Intensive Rotational Grazing Systems Research Articles

Association of herd composition, stocking rate, and duration of calving season with fecal shedding of Cryptosporidium parvum oocysts in beef herds

Objective To evaluate the association of herd demographics, parturition variables, stocking rate, and rotational grazing practices with the probability of fecal shedding of Cryptosporidium parvum from beef cow-calf herds in California. Design Cross-sectional study. Sample Population 38 beef cow-calf operations. Procedure Fecal specimens were collected and examined for C parvum oocysts, using immunofluorescent microscopy. Association between various demographic and management factors and the probability of shedding C parvum were statistically evaluated. Results Adjusted for age and month of collection of a fecal sample, cattle from herds with a high number of young calves (≤ 2 months old) on the day of sample collection, a high stocking rate (No. of cattle/acre/mo), or a longer calving season were more likely to shed C parvum oocysts, compared with cattle from herds with fewer young calves, a lower stocking rate, or a shorter calving season. Cattle from herds with a higher number of older calves (> 2 months old) on the day of sample collection were less likely to shed C parvum oocysts, compared with cattle from herds with fewer older calves. Using our multivariate model, rotational grazing systems or season of onset of calving were not associated with shedding status for C parvum oocysts. Conclusions and Clinical Relevance Reproductive management that would result in a shorter calving season and use of a lower stocking rate for cattle may be associated with reduced risk of C parvum shedding. Intensive rotational grazing systems and time of year for onset of calving season apparently have little effect on reducing prevalence of oocyst shedding. (J Am Vet Med Assoc 1999;215:1833–1838)

Impacts of forage grazing and cultivation on near-surface relative compaction

The study was conducted at the Lacombe Research Station, Alberta, on an Orthic Black Chernozem of loam to silt loam texture to investigate grazing impacts and cultivation on near-surface soil compaction. Four forages, smooth bromegrass (Bromus inermis Leyss 'Carlton'), meadow bromegrass (Bromus riparius Rhem 'Paddock'), a mixture of triticale (X Triticosecale Wittmack 'Pika') and barley (Hordeum vulgare L. AC Lacombe), and triticale were used for the study. Each forage species was subjected to heavy, medium and light intensity grazing. Measurements of bulk density and volumetric moisture content for the 0- to 10-cm depth interval were conducted using a surface moisture-density probe between spring 1994 and fall 1996. Relative compaction was calculated as the actual bulk density expressed as a percentage of the Proctor maximum density. Relative compaction values for all treatments and that for the benchmark were less than 90%, which is considered critical for limiting plant growth. Cultivation reduced bulk density under annual forages by only 3% and lowered it under heavy grazed annual treatments most. Regression analysis conducted on the dependence of bulk density to cumulative cow-days indicated a curvilinear relationship. Bulk density increased more rapidly with increasing cumulative cow-days for annuals compared to perennials. From a management perspective, adopting intensive rotational grazing systems for perennial and annual forages may not cause any serious surface compaction problems for soils in this area. Key words: Annuals, bulk density, cow-days, grazing intensity, perennials, volumetric moisture content

Farm structure, market structure and agricultural sustainability goals: The case of New York State dairying

AbstractThis paper explores issues of agricultural sustainability in relation to arguments to sustain the family labor farm and the theoretical justification for the recent increase in smallerscale milk processors and differentiated dairy product markets. Using a population of New York State dairy farm households, we identified farm structural variables that influence farmers' use of chemical pesticides and fertilizers and their consideration of intensive rotational grazing. Milk sales, division of hired labor on the farm, and ownership arrangements are found to be interrelated and predict relative use of chemical pesticides and fertilizers within a “conventional” confinement feeding system. Marketing strategies predict production practices within a confinement feeding system less reliably but do predict whether the farm has considered adopting an intensive grazing system. Farms that have higher saks, that use hired labor more extensively, and that are not single family operations are more likely to use chemical pesticides and fertilizers. Farms that sell to differentiated markets are more likely to look favorably on an eventual switch to an intensive rotational grazing system.

