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Apparent metabolic problems were observed in yearling steers grazing Russian wildrye (Elymus junceusFisch.) in spring or early summer. This study was initiated to determine what factors were involved in these metabolic problems. Forage samples were obtained from small plots established in an existing 10‐year‐old stand of Russian wildrye, growing on Temvik silt loam (flne‐silty, mixed Typic Haploborolls) soils. The objective of the experiment was to examine the effect of sampling dates and N, P, and K fertilization on the chemical composition and subsequent nutritional adequacy of this forage for grazing cattle. Levels of N, P, K, and in vitro digestible organic matter (IVDOM) in Russian wildrye declined consistently between weekly sampling dates both years. Forage Ca and Mg levels increased (P < 0.05) between initial and final sample dates, but weekly changes were not consistent between years. The tetany hazard to cattle grazing Russian wildrye appeared greater when evaluated by the ratio of forage K/(Ca + Mg) than when evaluated by estimated blood serum Mg data. Regrowth forage, although morphologically similar to early cut forage, appeared quite different chemically. Nitrogen fertilization increased (P < 0.05) forage N and K and consequently the K/(Ca + Mg) ratio. Nitrogen fertilization decreased (P < 0.05) forage P, but the decrease was not progressive with higher N levels. Fertilization with P increased (P < 0.05) forage P, but effects on other parameters were inconsistent. Potassium fertilizer had little effect on any parameters measured. The data indicated substantial differences in forage chemical composition as affected by year, season, and fertility, but the results did not suggest a cause of the severe scours, excessive urination and depressed weight gains which had been exhibited by yearling steers.

Five laboratory trials were conducted to determine the effects of microwave-oven drying on the chemical composition of forage samples collected via esophageal fistula. Trials 1, 2, 4 and 5 were conducted as randomized complete blocks with two replications for trials 1, 2 and 4 and three replications for trail 5, with a split plot arrangement of treatments due to the use of duplicate samples. Trial 3 was conducted as a randomized complete block with four replications. Results from microwave-oven dried samples were compared with those from samples dried in a conventional oven (forced air) or freeze dried (FD). The effects of sample size, drying time and sample freezing, with respect to conventional oven drying, were also studied. Ash, N and hemicellulose were not affected (P>.05) by drying methods. However, concentrations of acid detergent fiber (ADF), acid detergent fiber N (ADFN), and neutral detergent fiber (NDF) tended to be higher in samples dried in either a microwave or conventional oven compared with FD samples. In vitro digestible organic matter (IVDOM) was consistently lower (P<05) in conventional-oven dried samples, compared with samples dried in a microwave over for 15 to 30 min. Microwave-oven dried samples (15 to 30 min) had higher (P<.05) IVDOM than FD samples when the forage was very mature, but FD samples tended to be higher in IVDOM than microwave-oven dried samples when forage was immature. Samples that were microwave-oven dried for longer than 30 min had higher (P<.05) IVDOM than FD samples, suggesting that a chemical change had occurred in samples exposed to microwaves for an extended period. Extended drying time, sample freezing before drying and sample size had no (P>.05) effect on chemical composition of samples dried in a conventional forced-air oven. Data suggest that forage samples collected via esophageal fistula could be microwave-oven dried for 15 to 30 min followed by drying in a forced air oven at 50 C without substantial change in forage chemical composition.

Intermediate wheatgrass [Elytrigia intermedia(Host) Nevski] including the pubescent subspecies [E. intermediasubsp, barbulatum(Schur) A. Löve], is an important introduced cool‐season grass the plains of northern USA and southern Canada. It is susceptible, however, to foliar diseases, primarily those caused by Cochliobolus sativus, Pyrenophora tritici‐repentis, and Leptosphaeria nodorum. The primary objective of this study was to evaluate the effect of naturally occurring foliar diseases on the nutritive quality of a diverse group of intermediate wheatgrass germplasm selected for resistance or susceptibility to these diseases. A secondary objective was to examine the effect of plant height on nutritive quality and the development of foliar diseases. Herbage samples were collected from resistant and susceptible plants selected from 12 cultivars or strains on 29 July 1983 and 2 July 1985. Susceptible plants infected with foliar diseases (2‐yr means) were lower in N, and higher in neutral‐detergent fiber (NDF) (P< 0.05) than resistant plants. In 1985, susceptible plants had higher concentrations of acid‐detergent fiber (ADF), but there was no significant (P> 0.05) difference between resistant and susceptible plants with respect to cellulose and hemicellulose expressed on an NDF basis, indicating the affect of foliar diseases was on the cell contents, not on the cell walls. Correlation coefficients between disease ratings and in vitro digestible organic matter, N, and NDF were r= −0.27, −0.71, and 0.76, respectively, in 1983. Correlation coefficients involving these entities were lower in 1985. Plant height did not not affect the plants' resistance or susceptibility to foliar diseases. Results from this study demonstrate over a representative germplasm base that nutritive quality of intermediate wheatgrass is diminished by leaf spot diseases, and that leaf spot resistant plants maintain a higher nutritive quality in the presence of disease.

