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23
Forage & Nutrition
Guide 2018
60 mid-lactation dairy cows, with all cows offered grass
silage as the basal diet. Cows were also offered one of four
concentrates (10kg per day) through an out-of-parlour feeder.
The concentrates contained either 0 per cent, 16 per cent,
32 per cent or 48 per cent field beans (representing intakes
of beans of 0, 1.6, 3.2 or 4.8kg per cow each day). In the
diet containing 48 per cent field beans, the beans replaced
approximately 75 per cent of the soya bean meal and 50 per
cent of the rape seed meal. All four concentrates had the
same crude protein and starch content (19.3 per cent and
29.5 per cent on a fresh basis, respectively), and a similar
metabolisable energy content. The beans used in the study
(variety Fuego) were sourced from a local farm, and had been
dried to 16 per cent moisture content, before being milled and
incorporated into the concentrates.
OUTCOMES
The effects of including field beans in dairy cow diets is
presented in Table 1. The results clearly demonstrate that
dairy cows were able to consume up to 4.8kg of beans per day
with no negative effect on any measure of cow performance.
In addition, offering field beans did not affect methane
production. Therefore, field beans can be included in dairy cow
diets at higher levels than previously recommended without
having any detrimental effects.
The cost of beans to purchase varies considerably from year to
year, and to some extent mirrors the change in costs of other
protein ingredients. However, assuming costs for soya bean
meal and field beans of approximately Stg£300/t and £150/t,
respectively, margin-over-feed-costs (per cow per day) would
increase from £4.90 with the 0 per cent field bean treatment,
to £5.20 with the 48 per cent field bean treatment. This
represents a potential improvement in margin-over-feed-
costs of £5,400 for a 100-cow herd over a typical 180-day
winter feeding period.
This work is continuing and is examining the effects of higher
field bean inclusion levels on cow performance and fertility, as
well as the effects of post-harvest treatment of beans (moist
preservation using propionic acid, and degree of processing of
dried beans) on cow performance.