Effects of dietary additives identified as potential methane mitigators on production characteristics, wool quality and yield and tissue fatty acid composition of sheep

Abstract

Effects of dietary additives identified as potential methane mitigators on production characteristics, wool quality and yield and tissue fatty acid composition of sheep

The ability of dietary strategies to mitigate CH4 emissions must be balanced with their effects on animal performance in order to be widely adopted by producers. This thesis investigated promising supplements [P. freudenreichii, crude glycerin and two species of micro-algae (A. nodosum and Schizochytrium spp.)] in terms of their CH4 mitigation potential, effects on lamb production, fatty acid (FA) profile of lamb; and wool yield and quality characteristics. It is noted that there is a strong consumer push for a healthier FA composition of lamb and as such producers will inevitably shift production to meet consumer demands. Results presented here indicate the potential of P. freudenreichii to reduce CH4, but showed little effects on FA biohydrogenation. Supplementation of crude glycerin successfully replaced wheat in Merino ewe diets; however, no improvements were observed on wool yield or quality. The supplementation of Tasco® (A. Nodosum) did not affect production performance, but failed to favourably alter the FA profile of lamb as compared to other dietary oils. Conversely, DHA-Gold (Schizochytrium spp.) supplementation elicited a favourable shift in the FA profile of lamb through n-3 enrichment of both adipose tissue and skirt muscle. A further molecular investigation into the regulation of adipogenesis in lambs revealed differences in miRNA expression between subcutaneous and perirenal adipose tissues that could be influenced by micro-algae supplementation. As such, the results presented in this thesis suggest that although supplements may have the potential to reduce CH4 emissions, their effects on production may not always be favourable. In the current case, the supplementation of micro-algae (Schizochytrium spp.) proved to be the most effective at positively modifying the FA profile of lamb.