Replacing soybean meal with protein sources of European origin in protein concentrate for dairy cattle

Context

Soybean meal is the main exogenous protein source used in cattle feed for steady milk production, reflecting the advanced genetic selection of the last few decades.
Soya is intensively grown, mostly from GMO seeds and, apart from a few sustainable production routes, it creates quite a few environmental problems: deforestation, soil depletion, ecological impact of transport, etc. Having very little in the way of home-produced plant proteins (27% in 2008, Prolea 2009), the EU imports more than 30MT of soya every year (Prolea, 2009). This raw material is a nutritional benchmark, in terms both of its digestible protein content (246 to 277 g DVE/kg DM, CVB, 2000) and energy content (1150 FEM/kg DM) and its good digestible methionine and lysine balance, these being the main limiting amino acids in the dairy cow. It is a perfect supplement to maize silage which is widely made in Wallonia.
As most of the protein consumed by the animal is excreted in its faeces (about 75% in cattle), supplementing our livestock with large quantities of soybean meal has significantly increased the environmental nitrogen, resulting in eutrophication of water. However, in the last few years locally produced protein sources have become more generally available thanks, among other things, to the growth of the biofuel industries. Examples include rapeseed cake, a by-product of biodiesel manufacture, and distiller’s dried grains with solubles from bioethanol plants.
The cattle feed industry thus faces the sizeable challenge of replacing soybean meal with a combination of local protein sources without increasing the cost and without impairing animal production performance. The aims behind the pursuit of this new balance are lessening our reliance on soya, making the EU economically less dependent on outside markets and improving the overall sustainability of our livestock farming.

Objectives

The specific aim of this trial is to compare two nutritionally equivalent rations, one supplemented by a local protein based regulator and the other by a soya cake based regulator, on dairy cows’ milk production, the nitrogen efficiency of the feed, the milk composition and the cost of feed per litre of milk produced.

Results obtained

The trial involved two groups of 8 and 9 PN Holstein dairy cows, producing 26.5 ± 3.2 and 30.7 ± 5.4 L/d, with a lactating period of 204 ± 52 and 166 ± 70 days, respectively, at the start of the trial. The cows were milked twice a day, at 0630 hours and 1630 hours.
The study comprised two experimental periods in which each group of cows received two successive rations of the same nutritional value, designed for theoretical production of about 30 L/d (soya ration versus local ration, Table 1) according to a crossover experimental design.
Table 1. Centesimal, Chemical and Nutritional Composition of Feed Rations

Raw Materials	‘Soya' Ration	‘Local' Ration
Centesimal composition, % DM
Basal ration Grass silage Maize silage Wheat straw Protein concentrate Soya cake 46 Rapeseed cake Beet vinasse Optitek Sunflower cake Spent wheat grains Maize germ cake Urea NaCl Production concentrate	80.2 31.4 46.8 2.0 15.1 8.6 5.8 0.6 0.1 - - - - - 4.8	76.0 29.3 44.5 2.2 19.1 - 10.5 0.8 0.1 3.4 3.4 0.7 0.1 0.1 5.0
Chemical composition
DM, kg/d/cow OM, g/kg DMI Proteins, g/kg DMI Raw energy, kcal/kg DMI NDF, g/kg DMI ADF, g/kg DMI Fat, g/kg DMI	23.1 918 147 4260 374 286 33	23.0 918 150 4296 382 290 36
Nutritional composition⁴
FEM, FEM/kg DMI DVE, g/kg DMI OEB, g/kg DMI	900 83 14	891 81 17

The intake level was the same with both diets and no significant difference was observed in terms of milk production (Table 2).

	‘Soya' Ration	‘Local' Ration	P
Production, kg/d Fat corrected milk production, kg/d Butterfat content, % Fat, g/d Protein content, % Proteins, g/d Useful material, g/d Urea content, mg/dL	25.9 25.8 4.18 1081 3.61 931 2011 187	25.5 24.9 4.06 1031 3.57 905 1936 179	0.600 0.303 0.345 0.270 0.485 0.340 0.266 0.404

This result shows that soybean meal can certainly be replaced by European protein sources in high-production dairy cattle feed. It confirms that the pre-established rations are equivalent in nutritional terms.
The milk urea content and the protein efficiency were similar for both rations. The milk fatty acid pattern was likewise very similar, probably due to the small quantity of soybean meal replaced and also to the fact that the cake was of the ‘schroot’ type, i.e., with a very low residual oil content.
On the basis of May 2010 trade prices, the cost price of the ‘soya’ ration protein concentrate, excluding the cost of production, storage and transport, was €259/T (1007 FEM, 235 g DVE and 140 g OEB /kg DM), whereas the ‘local’ ration protein concentrate cost €197/T (953 FEM, 192 g DVE and 121 g OEB/kg DM). In relation to the quantity of digestible protein, on the other hand, the price difference becomes almost nil.
Factoring in the price of the forage (Deprez et al., 2007), straw and various concentrates, the feed price per 100 litres of fat corrected milk was very close for both diets at €11.85/100 L for the ‘soya’ ration and €12.25/100 L fat corrected milk for the ‘local’ ration.
In conclusion, these results confirm the production and economic feasibility of replacing soybean meal by home-grown protein sources in current market conditions. However, the price of soybean meal, assumed to be €300/T in this study, is a major factor in the attractiveness of either option. It should be noted that this calculation does not take account of the environmental benefit of using local protein sources.