Ruminant production systems have been criticized for their contribution to global greenhouse gases, yet U.S. beef and dairy systems have considerably reduced resource use and carbon emissions over time, according to a collection of studies presented by Dr. Jude Capper of Washington State University during this week's JAM 2011.
According to Capper, advances in nutrition, genetics and management allowed dairy cow productivity to increase 4-fold between 1944 and 2007, with 21% of the animals, 23% of the feed, 35% of the water and 10% of the land required to produce one kg. of milk in 2007 compared with 1944.
Similar advances in the U.S. beef industry facilitated a 31% increase in beef yield per animal and 124-day reduction in the time period from birth to slaughter between 1977 and 2007. Feedstuff use was thus reduced by 19%, water use by 14%, land use by 34% and the carbon footprint was 18% lower per kg of beef in 2007, she said.
Environmental gains result from a combination of improved productivity and reduced resource requirements within the non-productive sector of the supporting population, Capper pointed out. Individual cow and herd data records, she said, suggest that the dairy industry may continue to considerably improve milk yield before a plateau is reached.
Further gains may be made by reducing population body mass – producing cheddar cheese from Jersey cows (454 kg mature weight) with increased milk component concentrations (4.8% fat and 3.7% protein) compared with their Holstein cohorts (680 kg mature weight; 3.8% fat and 3.1% protein) reduced the carbon footprint per kg. of cheese by 20% despite the greater Holstein milk yield (29.1 kg/day vs. 20.9 kg/day).
Within the beef industry, Capper said desirable slaughter weight appears to have plateaued at an average of 590 kg, yet resource use and waste output may be mitigated by improving growth rate.
Growth-enhancing technology use within conventional beef production has reduced land use by 45% and carbon emissions by 42% per kg of beef compared with grass-finished systems, said Capper. To improve future environmental sustainability, she noted that it is crucial to maintain access to management practices and technologies that improve productivity.
JAM 2011 is taking place in New Orleans, La., and it the joint annual meetings of the American Dairy Science Assn. and American Society of Animal Science.