Rex D. Pieper

Forage intake by grazing livestock: a review.

Highlight: A wealth of experimental data has been accumulated on quantitative intake of pen-fed livestock; such information has been widely employed to develop a keener nutritional knowledge of such animals. Data of this type are, however, distressingly lacking for grazing livestock. The procedures used for measuring intake by animals under grazing conditions have often been disappointing, and many have provided unreliable data. Forage intake measurements with grazing livestock are more commonly expressed as g DM or OM/Wk -75 or simply as a percent of body weight. Most estimates of inta gk e for cattle and sheep grazing ranges in Western United States fall within the range of 40 to 90 g DM/Wkg’” or from 1 to 2.8% of body weight. Intake usually decreases with advancing plant maturity.

Overstory-understory relations in pinyon-juniper woodlands in New Mexico

Herbage biomass for blue grama (Boutdoua grdlis [H.B.K. Lag& pinyon ricegrass (Pfph&tu&un jimbriatum [H.B.K.] Hit&c.), New Mexico muhly (Muhihkgfa pcsrciflorcl Buckl.), other grasseq and forbs was estimated on 25 pinyon-juniper stands of varying overstory cover on the Fort Stanton Experimental Ranch insouthcentral New Mexico. Negative 2”d degree polynomial curvea best expressed the relationshipa between total understory and blue grama biomass and overstory canopy cover. Positive polynomial relationships were shown for cool-season graazs, New Mexico muhly, and pinyon ricegrass. Reducing pinyon-juniper canopy cover would likely increase blue grama production and reduce production of New Mexico mubly and pinyon ricegraas.

Satellite-based herbaceous biomass estimates in the pastoral zone of Niger.

Pastoralists in the Sahel of northern Africa are entirely dependent on their livestock, which graze on the annual vegetation produced during a relatively short summer rainfall season. The satellite-based normalized difference vegetation index, calibrated with ground-truth sampling of herbaceous biomass throughout the pastoral zone of Niger, was used to estimate standing biomass for the entire Nigerien pastoral zone. Data were obtained and analyzed during a 5-year period from 1986 through 1990. Techniques developed allow officials with the Government of Niger to estimate herbage available to support animal populations throughout the pastoral zone at the end of the growing season and plan grazing strategies for the impending dry season. End-of-season herbage standing crop varied from less than 200 kg ha-1 to nearly 1,700 kg ha-1 with locations and years. Strong biomass gradients were evident from mesic conditions in the southern pastoral zone to xeric conditions in the north.

Fire Effects on Blue Grama-Pinyon-Juniper Rangeland in New Mexico.

Highlight Study of an April 1964 fire in the blue grama-pinyon-juniper vegefa. flon WPe of New Mexico showed fhaf forage producfion was reduced szgnificanfly the first year on fhe burned area huf recovered by the end of fhe second. Species composifion of herbaceous vegefafion was no* significantly affecfed. Loss of live grass crowns was fully rwovered by.fhe second year. Liffer was sigmfmntly less on the burned area all three years of fhe study. About 24% of thejuniper and 13.5% of the pinyen pme were killed by the fire. Cholla less than one ff tall were damaged more by the fire than ihose 2 *o 3 ff *a,,.

Vegetational response to short-duration and continuous grazing in southcentral New Mexico.

Vegetational response of a nine-paddock, short-duration grazing cell was compared to that of a continuous pasture for a 5-year period in southcentral New Mexico. Differences in vegetational response to short-duration and continuous grazing on blue grama rangeland were small. Basal plant cover was slightly hither for the short-duration pastures, but end-of-season standing crop of all species was similar for both systems. Blue grama aboveground productivity and basal cover were higher for the short-duration pastures than for the continuously-grazed pasture. Possible short-term results from short-duration grazing include slightly higher stocking rates and a positive response of blue grama.

Plant distribution surrounding Rocky Mountain pinyon pine and oneseed juniper in south-central New Mexico

Within the pinyon-juniper woodland, trees and understory vegctation are interspersed with open areas forming a mosaic of vegetational patterns. While these patterns may be obvious to the careful observer, few quantitative evaluations of these gradients have been made. For example, Arnold et al. (1964) found rather drastic reductions in basal cover of grasses and forbs with increasing canopy cover. A similar trend was observed with herbage production. Everett et al. (1983) studied vegetational patterns in a singleleaf

Grass response following thinning of broom snakeweed.