Development of a Mobile Solar-powered Dairy Concentrate Feeder

A mobile, solar-powered, computer-controlled, concentrate feeder was built and tested with dairy cattle in an intensive rotational grazing system. The feeder successfully controlled individual feeding of a grain mix to 16 dairy cattle that were grazing pasture divided into nine paddocks. Folding stall gates were needed to protect each cow while eating. An experimental photovoltaic power supply was tested to evaluate the potential of using solar energy to power a mobile feeder. During the trial, the photovoltaic system provided approximately 38 MJ of energy. Although this did not meet the 120 MJ requirement of the feeder, calculations showed that photovoltaics could power such a feeder if the feeder were appropriately designed for the available power. The amount of feed dispensed to animals was measured to be within 6% of the programmed ration.

Maternal Performance of Brangus and Hereford x Brahman F1 Cows with Intensive Grazing Management of Two Forage Types1,2

AbstractA feeder-calf production system was evaluated on Coastal Plain soils in southwestern Arkansas. Two beef cow types [Brangus (BG) vs Brahman × Hereford F, (HBR)] were studied on two forage types [Tifton 44 hybrid bermudagrass (T44HB) vs common bermudagrass-dallisgrass (CBD)]. Two 9.6-ha pastures of each forage type were used with 30 cows (15 of each breed) on each pasture. An intensive rotational grazing system was used in which each pasture was subdivided into three 3.2-ha paddocks, and cows were rotated weekly from mid-April through mid-October. Simmentalsired calves were born in February-March and weaned in mid-October for yr 1988, 1989, 1990, and 1991. Birth weight (BIW) and 205-d weaning weights (WW) of calves were analyzed using a split-plot 2×2×2 factorial design. No two- or threeway interactions were significant (P>.05). Mean BIW for calves from cows on T44HB and CBD were 35.6kg and 35.8kg P>.05), respectively. Mean WW was higher for calves from cows on CBD than for calves from cows on T44HB (240.3 vs 235.1 kg; P<.10). Calves with BG dams had heavier BIW than calves with HBR dams (36.9 vs 34.6 kg; (P<.05); however, calves with HBR dams had heavier WW (241.9 vs 233.6 kg; P<.05). An efficiency ratio (ER) was calculated for each group as (total 205-d weight per group)/(total weight at weaning of cows exposed to breeding per group) × 100. There was no difference in ER due to forage type, but HBR cows had a higher ER than BG cows as a group (45.6 vs 37.6%; P<.05).

Weaning Rate of Brangus and Brahman × Hereford F1 Cows Under Intensive Grazing Management1,2

Weaning rate of Brangus (BG) and Brahman x Hereford F1, (HBR) cows on either Tifton 44 hybrid bermudagrass (T44HB) or common bermudagrass-dallisgrass (CBD) was studied. Simmental-sired calves were born in February-March the following year from each breeding season May 1 to June 30 of years 1987, 1988, 1989, and 1990. An intensive rotational grazing system with 30 cows on 9.6ha was used. Each of four 9.6-ha pastures (two of each forage) contained 15 BG and 15 HBR cows. The 9.6-ha pastures were subdivided into three 3.2-ha paddocks, and cows were rotated each week from mid-April through mid-October. The Coastal Plain soils in each pasture received a total of 190kg of nitrogen (N) per ha per year in five split applications of 38kg N per ha on 21-d intervals. Cows were wintered on the same pastures with a bermudagrass hay-soybean meal and milo diet. Interactions of year by forage, year by breed, and year by breed by forage were nonsignificant for weaning rate (P>.05). Weaning rate was not affected by the interaction of forage by breed (P<.05). Weaning rate favored the HBR breed (91.6 and 82.5, respectively, for HBR and BG, P<.05). Weaning rate for pasture main effects was 92.8 and 82.1 for cows on T44HB and CBD pastures (P<.05), respectively. Conception within 21-d estrus cycles within the breeding season did not differ by breed or pasture (P>.05). These data suggest that the HBR cow was more productive than the BG cow on both T44HB and CBD pastures under intensive grazing management.

Diet Selection by Cattle under High-Intensity Low-Frequency, Short Duration, and Merrill Grazing Systems

Diet Selection by Cattle under High-Intensity Low-Frequency, Short Duration, and Merrill Grazing Systems