Silage Update and Seasonal Trends
Preparation for winter is well underway and SAC consultants have been busy sampling silages up and down the country. The results of these analyses are summarised in Table 1, they are mainly from beef and sheep farms and will contain a mixture of pit and bale silages from both first and second cuts. Based on the average results dry matter content has not reflected the wet conditions experienced by parts of the country in spring/early summer, however it should be noted that 15% of all silages sampled did analyse below 25% dry matter (DM).
Table 1: key silage quality metrics
Average quality of silage samples looks good at an average ME of 10.4 MJ/kg DM and 12.1% protein. However, there does appear to be a trend that has been noticeable by SAC Consulting’s nutrition team, that there is a larger than normal proportion of forages that are low in energy (9-10ME) and high in protein (CP 14-16% DM) than we typically see. This results in a higher proportion of low energy rations increasing the need for cereals or concentrate feeds but reducing reliance on bought-in protein for some farms.
David Lawson (SRUC Grassland Specialist) has hypothesised the reason may be due to the cold spring, resulting in slow grass growth followed by a sudden growth spurt in May. Soil will start to release nitrogen (N) to the plant when it reaches a temperature of around 5°C but we don’t tend to see much significant release of N until soil temperature reaches between 9-10°C. When this change happens suddenly, it can result in an increased amount of nitrogen being released to the plant increasing its protein content and leading to a growth spurt, but this can come at a cost of sugars in the plant (i.e. energy!).
Reviewing the data of recorded soil temperature from Grasscheck GB, a clear pattern can be observed to support this theory with a cold April indicating slow grass growth leading to a sudden temperature increase in early to mid-May particularly when looking at Scottish soils compared to the rest of the UK when the soil temperature rises from 6.3 ⁰C on 29th April 2024, to 11.3ºC on the 13th May 2024.
The implications of this for rationing is that silages with a higher protein and lower energy may compromise growth rate of growing and finishing stock, if not balanced with an appropriate high energy feed such as a cereal or bought-in concentrate. Also, if not balanced correctly the excess protein would be converted to ammonia in the blood and expelled as urea, this uses energy, therefore a further cost to the animal.
The figures provided in Table 1 are intended to be used as guidance. It is important to have your own forage analysed to ensure accuracy when rationing. For example, feeding a 9ME silage to growing stock ad-lib compared to a 12.1ME silage fed ad-lib would result in a difference of 0.7kg of growth per day, if the 9ME silage was not supplemented appropriately.
Mary Young, Ruminant Nutritionist, Mary.Young@sac.co.uk
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Posted by Unearthed News on 13/12/2024
