Apparent digestibility, fecal particle size, and mean retention time of reduced lignin alfalfa hay fed to horses.

Reduced lignin alfalfa (Medicago sativa L.) has the potential to provide a higher-quality forage source for livestock by improving forage digestibility. This study was conducted to evaluate apparent digestibility when feeding reduced lignin and nonreduced lignin alfalfa hay to adult horses, and to examine mean fecal particle size (MFPS) and mean retention time (MRT) between alfalfa forage types. In 2017, reduced lignin ("54HVX41") and nonreduced lignin ("WL355.RR") alfalfa hay was harvested in Minnesota at the late-bud stage. Alfalfa hays were similar in crude protein (CP; 199 g/kg), neutral detergent fiber (NDF; 433 g/kg), and digestible energy (2.4 Mcal/kg). Acid detergent lignin concentrations were lower for reduced lignin alfalfa hay (74 g/kg) compared to nonreduced lignin alfalfa hay (81 g/kg). Dietary treatments were fed to six adult, stock-type horses in a crossover study. Experimental periods consisted of a 9-d dietary adaptation phase followed by a 5-d total fecal collection phase, during which horses were housed in individual boxstalls and manure was removed on a continuous 24-h basis. At 12-h intervals, feces were thoroughly mixed, subsampled in duplicate, and used for apparent digestibility and MFPS analysis. On day 2 of the fecal collection phase, horses were fed two indigestible markers, cobalt (Co) and ytterbium (Yb), which were fed as Co-ethylenediaminetetraacetic acid and Yb-labeled NDF residue, respectively. Additional fecal samples were taken at 2-h intervals following marker dosing until 96-h post-dosing to evaluate digesta MRT. Data were analyzed using the MIXED procedure of SAS, with statistical significance set at P ≤0.05. Dietary treatment (i.e., alfalfa hay type) was included as a fixed effect, while experimental period and horse were considered random effects. Dietary treatments were similar in dry matter intake (1.6% bodyweight) and time to consumption (7.6 h). Apparent dry matter digestibility (DMD) was greater for reduced lignin alfalfa (64.4%) compared to nonreduced lignin alfalfa (61.7%). Apparent CP and NDF digestibility did not differ between dietary treatments, averaging 78% and 45%, respectively. Dietary treatments were similar in MFPS (0.89 mm) and MRT for both liquid (23.7 h) and solid (27.4 h) phase material. These results indicate an improvement in DMD for reduced lignin alfalfa hay when fed to adult horses, with no change in forage consumption, fecal particle size, or digesta retention time.

Using Web-Based Surveys to Explore Equine Industry Practices and Future Research Needs.

Social media are an ever-present part of daily life and for researchers and may be a useful platform to increase potential participant pools for Web-based surveys. Although survey usage to evaluate practices in the equine community is not new, the use of social media to advertise and enhance the usage of Web-based surveys is novel. In 2018, the University of Minnesota (UMN) equine Extension program developed and administered two Web-based surveys through the UMN equine Extension Facebook page and monthly e-newsletter. Surveys focused on industry practices and motivating factors behind the usage of hay nets and methods to provide water in the winter to horses. Two thousand eighty-eight participants started the hay net survey with a completion rate of 96%, whereas the winter water survey had a completion rate of 94%, with 930 participants starting the survey. Participant demographics aligned with previous survey populations and represented all regions of the United States. Both surveys revealed information, which described current industry practices as well as future research needs. In addition, participants were asked if scientific research would impact future decision-making in regards to equine management. When exploring hay net practices, most participants responded "maybe" (48%, n = 527), whereas for the winter water survey, the majority responded "yes" (68%, n = 877). Web-based surveys administered through social media present multiple benefits, including savings of both cost and labor, compared with traditional mailed surveys. Despite the success observed with the present surveys, this methodology may not be suitable for organizations with limited social media followers.

The Effect of Goldfish (Carassius auratus) on Water Quality in Horse Stock Tanks.

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 during 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. 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 than metal tanks (P < .001); however, metal tanks had lower NTU and chlorophyll a (P ≤ .008). Adding goldfish resulted in lower TDS (P < .001); however, there was no effect on NTU or chlorophyll a (P ≥ .097). No parameters had an impact on horse preference (P ≥ .108). 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.

Estimation of Actual and Ideal Bodyweight Using Morphometric Measurements of Miniature, Saddle-Type, and Thoroughbred Horses.

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 years, nonpregnant) saddle-type (n = 209), adult (n = 249) and juvenile (<3 years, 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 (±standard deviation) 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 off by 5%-25%. Owner-estimated BW was within 8%-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 application.

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.