Extending the collection length of breath samples for methane emission estimation using the SF6 tracer technique

PINARES-PATIÑO C.; GERE J. I.; WILLIAMS K. E.; GRATTON R.; JULIARENA P.; MOLANO G.; FERNÁNDEZ S.; MACLEAN E.; SANDOVAL E.; TAYLOR G.; KOOLAARD J. P.

Banff

Conferencia; GREENHOUSE GASES AND ANIMAL AGRICULTURE CONFERENCE; 2010

Conventionally, the sulphur hexafluoride (SF6) tracer technique for the estimation of methane (CH4) emissions involves sample collections over 24 h repeated across 5-7 days. This schedule may not be practical under extensive grazing systems with low carrying capacity of grasslands. Here, we explored the possibility of a single sample collection over extended periods (5 and 10 days) as an alternative to daily sample collections. Eight rumen-fistulated non-lactating cows were housed in a facility enabling both natural and artificial ventilation and fed commercial silage to achieve a fixed and common daily feed intake of 6.4 kg dry matter per cow. Each cow was deployed with a fresh SF6 permeation tube and after a 10-day diet acclimatization, breath collections were conducted for CH4 emission estimation using the SF6 tracer technique. Eight sample lines were fitted to the collection harness, ensuring that a common mix of breath sample was available to each sampling line. Half of the sample lines collected breath samples into stainless steel cylinders using a steel bearing ball flow regulator (UNICEN-Argentina system, ARG), and half collected samples into PVC yokes using a capillary system as flow regulator (AgResearch-New Zealand system, NZL). Within each system and within the 10-day timeframe, common-source breath samples were collected either daily (ARG-1 and NZL-1), across two 5-day periods (ARG 1-5, ARG 6-10, NZL 1-5, NZL 6-10) or one 10-day period (ARG 1-10, NZL 1-10). Both the ARG 1-10 and NZL 1-10 collections were conducted in duplicate. Thus, within each system, 14 breath samples were collected from each cow, and following the 10-day tracer period, emissions of CH4 were measured using respiration chambers. Overall, the NZL system had larger sample collection success than the ARG system. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. 6) tracer technique for the estimation of methane (CH4) emissions involves sample collections over 24 h repeated across 5-7 days. This schedule may not be practical under extensive grazing systems with low carrying capacity of grasslands. Here, we explored the possibility of a single sample collection over extended periods (5 and 10 days) as an alternative to daily sample collections. Eight rumen-fistulated non-lactating cows were housed in a facility enabling both natural and artificial ventilation and fed commercial silage to achieve a fixed and common daily feed intake of 6.4 kg dry matter per cow. Each cow was deployed with a fresh SF6 permeation tube and after a 10-day diet acclimatization, breath collections were conducted for CH4 emission estimation using the SF6 tracer technique. Eight sample lines were fitted to the collection harness, ensuring that a common mix of breath sample was available to each sampling line. Half of the sample lines collected breath samples into stainless steel cylinders using a steel bearing ball flow regulator (UNICEN-Argentina system, ARG), and half collected samples into PVC yokes using a capillary system as flow regulator (AgResearch-New Zealand system, NZL). Within each system and within the 10-day timeframe, common-source breath samples were collected either daily (ARG-1 and NZL-1), across two 5-day periods (ARG 1-5, ARG 6-10, NZL 1-5, NZL 6-10) or one 10-day period (ARG 1-10, NZL 1-10). Both the ARG 1-10 and NZL 1-10 collections were conducted in duplicate. Thus, within each system, 14 breath samples were collected from each cow, and following the 10-day tracer period, emissions of CH4 were measured using respiration chambers. Overall, the NZL system had larger sample collection success than the ARG system. Further, the NZL system yielded more consistent CH4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains. 4 emissions than the ARG system. However, both systems yielded much lower (P < 0.05) CH4 emissions than the respiration chambers. Compared with the NZL system, the ARG system yielded better relationships between the tracer estimates and the chamber values. It is concluded that sample collection length can be successfully extended, but mismatch between tracer estimates and chamber values of CH4 emission remains.