Studies on the nutrition of farmed livestock : a thesis submitted for the degree of Doctor of Science of Massey University

Abstract

The work involves two main areas, namely advances · the feeding value of forages for ruminant animals and advances in the nutrition of alternative herbivore livestock, mainly red (temperate) deer, sambar (tropical) deer and goats. It is shown that absorption of amino acids limits protein deposition (N retention) in sheep fed fresh perennial ryegrass/white clover pasture ad libitum and that absorption of sulphur-containing amino acids (SAA) limits wool growth (a form of protein deposition) in sheep fed pasture conserved as hay or silage. Correlation analyses were used to show that extensive nitrogen (N) degradation in the silage fermentation process reduced N retention, wool growth, and voluntary feed intake (VFI) in sheep fed sole diets of silage. Methods were developed for reducing forage protein degradation by anaerobic microorganisms, initially using additions of the chemical formaldehyde to forages conserved as hay and silage and secondly by using fresh forages containing condensed tannins. Formaldehyde treatment dramatically reduced protein degradation in the silage fermentation process and when applied at an appropriate rate increased N retention, VFI and body growth in sheep. Formaldehyde treatment also increased wool growth in sheep fed hay or silage, but the responses were shown to be limited by forage SAA content, and increased body growth at constant feed intake.