Bite Count Research Articles

Comparing Techniques for Determining Steer Diets in Northern Chihuahuan Desert

Diets determined by bite count and microhistological analysis of esophageal extrusa and feces were compared for steers grazing on grass-shrublands in the northern Chihuahuan Desert. The study was conducted on the Chihuahuan Desert Rangeland Research Center near Las Cruces, New Mexico. The purpose was to determine the similarity of 3 dietary techniques on arid, heterogeneous rangeland. It was proposed that the number of bites of each species eaten was directly proportional to the weight eaten as determined by the 2 microhistological techniques. Samples of diets were collected in 4 seasons from 2 steers grazing in a continuous yearlong pasture and in season-long rotation pastures. The 3 dietary techniques did not give similar (p<O.10) estimates of the diets eaten by the steers. Mean similarity indices were highest (77%) comparing diets from analysis of esophageal and fecal material. Lowest mean similarity indices (57%) were from comparing diets from bite count and fecal analysis. Much of the discrepancy between techniques was because of different size plants being eaten and heterogeneity of plant distribution. An importance ranking of dietary species using the 3 techniques showed that the top 3 species comprised over 68% of the total diets. Any of the 3 techniques can be used to determine the common species in the diets which may be all that is necessary for some management and analysis needs.

Seasonal Grazing of Columbia Milkvetch by Cattle on Rangelands in British Columbia

There is a dearth of knowledge on the selection and utilization of Columbia milkvetch (Astragalus miser Dougl. ex Hook. var. serotinus) by grazing livestock on rangelands in British Columbia. Four grazing trials were conducted with cattle on Columbia milkvetch range in southern interior British Columbia. In the first 2 trials during 1990 and 1991 cattle grazed an upper grassland site in late spring. In 1992 and 1993, the animals grazed a lodgepole pine forest site during early summer. The density of Columbia milkvetch and its basal area were similar at both locations. The Columbia milkvetch was not a preferred species on the grassland site as indicated by the bite count technique that determined its percentage in the diet. Consumption of Columbia milkvetch increased gradually as other forage species were preferentially selected and depleted. On the grasslands, consumption of Columbia milkvetch by individual animals did not show an addictive pattern. At the forest site, utilization of Columbia milkvetch was determined on a weekly basis during 1992 and on a biweekly basis during 1993 by paired plots. In contrast to the grassland site, Columbia milkvetch was a preferred species at the forest site where it was utilized to a greater extent than grasses or other forbs. Approximately 80% of the Columbia milkvetch was utilized during 1992 and 60% during 1993, which was significantly greater than the utilization of grasses or other forbs. Forage nutrient analysis at the forest site indicated Columbia milkvetch had higher crude protein and lower ADF content than other forages but it caused livestock poisoning in 1993.

Social Facilitation Influences Cattle to Graze Locoweed

Many ranchers claim that if a cow starts eating locoweed, she will teach others to eat it. Three grazing trials were conducted to evaluate the role of social facilitation in starting cattle to graze locoweed. The first trial was conducted near Gladstone, N.M., using mature cows grazing woolly locoweed (Astragalus mollissimus var. mollissimus Torr). The second trial was conducted on the Raft River Mountains in northwestern Utah, using yearling cattle grazing white locoweed (Oxytropis sericea Nutt). The third trial was conducted to determine if aversion-conditioned yearling cattle would consume white locoweed when placed with cattle that were eating locoweed (loco-eaters). Cattle conditioned to eat locoweed and naive animals in trials 1 and 2 first grazed in separate pastures to evaluate their initial acceptance of locoweed. The groups in the respective trials then were placed together to evaluate the influence of social facilitation on locoweed consumption. Locoweed consumption was quantified by bite count. Naive cattle in trials 1 and 2 sampled small quantities of locoweed while grazing separately. However, they greatly increased locoweed consumption when placed with the loco-eaters. Aversion-conditioned cattle in trial 3 did not consume locoweed while grazing separately. When placed with loco-eaters, they gradually increased consumption of white locoweed, in contrast to the immediate acceptance of locoweed by naive cattle in trials 1 and 2. The aversion extinguished and averted animals eventually accepted white locoweed at levels comparable to loco-eaters. Results of this study demonstrate that social facilitation can cause cattle to start eating locoweed.

Seasonal Grazing of Locoweeds by Cattle in Northeastern New Mexico

Locoweed poisoning generally occurs in early spring. We evaluated cattle grazing of woolly locoweed (Astragalus mollissimus var. mollissimus Torr.) at Gladstone, N.M., and of white locoweed (Oxytropis sericea Nutt. ex T&G) at Capulin, N.M., through the spring and into early summer as the phenological development of warm-season grasses progressed from dormancy to rapid growth. Diets of 8 mature cows were quantified by bite count at each location. Cattle initially rejected woolly locoweed at Gladstone, even though it was the only green forage available in late March and early April. Gladstone cattle were then restricted to a small 7-ha pasture where high grazing pressure and limited feed forced them to graze woolly locoweed (41% of bites). When these cows returned to a larger pasture of unlimited forage availability, they continued eating woolly locoweed (23% of bites). At Capulin, cattle with a history of eating locoweed (loco-eaters) consumed more white locoweed (23% of bites) thin cattle without a history of eating locoweed (6% of bites) during the April grazing period. When warm-season grasses started rapid growth and locoweed matured in June, cattle ceased grazing both locoweed species.

