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Wednesday 26 July 2017

An alternative dairy supplement

Dairy farmers can cut costs by using by-products to supplement grass in their cows' diets

Palm kernel is used extensively in New Zealand to supplement grass in cows' diets
Palm kernel is used extensively in New Zealand to supplement grass in cows' diets

Karina Pierce

Cereals and soyabean meal (SBM) are commonly used to bridge the gap between grazing and the dairy cow's overall nutritional requirements.

Yet farmers are vulnerable to the volatility of the price of cereals and soyabean on the international markets which naturally creates uncertainty in dairy production systems that are more reliant on these feeds.

By-products, also known as co-products, are secondary products of ethanol, food and oil production and are used extensively in animal diets around the world.

By-products such as palm kernel expeller (PKE), soya hulls (SH) and dried distillers grains (DDG) can be used for energy and protein in cows' diets.

In New Zealand, palm kernel is used extensively to supplement grass.

Yet, the perceived negative effects of by-products on animal performance and palatability have limited their use. However, the use of these by-products in Ireland has increased significantly as can be seen in the table below, with an increase in imports of DDG, PKE and SH of 32pc, 65pc and 60pc respectively from 2009 to 2014.

Lyons Farm research

While by-products supplementation has increased, there is limited Irish research on their use in pasture based dairy production systems.


We set out in a study at UCD's Lyons Research Farm to measure the production and metabolic response of increasing levels of by-products in the diet of dairy cows at grass.

Given the increasing focus on the environment, we also wanted to assess what effects, if any, these feeds have on the excretion of nitrogen and phosphorus relative to cereal and soyabean meal based diets.

This study, which was funded by Department of Agriculture through the Research Stimulus Fund, was carried out during April-June 2014 and involved 48 early-mid lactation spring calving cows.

The trial lasted 70 days and cows were offered one of four concentrates types, fed at 6kg/cow/day through the milk parlour along with grazed grass.

All feeds were fed as pellets of good physical quality.

Treatment 1 (BP35) acted as the control with high levels of barley and soyabean meal and 35pc by-products, Treatment 2 (BP55) had lower levels of barley and soyabean meal and 55pc byproducts,

Treatment 3 (BP75) had reduced levels again of barley and soyabean meal and 75pc byproducts and the last treatment, Treatment 4 (BP95) did not contain any barley or soyabean meal and therefore was composed of by-products only.

SHs, DDGs, PKE were included in the concentrates in equal proportions.

Animals were grazed as a single group and were offered fresh allocations of pasture twice daily (20 kg DM/day) to ensure that grass intakes were not restricted.

Concentrates were formulated to be 16pc crude protein and energy levels decreased slightly from BP35 to BP95 (0.95 to 0.92 UFL). Corn distillers was used as the source of DDG.

Measurements

On a daily basis, milk yield was recorded and grass was measured and sampled.

Weekly, milk samples were taken for composition and quality analysis (fat, protein, casein, lactose, SCC) and cows were weighed and body condition was also scored weekly.

Rumen samples were analysed for pH and other rumen parameters such as volatile fatty acids and ammonia.

Such measurements provide a good indication of rumen health.

As the study was conducted in early-mid lactation, blood samples were also taken on a weekly basis, to measure indicators of energy balance such as NEFAs, BHBs and glucose.

Different concentrate feeds can influence grass intake, so grass consumption was also measured during the experiment.

In addition, excretion of nitrogen and phosphorus were measured to see what impact, if any, feeding these by-products would have on nutrient excretion through urine and faeces.

Methane would also be an important consideration but wasn't measured here.

Results

The study demonstrated that there was no effect of concentrate offered on any parameter measured in the study.

Intake of dry matter (DM - grass and total DM), milk production and composition (milk yield, fat, protein, lactose, casein, SCC), cow BCS and body weight, rumen and blood parameters were not affected by dietary treatment.

Equally, nitrogen and phosphorus excretion were unaffected by diet.

Price

As feed costs represent a large proportion of the total costs of milk production, value for money is very important.

At the time of this study, the cost differential between BP35 (high cereal, soyabean concentrate) vs BP95 (all by-product concentrate) was approximately €20/tonne.

This offers the opportunity for cost saving at farm level considering that the lower cost ration (BP95) did not have any negative impact on performance.

This is particularly relevant when margins at farm level are under pressure.

The results from this study demonstrate that increasing the inclusion levels of DDG, SH and PKE in the concentrate of pasture fed dairy cows is possible without negatively impacting on milk production, rumen health, the metabolic status of the dairy cow or excretion of nitrogen and phosphorus.

Just as importantly, this study shows that barley can be fed at reasonably high levels to cows at grass without having a negative impact on performance because cows fed BP35, which contained 6kg of barley at 45pc inclusion, consumed nearly 3kg of barley.

Karina Pierce lectures in dairy production at UCD

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