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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Mechanical Conditioning on Aerobic Respiration of Alfalfa

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

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 1998
Publication Date: N/A

Interpretive Summary: Forage crops constitute an important part of the rations of ruminant animals such as cattle and sheep. Severe mechanical processing, known as conditioning, has been shown to increase the digestibility of forage crops while accelerating their field-drying time to minimize nutrient loss due to rain damage. Another source of nutrient loss is caused by respiration, the conversion of sugars to water and carbon dioxide. Since little is known about how severe conditioning affects this kind of loss, a study was carried out to compare respiration losses over time in unconditioned and severely conditioned alfalfa. Two different temperatures, 88 deg F and 52 deg F and two different crop moistures, approximately 80% and 50%, were tried. The quantity of carbon dioxide given off by the plant material was used to determine the respiration losses. Losses started out very slowly in severely conditioned material, relative to conditioned material, but after about 12 hours they accelerated due to microbial activity and eventually overtook the losses in the conditioned material. Under conditions typically experienced in field-drying of forage, losses in severely conditioned material would not exceed those in unconditioned material. A possible exception might be prolonged exposure to high temperature and high moisture conditions. This means that the benefits of extreme conditioning can be attained without increases in respiration losses. Severe conditioning of forage crops has the potential for both increasing the profitability of livestock production and for reducing the cost of livestock products to the consumer.

Technical Abstract: Unconditioned and macerated alfalfa samples at approximately 55 and 80% moisture wet basis (w.b.) were incubated at 11 and 31 deg C for 48 h. Respiration rates of CO2 from each sample were measured. Respiration of CO2 from unconditioned alfalfa samples appeared to be due to plant cell respiration while respiration of CO2 from the macerated alfalfa samples appeared to be due primarily to microbial growth. Typically, the initial respiration rates of CO2 from the macerated samples were less than the control samples. When the samples were incubated at 31 deg C, the rates at which CO2 respired 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 th control samples.

Last Modified: 7/31/2014
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