SummaryReasons for performing study : We hypothesised that seasonal pasture myopathy (SPM), which closely resembles atypical myopathy (AM), was caused by ingestion of a seed-bearing plant abundant in autumn pastures. Objectives: To identify a common seed-bearing plant among autumn pastures of horses with SPM, and to determine whether the toxic amino acid hypoglycin A was present in the seeds and whether hypoglycin metabolites were present in SPM horse serum or urine. Methods: Twelve SPM cases, 11 SPM pastures and 23 control farms were visited to identify a plant common to all SPM farms in autumn. A common seed was analysed for amino acid composition (n = 7/7) by GC-MS and its toxic metabolite (n = 4/4) identified in conjugated form in serum [tandem mass spectrometry (MS/MS)] and urine [gas chromatography (GC) MS]. Serum acylcarnitines and urine organic acid profiles (n = 7) were determined for SPM horses. Results: Seeds from box elder trees (Acer negundo) were present on all SPM and 61% of control pastures. Hypoglycin A, known to cause acquired multiple acyl-CoA dehydrogenase deficiency (MADD), was found in box elder seeds. Serum acylcarnitines and urine organic acid profiles in SPM horses were typical for MADD. The hypoglycin A metabolite methylenecyclopropylacetic acid (MCPA), known to be toxic in other species, was found in conjugated form in SPM horse serum and urine. Horses with SPM had longer turn-out, more overgrazed pastures, and less supplemental feeding than control horses. Potential relevance: For the first time, SPM has been linked to a toxin in seeds abundant on autumn pastures whose identified metabolite, MCPA, is known to cause acquired MADD, the pathological mechanism behind SPM and AM. Further research is required to determine the lethal dose of hypoglycin A in horses, as well as factors that affect annual seed burden and hypoglycin A content in Acer species in North America and Europe.

Cover crops can provide ecological services and improve the resilience of annual cropping systems; however, cover crop use is low in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations in the upper Midwest due to challenges with establishment. Our objective was to compare three planting methods to establish cover crops (winter rye [Secale cereale L. ‘Rymin’], red clover [Trifolium pretense L. ‘Medium’], hairy vetch [Vicia villosa Roth], field pennycress [Thlaspi arvense L. ‘MN‐106’], and a mixture of oat [Avena sativa L.], pea [Pisum sativum L.], and tillage radish [Raphanus sativus L.]) (MIX) in corn at the seven‐leaf collar stage. Planting methods included directed broadcast into the inter‐row (DBC), directed broadcast with light incorporation (DBC+INC), and a high‐clearance drill (DRILL). The DRILL method achieved greater fall biomass than DBC for all species except pennycress, and DRILL and DBC+INC increased red clover and hairy vetch spring biomass compared with DBC. Cover crops did not affect corn grain or silage yield and reduced yield of the subsequent soybean crop by 0.4 Mg ha−1 (10%) only when poor termination of hairy vetch occurred at one site. Cover crops with >390 kg ha−1 of spring biomass reduced soil nitrate‐N compared with the no‐cover control. These results support that cover crops can be interseeded into corn at the seven‐leaf collar stage in the upper Midwest to reduce soil nitrate‐N while maintaining corn and subsequent soybean yields; however, effective cover crop termination is critical to avoid competition with the subsequent soybean crop.

Core Ideas Reduced lignin and reference cultivars did not differ in forage accumulation. Forage accumulation was greater with a fall harvest or a 40‐d cutting schedule. Reduced lignin alfalfa averaged 8% less acid detergent lignin and 10% greater neutral detergent fiber digestibility. Cutting treatments with shorter harvest intervals increased forage nutritive value. Delaying reduced lignin alfalfa harvest increased forage mass and maintained quality. Reduced lignin alfalfa (Medicago sativa L.) cultivars have the potential to increase the feeding value of alfalfa for livestock by improving forage fiber digestibility and to increase harvest management flexibility. The objectives were to compare the forage accumulation and nutritive value of reduced lignin and reference alfalfa cultivars when subject to diverse cutting treatments in the establishment and first production year. Research was established in 2015 at four locations in Minnesota. Reference alfalfa cultivars 54R02, DKA43–22RR, WL 355.RR, and the reduced lignin cultivar 54HVX41 were subject to cutting treatments with variable intervals between harvests. Cultivar by cutting treatment interactions were not significant (P > 0.05), but cultivar and cutting treatment effects were significant. Cultivars did not consistently differ in forage accumulation. Establishment year forage accumulation was greater when a fall harvest was taken, and first production year forage accumulation was generally greatest when alfalfa was harvested on a 40‐d cutting schedule. Compared to reference alfalfa cultivars, 54HVX41 had an average of 8% less acid detergent lignin (ADL) and 10% greater neutral detergent fiber digestibility (NDFD) but was similar in crude protein (CP) and neutral detergent fiber (NDF) concentrations. Cutting treatments with shorter harvest intervals increased forage CP and NDFD and decreased NDF and ADL concentrations. With a 5‐d harvest delay, 54HVX41 harvested on a 35‐d harvest interval had a 21% gain in forage mass and a 3% reduction in relative forage quality (RFQ) compared to reference cultivars harvested on a 30‐d harvest interval, which could allow for increased management flexibility.

