Advances in Equine Health and Management II: Grazing Winterhardy Perennial Ryegrass, Estimating Bodyweight, and Evaluating Novel Methodologies for Livestock Water Quality

Abstract

The horse industry provides $122 billion dollars of value added to the U.S. economy, with a $50 billion dollar direct impact to GDP (AHC, 2017a). The use of horses is incredibly diverse, ranging from rescues and recreation sectors to working horses and the competition and racing sectors. Horse owners and enthusiasts are a welcoming community with a strong desire to educate themselves and improve the health of their horses, increase production of their land, and minimize labor and feed costs. In the age of digital media, there are numerous online forums and popular press websites to share information. In addition to, and perhaps despite this, many owners look for scientific information to validate their management decisions. This feedback allows us to keep track of questions and issues that horse owners are having today. In turn, this leads us to new research to answer these questions. Three specific areas of interest are highlighted in this dissertation—alternate forages and ways to improve existing pastures, how to manage horse bodyweight and body condition, and ways to ease or reduce the labor involved in farm management. Perennial ryegrass (PRG) is a high quality and yielding forage that, until recently, lacked the winterhardiness to persist in the upper Midwest. The objective was to evaluate the yield, persistence, forage nutritive value, and livestock preference of a new winterhardy PRG cultivar (‘Forageur’) grown in monoculture and in mixture with white clover under horse and cattle grazing. Research was conducted in St. Paul (SP) and Grand Rapids, MN (GR). Meadow fescue (MF), tall fescue (TF), orchardgrass (OG), and three perennial ryegrass varieties (‘Forageur’, ‘Remington’, and ‘Spreader IV’) were seeded in 2015 (SP) and in 2016 (GR); and were grazed for 2 days by either 6 adult horses (SP) or by 6 cow-calf pairs (GR). Prior to grazing, forage yield and nutritive value samples were collected, and post-grazing, fields were visually assessed for the percentage of forage removal to determine livestock preference. Yields of PRG cultivars were similar but lower yielding (6.9 to 7.6 Mg ha-1) compared to other CSG. Persistence was similar among all CSG in SP; however it was lower for PRG in GR. ‘Forageur’ was highly preferred by both horses (≥74% removal) and cows (≥70% removal) and was consistently among the highest for crude protein (CP; 200 g kg-1), equine digestible energy (Equine DE; 2.35 Mcal/kg), and bovine metabolizable energy (Bovine ME; 2.6 Mcal/kg), moderate for nonstructural carbohydrates (NSC; 136 g kg-1), and among the lowest for neutral detergent fiber (NDF; 518 g kg-1). This research suggests that ‘Forageur’ is viable PRG cultivar to use in upper Midwest livestock pastures. Adding breed type, height, and neck circumference to body length and girth circumference improves bodyweight (BW) estimation in different breeds of horses; however, equations have not been developed for all breed types. The objectives were to develop BW estimation equations for Miniature, saddle-type, and Thoroughbred horses using morphometric measurements. Measurements were collected on adult (≥ 3 yr, non-pregnant) saddle-type (n=209), adult (n=249) and juvenile (< 3 yr, n=61) Miniatures, and adult Thoroughbreds (n=100). Personnel determined body condition score (BCS), measured withers height and girth circumference at the third thoracic vertebra, body length from the point of the shoulder to the point of the buttock and to a line perpendicular to the point of the buttock, and neck circumference at the midway point between the poll and withers. Each horse was weighed using a livestock scale. Bodyweight estimations equations were developed using linear regression modeling and log transformation. Mean (±SD) BCS was 6.1 (±0.8), 5.4 (±0.6), 6.0 (±1.0) and 5.0 (±0.6) for adult and juvenile Miniatures, saddle-type, and Thoroughbreds, respectively. Bodyweight estimation equations developed through the current research were within 4% of the scale BW, and offered improvements over previous BW estimation equations and weight tapes, which were inaccurate by 5 to 25%. Owner estimated BW was within 8 to 15% of scale BW. Morphometric measurements were successfully used to develop BW equations for Miniature, saddle-type and Thoroughbred horses. The equations will assist owners and professionals with managing horse BW and will be added to the Healthy Horse app. Goldfish (Carassius auratus) have been reported as a method to keep water tanks clean; however, little information exists on this approach. The objectives were to evaluate the efficacy of goldfish on maintaining water quality in tanks and to evaluate the frequency that this method is used. The first objective was completed June through October 2017 in St. Paul, MN using plastic and metal 379 L stock tanks, each with and without goldfish in a drylot that housed six adult horses. The stocking rate was 5 goldfish per tank, and all tanks were refilled when any tank reached 190 L. Daily readings of total dissolved solids (TDS) and water turbidity (NTU), and weekly samples to measure chlorophyll a were taken. At the end of each 28-day period, tanks were cleaned and rotated. Plastic tanks had lower TDS compared to metal tanks (P < 0.001); however, metal tanks had lower NTU and chlorophyll a (P ≤ 0.008). Adding goldfish resulted in lower TDS (P < 0.001); however, there was no effect on NTU or chlorophyll a (P ≥ 0.097). The second objective was completed using an online survey that was open from October 31 until December 15, 2018. Of the 672 completed surveys, 56% had not tried using goldfish in water tanks, 26% had utilized goldfish in the past, and 18% currently used goldfish. The inclusion of goldfish in water tanks did not affect all water quality parameters; however, 44% of survey respondents had tried, or were currently using, this management method.