With forages constituting the major proportion of diets on extensive and semi-extensive systems, it is vital to understand the true feed value of silage if diets are to be balanced, performance optimised and costs managed effectively, says Rosie Miller, ruminant nutritionist with Trouw Nutrition GB.
She says: “If you do not know the level of performance forages can support, how can you decide the quantity of supplementary feed needed to achieve target growth rates and carcase composition?”
An analysis will give accurate information to use as a base for diet formulation, helping ensure optimum energy, protein and dry matter intakes, while improving rumen health.
Ms Miller says: “If we look at energy content, the ME of silage can vary from about 9.3MJ, for a poorly fermented cut of mature grass, to 11MJ for a well-made crop from a newer ley cut at the optimum growth stage.”
She says an analysis will also give valuable information about how much cattle might be expected to eat. Silage with a higher D value and intake potential can be expected to support higher intakes, but without an analysis, it is impossible to assess this.
Ms Miller says a 300kg animal fed a 9.3MJ silage would grow at a rate of 0.7kg/day on an adlib silage system, weighing 440kg at the end of a 200-day winter.
If the same animal had been fed an average 10.1ME silage, the weight at the end of winter would have been 480kg, a benefit of 40kg for no additional costs.
She says: “Knowing forage quality allows you to better predict growth, more accurately meet specification and adjust supplementary feeding.
“In most cases, the real benefit of understanding silage quality is to achieve market targets with the correct use of concentrates, which will ultimately save money.”
The table compares diets to achieve a 1kg daily gain from a 300kg animal with a 7kg DMI. With average silage, growth will be achieved from 2.8kg of blend supplementing silage. However, with a poor silage, 4kg of blend would be required.
“This is a saving of 1.2kg blend per day to achieve the same growth rate. This equates to a saving of 240kg or about £58/animal over winter. The benefit is even greater if a high quality silage is fed.
“The best big bale silage analysed this year by Trouw Nutrition GB has an energy content of 11MJ. Using this silage, the 1kg daily liveweight gain could be achieved entirely from forage, saving 800kg of blend per animal over winter.
“The risk is, without knowing the analysis, the incorrect amount of concentrate will be fed, either substituting concentrate for forage or underfeeding and suffering reduced growth rates and higher costs due to extended days to finish.”
Ms Miller says an analysis will help maximise rumen health, explaining the acid load and fibre index are an indication of how silage will perform in the rumen.
She says: “A forage made from older grass may have a higher fibre index and will need balancing with rapidly fermentable energy and protein sources.
“Conversely, a good quality, higher energy silage may have an increased acidosis risk, especially if mixed with excess cereals.
“Knowing exactly what you are feeding in the forage portion of the diet can have a huge impact on performance and costs. It is something which is quick and easy to do and your feed advisor will be familiar with the process.
“You cannot change the forage you have available to feed, but using the analysis to make sure you get the best from the forage you have while maximising performance and controlling costs will help improve margins this winter.”
|POOR (9.3 ME)||AVERAGE (10.1ME)||HIGH (11.2 ME)|
Source: Trouw Nutrition GB - Note: based on a 300kg animal with a 7kg DMI.