Dairy cow nutrition

Why is this research important?

In pasture-based systems, the diet of the cow can comprise almost completely of human inedible ingredients resulting in a large contribution to net food production. High pasture inclusion levels can support resilient family-farm incomes and an animal welfare friendly image while also increasing concentrations of beneficial nutrients in milk including omega-3 polyunsaturated fatty acids, vaccenic acid and conjugated linoleic acid. Growing environmental challenges such as greenhouse gas emissions, nitrogenous losses to air and groundwater and loss of natural ecological habitats will require pasture-based systems to adapt and innovate. Outlined below are a number of investigations into nutritional strategies that can potentially reduce the environmental emissions from pasture-based systems, while also optimizing dairy cow performance.

What the research tells us

Feed chemistry and nutritional modelling

The lack of routine feed evaluation in Ireland creates barriers to adoption of environmental nitrogen emissions mitigation strategies such as low crude protein concentrate supplementation. Preliminary investigations to adapt the Cornell Net Carbohydrate and Protein System (CNCPS) model to Irish pasture-based systems have been promising. Further work is on-going in this area to increase our understanding of the nutritional status of grazing dairy cows. This is being achieved by utilising novel feed chemistry techniques (i.e. fibre digestibility and protein fractionation), developing rapid feed evaluation methods (i.e. dry and fresh spectroscopy analysis, forward prediction models) and by further evaluating/developing nutritional models for Irish pasture-based systems.

Milk fat synthesis

Milk fat is important for the production of butter, cheese, cream and whole milk powder; hence, it contributes substantially to the economic value of milk. Milk fat is also considered the most variable milk component with many nutritional and non-nutritional factors proposed to affect its production. Previous research has shown that the highest prevalence of a reduction in milk fat concentration occurred in April and May for both spring and autumn calving dairy cows, suggesting that time of year was more important than stage of lactation.

Experiments are underway investigating the effect of the basal pasture diet, concentrate feeding level (i.e. 0 to 4.6 kg/cow/day) and concentrate type (i.e. starch, fibre and rumen-protected fat ingredients), as well as, animal genotype (High EBI, average EBI, Jersey) on milk fat synthesis.

Reducing nitrogen emissions

European Union policies such as the Water Framework Directive and the Nitrate Directive have increased the focus on nitrogen emissions from agricultural sources. Irish agriculture will have to reduce nitrogen emissions or be at risk of imposition of fines, limitations on overall production and reputational damage.

Current experiments are investigating a number of nutritional strategies that can potentially reduce nitrogen emissions. These highly detailed and laborious experiments collect and quantify total nitrogen excretion from lactating dairy cows. The effect of sward type (i.e. grass, grass-clover, grass-clover-plantain) and chemical inorganic nitrogen application rates are being investigated.

Experiments are investigating the effect of concentrate crude protein supplementation (i.e. 8 to 15% CP on a fresh weight basis) and rumen-protected amino acid supplementation (i.e. methionine and lysine) on milk production and nitrogen emissions across the grazing season.

Red-clover silage

Maximising the proportion of pasture in the lactating dairy cow’s diet has been shown to increase dairy farm profitability and sustainability. Occasionally however, pasture supply deficits and inclement weather can necessitate silage supplementation.

In indoor feeding systems, the effects of feeding red clover-silage to dairy cows have been widely investigated. Results suggest that red clover-silage has a faster rate of fermentation, a faster particle breakdown and transits more rapidly through the rumen, resulting in increased dry matter intake and improved milk production when compared to perennial ryegrass-silage.

There are only a limited number of studies investigating the effect of feeding red clover-silage when pasture comprises a substantial part of the diet. Current experiments are investigating, within a pasture-based context, the effect of silage type (i.e. grass-silage, grass red clover silage), level of silage supplementation (i.e. restricted, ab-lib) and concentrate crude protein concentration on milk production and nitrogen emissions. In addition, experiments are investigating the effect of red clover silage on dairy replacement heifer performance over their first winter period.

Dairy cows participating in an animal nutrition experiment

Output

Links to papers

Feed chemistry and nutritional physiology papers:

More information

Contacts

Dairy cow nutrition research: Michael Dineen (Michael.Dineen@teagasc.ie)
Dairy cow nutrition knowledge transfer: Joe Patton (Joe.Patton@teagasc.ie) and James Dunne (James.Dunne@teagasc.ie)