Tocopherol and carotenoid levels in baled silage and haylage
Baled silage and haylage are commonly used feeds for horses. The researchers of this study were curious about what happens to the levels of vitamins of these feeds. This is because they are looking for answers if these wrapped forages are suitable for horses. The focus is on Vitamin E, which are tocopherols and provitamin A which are carotenes.
It is known that Vitamin E can be lossed in barley that has been wrapped air-tight. So the question is, is this the same in wrapped forages? And does Vitamin A (carotene) undergo the same process? Also known is that carotene and tocopherol are destroyed due to oxidation.
Early investigation shows that vitamin E from a natural source was more effective at elevating plasma tocopherol levels in horses than synthetic Vitamin E. That's why it is important to keep the Vitamin E levels in forages close to the initial levels in the fresh crop. The best source for Vitamin A is also in fresh crop (grass).
In this experiment they used the first cut of the same field. After mowing, three sections of the cut down grass where processed in different moments. The silage was wrapped 4h after mowing (DM level 300g/kg). The first batch haylage was wrapped 20h after (DM level 500g/kg), the second batch haylage came 10h after the first (DM level 600g/kg). Of each crop they made round and square bales.
They took 1200g of each crop just before baling and froze these samples. After 11 months of storage they took samples of each crop and compared them to the first samples.
You could say the first haylage batch generally contained less tocopherol and carotene than the silage and second haylage batch.
Silage bales (square) and haylage bales (round and square) contained 0.60 of initial tocopherol content and 0.86 of initial carotene content after ensiling. This is higher than Silage (round) and first haylage batch (round and square) which contained 0.39 of initial tocopherol content and 0.33 of initial carotene content.
Therefore, you can not say there is a clear relation between degree of fermentation and content of tocopherol or carotene.
Expert opinion by Jantine Steehouder
Sadly the study did not compare these levels to hay (no wrapping). Hay is considered to be the best form of forage in a horse diet. It is really interesting to see what different it is to silage, haylage and fresh crop.
Also, the study is only about the levels of these two nutrients and how to best preserve them. It shows nothing of the overall effect of the silage or haylage for the body. Therefore, the nutrients in silage and haylage from the second batch could be at their best, but that is not the only factor what makes it a healthy forage for horses. Other factors (like acids, molds, dry matter (DM), state of fermentation, etc) are as important.
> From: C.E. Müller et al., Animal Feed Science and Technology 137 (2007) 182-197. All rights reserved to Elsevier B.V.. Click here for the online summary.