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.
Rotational grazing is a recommended practice for grazing livestock, but little is known about its benefits with respect to grazing horses. The objective of this study was to investigate the effects of continuous (CON) and rotational (ROT) grazing on forage nutrient composition and whether those concentrations influenced circulating glucose and insulin concentrations in the grazing horse. Twelve mature Standardbred mares were paired by age and weight and randomly assigned to 1 replicate of either a 1.5 ha cool-season grass CON or ROT system for a total of 3 mares in each system. Mares on CON were allowed to graze the entire system at all times, whereas mares on ROT were given access to a 0.4 ha pasture section and stress lot where they were confined during inclement weather and slow forage growth. Blood and feces from horses and forage from each system were sampled over one 24-h period in June, August, and October. Blood was assessed for plasma glucose (GLU) and serum insulin (INS), feces for pH, and forage for nutritional composition. Data were analyzed by ANOVA with repeated measures with significance set at P < 0.05. There were no treatment differences for water and ethanol soluble carbohydrates (WSC and ESC, respectively), starch, ADF, and NDF, but CP was lower in ROT compared to CON (P = 0.04). With respect to month, WSC were highest in June compared to August and October, whereas ESC were highest in June compared to only August. Starch was lower in October than in June and August. Concentrations of ADF and NDF were lowest in October compared to June and August. Crude protein was higher in October than June and August. Plasma GLU and serum INS were affected by season and time of day but not grazing system. For all horses, GLU was highest in August (105.6 ± 1.3 mg/dL), whereas INS was highest in October (0.
Many methods exist for estimating species composition, but few studies compare those useful in improved horse pastures. The objective of this study was to examine 4 techniques for estimating desirable forage species composition in 2 cool-season horse pastures based on prevalence estimates, repeatability, bias, and practicality, and to select a method for use in a subsequent grazing study. The techniques included Equine Pasture Evaluation Disc (EPED), Line-Point Intercept with 3 transects of 50 observations each (LPI 3-50), LPI with 5 transects of 30 observations each (LPI 5-30), and Step Point (StPt). A generalized linear-mixed effects model procedure of SAS (GLIMMIX) with a logit link was used to test for differences among each species separately. When methods were significantly different (α = 0.05), pairwise comparisons were performed using a paired t-test. The methods did not differ in detecting creeping bentgrass (P = 0.3334) or orchardgrass (P = 0.4207), but there were differences for Kentucky bluegrass (P = 0.0082), tall fescue (P = 0.0314), and other (P = 0.0448). Repeatability plots displayed lower method repeatability as species prevalence increased. Agreement was analyzed between pairs of methods by grass species. Five out of 30 pairs showed significant overall bias (P = 0.0114, 0.0045, 0.0170, 0.0328, and 0.0404), and 3 of them were between LPI 3-50 and EPED. The LPI 3-50 and LPI 5-30 techniques agreed perfectly in prevalence and bias, as did StPt and EPED, meaning they can be used interchangeably. The techniques LPI 3-50 and EPED were the most dissimilar methods. In conclusion, StPt can be used interchangeably with LPI, but StPt was selected due to its thorough representation of the pastures and ease of use.
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