Research from SRUC has found that greenhouse gas emissions from dairy cattle can be significantly reduced through housing dairy cows all year round and breeding them for increased productivity.
The seven year research project found that in systems where the cows were of high genetic merit (bred for high milk yield) and fed a diet low in forages like silage or grass, but boosted by concentrates, greenhouse gas emissions were 24% less than in systems using average herds fed on a high forage diet. The reductions are in terms of emissions per unit of milk produced.
The experimental herd was representative of the comparatively small number of herds in Britain that are kept indoors all year. The control cows – those which were of average genetic merit and grazed outside on grass for at least part of the year – are typical of most dairy herds in Scotland. The research suggests that if these producers switched to a high genetic merit/low forage system there could be big gains in terms of reducing the environmental impact of the dairy sector.
These findings present a conundrum for policymakers. While the high genetic merit, indoor route is potentially better environmentally. housing cows all year round is unpopular with many consumers. In addition early breeding programmes, concentrating on yield alone, attracted criticism because of concerns over health and welfare issues like lameness and mastitis (although modern breeders now address those issues, recognising that a long lived robust cow is as important as high yield).
The research was carried out as part of a PhD project by Stephen Ross at SRUC’s Crichton Royal Farm and published by SRUC’s Rural Policy Centre.
Stephen says: “This project suggests that further genetic improvement of the national herd combined with low forage feeding could see greenhouse gas emissions of dairy systems fall substantially. Even if farmers can only make a change in one area, either by improving their animals through breeding, or switching to indoor systems feeding low forage, they could still see their emissions fall.”
Currently just 8% of dairy units in the UK house their cows throughout the year, and it is only in these systems that a low forage diet is really practical. In this particular project the low forage diet was 50% forage and 50% concentrate with cows kept indoors all the time. In the high forage system cows grazed in summer months and were housed in winter and fed a ration which was 80% forage.
Dairy cows of high genetic merit are still rare in the UK, yet by simply increasing the number of high yielding animals the environmental impact of the sector could be reduced. In this experiment the high genetic merit line fed on a high forage diet still produced 7% less emissions.
There are various reasons why the low forage/high productivity combination leads to lower emissions. Simply put, high yielding cows produce more milk without producing extra emissions. Where cows are housed and fed less forage more food has to be bought in. However, they need less land and use less inorganic fertiliser and so again here emissions are reduced.
The full research briefing is available on the RPC’s website.
Source: SRUC
