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United States Department of Agriculture

Agricultural Research Service

Title: Aerobic Respiration of Alfalfa As Affected by Level of Conditioning

Authors
item Kraus, Timothy - NEW HOLLAND-NA
item Koegel, Richard
item Muck, Richard

Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 15, 1998
Publication Date: N/A

Interpretive Summary: Intensive mechanical processing (conditioning) of forage crops like alfalfa, which ruptures a high fraction of the plant cells, has been shown to hasten field drying, thus reducing rain damage. In addition, feeding trials have shown that intensively conditioned forage is more digestible than conventional material yielding 8-15% more energy. Both effects result in increased value. Some of the highly digestible carbohydrates in forages are lost due to continued respiration as the plants dry down in the field. If drying is slow or insufficient, microbial respiration can lead to additional losses. The question has been raised whether intensive conditioning would decrease or increase respiration losses under good or poor drying conditions, respectively. Chambers with controlled temperature and moisture were established for both severely conditioned and unconditioned alfalfa. Carbon dioxide, a product of respiration, was measured as it left the chambers. Initially, the respiration of unconditioned material was higher and appeared to result from plant respiration. However, after 12 hours, carbon dioxide from the intensively conditioned material increased rapidly and could be as much as four times that of the unconditioned alfalfa. It appeared to be the result of microbial respiration. It was concluded that for forage crops which field- dried within 12 hours, respiration losses would be less for intensively conditioned forage than for control material. It may, however, be inadvisable to intensively condition crops under poor weather conditions. Appropriate processing of forage crops during harvest can increase the nutrients available to animals. This can increase the profitability of forage-based enterprises such as dairy and beef production.

Technical Abstract: Unconditioned and macerated alfalfa samples at approximately 55 and 80% moisture wet basis were incubated at 11 and 31 deg C for 48 h. Rates of CO2 production from each sample were measured. The CO2 from unconditioned alfalfa samples appeared to be due to plant cell respiration while CO2 from the macerated alfalfa samples, particularly at 31 deg C, appeared to be due eprimarily to microbial growth. Typically, the initial rates of CO2 production from the macerated samples were less than the control samples. When the samples were incubated at 31 deg C, the rates at which CO2 evolved from the macerated samples increased exponentially to approximately 4 times that of the control samples at approximately 12 h after the samples had been macerated. Consequently, the cumulative loss of DM from the macerated samples during the first 12 h of incubation was less than that of the control samples; however, after 12 h of incubation, loss of DM from the macerated samples increased to nearly twice the level of the control samples.

Last Modified: 9/21/2014
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