Silage testing - the starting point in making winter gains
Stemming from poor quality silage and inadequate feeding programmes, the winter period often marks a period of underperformance on dairy-beef farms.
Tommy Cox, Advisor on the Teagasc DairyBeef 500 Campaign, looks at the importance of silage testing – the starting point in ensuring your weanlings and finishing stock perform as they should over the winter months.
The recent fine spell was well and truly welcomed by farmers right around the country and, in some ways, it has potentially somewhat salvaged what was a very difficult summer.
As we head into October, the housing of stock will become inevitable in the coming weeks. As stock move indoors, grass silage will contribute to a high proportion of the diet of animals over the course of the housing period.
Grass silage will typically make up around one-quarter to one-third of total feed dry matter (DM) consumed on drystock farms over the year. When compared to grazed grass, it is quite expensive to produce. However, when taken as part of an integrated grazing system, it is good value compared to concentrates and alternative forages.
While most beef farms have tended to secure an adequate supply of silage tonnage in recent years, average silage quality, as measured by dry matter digestibility (DMD), remains consistently poor on drystock farms at 65-67% DMD.
Silages of such quality are only capable of supporting a daily live weight gain of 0.3-0.4kg/day without the inclusion of meal, well behind the targets set for steer and heifer weanlings of 0.6kg/day, finishing heifers of 0.9kg/day and finishing steers of >1kg/day.
Completing a silage analysis
Completing a silage analysis is the first step to seeing what quality silage is available. Once this has been completed, a feeding strategy can be put in place to ensure that the nutritional requirements of stock are met and that the desired level of performance is achieved over the winter. Visual assessment alone is not adequate to determine silage quality. A laboratory test will provide accurate information on silage nutritive value and preservation, thus allowing informed concentrate feeding decisions to be made. Table 1 outlines the key parameters tested and the desired target in each area.
Table 1: Key information provided from silage analysis
| Unit of measure | Meaning | Low | High | Target |
|---|---|---|---|---|
| Dry matter (%) | Feedstuff less water content | 13-17 | 40-55 | 28-32 |
| pH | Measure of acidity | 3.4-3.7 | 4.5-5.5 | 3.8-4.5 |
| Ammonia - N (%N) | Indicator of grass N content at cutting | 4-7 | 15-25 | <10 |
| NDF (% DM) | Measure of forage fibre and intake potential | 42-47 | 55-65 | <44 |
| DMD (%) | Measure of quality | 55-65 | 76-80 | >72 |
| ME (MJ/kg DM) | Energy content (linked to DMD value) | 8-9 | 11-12 | >11 |
| UFV/UFL (unit/kg DM) | Energy content (linked to DMD value) | 0.6-0.7 | 0.89-0.96 | >0.89 |
| Crude protein (% DM) | Measures N as indicator of true protein content | 7-9 | 15+ | >13.5 |
| Ash (% DM) | Indicator of soil contamination | 5-6 | 12-15 | <8.6 |
Calf-to-beef systems require superior quality silage, as animals have to perform at every stage of the production system. A strong emphasis on both silage quality and forage analysis is placed amongst the participating farmers in the Teagasc DairyBeef 500 Campaign, and this generally pays off as they are doing an excellent job in terms of silage quality.
Silage analysis is currently ongoing on all Teagasc DairyBeef 500 farms and results to date are positive; the majority of the silage is testing with a DMD of 70 or greater. This is the type of silage that is required on these farm, otherwise high levels of concentrate supplementation will be needed.
Taking a silage sample
Silage samples must be taken carefully to ensure correct results. A period of 5-6 weeks should elapse between ensiling and sampling. A long core sampler should be used with 3-5 cores taken from well-spaced points on or between diagonals on the pit surface. Alternatively sample an open pit by taking nine grab samples in a ‘W’ pattern across the pit face. When testing bales, a number of samples from each batch are needed to get a representative sample.
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