Effect of a Reduction in Concentrate Price on Feed Costs and its Implication for Grass Silage in the Diet of Lactating Dairy Cows

The proposed reduction in the price of cereals (29%) under the EC price reform proposals for agricultural produce will have n large effect on feed costs and on the balance between grass silage and concentrates in the diet of lactating dairy cows while indoors. The effect of n reduction in the price of dairy concentrates with varying silage production costs on the daily feed costs for a 525 kg cow yielding 25 kg milk/day in early lactation, while losing 0.5 kg/day body weight, was calculated when given a mixed diet of grass silage and concentrates to provide an MB intake of 164 MJ/day. Silage production cost (IR£315/ha) was influenced by the yield and quality of first cut silage, with ·settled silage yields of 4.5, 5.3 and 6.3 tonnes DM/ha for silages H (75% DMD), G (70% DMD) and M (65% DMD) and costing IR£70, IR£60 and IR£50/t DM, respectively. Inclusion of a land charge (IR£125/ha) increased silage costs to JR£98, IR£84 and IR£70/t DM for silages H, G and M, respectively. The effect of the level of silage offered, i.e., restricted or ad lib, (6-IO kg DM/dny) when appropriately supplemented to provide 164 MJ ME/day with a standard dairy concentrate (87% DM, 18% CP, 12.5 MJ ME/kg DM) and costing either IR£160, IR£130 or IR£100/t, on feed costs was calculated. When a land charge was excluded increasing silage intake to replace concentrates reduced daily feed costs to a similar extent for all silages, by an average of 9.0, 6.1 and 3.3 lRp/lcg DM extra silage at concentrate prices of IR£160, IR£130 and IR£IOO/t, respectively. The addition of a land charge increased feed costs ( + 12- 28 p/day) and reduced the saving achieved by replacing concentrates with silage, to 6.6, 3.7 and 0.9 IRp/kg DM extra silage, respectively, as concentrate prices declined. Increasing silage intake ( + 1- kg OM/day) and its quality ( +5% DMD) by earlier cutting at the expens�� of yield reduced feed costs at concentrale prices of IR£130 to IR£160/t but not at JR£100/t, and only at IR£160/t if a land charge was included. At similar intakes of silage higher yields of settled silage were required for H and G silages (5.6 and 6.0 t DM/ha respectively) to be competitive with M silage when concentrate prices were low.