Complete removal of broom snakeweed resulted in perennial grass production 833% of that on untreated rangeland after one growing season, and 712% and 300% the second and third year, on a pasture heavily grazed and in poor range condition. On a moderately grazed pasture in good range condition, grass standing crop increased 42% the first year, 81% the second, and 25% the third compared to untreated rangeland. Perennial grass production on the heavily grazed pasture was far below that on the moderately grazed pasture at the start of the study (40 vs 454 kg/ha). After 3 years, with complete broom snakeweed removal and no grazing, perennial grass production was comparable on the pastures once heavily and moderately grazed (1014 vs 939 kg/ha, respectively). Broom snakeweed (Xanthocephalum sarothrae) is a serious perennial weed problem on rangeland in New Mexico. The problem is two-pronged in that, under some conditions, broom snakeweed is poisonous, causing abortion in cattle (Sperry and Robinson 1963), and the weed competes with more valuable forage plants (Ueckert 1979). Platt (1959) estimated that species of the genus Gutierrezia (since treated as Xanthocephalum, Correll and Johnson 1970) occurred on more than 350 million ha of rangeland in the United States. Broomr snakeweed is native on about 60% of New Mexico rangelands. Broom snakeweed populations have increased and subsequently decreased in a cyclic pattern at the Fort Stanton Experimental Ranch in New Mexico following droughts in 1970-71, 1974, and 1976 (Pieper and Donart 1973). Above-average fall, winter, and spring precipitation following drought years appears to be related to the establishment of broom snakeweed on the blue grama (Bouteloua gracilis) range. Since some studies (Jameson 1970, Vallentine 1971) and observations indicate that broom snakeweed populations are cyclic, it seems logical to assume that these plants are fairly short lived. Dittberner (1971) analyzed permanent quadrat records from the Jornada Experimental Range in southern New Mexico collected over a 53-year period and found the average life span of all age classes of snakeweed to be about 2.5 years. Dittberner determined that nearly 70% of the broom snakeweed seedlings die in the first year. Plants living beyond the first year were found to have an average life span of about 4 years. Longevity of the oldest plants ranged up to 15 years. Mature broom snakeweed begins its seasonal growth in late winter to early spring in the Southwest (Ragsdale 1969). Dormant buds, developed in a band above and below the root crown, initiate growth earlier than associated grasses. Because of the competitive advantage from this early growth, there is evidence that production of perennial grasses is decreased where broom snakeweed densities are high. Ueckert (1979) reported herbage production on short grass range to be severely reduced under a dense stand of broom snakeweed. When Ueckert reduced broom snakeweed by 25 and Authors are assistant professor, professor, and professor, Department of Animal and Range Sciences, New Mexico State University, Las Cruces. This report was submitted as Journal Article 793, Agricultural Experiment Station, New Mexico State University, Las Cruces 88003. Manuscript received July 27, 1980. 50%, there was no effect on grass production. However, when all broom snakeweed plants were removed, grass production increased 107%. Broom snakeweed apparently undergoes intraspecific competition as well as interspecific competition with other species (Ueckert 1979). The degree of competition appears dependent upon the population density and the competitive ability of associated species. The objective of this study was to investigate the response of associated species to the removal of broom snakeweed competition. Study Area and Procedures The study was conducted on the Fort Stanton Experimental Ranch 6 km east of Capitan, New Mexico. Average annual precipitation is about 39 cm, with over 60% falling from June through September. Open grasslands on mesas and plateaus are dominated by blue grama. Woodlands occupy steep slopes and rugged hills and are dominated by pinyon and juniper (Pinus edulis and Juniperus monosperma) and wavy-leaf oak (Quercus undulata). Elevation on the ranch varies between 1950 and 2250 m. Two locations selected in 1977 on the Fort Stanton Station represented areas under different grazing intensities and range condition. One area was located in a pasture continuously grazed year-long since 1969 at a heavy stocking rate (18.9 ha/AU). This pasture was considered to be in poor range condition. The second location was in a moderately grazed pasture (23 ha/AU) in good range condition that had also been grazed since 1969. The soil at both locations is from the Dioxice loam series, which is classified as a fine loamy mixed mesic aridic calciustoll. ln May 1977 fences were constructed to exclude grazing from a 0. 1-ha area in each of the two pastures. The fenced areas encompassed a relatively homogeneous stand of I-year-old broom snakeweed plants. Broom snakeweed density was determined by counting all plants within 9 m2 plots, calculating a mean for the exclosure, then uniformly thinning the plants to a desired level by clipping at ground level. Broom snakeweed was reduced by 0, 25, 50, 75, or 100% of the mean density in the heavily grazed pasture, and by 0, 33, 50, 67, and 100% in the moderately grazed pasture. Treatments were replicated four times in a randomized complete block design at each location. Basal cover and standing crop of grasses and forbs were determined annually in the fall at each location. Basal cover was determined by randomly placing a 1 0-point frame along 15 line transects in each plot and recording basal hits for broom snakeweed, forbs and perennial grasses. Herbage standing crop was determined for each species by clipping four 0.25 m2 quadrats in each plot at the end of the growing season. New areas were clipped each season during the 3-year study. All clipped vegetation was separated by species in the field and later oven-dried at 600 C for 72 hrs before weighing. Basal cover and standing crop data were analyzed by analysis of variance. Duncans multiple range tests were used to separate differences among means where appropriate. JOURNAL OF RANGE MANAGEMENT 35(2), March 1982 219 This content downloaded from 207.46.13.129 on Mon, 27 Jun 2016 05:35:25 UTC All use subject to http://about.jstor.org/terms Table 1. Mean density (plants/rM2) of broom snakeweed after thinning plants in May 1977. Natural mortality further reduced the density of plants in 1978 and 1979. Mean density on 10/77 Reduction Mean density on 10/78 Change Mean density on 10/79 Change Heavily grazed pasture 0 100 0.2 1.0 0.4 2.0 6.2 75 4.3 -30.4 0.2 -96.4 12.6 50 7.9 -37.2 1.8 -85.8 18.8 25 8.6 -54.4 0.8 -95.9 25.0 0 9.0 -64.0 1.2 -95.1