Relationships between dry matter distribution among plant components, growth rates, in vitro digestible organic matter (IVDOM), and water‐use efficiency (WUE) have not been defined for cool‐season wheatgrass species grown on the Northern Great Plains. Three cultivars each of crested wheatgrass [Agropyron desertorum(Fisch. ex Link) Schult.], intermediate wheatgrass [Elyfrigia intermedia(Host) Nevsk: Syn: A. infermedium(Host) Beauv.], and western wheatgrass (Pascopyrum smithii(Rhdb.) Love Syn: A. smithiiRydb.] were field grown and sampled over a 3‐yr period to define these relationships. The soil was a Parshall fine sandy loam (coarse‐loamy, mixed Pachic Haploboroll). Forage was harvested at three dates to measure IVDOM, WUE, forage yield, leaf area index (LAI), and leaf and stem dry matter. Significant differences were mainly present among cultivars of western wheatgrass compared to those of crested and intermediate wheatgrass. ‘Rodan’ western wheatgrass partitioned more dry matter into stems than leaves, which resulted in lower LAI, leaf/stem ratio (LSR), and IVDOM. However, Rodan had higher WUE and forage yield than did ‘Flintlock’ and ‘Rosana’ western wheatgrass. Although forage yield and IVDOM differed among western wheatgrass cultivars, there were no differences in total digestible organic matter. Growth analysis showed Rodan western wheatgrass to be more efficient than Flintlock and Rosana in accumulation of dry matter per unit of photosynthesizing leaf surface. These results suggest that partitioning of dry matter into leaves and stems is a primary factor in determining WUE and digestibility, especially for western wheatgrass.

Four experiments were conducted to estimate the dry matter (DM) intake and utilization of irrigated pasture forage by cattle, and to determine the effect of supplemental corn on intake and utilization. Weight gain and predicted intake of monozygotic twins grazing irrigated pasture forage were not different (P> .05) from weight gain and measured intake of their counterparts fed the same forage in drylot. Predicted total DM intake (as a percent of body weight) of steers with and without 1.36 kg corn per head daily while grazing irrigated pasture was not different (P> .05). However, supplemental corn reduced (P< .05) forage DM intake by approximately the amount of DM supplied by the supplement. Steers consuming fresh forage and 1.36 kg corn per head daily retained more (P< .05) nitrogen than those receiving fresh forage alone. Apparent DM digestibility was not increased (P> .05) with 0.45 kg supplemental corn daily, while it was increased (P< .05) with 1.36 kg corn.

Two growth trials and a digestion trial were conducted to determine the feed value of dehydrated corn plant pellets (DCPP). Properly supplemented DCPP produced gains in growing calves that were not different than those produced with corn silage. However, since the starting material was finely ground before pelleting, DCPP may have passed through the animals' digestive tracts more rapidly than corn silage, resulting in higher dry matter intake (P>.05), lower digestibility (P<.05) and poorer efficiency of gain (P>.05). Coarser grinding of the corn plant prior to pelleting might result in a slower rate of passage of the DCPP and hence, greater utilization of it by the animal.The feasibility of using DCPP will depend upon the cost of processing in relation to the price of silage and the dry matter losses which occur in the silo.Regardless of the cost, DCPP may play an important role as a starting ration for feedlot cattle or as an emergency feed on pastures during periods of inclement weather.

Preliminary experiments were conducted to determine the in vitrofermentation time periods when measurements should be made to estimate maximum digestion rate. Using cellulose digestion and dry matter disappearance as criteria, it was established that with the system employed, this period occurred between 5 and 11 hours. These two measurements were then made on a series of 65 forage samples at 5, 8 and 11 hours. Digestibility values at each time interval and the rate of digestion values, calculated for the intervals 5 and 8, 8 and 11 and S and 11 hr. were correlated with in vivodigestibility data. The correlation coefficients obtained with the rate data were of the same magnitude as those obtained with in vitrodata taken at a specific time.