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Title: Forage nutritive value of plant samples collected by clipping or rumen evacuation

Author
item Turner, Kenneth
item Neel, James
item PETERSON, BREKKE - Orise Fellow
item Todd, Richard
item Moffet, Corey
item Gowda, Prasanna
item Steiner, Jean

Submitted to: Grazinglands Research Laboratory Miscellaneous Publication
Publication Type: Proceedings
Publication Acceptance Date: 5/29/2016
Publication Date: 6/14/2016
Citation: Turner, K.E., Neel, J.P., Peterson, B., Todd, R.W., Moffet, C., Gowda, P., Steiner, J.L. 2016. Forage nutritive value of plant samples collected by clipping or rumen evacuation. Pp. 40-45. In: R.W. Todd and A. Campbell (Eds). Proceedings-Great Plains Grazing Field Research Symposium, 14 June 2016, Oklahoma State University, Stillwater, OK. Available: https://drive.google.com/file/d/0B5YS3Y9RTDyiQV9IUURWY2NNNW8/view?pref=2&pli=1.

Interpretive Summary: Methane production in ruminants is associated with low feed nutritive value (especially digestibility) and dry matter intake levels. Knowing forage digestibility and intake by grazing animals is important to understand methane production from individual animals. We compared the nutritive value, including digestibility, of forage samples collected from a mixed sward of native warm-season grasses growing in the southern Great Plains. Forage samples were collected by hand clipping from the sward or collected from the rumen after beef steers grazed these mixed swards. Evaluation of rumen samples which accounted for selective grazing by cattle resulted in increased estimates of digestibility and crude protein, and less fiber compared to hand-clipped forage samples. Forage digestibility information can be coupled with fecal output estimates from cattle to give a more accurate prediction of forage intake by grazing beef cows. Overall, this information will aid scientists and researchers in understanding greenhouse gas inventories, especially methane, being developed across diverse production environments and can aid in predictive modeling efforts.

Technical Abstract: Knowing nutritive value and intake of forage by an animal is important to understand methane production data from individual animals in a grazed environment. Digestibility of forages is typically evaluated as the in vitro dry matter disappearance (IVDMD) using a clipped forage sample; however, beef cattle are selective grazers and do not consume the same plants as are obtained from clipping. The overall objective was to compare nutritive value, including IVDMD, of forage samples collected from a mixed native warm-season grass pasture by clipping or using a rumen-evacuation technique. There was a Month x Sample Method interaction (P < 0.001) for IVDMD, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) and was dependent on the growth stage of the plants during the growing season. Overall, forage samples collected from the rumen compared to clipping were higher (P < 0.001) in IVDMD % (59.8 ± 1.3 vs. 53.8 ± 0.7) and CP % (10.1 ± 0.3 vs. 5.7 ± 0.2), but lower in NDF % (72.4 ± 0.5 vs 77.7 ± 0.3) and ADF % (38.2 ± 0.6 vs.43.8 ± 0.4). Forage IVDMD data derived from rumen samples can better account for selectivity by grazing cows. This data will be coupled with data on fecal output to better predict forage intake by beef cows grazing native warm-season pastures in the southern Great Plains. In addition, this information will help in the understanding of methane inventories related to beef cattle production.