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i ~ - ,. Table 2. Nutritional quality of diets selected by cows from the pastures. November January Crude protein % 12.6 7.3 NDF % 53.8 64.6 IVTD % 62.2 60.1 Forage Yield Forage yield for all three pastures averaged 865 lbs/acre (DM basis). The average yield for forage kochia was estimated to be 588 lbs/acre and crested wheatgrass was 277 lbs/acre. Pasture yield decreased substantially throughout the duration of the study. Total yield decreased from 1160 lbs/acre in November to 412 lbs/acre by the end of January. Over time there was an estimated 458 Ib decrease in forage kochia and a 290 ]b decrease in crested wheatgrass. The forage kochia yielded significantly more than did the crested wheatgrass on average (310 lb/acre more). Despite the drop in forage availability, the cattle had access to adequate forage to select a diet that met or exceeded their nutrient requirements. However, it appears that cows should be removed from pastures at about the level of residual forage that we observed so that diet quality does not fall below maintenance requirements. Animal Performance Average body condition score for the cows on pasture was 5.3 and in the feed pens 5.6. The average condition score for pastured and penned cows increased over the 84 days .5 and 1.2 respectively. Average backfat increased .11 inches for the animals on pasture and .33 inches for the animals in the feed pens. Considering that there was no supplementation for the pastured cows, their performance was very good. The winter, however, was mild and the forages may have retained a higher-than-normal overall quality. Body condition score and backfat for the pasture treatment cows remained ideal. The cows fed in the pens had higher than desired condition score and backfat which was a result offree-choice alfalfa hay, although the difference between backfat levels determined in the pasture treatment cows and pen treatment cows was statistically insignificant. This indicates that the winter grazing system was comparable to feeding traditionally stored feeds for animal performance. From an economic sense, a grazing system would be more profitable because it would cost approximately $45-$50 / AUM to feed stored feeds and only about $16-$20 / AUM to pay for pasture rent and fees. Grazing systems are also much less labor intensive. Other Research Crude protein has been reported to range from 14 to 8 % during the period of August to Mazch, respectively. The University of Wyoming found that forage kochia tested 7.7 % crude protein in late February, and was higher than 12 perennial grasses and three legumes (Table 1). They also reported lower NDF and ADF than other tested species (Table 1). Because NDF and ADF are related to forage intake and digestibility, this indicates forage kochia has a high nutritive value during the winter. Dr. David Koch (Univ. of Wyoming) evaluated cows grazing forage kochia on the Broadbent Ranch in Uinta County, WY. The cows grazed from early January until mid-March and calved in late-Mazch. A seed crop had been harvested from the kochia, leaving most of the remaining plant below snow. The kochia yielded 8301bs per acre of dry matter compared to 33 ]bs per acre in an adjacent sagebrush range. The cows were provided 21bs per day of a grain-based supplement that contained 13% crude protein during the coldest period. The cows improved 2 points in body condition score during the grazing period. The kochia tested over 7.5 % crude protein at the end of the trial. s_