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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #112938
Title: PREDICTING WEIGHT GAIN OF GRAZING STEERS BY THE KINETICS OF IN VITRO GAS PRODUCTION OF EXTRUSA SAMPLES FERMENTED IN NITROGEN SUPPLEMENTED AND UNSUPPLEMENTED INCUBATION MEDIUM

Author
item Blummel, Michael
item Grings, Elaine
item Haferkamp, Marshall

Submitted to: European Association of Animal Production Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2000
Publication Date: 6/1/2000
Citation: BLUMMEL, M.R., GRINGS, E.E., HAFERKAMP, M.R. PREDICTING WEIGHT GAIN OF GRAZING STEERS BY THE KINETICS OF IN VITRO GAS PRODUCTION OF EXTRUSA SAMPLES FERMENTED IN NITROGEN SUPPLEMENTED AND UNSUPPLEMENTED INCUBATION MEDIUM. EUROPEAN ASSOCIATION OF ANIMAL PRODUCTION PROCEEDINGS. 2000. p. 19-20.

Interpretive Summary: The relationship between gas production (GP) of extrusa diet samples (EDS)and weight gain (WG) of steers was examined. Six 12-ha pastures were allocated to 2 treatments with 3 replications (T1 = control and T2 = pasture treated for annual grasses). Each pasture was stocked with 8 crossbred steers and was grazed from May to September 1995. Steers were weighed every 30 days and gains were calculated for monthly periods. Extrusa samples were collected every 30 days using 3 esophageally fistulated yearling heifers per pasture. In vitro GP and 48 hr in vitro organic matter digestibility (IVOMD) of EDS were conducted in nitrogen (N) supplemented (N-rich) and N unsupplemented (N-low) incubation medium. Gas production was recorded after 2, 4, 6, 8, 10, 12, 14, 16, 24, 30, 36, 48, 54, 60, 72, and 96 hrs of incubation and fit to 2 exponential (exM) and to 2 sigmoidal models (sigM). Exponential models fit gas production profiles from May to June better (P < 0.05) than sigM but the reverse was true for later periods. In N-low medium, asymptotic values of gas production of exM and sigM tended to be inversely related to WG while these relationships were positive (P < 0.05) in N-rich medium. In all models and in both N levels rates of GP were positively (P < 0.0001) related to WG accounting for a maximum of 92% of the variation in gain. Highest correlation between individual gas volumes and WG were observed for incubation periods of 4 to 10 hrs in N-rich incubations and for 12 to 30 hrs in N-low incubations accounting for a maximum of 94 (P < 0.0001) and 88% (P < 0.0001) of the variation in WG, respectively. The 48 hr IVOMD accounted for 96 and 87% of the variation in WG in N-low and in N-rich medium, respectively.

Technical Abstract: The relationship between gas production (GP) of extrusa diet samples (EDS)and weight gain (WG) of steers was examined. Six 12-ha pastures were allocated to 2 treatments with 3 replications (T1 = control and T2 = pasture treated for annual grasses). Each pasture was stocked with 8 crossbred steers and was grazed from May to September 1995. Steers were weighed every 30 days and gains were calculated for monthly periods. Extrusa samples were collected every 30 days using 3 esophageally fistulated yearling heifers per pasture. In vitro GP and 48 hr in vitro organic matter digestibility (IVOMD) of EDS were conducted in nitrogen (N) supplemented (N-rich) and N unsupplemented (N-low) incubation medium. Gas production was recorded after 2, 4, 6, 8, 10, 12, 14, 16, 24, 30, 36, 48, 54, 60, 72, and 96 hrs of incubation and fit to 2 exponential (exM) and to 2 sigmoidal models (sigM). Exponential models fit gas production profiles from May to June better (P < 0.05) than sigM but the reverse was true for later periods. In N-low medium, asymptotic values of gas production of exM and sigM tended to be inversely related to WG while these relationships were positive (P < 0.05) in N-rich medium. In all models and in both N levels rates of GP were positively (P < 0.0001) related to WG accounting for a maximum of 92% of the variation in gain. Highest correlation between individual gas volumes and WG were observed for incubation periods of 4 to 10 hrs in N-rich incubations and for 12 to 30 hrs in N-low incubations accounting for a maximum of 94 (P < 0.0001) and 88% (P < 0.0001) of the variation in WG, respectively. The 48 hr IVOMD accounted for 96 and 87% of the variation in WG in N-low and in N-rich medium, respectively.