Farm Ireland
Independent.ie

Sunday 20 August 2017

Hitting targets in feed nutrition

Good management of ration requirements will help maximise animal performance and profit throughout the winter months

The percentage of grain in the crop is predicted to be phenomenal due to the heat in May
The percentage of grain in the crop is predicted to be phenomenal due to the heat in May

Siobhan Kavanagh

To maximise animal performance and profit from winter finishing, farmers need to achieve certain nutritional targets during the coming months.

These targets include intake, energy, protein, minerals, starch and sugar, and fibre.

Intake

Performance is driven by intake and in the case of winter finishing, large intakes of high digestibility forage and/or concentrate feeds are essential to achieve good levels of performance.

It is critically important that intake is recorded on a weekly basis in a finishing unit to highlight any issues around intake and performance. Without high dry matter intakes, animals will not perform. If there is a diet feeder in the yard, measuring intake is relatively easy. Otherwise, it may involve weighing a few blocks and keeping a record over a few days, every few weeks. Unlike the dairy farmer, the beef finisher does not have the luxury of a bulk tank reading to gauge animal performance, so indicators such as intake are important.

Typical intake on a grass silage-based diet for finishing steers and heifers is 1.6-1.8pc liveweight (LW), with an average of 1.7pc LW. This will vary hugely depending on forage quality and feed management.

For example, a finishing steer on grass silage plus concentrates at 600kg LW might be expected to consume 10.2kg dry matter (600kg x 0.017 = 10.2kg dry matter (DM)).

If grass silage is used as a component of a finishing diet, then it must be high digestibility, high DM material. Grange research has shown that silage intake declines by 25-30pc as silage dry matter digestibility (DMD) goes from 75pc to 60pc.


Including alternative forages such as forage maize or whole crop cereal silage will increase intake by 10-15pc, while ad-lib meal feeding will raise intake further (see Table 1).

Energy

Energy is the most limiting nutrient for a finishing animal.

Table 2 outlines the energy costs associated with maintaining the animal at two levels of gain -- 0.5kg and 1kg liveweight gain (LWG).

Maintenance costs are a significant proportion of the feed costs of an animal, particularly at low to moderate production levels.

Feed efficiency is highest at the higher level of gain, all else being equal.

In real terms, for an animal growing at 0.5kg LWG/day, the energy cost associated with 100kg will be 1,360 UFV or 1.43t of concentrates (UFV = 0.95), while at a growth rate of 1kg/day, the cost will be 920 UFV or 0.97t of concentrates.

If the concentrates cost €200/t, the cost difference between the two animals is €102.

Protein

The protein requirements of bulls are higher than steers, which are higher than heifers.

This is because of the rapid growth in bulls and the greater lean meat deposition in bulls than steers and heifers. The specifications defined in Table 3 relate to the complete diet specification, ie forage and concentrates.

Minerals

Cattle need minerals to stay in good health. It is recommended they are fed to all finishing animals. Feeding rates will vary between suppliers but, as a rule of thumb, finishing animals should be offered 20g minerals/100kg LW. For example, a 500kg animal will need 20 x 5 = 100g of mineral a day. Always check the bag for feeding rate. Overfeeding minerals can be as problematic as underfeeding.

Particular attention to minerals is needed in several areas:

  • Feeding high levels of straights such as barley, which is low in calcium.
  • Feeding alternative forages such as forage maize and whole-crop cereal silage, whose mineral contents are low.
  • High concentrate feeding: It is important that a standard beef ration is not used for high-concentrate feeding as the mineral specification will be in excess of requirements and may lead to poor performance and the risk of toxicity and severe diarrhoea.
  • High moisture grains are low in vitamin E.

Starch & sugar

There is no specific requirement for starch and sugar in the diet. However, most high-energy feeds are based on starch or sugar or readily digestible fibre -- or a combination of all three.

The type of starch will have an impact on the risk of digestive upsets in finishing animals. Starch in maize is broken down more slowly than wheat, which is more rapidly broken down than barley in the rumen.

Starch in forage maize is slowly digested, while the sugar in fodder/sugar beet is more rapidly digested. A combination of sources reduces the risk of digestive upset, but there is no substitute for good feed management.

Fibre

Beef cattle are ruminant animals and, as such, require a fibre source to sustain healthy rumen function.

The minimum roughage requirement of a finishing animal is 10-15pc of DM intake.

On a conventional diet of grass silage plus 5.5kg of meal, forage intake is 50pc of total dry matter intake (TDMI). On a high concentrate diet, 10-15pc of TDMI must be supplied as a roughage source.

Grass silage, hay, straw, maize silage and whole-crop cereal silage are all sources of fibre.

For ad-lib concentrate diets, hay, haylage or straw are most suitable but care should be taken that animals don't over consume hay/haylage as this will limit animal performance.

Opinion differs as to whether the roughage source should be mixed with the concentrate in a total mixed ration or fed separately. Offering a separate roughage source allows the animal to gauge its roughage needs (see Table 4).

Irish Independent