Comparison of fecal analysis and rumen evacuation techniques for sampling diet botanical composition of grazing cattle.

Fecal samples, evacuated rumen samples, and non-evacuated rumen samples were compared at different seasons as techniques for determining diet botanical composition of cattle. The study was conducted at the New Mexico State University College Ranch near Las Cruces. Six rumen-fistulated steers were used spring (28 May-7 June), summer (19 July-8 August). fall 1989 (1-17 October), winter (8-28 January) 1990; 4 rumen-fistulated steers were used during summer (24 July-4 August) 1990. Sampling techniques differed (P < 0.05) for the proportion of some plant species in steer diets at certain seasons. In most cases, these differences were observed only for minor forage species. Similarity (%) between fecal samples, evacuated rumen samples, and non-evacuated rumen samples varied with season and with the particular techniques being compared. Similarity (%)between fecal samples and evacuated rumen samples (74%), and highest in summer (1989) between fecal samples and non-evacuated rumen samples (93%). Differential digestion, sampling procedures, and observer errors may explain these differences. For practical purposes, fecal analysis appears to be one of the best techniques to evaluate diet composition of large herbivores.

Range condition from an ecological perspective: modifications to recognize multiple use objectives.

Two changes in traditional range condition analyses are recommended: (1) to replace the terms excellent, good, fair, and poor with ecological equivalents of climax, late seral, mid-seral, and early seral in cases where this is practical; and (2) to develop relationships between products (e.g., livestock, wood products, water) or conditions (e.g., infiltration, site stability, erosion) and successional stage or state. Such information will allow the land manager to evaluate possible tradeoffs between managing for a particular successional stage or state and particular goods or

Vegetational Evaluation of Pinyon-Juniper Cabling in South-Central New Mexico

Vegetational comparisons were made between areas where pinyon-juniper vegetation had been cabled in 1954 and uncabled areas. Total tree density on the cabled areas was about 80% of that on control areas. Basal area and canopy cover of trees was substantially lower on control areas than on cabled areas. Rhus trilobata and Xanthocephaium sarothrae apparently were the only shrubby species that responded to the cabling treatment. Basal cover of Bouteloua gracilis, Eragrostis erosa, and Muhiknbergia pauciflora was significantly greater on the control areas than on the cabled area. About 27% of the land area of New Mexico is covered by pinyon-juniper vegetation (West et al. 1975). These woodlands provide forage for livestock and game, provide products such as fuel, Christmas trees, posts, charcoal, nuts, serve as major watershed areas; and provide recreational opportunities for many people (Hurst 1977). Some evidence indicates that pinyon and juniper are invading grassland vegetation (Johnsen 1962, Little 1977, Springfield 1976). Consequently, considerable effort has been spent to control pinyon-juniper vegetation in the Southwest. In Arizona alone, over 200,000 ha have been treated for juniper control (Skau 1961). Chaining or cabling is a mechanical means of control whereby a large anchor chain or cable is dragged between two crawler-type tractors. Chaining is recommended for use on areas with mostly large, mature trees and few seedlings (Arnold et al. 1964, Jameson and Reid 1965, and New Mexico Interagency Range Committee 1968). Many areas in New Mexico have been cabled or chained, but few have then been evaluated to determine the vegetational response to the treatment. The objective of this study was to compare the vegetation on areas cabled two ways in 1954 with comparable, uncabled areas.