The number of dairy cows entering sheds has significantly increased in the last number of days and as weather and grazing conditions deteriorate dairy cows will be offered grass silage. The mixed summer weather has made it significantly difficult to ensile top quality grass silage in some areas.
Having silage analysed is really important, and I always encourage farmers to ensure they take a representative sample for nutritional analysis. In order to take a valid representative grass silage sample, I advise using a long core sampler 3-5 points across the pit to within 0.5m of the pit floor.
If taking the sample from the pit face take at least 9 -10 grab samples in a ‘W’ pattern and mix thoroughly to ensure an even sample. It is vital to remove as much air as possible and post immediately. I cannot understate how important it is to know the quality of the silage being fed. The quality of winter forage being fed will underpin the degree and rate of weight gain and productivity of the herd.
Interpreting your Silage Analysis
pH- This is the indicator of preservation quality and fermentation. The optimum pH should be 3.8-4.2. Very acidic grass silage will result in poor feed intake and high ammonia content.
Ammonia- This is the indicator of protein breakdown during preservation, feed quality and palatability. High nitrate content will further impact this ammonia content. It is recommended that Ammonia should be below 5%.
Dry Matter- This is a very important parameter that will have a significant impact on intake and preservation values. Low values will result in poor intake and stability. Optimum Dry Matter should be 25-30%
Dry Matter Digestibility- This is a key measure of quality and will have a major impact on intake and energy value. Harvest and heading date will underpin this value. The optimum Dry Matter Digestibility should be above 70%.
Metabolizable Energy (ME) – This is linked directly to Dry Matter Digestibility. It should be as high as possible with an optimum of 11-12.5 MJ/KG DM.
If there is a history of any underlying metabolic problems presenting such as milk fever, difficult calving, weak calf syndrome, metritis, ketosis, retained placentas etc it can be worthwhile to analyse for nutritional parameters and mineral content of grass silage.
To avoid such problems at calving, the dry period is the optimum time to correct and limit these associated problems. Most farmers across the country now recognize that the diet of the pre calving cow needs to altered in the last three weeks prior to calving to ensure a smooth transition from non-lactating to lactating. In the majority of cases, a high quality pre-calver offered 6-8 weeks prior to calving will help prevent the prevalence of metabolic disorders. It is very important to ensure that the content of calcium is below 1% and that there is a high content of magnesium, sodium, phosphorus as well as elevated levels of selenium. The presence of Vitamin E will be important to boost immunity and at least two sources of copper and zinc. I would also highly recommend to analyse for Iodine when undertaking a mineral content analysis on grass silage.
For assistance with interpreting your silage sample results or for any assistance on the nutrition of your herd please do not hesitate to contact a member of the Connolly’s RED MILLS ruminant team. We have tailored mineral ranges to help prevent the incidence of metabolic disorders at calving.
- herd management