Balancing silage quality and concentrate feeding on calf to beef farms

Grass silage is an important winter feed in calf to beef systems. Balancing this forage with the correct quantity/quality of concentrate is key to achieving the desired winter weight gains.

Why complete a silage analysis?

The starting point in balancing calf to beef diets over the winter months is the completion of a silage analysis. Visual assessment alone is not adequate to determine silage quality and laboratory testing is recommended. This testing procedure will provide information on silage nutrition value and preservation from which informed concentrate feeding decisions can be made.

A breakdown of dry matter (DM), dry matter digestibility (DMD), metabolisable energy (ME), UFV, UFL, pH, crude protein and other relevant information will be generated, while mineral profiling (macro and trace) of silage can be obtained through a wet chemistry analysis.

Correct sampling procedure

Poorly taken silage samples often lead to inaccurate results. Remember a period of 5-6 weeks should elapse between ensiling and sampling, with a long core sampler used.

3-5 cores from well-spaced points on or between diagonals on the pit surface should be sampled, with each sample taken to within 0.5m of the pit floor. When collecting, discard the top 5 inches of each core before mixing into a composite sample. Alternatively, sample an open pit by taking nine grab samples in a ‘W’ pattern across the pit face. Exclude air, seal well in a bag and avoid posting samples late in the week. When testing bales, a number of samples from each batch of bales made must be taken in order to get a representative sample. Finally, use only Forage Analysis Assurance Group (FAA) accredited labs when having silage samples analysed.

Winter weight gain requirements

Calf to beef systems require superior quality silage, as animals have to perform at every stage of the production system. Table 1 highlights the targeted average daily gains (ADG) of animals over the winter months for various production systems.

Table 1: Daily winter weight gain targets for spring born calf to beef animals at various stages

Matching silage quality and concentrate feeding

Concentrate supplementation provides energy and protein to an animal’s diet that may be lacking in silage. Calf-to-beef systems require excellent quality silage (DMD of >72).

Additional meal supplementation will be required to improve the overall energy/protein density of the diet where silage quality is sub-optimal. Growing and finishing animals have varying requirements for energy and protein – one concentrate will not do both.

Additionally, ensure animals are adequately provided with minerals, either through the concentrate or additional supplementation. For more detailed information on balancing silage quality and concentrate feeding, contact your local Teagasc advisor.

Energy

Energy is typically the most limiting factor in beef diets. In terms of rations, weanling rations have a requirement of >0.94UFL, while >0.92UFV is necessary for finishing rations. Table 2 provides guideline daily concentrate feeding rates depending on the quality of silage (DMD) available.

Table 2: Guideline daily feeding rates based on silage quality (DMD)

Protein

After energy, protein is the next limiting factor in the winter diet of dairy-beef animals. Always balance the protein content of the concentrate with the protein content of silage. Weanling rations should have a crude protein content of 14-16%, while 11-14% is needed for finishing rations.

Table 3: Crude protein (%/kg fresh weight) required in concentrate feeds for grass-silage based diets

This article was adapted from a DairyBeef500 factsheet. For more information on the DairyBeef 500 Campaign, click here.