"There is a lot of confusion surrounding the best way to measure environmental impact of the dairy industry. Which way do think best reflects the real impact?"
The dairy industry exists to produce milk, cheese, butter and other dairy products in addition to by-and co-products such as beef and leather - it does not exist to produce cows, heifers or other animals. The environmental impact is best and most accurately served and compared between systems by expressing on a “per unit of dairy” basis, e.g. per litre, kg or tonne of product. Although it’s tempting to express per head of cattle, this leads to considerable confusion – nobody would suggest that a 400 kg Jersey cow would eat as much or emit as much greenhouse gas as a 680 kg Holstein cow, and nor would they produce the same amount of milk, yet they would be counted as the same animal on a “per head” accounting system. The question then becomes whether the “per unit” metric is sufficient, or whether account should be taken of the nutrient content of differing products so that, for example, fluid milk could be compared to cheese or to soy-based beverages. It seems likely that an environmental impact per nutrient supply unit may be used in future.
Expert Answer by: Judith Capper
"Historically, lactating cows producing 35 litres of milk have been fed diets of 17% crude protein. However, recent research suggests that you can decrease this to as low as 15%. Have you ever tried applying this concept and, if so, what ration changes should be implemented?"
From experience, decreasing dietary protein from 17 to 15% does not necessarily lead to lower yield – it is all about choosing the right feedstuffs, calculating the ration adequately and focussing on nitrogen efficiency. However, you have to start with a good foundation -no feedstuff or ingredient can replace a good quality forage and good management. Once this is ensured, the nutritionist’s attention has to turn to optimal feeding of the rumen bacteria so that maximum microbial yield is achieved. One criterion to follow is the soluble crude protein to rumen degradable protein ratio as this really ensures maximal rumen microbial growth and activity. The danger of a ration below 0.52 is a lack of non-protein nitrogen in the rumen during the day but this can easily be overcome by the inclusion of Optigen. The solution is to feed the rumen first then complete the intestinal protein supply with a high quality protein source
Expert Answer by: Sylvie Andrieu
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