Variation in the grazing behaviour of dairy cows measured by a vibrarecorder and bite count monitor

Ten Friesian dairy cows were fitted on the neck with a Walker pedometer to evaluate the pedometer as a low-cost means of recording grazing bite number, and a Vibrarecorder for comparison and to evaluate the between-cow and between-day coefficients of variation (CV) of grazing bouts, in order to evolve an optimum recording strategy. The total number of daily bouts averaged 5.01 with a mean duration of 1.85 h, giving a total grazing time of 9.27 h per cow per day. The grazing time recorded by the Virarecorders was generally linearly related to total daily bites recorded by the pedometers, although in some cases a quadratic function was significant which was assumed to arise from variation in the biting rate at high grazing times. The between-cow CV of daily grazing time was greater than the between-day CV, but at certain times of the day, particularly at night, the between-day CV was very high. More variation occurred in grazing bout duration than bout number and the variation in total bite number tended to be greater than grazing time.

BEEF CATTLE NUTRITION AND PERFORMANCE ON SEEDED CLEARCUTS IN SOUTHERN INTERIOR BRITISH COLUMBIA

The nutrient content of diets consumed, using a bite count technique, and the performance of beef cows and their calves grazing spruce and pine clearcuts in the southern interior rangelands of British Columbia on continuously and rotationally grazed pasture systems were evaluated in a 3- to 5-yr study. Forage species and plant parts ingested by cows were collected by hand clipping to simulate the diet. Nutrient composition of each sample forage was determined chemically and the nutrient levels of cattle diets were estimated from the bite counts of forages consumed and the chemical composition of the clipped samples. Dietary deficiencies, based on estimates of dietary intake of cows and chemical composition of samples, were noted for protein and phosphorus during August and September (rotational grazing); sodium during September; iodine, copper and zinc throughout the grazing season with the exception of zinc in the September diet of rotationally grazed cows. Selenium was adequate to excessive in the diet. Cow diets consisted of from 50 to 72% grass, from 23 to 42% forbs and from 4 to 20% shrubs. The diversity of diet components maintained nutrient levels of the diet above those provided by grass alone. Weight gains of cows and calves were obtained at monthly intervals for 3 yr and seasonally for 5 yr. There were no significant differences in cow performance among years or between grazing treatments. Cows gained an average of 0.22 kg d−1 over a 90-d grazing period. Average daily gains of cows decreased from 0.55 kg in July to −0.21 kg in September. Calf gains were significantly different between treatments over 5 yr. Calf gains averaged 0.92 kg−1 d on the continuously grazed pastures vs. 0.83 kg d−1 on those rotationally grazed. Total beef production of saleable beef (calves) under the continuous and rotational grazing system was 72.7 kg ha−1 and 65.3 kg ha−1, respectively. Key words: Beef cattle, production, nutrition, clearcuts, daily gains

Cattle Diets on Seeded Clearcut Areas in Central Interior British Columbia

The bite count technique was used to estimate the botanical composition of cattle diets for deferred rotation and continuous grazing systems on seeded forest range previously clearcut of spruce and pine. There was more variability in diets among grazing periods and years within grazing systems than between grazing systems. Grass, forbs, and shrubs averaged 58.5%, 33.5%, and 9%O of the diet, respectively. Orchardgrass, timothy, bromegrass, horsetail, lupine, aster and willow were the major forage species consumed. Diets changed moderately from July through August with a more pronounced change in September. With advanced maturity of grass during dry years, forb usage increased, with some instances of use as high as 54% of the diet. Much of the central interior of British Columbia above 1,000 m elevation is characterized by stagnant stands of Engelmann spruce (Picea engelmanii) and lodgepole pine (Pinus contorta var latifolia) with little understory. In recent years many areas that were clearcut or burned by wildfire have been seeded with nonrhizomatous domestic grasses and legumes to provide a summer forage base for cattle grazing. The same cleared areas are important to foresters for sustained yield of wood. Thus natural regeneration or plantation planting and growth of conifers is of prime importance on the same land that is vital to sustained grazing. These 2 uses are not always compatible so land use becomes an issue. An initial study to resolve the issue of grass production and grazing on tree production was initiated by Clark and McLean (1978), who reported satisfactory tree survival and growth when proper grazing techniques were followed. In continuing to resolve this issue, this study reports an initial documentation of cattle diets under 2 grazing management practices designed to protect silviculture interests while providing management alternatives to cattle producers. This information is valuable to land managers in prescribing future seedings and to resource managers in prescribing grazing management of cleared areas that are being reforested.