Breed and nutritional effects of the composition of faeces, urine, and plasma from Hereford and Brahman X Hereford steers fed on high and low quality diets

Abstract

A comparison is presented of the composition of the faeces, urine, and plasma when Hereford and Brahman x Hereford steers were fed two different quality diets at three levels of intake.

On a high quality diet (lucerne hay), the Brahman x Hereford steers produced significantly less faecal dry matter, total nitrogen, and non-dialysable nitrogen than the Hereford steers, but there were no significant differences between the breeds or between animals within a breed in total urinary nitrogen or any of its major constituents.

On a low quality diet (blue grass–spear grass hay) the two breeds were not significantly different in faecal dry matter, total nitrogen, or non-dialysable nitrogen. The Brahman x Hereford steers excreted more total nitrogen, urea, and creatinine in their urine, part of which could be attributed to a higher liveweight; and they had significantly lower nitrogen balances. In animals of the same breed, water intake and urine volume were negatively correlated with plasma urea and nitrogen balance and positively correlated with urinary total nitrogen, creatinine, and uric acid.