NET ZERO

from Dairy Farmer November 2021

TECHNOLOGY

While 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 cu ing 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 lter down to farm level.” e 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 ma er [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 of rape in the UK. But the problem with the distillers’ products is their availability heavily depends on production. e 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. is equates to a loss of about 1MJ of energy/kg DM, which he says soon adds up in a dairy cow ration. is energy de cit is one of the rst 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. e energy de cit 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, o en 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 nding the right balance between all the protein sources.” e amino acid pro le of alternative feeds and how well they suit the requirements of the dairy cow must also be considered.

He says: “Rape has a much be er amino acid pro le for dairy cows than soya does. e two amino acids we focus on with dairy ca le tend to be lysine and methionine. e 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 be er protein source.”

Mr Hall says ideally rations should be formulated using the cows’ actual requirement for protein. Cows do not have a speci c 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

Rape has a much better amino acid profile for dairy cows than soya does

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

Rations need to be carefully balanced when considering alternative protein, sources such as rapeseed meal and maize and wheat distillers.

at an intestinal level should be used, and this is a combination of protein obtained from rumen microbes and protein available which has bypassed the rumen.

Mr Hall says: “I advise working with a nutritionist, ge ing that balance right can be a bit of a headache depending on the split of forages in the diet.

“People on very high maize diets might need to feed a higher amount of rape because of the lower protein concentration of a maize silage, whereas those on grass silage might be able to get away with a li le bit less.”

Mr Hall says other alternatives include prairie meal and protected protein sources.

However, prairie meal, despite being a very suitable swap for soya, is not produced in the UK and so still incurs the high air miles associated with importing soya. It is also very expensive at between £600-£800/tonne.

“Protected sources of protein, such as protected rape, provide a good option to replace some of the bypass protein in soya, but when we are looking at protected proteins it is always important to remember 70% of an animal’s protein requirement come from rumen fermentable sources.”

However, despite this, trial work shows the potential for an increase in DM intake when cows are fed protected sources of protein.

Mr Hall says it can make the diet more palatable, due to the higher energy density, balances the CP in the overall diet and makes more e cient use of protein, which he says o en drives DM intake.

Volatility

One of the biggest problems with switching away from soya is the volatility of the raw material market, says Mr Hall. Sometimes what can be achieved by feeding a lower level of soya costs more when being forced to feed extra rapeseed meal.

He says: “One month it will be incredibly cost e ective to switch to 100% rape, but the next month it might be the worst decision ever. It completely depends on raw material markets.”

Although it looks likely farmers will eventually be required to make the switch away from feeding soya, Mr Hall says he would advise farmers not to panic about it just yet.