Effects of specialisation in cattle production on ecologically harmful emissions

The effects of intensification in dairy cattle upon ecologically harmful em issions was investigated using a theoretical model of change in the traits of a dairy cattle population under selection. The demand for milk by the co nsumer was assumed to be a constant. Therefore, an increase in milk yield p er cow and per year would lead to a reduced dairy cattle population with a lowered capacity for beef production. The effects of compensating the reduc tion of beef output from the dairy cattle population by additional rearing of purebred beef cattle was simulated. The amount of nitrogen (N), phosphor us (P) and methane (CH4) emitted by the two different production systems is used to measure their degree of environmental compatibility. Limits in vol untary feed intake play an important role in the input/output relationships and were given important emphasis in the modelling process. Despite a redu ction in the size of the total population (both dairy and beef cows) needed to maintain milk and beef protein production, the calculated corresponding emissions of N, P and CH4 were increased by 0.5 to 3.0%. (C) 1999 Elsevier Science B.V. All rights reserved.