Excessive BW has become a major health issue in the equine (Equus caballus) industry. The objectives were to determine if the addition of neck circumference and height improved existing BW estimation equations, to develop an equation for estimation of ideal BW, and to develop a method for assessing the likelihood of being overweight in adult equids. Six hundred and twenty-nine adult horses and ponies who met the following criteria were measured and weighed at 2 horse shows in September 2011 in Minnesota: age ≥ 3 yr, height ≥ 112 cm, and nonpregnant. Personnel assessed BCS on a scale of 1 to 9 and measured wither height at the third thoracic vertebra, body length from the point of shoulder to the point of the buttock, neck and girth circumference, and weight using a portable livestock scale. Individuals were grouped into breed types on the basis of existing knowledge and were confirmed with multivariate ANOVA analysis of morphometric measurements. Equations for estimated and ideal BW were developed using linear regression modeling. For estimated BW, the model was fit using all individuals and all morphometric measurements. For ideal BW, the model was fit using individuals with a BCS of 5; breed type, height, and body length were considered as these measurements are not affected by adiposity. A BW score to assess the likelihood of being overweight was developed by fitting a proportional odds logistic regression model on BCS using the difference between ideal and estimated BW, the neck to height ratio, and the girth to height ratio as predictors; this score was then standardized using the data from individuals with a BCS of 5. Breed types included Arabian, stock, and pony. Mean (± SD) BCS was 5.6 ± 0.9. BW (kg) was estimated by taking [girth (cm)(1.48)6 × length (cm)(0.554) × height (cm)(0.599) × neck (cm)(0.173)]/3,596, 3,606, and 3,441 for Arabians, ponies, and stock horses, respectively (R(2) = 0.92; mean-squared error (MSE) = 22 kg). Ideal BW (kg) was estimated by taking [length (cm) × 2.8] + [height (cm) × 4.2] - 611, 606, and 577 for Arabians, ponies, and stock horses, respectively (R(2) = 0.86; MSE = 24). Equids with a BCS of ≥ 7 had a greater likelihood of being overweight, and the model suggested cutoffs at the 48th and 83rd percentiles for underweight and overweight individuals, respectively. Morphometric measurements were successfully used to develop equid BW-related equations.

Cool‐season grasses are rarely evaluated under horse grazing. The objectives of this study were to evaluate preference and forage nutritive value of cool‐season grasses while grazed by horses (Equus caballus L.). Research was conducted in 2010 and 2011 in Minnesota. Four horses rotationally grazed tall fescue [Schedonorus phoenix (Scop.) Holub], meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], quackgrass [Elymus repens (L.) Gould], smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus biebersteinii Roem. & Schult.), reed canarygrass (Phalaris arundinacea L.), perennial ryegrass (Lolium perenne L.), timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), creeping foxtail (Alopecurus arundinaceus Pior.), and orchardgrass (Dactylis glomerata L.) monthly during the growing season. Kentucky bluegrass, timothy, and meadow fescue were the most preferred grasses, with most grazing events removing >60% of the available forage, while meadow bromegrass, creeping foxtail, reed canarygrass, and orchardgrass were less preferred, with grazing removing <50% of available forage (P ≤ 0.0027). Perennial ryegrass, quackgrass, and smooth bromegrass had a higher concentration of crude protein than Kentucky bluegrass, orchardgrass, creeping foxtail, or timothy (P ≤ 0.0027). Quackgrass had a lower neutral detergent fiber (NDF) concentration than creeping foxtail or smooth bromegrass (P = 0.0001). Perennial ryegrass and meadow fescue were higher in NDF digestibility, while creeping foxtail and Kentucky bluegrass were lower (P = 0.0001). Timothy, Kentucky bluegrass, meadow fescue, and perennial ryegrass had higher nonstructural carbohydrate (NSC) concentrations than meadow bromegrass, orchardgrass, or reed canarygrass (P ≤ 0.0001). Horses showed distinct preferences among grasses; however, only NSC was positively correlated with horse preference.