Effects of 27 mo of rotational vs. continuous grazing on horse and pasture condition

Abstract

The objective of this study was to determine whether rotational grazing generates horse, pasture, or cost benefits over continuous grazing. The study established two replicates (1.57 ha each) of rotational (R; four grazing sections and a stress lot per replicate, where horses were fed a moderate quality grass hay at 2% of body weight when not grazing) and continuous (C) grazing systems (treatments). Twelve Standardbred mares were grazed for an overall stocking rate of 0.52 ha/horse (n = 3 in each pasture). Recommended management practices for each grazing system were followed for 27 mo including three grazing seasons. Samples were collected monthly between 0800 and 1000. Results were analyzed in SAS (V9.4) using mixed model repeated-measures analysis of covariance, chi-square tests of association, and two-sample t-tests. Alpha level was set at P < 0.05. The C horses were maintained on pasture for 100% of the study duration (844 d; August 1, 2014 to November 22, 2016), while R horses had access to pasture for approximately half of this time (408 ± 33 d). The average length of grazing bout per rotational grazing section during the grazing season increased numerically each year from 7.88 ± 0.76 d in 2014, 10.0 ± 0.61 d in 2015, and 10.9 ± 0.80 d in 2016. Average horse body condition score (BCS) and body fat differed by treatment, with C horses (BCS 6.3 ± 0.05, 17.9 ± 0.15% body fat) greater than R horses (BCS 5.9 ± 0.05, 16.8 ± 0.15% body fat). Both sward height and herbage mass were greater in R (11.8 ± 0.1 cm tall; 1,513 ± 41 kg/ha) than C pastures (6.9 ± 0.1 cm tall; 781 ± 35 kg/ha). The R pastures had higher proportions of vegetative and total cover, planted grasses (tall fescue and orchardgrass), and weeds but lower proportions of grass weeds (nonplanted grasses) and other (rocks, litter, bare ground, etc.) as compared with C pastures. Digestible energy, acid detergent fiber, and calcium were higher in R vs. C pastures; however, crude protein was lower in R vs. C pastures. There were no significant differences between treatments for average monthly amount of hay fed (C, 597 ± 34.1 vs. R, 659 ± 34.1 kg) or average monthly pasture maintenance cost (C, $17.55 ± 3.14 vs. R, $20.50 ± 3.14). This study is one of few replicated experiments comparing the effects of rotational and continuous grazing for horses on pasture quality, horse condition, and production costs. The results here support the recommendation of rotational grazing for production, environmental, and ecological purposes.

Yield, nutrient composition, and horse condition in integrated crabgrass and cool-season grass rotational grazing pasture systems

“…The HM of CSG in the EARLY period are within ranges documented in previous equine grazing studies conducted in the Mid-Atlantic states by Jordan et al (1995) (1,588–4,070 kg/ha) and McIntosh (2007) (2,612 kg/ha) for this period of the grazing season. These HM values are also similar to historical late-spring and early-summer yields reported in prior years for fields used in the current study ( Williams et al, 2020 ).…”

“…This study was conducted in 2019 at the Ryder’s Lane Environmental Best Management Practices Demonstration Horse Farm (Rutgers, The State University of New Jersey; New Brunswick, NJ). Pasture soil was a silty clay loam comprised of FapA (Fallsingotn loams, 0% to 2% slopes, Northern Coastal Plain), NknB (Nixon loam, 2% to 5% slopes), and NkrA (Nixon moderately well-drained variant loam, 0% to 2% slopes) ( Weinert and Williams, 2018 ; Williams et al, 2020 ). Bi-annual soil tests are conducted at the study site, and lime and fertilizers were applied to adjust soil fertility to optimum ranges based on soil test results, with the most recent applications preceding initiation of grazing in 2019.…”

“…A 0.5 m wooden square was placed randomly at four sites in each 0.25 ha section of pasture, and forage in each square was clipped to 7.6 cm to represent minimum allowed grazing height. Forage clipped was placed in a paper bag and dried at 60 °C in a Thelco (Precision Scientific, Chicago, IL) oven to remove moisture content and obtain a DM weight, which was used to estimate HM yield ( Williams et al, 2020 ). Twenty measurements were taken per section of pasture.…”

“…Forage nutrient composition was analyzed by collecting representative pre-grazing samples hand-clipped to a 7.6 cm height. Samples were collected by walking in a random zig zag pattern throughout the pasture section, clipping forage every 30 paces ( Williams et al, 2020 ). All samples were collected between 0800 and 1000 h on the day of rotation.…”

“…Leaving horses on low productivity pastures can result in overgrazing with potential for negative environmental impacts. If forage is overgrazed, over time vegetative cover (VC) will be reduced ( Williams et al, 2020 ), increasing the potential for soil erosion and nutrient runoff ( Butler et al, 2007 ). Furthermore, overgrazing may result in long-term decreased forage stand persistence and weed invasion ( Weinert and Williams, 2018 ).…”