Releases Archive 2008

Forage maize offers considerable potential as a high quality forage for winter feeding of dairy cows in Northern Ireland. Continual improvements and availability of forage maize varieties suitable for growing in many areas of Northern Ireland have been made over recent years. Recommended forage maize variety lists are available for both open establishment and plastic mulch type management systems (DARD ‘Forage Maize Varieties for 2008’, Gilliland). From a dairy cow production point of view, the positive effects of including maize silage can be considerable. However the benefits of including maize in the diet are dependent on many factors including the quality of the maize silage, grass silage quality, maize silage inclusion rate, concentrate feed level and total protein content of the diet.

When maize silage was offered in combination with grass silage (50:50 of forage dry matter) as compared with grass silage alone, inclusion of maize silage increased forage dry matter intake by an average of 3.8kg (39%) of DM per day from approximately 9.8kg of DM per day with grass silage to 13.6kg of DM per day with grass/maize silage. This increase in forage intake with the inclusion of maize increased greatly when the quality of the grass silage decreased, with a 4.7kg of DM per day lower intake with low quality grass silage compared with a 2.3kg of DM per day lower intake with good quality grass silage when compared to the grass/maize silage mix.

Addition of maize silage increased milk yield by 2.4kg per day from 28.5kg per day (grass silage) to 30.9kg per day (grass per maize silage), increased the protein yield from 3.06% to 3.22% and increased the overall yield of fat plus protein by 12.4% (Table 1). More detailed analysis of results on energy efficiency also suggest that with maize silage inclusion, more feed energy is directed towards body reserves i.e. cows on mixed maize/grass silage lose less weight in early lactation. However, the improved milk yield, protein percentage and fat plus protein yield achieved with the addition of maize silage is solely dependant on the quality of grass silage produced. As the quality of grass silage increases the benefits of the addition of forage maize diminish with good quality grass silage marginally outperforming maize/grass silage on some occasions.  

Table 1. The effects of addition of maize silage on milk yield and milk composition

The overall benefits of inclusion of maize silage are dependent on many factors such as grass silage quality, maize silage yield and quality, concentrate price, milk price and the overall cost of production of the forages (Table 2). The AFBI Hillsborough study identified an overall financial benefit of £0.52 per cow per day with the addition of maize silage compared to grass silage alone, which equates to a £80 per cow margin over feed over the winter period when maize silage was added to the winter diet.

Table 2. The effects of the addition of maize silage on costs of inputs, value of output and margins¹

¹ Assumed costs: grass silage £85 per tonne DM, maize silage grown under plastic £73.00 per tonne DM, concentrate £206 per tonne fresh weight. Base milk price of 25 per litre, with a bonus of 0.018 and 0.032 pence per 0.01% for differences in milk fat and protein from the base milk composition (4.0 and 3.18% respectively)

² Based on average daily milk yield corrected to standard milk composition of 4.0 and 3.18% for butterfat and protein respectively

³ Assumes housed lactating period of 150 days

Improvements in maize varieties suitable for growing in suitable regions in Northern Ireland make maize a viable option for winter feeding. In addition recent AgriSearch and DARD co-funded studies at AFBI Hillsborough have shown that there may be financial benefits in terms of cow performance for the Northern Ireland dairy producer in offering maize silage as part of the winter diet.