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hile some processors, including Waitrose and Marks & Spencer, now require their farmers to feed dairy cows a soya-free diet, Mark Hall, Trouw Nutrition ruminant technical manager, says there is a certain amount of confusion among farmers. Rather than cutting soya completely, he says there will be a migration towards using soya from sustainable sources over the next few years. However, for farmers who are already looking to reduce the environmental impact and air miles associated with their bought-in feed, there are alternatives available. Mr Hall says: “Home-grown sources of protein are certainly gaining popularity and a lot of compounders have released their own soya-free ranges of compound feeds, which has started to filter down to farm level.” The reason soya is such a popular protein source in dairy cow diets is down to its high protein content combined with high levels of energy. Mr Hall says: “It contains anywhere from 46-50% crude protein [CP] and it is an incredibly high energy product. You are looking at 13.5MJ of metabolisable energy [ME] per kg of dry matter [DM]. It really does tick all the boxes from a dairy cow ration point of view.” Rapeseed meal and maize and wheat distillers are the main alternatives available to farmers in the UK, he says. “We are able to grow plenty
Rape has a much better amino acid profile for dairy cows than soya does MARK HALL
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Although the prospect of having to feed dairy cows without the addition of soya is not imminent, many farmers and some processors are beginning to look for alternatives. Hannah Noble weighs up the options.
Not all protein was created equal of rape in the UK. But the problem with the distillers’ products is their availability heavily depends on production. The supply is not always consistent.” Rapeseed meal has a reasonable protein content between 35-38%, but compared with soya its energy density is low at 12.5-12.8MJ/ kg DM of ME, says Mr Hall. This equates to a loss of about 1MJ of energy/kg DM, which he says soon adds up in a dairy cow ration. This energy deficit is one of the first things to take into account when making the switch from soya to an alternative source of protein. He says: “So it is really important to correct for that energy drop when
you start swapping soya for rape. The energy deficit could be replaced with wheat or barley, or fats depending on the diet.” Conversely, Mr Hall says wheat and maize distillers are very high in energy, often upwards of 13-14MJ/kg DM, but they are slightly lower in protein, typically 25-35% dependent on source. He says: “In order to get the required level of protein in the diet, you have to feed quite a bit more, so it is all about finding the right balance between all the protein sources.” The amino acid profile of alternative feeds and how well they suit the requirements of the dairy cow must also be considered.
He says: “Rape has a much better amino acid profile for dairy cows than soya does. The two amino acids we focus on with dairy cattle tend to be lysine and methionine. The ideal ratio is 2.8 lysine to 1 methionine. “Rape would be much closer to that 2.8:1 ratio than soya, so from that point of view it is actually a better protein source.” Mr Hall says ideally rations should be formulated using the cows’ actual requirement for protein. Cows do not have a specific requirement for CP, which is a basic calculation derived from the amount of nitrogen contained within a feed. Instead, he says the actual protein required to support milk production
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