23 September 2010

3 minute read

Europe

The key finding of this study was that a dietary protein content of 14.5 per cent of total dry matter in early lactation was inadequate, and as a result, margin over feed costs was reduced. However, the study highlighted that there is scope to reduce dietary protein levels after mid lactation without a loss in performance, and with savings in feed costs.

This full lactation study examined the effects of a range of dietary protein levels (11.5, 14.5 and 17.5 per cent of total diet DM) on dairy cow performance. The study was conducted at the Agri-Food and Biosciences Institute (AFBI) Hillsborough and was co-funded by DARD and AgriSearch.

A number of the key findings are summarised below:

Food intake was unaffected when the protein content of the diet was reduced from the high to the medium level, although milk yield was reduced by 3.5 litres per cow per day (Table 1). Offering a low protein diet reduced milk yield by approximately 10.0 litres per cow per day. This level of protein was clearly inadequate.

Because of their lower milk yields, cows offered the low protein diet returned to positive energy balance earlier (week-4 post calving) than those offered either the medium (week-6 post calving) or high protein diets (week-12 post calving).

However, dietary protein level had no significant effect on any of the fertility measurements examined (Table 2), although there were trends towards improved fertility with the lower protein diets.

The study also examined the effect of reducing dietary protein levels in mid lactation. Half of the cows offered the high protein diet had their dietary protein level reduced to medium at day 150 of lactation. There was no detrimental effect on milk yield from this reduction in protein level in mid lactation, while overall feed costs were reduced by £41 per cow.

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