Home / Research Supervisor Connect / Supervisor details

About Dr Alex Chaves

My research in animal nutrition and rumen microbiology focuses on understanding how changes in diet can be used to reduce greenhouse gas emissions from ruminants, while ensuring acceptable animal performance and sustainability of farm production systems.

My most significant contribution to this field is my novel and innovative research into the use of supplementary feeds to reduce methane emissions for environmental benefit. I played a lead role in this multi-million (Canadian) dollar Project, undertaken over three years as a visiting scientist at Agriculture and Agri-Food Canada, Lethbridge Research Centre (Alberta, Canada). I was responsible for designing and carrying out all experiments and disseminating the results by publications and conference presentations. I evaluated the effects of different types of essential oils and saponins (i.e.: plant extracts) on rumen fermentation, feed digestibility and microbial populations using in vitro (laboratory) and in vivo techniques. The results of the research clearly indicate that there is potential to select plant extracts or essential oils that selectively reduce methane production, at least in vitro. The research generated significant interest in the field of rumen microbiology and, following its publication as a chapter in the textbook "Advances in Medicinal Plant Research", it has subsequently been presented at 20 conference proceedings and has been the subject of 15 peer review publications. One of these articles was rated number 4 in the "Top 10 Most Downloaded Articles" list on the ScienceDirect website in March-2011. Another significant contribution to the research field of this proposal is my novel and innovative research in the use of distillers grains into ruminant diets to optimise animal performance and energy utilisation. The results of this research clearly demonstrated that distillers grains could be used at up to 60% of the diets of ruminants. The research generated significant interest in the field of ruminant nutrition and resulted in four other papers.

My PhD studies in this field represented a comprehensive analysis of the effects of ryegrass maturation on nutritive value to dairy cows, and covered chemical composition, rates of ruminal degradation and products of digestion (volatile fatty acids and ammonia production). This was the first time that a fresh mincing procedure (instead of the traditional method of freeze-dried and ground to 1-mm) was used in studies to provide material for in vitro and in sacco incubations in order to mimic cow digesta. The extensive data collected in these studies is now integrated into a data base for New Zealand pastoral systems, widely used in the field to provide information to improve supplementation of dairy cows. This research resulted in 7 well-cited peer review articles and was presented at 13 international conferences. In addition, the procedure for a rapid and accurate laboratory lignin determination was published and awarded best paper at the 2002 NZ Grasslands Conference.I completed a very productive postdoctoral fellowship in dairy science at the National Institute for Agronomy Research (INRA; URMPL - St-Gilles), France during 2004, investigating the impact of rumen inert bulk on feed intake in grazing dairy cows. I then became a visiting scientist at Agriculture and Agri-Food Canada, located at Lethbridge Research Centre in 2005, where I worked until 2008. In this period I analysed the impact of essential oils and saponins on rumen digestibility and microbiology and helped attract substantial research funding for the work. I have maintained strong links with these first-class laboratories in New Zealand, France, Canada as well as in Brazil, Norway, and USA. This important links have provided me with continuity in international collaborations in the research areas which I have brought to the University of Sydney, where I have also established new areas of inquiry. In 2009 I spent several weeks completing experimental analyses at Lethbridge with Dr Tim McAllister (who is now an honorary associate of the Faculty of Veterinary Science), using equipment which I cannot access locally, and sustaining my involvement with a large, well-funded research group on the use of essential oils and plant extracts to reduce methane production from ruminants. Currently I still have a strong collaboration with Agriculture and Agri-Food Canada. One of my PhD students, Jorge Stagno Avila, is in Lethbridge at the moment running our collaborative experiments. Dr McAllister visits the University of Sydney yearly, which also helps to maintain and strengthen our collaboration.

Selected publications

  1.  
    Au, F., McKeown, L. E., McAllister, T. A. and Chaves, A.V., 2010. Fermentation characteristics of corn-, triticale-, and wheat-based dried distillers grains with solubles in barley-based diets determined using continuous and batch culture systems. Journal of the Science of Food and Agriculture 90: 2074–2082. ERA = A; IF=1.386
  2.   Wierenga, K. T.; McAllister, T. A.; Gibb, D. J.; Chaves, A.V.; Okine, E. K.; Beauchemin, K. A.; and Oba, M. 2010. Evaluation of triticale dried distillers grain as a substitute for barley silage in feedlot finishing diets. Journal of Animal Science 88: 3018-3029. ERA = A; IF=2.466
  3.   McKeown, L. E.; Chaves, A.V., Oba, M.; Dugan, M. E. R.; Okine, E. K. and McAllister, T. A. 2010. Effect of replacing barley grain with triticale-based dried distillers grains with solubles on nutrient digestibility, lamb growth performance and carcass traits. Canadian Journal of Animal Science 90: 87-98. ERA = B; IF=0.68
  4.   McKeown, L. E.; Chaves, A.V.; Oba, M.; Dugan, M. E. R.; Okine, E. K. and McAllister, T. A. 2010. Effects of corn-, wheat- or triticale-based distillers grains with solubles on in vitro fermentation, growth performance and carcass traits of lambs. Canadian Journal of Animal Science 90: 99-108. ERA = B; IF=0.68
  5. Wang, Y.; Chaves, A.V.; Rigby, F.L.; He, M. L. and McAllister, T. A. 2010. Effects of hops on ruminal fermentation, growth, carcass traits and shedding of Escherichia coli of feedlot cattle. Livestock Science 129: 135–140 ERA = B; IF=1.41
  6. Berthiaume, R.; Benchaar, C.; Chaves, A.V.; Tremblay, G. F.; Castonguay, Y.; Bertrand, A.; Bélanger, G.; Michaud, R.; Lafrenière, C.; McAllister, T.A. and Brito, A. F. 2010. Nonstructural carbohydrate concentration in alfalfa affects fermentation and microbial protein synthesis in continuous culture. Journal of Dairy Science 93: 693-700. ERA = A; IF=2.466
  7. Fung, Y.T.E.; Sparkes, J.L.; van Ekris, I.; Chaves, A.V. and Bush, R.D. 2010. Effects of feeding fresh citrus pulp to Merino wethers on wool growth and animal performance. Animal Production Science 50: 52–58. ERA = A; IF=0.917
  8. Chaves, A.V.; Schei, I.; Wang, Y.; McAllister, T.A. and Benchaar, C. 2009. Effects of carvacrol and cinnamaldehyde on microbial fermentation when added to a barley- or corn-based diet in a continuous-culture system. Canadian Journal of Animal Science: 89: 97-104. ERA = B; IF=0.68

  9.       Holtshausen, L., Chaves, A.V., Beauchemin, K. A., McGinn, S. M., McAllister, T. A., Odongo, N. E., Cheeke, P. R. and Benchaar, C., 2009. Feeding saponin-containing Yucca schidigera and Quillaja saponaria to decrease enteric methane production in dairy cows. Journal of Dairy Science 92: 2809-2821. ERA = A; IF=2.466

  10.       Ohene–Adjei, S.; Chaves, A.V.; McAllister, T.A.; Benchaar, C.; Teather, R.M.; Forster, R.J. 2008. Evidence of increased diversity of methanogenic archaea with plant extract supplementation. Microbial Ecology 56: 234–242. ERA = A; IF=3.251