Graduate Thesis Or Dissertation
 

Influence of spring crested wheatgrass production on intake of grazing steers

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1g05fg34n

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  • Research was initiated at the Squaw Butte Experimental Range in southeastern Oregon to study the influence of crested wheatgrass (Agropyron desertorum (Fisch.) Schult. ) herbage availability on relative dry matter intake (DMI) of yearling steers. Herbage dry matter production on an 18 ha range and daily fecal production of yearling steers were measured during April, May and June of 1970 and 1971. Herbage production was estimated from oven dry samples obtained by clipping plots to ground level during eight trials in 1970 and four trials in 1971. Total fecal production, determined from steers equipped with fecal collection harnesses and bags, was used as an index of relative DMI. Dry matter digestibility (DMD) of the herbage was assumed to remain constant with advance in season. The validity of this assumption was checked using three methods to estimate DMD: in vitro digestion plus pepsin (IVP), lignin ratio (LR) and in vitro digestion of cell wall constituents (TD). Dietary samples were collected from esophageally fistulated steers in 1971 to consider the influence of selectivity on DMD estimates. Dry matter digestibility estimates from clipped and dietary samples were significantly different (P < 0.01) within all trials. Because DMD estimated from the three methods did not remain constant, quantified estimates of DMI were calculated using the fecal production to indigestibility ratio. Although no direct comparisons were made, estimates of DMI from TD were consistently lower than DMI estimated from IVP or LR; but, all methods of estimating DMD showed the same relative influence of herbage availability on DMI of grazing steers. Dry matter intake was not limited when herbage availability equaled or exceeded 135 or 176 kg/ha during 1970 and 1971, respectively.
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