|O'Donnell, Colm - SILSOE RES INST., IRELAND|
Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 15, 1998
Publication Date: N/A
Interpretive Summary: Cattle can best utilize the nitrogen in alfalfa if the nitrogen remains in protein form. Unfortunately when alfalfa is preserved in a silo rather than as hay, much of the protein can be broken down into nonprotein forms of nitrogen. The reason for the protein breakdown in the silo is that the oxygen-free or anaerobic environment in the silo causes the rapid death of plant cells, releasing enzymes that break proteins into many small parts. Today, many fruits and vegetables are stored in modified atmospheres before sale. The modified atmosphere contains lower levels of oxygen and higher levels of carbon dioxide than normal air. The goals are to provide enough oxygen to keep the plant cells alive but also to create an environment where spoilage microorganisms cannot grow rapidly. This technology was studied as a means of reducing protein loss in alfalfa. We found that a modified atmosphere was able to consistently reduce protein losses. However, the modified atmosphere kept the alfalfa cells alive only for 3 days after placing the crop in storage. Thereafter, the presence of oxygen in the silo only served to promote the growth of spoilage microorganisms. Overall, modified atmosphere for a controlled period at the beginning of ensiling would appear to be advantageous in alfalfa protein preservation, but many details remain to be solved to develop a practical system for use on the farm.
Technical Abstract: The potential of a modified atmosphere (MA), containing 3% oxygen, 12% carbon dioxide and 85% nitrogen, to reduce proteolysis in alfalfa silage was investigated in three experiments. The first two experiments examined the effects of MA and ensiling plus control, sugar, ammonia and low temperature treatments in a 2 x 4 factorial design on proteolysis in direct tcut and wilted alfalfa, respectively. A third experiment examined the duration of cell viability under MA and ensiling and the effect of this on silage soluble nonprotein nitrogen. Modified atmosphere consistently reduced soluble nonprotein nitrogen and improved retention of true protein in alfalfa relative to ensiling. Modified atmosphere was capable of extending cell viability in the silo for two to three days, and in this period little dry matter loss occurred. There was no benefit to extending the MA beyond the period of cell viability as extensive dry matter loss from microbial spoilage occurred at longer storage times. In direct cut alfalfa, only low temperature improved protein preservation relative to the control treatments under both MA and anaerobic conditions. In wilted alfalfa, none of the treatments improved protein preservation relative to control. Overall, the results of this and previous studies showed good protein preservation in alfalfa from use of MA, but there remain many practical issues to be explored, including the feeding value of MA-stored alfalfa.