Green Acres: Analysing silage quality across all participating farms
Last week, AgriLand published a case study on Teagasc Green Acres Calf to Beef Programme participant Pat Collins.
The study involved how silage samples are taken on-farm and how the results can be interrupted when it comes to the feeding rate of silage or the formulation of diets over the winter months.Also Read: Case study: Taking and interpreting grass silage sample results in Co. Cork
In this article – now that all silage sample results have been obtained by dedicated programme advisors Seán Cummins and James Fitzgerald – we will examine the results across all participating farmers involved in the programme.
We will also look at concentrate supplementation rates – based on the quality of silage – needed to achieve target weights over the winter period.
Looking at the results in more detail, generally speaking the quality of the silage is good, with dry matter digestability (DMD) coming in at 71% for first cuts and 66% for second-cut silage on average, across all participating farms.
However, it must be noted that there is a wide range of results across the individual farms. DMD figures ranged from 63.1% to 75.6% for first-cut silage and from 61.8% to 72% for second cuts.
Dry matter (DM) results varied from 20.5% to 61.9% on first-cut silage, while results varied from 19.7% to 43.7% on second cuts.
Silage pH levels ranged from 3.7 to 5 on first cuts and 4.3-5.2 on second-cut silage. Looking at the ammonia – N levels, first-cut silage ranged from 3.3% to 14.9%, while second cuts ranged from 3.8% to 14.8%.
The crude protein levels for first cut and second-cut silage varied from 9.9% to 16.3% and from 10.2% to 13.9% respectively.
Finally, the energy value (MJ/kg) results varied from 8.2 to 10.9 on first-cut silage and from 8.8 to 10.4 on second cuts.
The feeding levels needed to achieve a minimum target of 0.6kg/day average daily gain (ADG) for weanlings wintered indoors – on a diet of grass silage and concentrates – is largely dependent on the quality of the silage being offered.
Huge savings on wintering costs – through reducing the level of meal supplementation – can be achieved if silage quality is high.
Very high quality silage (75% DMD) has the potential to achieve the target ADG of 0.6kg on its own, while very poor quality silage (55% DMD) needs to be supplemented with 3.5kg/day of meal to achieve the same level of ADG (see table below).
A ration fed to weanlings over the first winter must have a medium-to-high value (0.9-0.96UFL) and have a crude protein content of 16%; if silage is low in protein, this must be higher.
The ration must also contain adequate minerals and vitamins. Moreover, front loading meal at the start of the winter feeding period can maximise the use of compensatory growth during the following spring.
An example of a ration that meets the above criteria is: 45% rolled barley; 30% soya hulls; 15% maize distillers; and 10% soya bean meal; this ration will have a crude protein content of 16%.
It is not possible to finish animals on grass silage alone, even with very good-quality, high-DMD silage; some concentrate supplementation is needed. However, the better the quality of silage offered, the less concentrates required to finish animals.
Looking at daily target weights of Friesian and early-maturing steers, an ADG of 0.85-1.05kg/day and 0.80-1.00/kg respectively is required; a silage quality of 72% DMD or greater is targeted.
When it comes to the concentrates offered to finishing steers, the energy density should be a minimum of 0.92UFL/kg.
The protein requirement of a ration or concentrate will vary with the type of animal.
The table below details the targeted crude protein (CP) requirements for rations at various forage protein contents; farmers should always balance the protein content of the concentrate with the protein content of the forage.
When forage makes up a large proportion of the diet, fibre levels are likely to be adequate. When feeding meals ad-lib, ensure that animals receive at least 10-15% of their dietary DM as straw, hay or grass silage in order to maintain rumen function.
Unless feeding minerals separately, check that minerals are included in the concentrate mix. All finishing animals should receive appropriate minerals for the duration of the finishing period. For grass silage-based diets, this is a general purpose mineral.
The animals’ water requirements depend on the proportion of dry feeds (concentrates) in the diet. Animals receiving ad-lib meal will have a much higher requirement for water than animals on a grass silage-based diet.
Under normal conditions (free access to feed, silage, etc and water), an animal will consume approximately 20L of water over a 24-hour period. This could be 1.5-2.0 times greater for ad-lib concentrate systems.