Intake and productivity of lambs grazing leafy or stemmy forage rape and the effect of energy or protein supplements
H. Dove A C and J. A. Milne BA CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
B Macaulay Institute, Craigiebuckler, Aberdeen AB15 8HQ, Scotland.
C Corresponding author. Email: hugh.dove@csiro.au
Australian Journal of Experimental Agriculture 46(7) 763-769 https://doi.org/10.1071/EA05323
Submitted: 29 November 2005 Accepted: 12 April 2006 Published: 8 June 2006
Abstract
Weaned lambs grazed forage rape in a leader-follower grazing system to create leafy and stemmy swards. Stemmy swards had a lower herbage mass and leaf content, a much higher stem and neutral detergent fibre content, and a lower N content. Lambs grazing both swards were given either no supplement or daily supplements of rolled barley (energy) or rolled barley plus formaldehyde-treated soyabean meal (protein). Half the lambs in one replicate were also given supplementary copper to counter possible effects of S-methyl-L-cysteine sulphoxide ingestion from the forage rape. The copper supplement had significant effects on liver copper content, plasma copper and the percentage of red blood cells with Heinz bodies, but there was no effect on liveweight gain compared with lambs which did not receive copper. Lambs grazing the stemmy sward ate less herbage, but much more of the supplements, in both absolute and proportional terms. Herbage intake was not influenced by supplement type. Substitution between herbage and supplement was low (<0 to 12%) and not notably different between the crop types or supplements. Liveweight gains on the leafy crop (160–200 g/day) were higher than on the stemmy crop (114–143 g/day) with significantly higher gains in lambs given the protein supplement. Supplementation did not influence carcass weight or the rates of carcass protein or fat gain, which were all higher in lambs grazing the leafy crop. The results suggest that protein supplements may improve the liveweight gain of lambs grazing forage rape.
Additional keywords: herbage intake, substitution, supplement intake.
Acknowledgments
We gratefully acknowledge the skilled assistance of Stuart Lamb, Angela Spence and Heather McCormack, and the staff of Hartwood Research Station, Strathclyde, Scotland.
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