Sources of Variation in Chemical Composition of Forage Ingested by Esophageal Fistulated Cattle

Abstract

Esophageal fistulated cattle were used to collect samples of grazed forage. Within-day, daily and animal variation in the lignin and nitrogen contents of the forage samples were determined in ten trials during three growing seasons. Within-day differences in the nitrogen and lignin content of forage samples were not consistent. Daily and animal variation of these chemical constituents in the diet were highest when the mean content of each was highest in the forage and when a wide variety of forage species was being consumed. Summarizing all trials, sampling forage with three animals per treatment for four consecutive days permitted the detection of differences of 10% of the mean nitrogen content at the 10% level of significance with 85% confidence. More animals would be required to make precise measurements of the lignin content of the diet.