual manner on a between-period basis (i.e. within animals) had constant terms which differed significantly among animals but not from one fraction of the herbage to another.