Winter blanketing practices: An online survey of North American horse owners.

Blanketing is a highly debated practice utilized in the equine community as part of winter horse management. Despite this, little research is available on the prevalence, reasoning, and management decisions related to use of blankets for horses in North America. Therefore, the objective of this study was to develop an understanding of blanketing management practices and beliefs of North American horse owners. A 33-question, branched online survey was developed and available between December 1, 2020 and January 5, 2021 and advertised using social media and e-newsletters. The FREQ procedure for Chi-squared analysis in SAS was used when comparisons were made between participant-reported frequencies. There were 1,450 respondents from North America who completed the survey. Demographic information indicated the majority of respondents were from the Midwest region of the United States (68%); however, geographical region did not impact the frequency of blanket usage (P = .17, X2 = 8.99). When respondents were asked to self-report discipline, recreational riding was the most prevalent (40%). Overall, 54% of respondents (n = 790) reported blanketing the majority of their horses during the winter. The most frequently selected reason respondents chose to blanket horses was exposure to precipitation (78%). Out of the respondents who did not blanket the majority of their horses (n = 660), the primary reason for not blanketing was access to shelter (50%). This survey provides valuable information on blanketing and winter management practices reported by horse caretakers in North America and will help direct future research and education efforts.

Plasma Amino Acid Concentrations of Horses Grazing Alfalfa, Cool-Season Perennial Grasses, and Teff.

The impact of forage species on plasma amino acid (AA) concentrations of grazing horses (Equus caballus L.) is unknown. The objectives of this study were to determine the impact of different forage species on plasma AA concentrations and protein synthesis. Research was conducted in July in St. Paul, MN, USA. Alfalfa (Medicago sativa L.), mixed perennial cool-season grasses (CSGs), and teff (Eragrostis tef [Zucc.] Trotter) pastures were grazed by six horses randomly assigned to one of three forage types in a replicated Latin-square design. Horses had access to pasture each day. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2 and 4 hours after turnout. Corresponding forage samples were taken by hand harvest and analyzed for AA concentrations. Equine muscle satellite cell cultures were treated with sera from grazing horses to assess de novo protein synthesis. Data were analyzed using PROC MIXED in SAS. When evaluating forage, AA concentrations were generally lowest in teff and highest in CSG (P ≤ .05). Significant differences in threonine concentration in the plasma were observed; there was no effect on de novo protein synthesis of cultured equine myotubes treated with plasma obtained from the grazing horses (P ≥ .20). As a result, although there were significant differences in forage AA content, only plasma threonine concentration was different at 4 hours with no effect on protein synthesis of cultured equine satellite cells.

Glucose and Insulin Response of Aged Horses Grazing Alfalfa, Perennial Cool-Season Grass, and Teff During the Spring and Late Fall.

Spring and late fall grazing can lead to metabolic problems in horses (Equus caballus L.) as a result of elevated nonstructural carbohydrates (NSC) in pastures. Therefore, the objectives were to determine the impact of different forage species on blood glucose and insulin concentrations of horses during the spring and late fall. Research was conducted in May (spring) and October (late fall) in St. Paul, MN. Alfalfa (Medicago sativa L.) and mixed perennial cool-season grasses (CSG) were grazed in spring, and CSG and teff (Eragrostis tef [Zucc.] Trotter) were grazed in late fall by six adult horses randomly assigned to a forage in a cross-over design. Jugular catheters were inserted 1 hour before the start of grazing, and horses had access to pasture from 8 AM to 4 PM in the spring and 8 AM to 12 PM in the late fall. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2 hours intervals after turnout. Plasma and serum samples were collected and analyzed for glucose and insulin, respectively. Corresponding forage samples were taken by hand harvest. Seasons were analyzed separately, and data were analyzed using the MIXED procedure in SAS with P ≤ .05. Teff had lower NSC compared with CSG in the late fall (P ≤ .05) with subsequently lower average glucose, average insulin, and peak insulin in horses grazing teff compared with CSG (P ≤ .05). These results suggest grazing teff could lower the glucose and insulin response of horses during late fall.

