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Quality of forage and cattle diets on the Wyoming high plains Grazing crested wheatgrass Agropyron desertorum.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Hart, Richard Harold Abdalla, O. M. Clark, D. H. Marshall, M. B. Hamid, Mr Hami |
| Copyright Year | 1983 |
| Abstract | Diets of cattle grazing crested wheatgrass [Agropyron deserrorum (Fisch.) Schult.] or native range pastures and major forage species in these diets were analysed for crude protein (CP), acid and neutral detergent fiber (ADF and NDF), lignin, and in vitro dry matter disappearance (IVDMD) 1975-1978. Objectives were to determine (1) rate of change in forage quality, (2) effect of weather on rate of change, and (3) degree of selection for diet quality by cattle. CP of 6 forage species declined .03-.23 percentage points/ day, while IVDMD declined .06-.90 points/day. CP and IVDMD of western wheatgrass (Agropyron smithii Rydb.), blue grama [Bocrteloua grucifis (H.B.K.) Lag. ex Steud.], and scarlet globemallow [Spaherulcea coccinea (Pursh.) Rydb.] were high in spring, while ADF, NDF, and lignin were low, but quality of grasses decreased much faster than that of the forb. Quality of needleandthread (Stipu comata Trin. & Rupr.) was lower than that of the other two grasses in spring, but CP declined more slowly then, while IVDMD declined at the same rates as that of blue grama and western wheatgmss. Quality of sedges (Cruex spp.) was similar to that of western wheatgmss and blue grama in spring, but CP decreased faster while fiber components increased slower than those of grasses. CP of western wheatgrass and blue grama was increased by abundant spring rainfall, while that of blue grama increased after heavy summer mins. As the season progressed, cattle on range selected diets higher in crude protein and lower in cellulose than expected on the basis of botanical composition of the diet and composition of individual species. Quality of forage consumed increased markedly in mid-July when immature blue grama replaced needleandthread in the diet. Quality of crested wheatgmss declined faster than that of range grasses, although it was higher early in the spring. Diets of cattle on crested wheatgmss pasture in early spring were lower in quality than clipped crested wheatgmss, because of consumption of standing dead material, but diets were higher in quality than clipped grass in late spring. Performance of grazing animals, including weight gain, reproductive success and other parameters, isdetermined by both intrinsic and extrinsic factors. Chief among extrinsic factors are forage intake and forage quality, and forage intake is partially dependent upon forage quality. Therefore, information on forage and diet quality is essential to any prediction or modeling of livestock production on pasture or range. Forage quality may be expressed as digestible nutrient concentration (dry matter, specific nutrients, or energy) and/ or concentration of components which limit digestibility (fiber, lignin, and silica). It is well known that quality decreases with advancing maturity of forage species; nutrient concentration and digestibility decrease and concentration of digestion-limiting components increases. What is needed are (I) reliable estimates of the rate at Hart is research agronomist. USDA, ARS. C are former graduate assistants, Range Science, kFe yenne, WYO.; Abdalla and Hamid partment, Colorado State Um,versity; Clark, Marshall, Hagerand Waggonerareformergraduateassistantsandanlmal nutritionist, respectively, Animal Science Division. Univeristy Of Wyoming. This research was carried out at the High Plains Grasslands Research Station, 8408 Hildreth Road? Cheyenne, Wyo. 82009, under cooperative agreements of USDA, ARs, with Umveristy of Wyoming and Colorado State University. Manuscript received June 15, 198 I. which these changes occur in forages and diets; (2) information as to the degree which diet selection by the grazing animal can compensate for the decline in forage quality; and (3) understanding of the extent to which variations in rainfall and temperature can change forage quality. Forage and cattle diets from crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] and native range pastures were sampled at the High Plains Grasslands Research Station, Cheyenne, Wyo., from 1975 through 1978. Samuel and Howard (1982) determined and published the botanical composition of cattle diets on range from samples which werecollected 19751977. This paper will present information on chemical composition and in vitro digestibility of these same diet samples, and of forage samples collected at the same time from the same pastures. Such information should prove helpful in explaining seasonal patterns of livestock gains, in helping range managers to develop grazing systems to maximize use of forages when quality is high, and in modeling the plant-animal interactions in range and pasture ecosystems. Materials and Methods The pastures and sampling procedures have been described by Samuel and Howard (1982). Esophageal-fistulated cattle collected diet samples from a crested wheatgrass pasture stocked with cowcalf pairs and heifers at 0.5 I AUM/ ha in May and June, and two native mixed-grass range pastures stocked at 0.12 and 0.23 AUM/ha June through November. In 1975, samples were collected biweekly, with collections in the morning of the first day and late afternoon of the following day. Animals were fasted overnight or for several hours before collection, respectively. From 1976 through 1978, diet samples were collected in the morning and afternoon in alternate weeks, two days per week. Two to 4 animals were collected in each pasture at each collection date. Following collection, samples were lightly squeezed by hand and oven-dried at 600 C for 48 hours. At the same time diet samples were collected, samples of major forage species in the diet were clipped and collected. Only current year’s growth was clipped to l-2 cm from the ground, but no attempt was made to collect only green forage or to collect the same plant parts being selected by the cattle. These samples also were oven-dried at 60’ C for 48 hours. Dried forage and diet samples were ground to pass through a I-mm screen and were stored in plastic bags to await analysis. Crude protein was determined by the Kjeldahl method as described by AOAC (1960). The Goering and Van Soest (1970) procedure was used to determine neutral detergent fiber, acid detergent fiber, and lignin. In vitro dry matter dissappearance (IVDMD) was determined using the modified Tilley and Terry (1963) method. Species and diets analyzed and components analyzed for differed somewhat among years, as shown in Table 1. Analysis of variance for unbalanced designs was used to evaluate differences between pastures and times of sampling; variance among fistulated animals within pastures was used as an error 46 JOURNAL OF RANGE MANAGEMENT 36(l), January 1963 Table 1. Dates on whkh cattle dkts and forage were sampled, characterization of mealg used t0 calculate regressions, and pammeters measured. |
| Starting Page | 46 |
| Ending Page | 51 |
| Page Count | 6 |
| File Format | PDF HTM / HTML |
| DOI | 10.2307/3897980 |
| Volume Number | 36 |
| Alternate Webpage(s) | https://journals.uair.arizona.edu/index.php/jrm/article/download/7463/7075 |
| Alternate Webpage(s) | https://doi.org/10.2307/3897980 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
