Feeding challenges with late harvested maize
1 January 2016
The results of the analysis of over 3000 maize silage samples are beginning to give a clear picture of how maize silages will feed this winter and what will need to be done to get the most from forage, especially late harvested crops.
“Compared to last year, we are seeing 2% lower dry matter on average and 1.7% lower starch. NDF and ME levels are similar to last year but the intake factor is lower (see table),” comments Trouw Nutrition UK Technical Director Dr John Allen.
“Starch degradability is already high for the time of year at 72%. This will increase with time in the clamp, boosting rumen fermentable carbohydrate supply. This will need to be monitored closely through regular repeat forage analysis to ensure rumen acid load and acidosis do not become a problem.”
Dr Allen cautions there may be specific problems with later harvested crops. In general the problem crops will be those that have a lower dry matter. To date 15% of crops analysed have a dry matter below 23% which is a far higher proportion than in a ‘normal’ year. These wetter crops also have an increased fibre content and lower starch, indicative of the growing season (see table).
“While the ME is reasonable, the intake potential is only 87% of the season’s average, implying it will be a challenge to get cows to eat target quantities. On a simple energy basis, 5kg DM intake of the average maize silage will require 17.2 kg fresh matter and provide 57.5 MJ/day, equivalent to 11.5 litres. However, the intake factor suggests only 4.4 kg DM of the average ‘wet’ maize silage would be eaten, requiring 24.3kg fresh matter and this will supply 48.4MJ, sufficient for just 9.7 litres, nearly 2 litres less than this season’s average.
“Clearly, these wetter maize silages will require balancing with higher energy concentrate feeds with daily intakes monitored to ensure appetite is being met. Refusals must be recorded and reacted upon accordingly.”“Overall, the lower starch content in these wetter crops means that rumen available and by-pass starch levels will be lower than for the average crop. This will reduce the rapidly fermentable starch required for rumen microbial digestive activity and means more rapidly fermentable carbohydrates will need to be fed in the diet to compensate.
“The key to getting the most from maize silage this winter will be regular analysis of the crop so you understand the quality of feed available. Then make sure the rationing system being used by your nutritionist can make full use of the complete analysis to ensure maximum rumen performance to support efficient milk production.”