Annual medic (Medicago spp.) pastures that produce high levels of good quality forage are well suited to grazing and are used extensively throughout dryland farming regions of the world. In these regions, they are normally an integral component of cropping rotations because they allow for reductions in weed and disease problems in addition to increasing soil N levels for subsequent crops. The objective of this research was to investigate the performance of 17 annual medic cultivars and experimental lines for their potential use as self‐regenerating annual pastures in the dryland cropping region of southeastern Wyoming. Dry matter and seed production capabilities were recorded over three seasons, 1996 to 1998. Growth phase development following different emergence times was evaluated in two seasons, and the forage quality was assessed for medic cultivars and lines grown in the 1997 season. Results revealed that the M. rigidula (L.) All. line, SA10343, consistently produced the greatest level of dry matter, with more than double the amount of forage than nearly all other cultivars. Dry matter production was related to the period of growth and development where higher yielding cultivars showed extended periods of vegetative growth. In general, the southeastern Wyoming climate substantially reduced the growth and development periods of medic cultivars bred in southern Australia. Given the overall performance of all cultivars, it was determined that the M. rigidula species had the greatest potential for further development in this environment.

Soil organic carbon levels have declined 24 to 60% on many Great Plains soils since initial cultivation. Integrated crop and livestock systems could help reverse this trend, therefore we examined the extent of use, the factors affecting use, and the potential for this system. The 1992 U.S. Department of Commerce data indicate that land in integrated systems is limited to less than 10% of the agricultural land. However, expiration of the USDA Conservation Reserve Program (CRP) has created interest in integrated systems. Economists report that after CRP contracts expire, perennial forages and livestock systems may be the most profitable; however, a survey of growers indicates that 63% of all CRP acres will go back to crop production. Recent research in Wyoming shows that returning CRP land to production using wheat (Triticurn aestivum L.)‐fallow practices quickly degrades soil quality. A doubling of grazing fees would mean an 18% reduction in demand for public land, which could mean more options for CRP acreage after contract expiration. Exemplified successful systems are the Australia wheat‐sheep (Ovis aries L.) system, perennial legume‐wheat rotation in southern Alberta, grass community establishment on marginal Wyoming cropland, and an alternative (organic) farming system in South Dakota. Benefits include the opportunity for soil quality improvement, economic diversity, and pest control. However, tradition, lack of managerial experience, and necessary alteration in farm‐ranch infrastructure may slow adoption. Generally, dryland integrated systems are agriclimatic zone specific, and represent a potential ecologically and economically sustainable form of agriculture. Scientists and producers have to identify and develop appropriate integrated systems that fit the natural resource base. Research Question Soil organic carbon levels have declined on Great Plains soils since initial cultivation. Integrating crop and livestock production systems may be one of the ways to halt or reverse this trend. Our objective is to examine the extent, factors limiting more widespread use, and the potential of integrated crop and livestock production systems in the Great Plains. Literature Summary A 1957 review documented the effects of cultivation on soil carbon and N from 24 Great Plains Research Stations and reported losses of 24 to 60% from soils cultivated for 30 to 43 yr. More recent studies from the Great Plains report similar losses of soil organic carbon with cultivation. The desire to reverse this continuing soil degradation led to the establishment of the USDA Conservation Reserve Program (CRP) and motivated a greater interest in alternative cropping systems. Integrating crop and livestock production systems has been successful in Australia, as revealed by examining the benefits of management alternatives on Australian wheat yields from 1860 to 1980. The decline in wheat production, starting in 1860 continuing until 1900, went from an average of 12.8 to 7.5 bu/acre. The use of superphosphate, fallow, and new varieties, bro...

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Angus × Gelbvieh rotationally crossbred yearling heifers (n = 99, yr 1; n = 105, yr 2) were used in a 2-yr randomized complete block design experiment with repeated measures to determine the effect of feeding camelina biodiesel coproducts (meal and crude glycerin) on serum concentrations of triiodothyronine, thyroxine, insulin, β-hydroxybutyrate, and glucose, as well as on growth and reproductive performance. Heifers were assigned to 1 of 15 pens, and pens were assigned initially to receive 7.03 k·•heifer(-1)·d(-1) of bromegrass hay plus 0.95 kg·heifer(-1)·d(-1) of 1 of 3 supplements for 60 d before breeding: 1) control (50% ground corn and 50% soybean meal, as-fed basis); 2) mechanically extracted camelina meal; or 3) crude glycerin (50% soybean meal, 33% ground corn, 15% crude glycerin, 2% corn gluten meal; as-fed basis). Preprandial blood samples were collected via the jugular vein on d 0, 30, and 60 of the feeding period. A 2-injection PGF(2α) protocol (d 60 and 70 of the study) was used to synchronize estrus. Heifers were artificially inseminated 12 h after estrus was first detected. Heifers not detected in estrus within 66 h received a GnRH injection and were artificially inseminated. Dietary treatment × sampling period interactions were not detected (P = 0.17 to 0.87). Dietary treatment did not affect BW (P = 0.44 to 0.59) or serum concentrations of thyroxine (P = 0.96), β-hydroxybutyrate (P = 0.46), glucose (P = 0.59), or insulin (P = 0.44). Serum concentrations of triiodothyronine were greater (P = 0.05) in heifers fed camelina meal. Additionally, dietary treatment did not affect the percentage of heifers detected in estrus before timed AI (P = 0.83), first-service pregnancy rates of those heifers detected in estrus (P = 0.97), or overall first-service pregnancy rates (P = 0.58). Heifers fed camelina meal, however, had greater (P = 0.05) first-service pregnancy rates to timed AI than did heifers fed the control and crude glycerin supplements. The cost per pregnancy was similar for heifers fed the crude glycerin or the control supplement, whereas the cost per pregnancy was the least for heifers fed camelina meal. We conclude that camelina coproducts can replace conventional corn-soybean meal supplements in the diets of developing replacement beef heifers.