Having silage in storage, whether purchased or made on-farm, is essential as a supplementary feed for times when pastures are in a low-growth period or for additional feed inputs at various times in the livestock cycle. Making silage on-farm is an excellent way to utilise surplus pasture and maintain good pasture quality in lush growing seasons.
But – not all silages are equal. There has been a lot written about how to make good quality silage, but even so, it is not always easy and weather is usually the biggest challenge. In these last couple of years that has been even more apparent.
Hill Labs offers an array of silage test options to allow feed managers to utilise their available silage best – depending on the test results, decisions can be made about which livestock to feed a particular silage line to best advantage. The test may be as simple as Dry Matter% only, or more usefully, the recommended Silage profile, which includes the key quality measures and also a few fermentation measures such as pH, Ammonium-N and lactic acid.
Fig. 1: Hill Labs sample submission mobile app screen for selecting Silage tests.
However, for only slightly more cost a Silage & Volatile Fatty Acid profile should be considered – especially where silage dry matter is low when silage is made in a wet summer, and sufficient wilting was impossible.
In low dry matter silages, the fermentation is usually slow and less lactic acid is created than is needed to achieve a fast pH drop for preservation. Acetic acid can be high in this case, or even worse the fermentation is dominated by clostridia with production of butyric acid. Levels of butyric acid greater than 0.5%DM may affect animal intake, production and palatability. While high levels of acetic acid are generally undesirable (indicative of poor fermentation), it can be useful in inhibiting yeasts responsible for aerobic spoilage. Microbial inoculants containing Lactobacillus buchneri are intended for this purpose, and produce acetic acid, which does not appear to affect animal intake.
The histogram shown in Fig. 2 is a snapshot of fermentation acids from a small number (n=80) of pasture silages analysed at Hill Labs this year. While it is too small a data-set to be significant, the high levels of butyric acid in low dry matter silages can be seen.
Fig. 2: A snapshot of pasture silage fermentation acid results (n=80) for a series of dry matter levels as analysed at Hill Labs Jan-June 2023. “Good” pasture silage typically has lactic acid levels of at least 6%DM
The fermentation acid profile (SilageVFA profile) is probably more useful in pit silages than baleage, as baleage is usually much drier and levels of lactic acid are generally lower (with slightly higher pH results). Preservation in baleage relies less on fermentation and more on packing and wrapping dry, wilted grass so that air is excluded. Even so, there is still fermentation going on, but the higher dry matter is likely to reduce the risk of clostridia fermentation and butyric acid formation.
Customers can easily select any Silage test as shown in the Sample Submission Mobile App screen in Fig. 1 – clicking on the small 
symbol will provide the details of analytes within the profile. Otherwise, our Feed Sample Submission kit has a form with these options to tick. Kits can be ordered through our website and more information is available by contacting an agricultural client services manager.