Cultured equine satellite cells as a model system to assess leucine stimulated protein synthesis in horse muscle.

Leucine has been shown to stimulate the mammalian/mechanistic target of rapamycin (mTOR) signaling pathway which plays numerous key regulatory roles in cell growth, survival, and metabolism including protein synthesis in a number of species. However, previous work with equine satellite cells has suggested distinct species differences in regards to physiological effects and the magnitude of responses to growth factors and regulators. Because there is limited research available regarding the role of leucine in regulating equine skeletal muscle protein synthesis, the objective of this study was to evaluate the effect of leucine on the mTOR signaling pathway in cultured equine satellite. Protein synthesis was evaluated by measuring the incorporation of [3H] Phenylalanine (3HPhe) in equine satellite cell myotube cultures treated with a leucine titration ranging from 0 to 408 µM. Our results show a 1.8-fold increase (P < 0.02) in protein synthesis at levels slightly greater than those found in the general circulation, 204 and 408 µM when compared to a no leucine control (0 µM). Puromycin incorporation, a nonradioactive surface sensing of translation (SUnSET) methodology, was also measured in cells treated with leucine (LEU; 408 µM), a no-leucine control (CON), and a puromycin-negative vehicle (PURO-). These results demonstrated a 180% increase (P = 0.0056) in puromycin incorporation in LEU compared to CON cultures. To evaluate the mTOR signaling pathway, equine satellite cell myotube cultures were treated with leucine (LEU; 408 µM) or a no-leucine control (CON) in the presence or absence of rapamycin (LR and CR, respectively), an inhibitor of mTOR. The mTOR inhibitor, rapamycin, suppressed phosphorylation of mTOR (P < 0.01) and rS6 (P < 0.01) with an increase in phosphorylation of rS6 in leucine-treated cultures observed when compared to control cultures (P < 0.05). Similarly, there was a 27% increase (P < 0.005) in the hyperphosphorylated γ-form of 4E-BP1 compared to total 4E-BP1 in LEU compared to CON cultures with leucine-induced phosphorylation of 4E-BP1 completely blocked by rapamycin with a smaller decrease observed in CR compared to CON cultures. The major finding of this study was that leucine activated the mTOR translation initiation pathway and increased transcription of global proteins in cultured equine satellite cells. Use of the cell culture system with primary equine muscle cell lines provides the opportunity to distinguish the impact of leucine on muscle and protein synthesis, independent of systemic interactions.

Glucose and Insulin Response of Horses Grazing Alfalfa, Perennial Cool-Season Grass, and Teff Across Seasons.

Elevated nonstructural carbohydrate (NSC) values in pasture forages can cause adverse health effects in some horses (Equus caballus L.). The objectives of this study were to determine the impact of different forage species on blood glucose and insulin concentrations of horses throughout the grazing season. Research was conducted in July (summer) and September (fall) in St. Paul, MN. Alfalfa (Medicago sativa L.), mixed perennial cool-season grasses (CSG), and teff (Eragrostis tef [Zucc.] Trotter) pastures were grazed by six horses (24 ± 2 years) that were randomly assigned to one of three forage types in a replicated Latin-square design. Jugular catheters were inserted 1 hour before the start of grazing and horses had access to pasture each day from 08:00 to 16:00 hours. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2-hour intervals following turnout. Plasma and serum samples were collected and analyzed for glucose and insulin, respectively. Corresponding forage samples were taken by hand harvest. Seasons were analyzed separately and data were analyzed using the MIXED procedure in SAS with P ≤ .05. Teff generally had lower (P ≤ .05) equine digestible energy, crude protein, and NSC compared to the other forages. Differences in peak insulin were observed between horses grazing CSG and teff during the fall grazing (P ≤ .05). These results suggest grazing teff could lower the glucose and insulin response of some horses.