Journal of animal science.
Publisher:
American Society of Animal Science
Frequency: Monthly,
Country: United States
Language: English
Author(s):
American Society of Animal Science., American Society of Animal Production.
Start Year:1942 -
ISSN:
0021-8812 (Print)
1525-3163 (Electronic)
0021-8812 (Linking)
1525-3163 (Electronic)
0021-8812 (Linking)
Impact Factor
3.3
| NLM ID: | 8003002 |
| (DNLM): | J12580000(s) |
| (OCoLC): | 01782370 |
| Coden: | JANSAG |
| Classification: | W1 JO536H |
The effect of initiation of exercise training in young horses on vitamin K status. Twelve Quarter Horses, 18 to 24 mo of age and having an average body weight of 460+/-12 kg, were randomly assigned to one of two exercise treatments (control and exercise) to study the effect of initiation of exercise training in young horses on vitamin K status. The control treatment consisted of hand-walking the horses 7 min/d and 5 d/wk for 180 d. Exercise consisted of the following treadmill exercise regimen: 2 min at 4.5 to 5.4 m/s, 3 min at 13.4 to 14.3 m/s, and 2 min at 4.5 to 5.4 m/s on 5 d/wk for 180 d. Both groups were allowed free access to brome grass hay (273 mg of phylloquinone/1...
Plasma cortisol and ACTH concentrations in the warmblood horse in response to a standardized treadmill exercise test as physiological markers for evaluation of training status. Reliable physiological markers for performance evaluation in sport horses are missing. To determine the diagnostic value of plasma ACTH and cortisol measurements in the warmblood horse, 10 initially 3-yr-old geldings of the Hannovarian breed were either exposed to a training schedule or served as controls. During experimental Phase 1, horses were group-housed, and half of the horses were trained for 20 wk on a high-speed treadmill. During Phase 2, groups were switched and one group was trained for 10 wk as during Phase 1, whereas the control group was confined to boxes. During Phase 3 horses w...
Physiological responses of horses to 24 hours of transportation using a commercial van during summer conditions. Fifteen mature horses (mares, n = 6); geldings, n = 9) were used to assess the physiological responses of 24 h of transport in a commercial van under California summer conditions. The study was conducted on four consecutive days, and data were collected on d 1 and d 2 to obtain baseline values and to determine any diurnal variation in the individual measurements. Travel commenced on d 3 at 0800 for 24 h, with a total of 1,622 km traveled. Blood samples were collected at 0800, 1100, 1400, 2000, and 0200 each day. Horses were weighed and rectal temperatures recorded at 0800 each day and at 2000 ...
Dietary carbohydrates and fat influence radiographic bone mineral content of growing foals. Hydrolyzable carbohydrate intake in horse diets may become excessive when rapidly growing pastures are supplemented with grain-based concentrates. The substitution of fat and fiber for hydrolyzable carbohydrate in concentrates has been explored in exercising horses but not in young, growing horses. Our objective was to compare bone development in foals that were fed pasture and concentrates rich in sugar and starch (corn, molasses) or fat and fiber (corn oil, beet pulp, soybean hulls, oat straw). Forty foals were examined, 20 each in 1994 and 1995. In each year, 10 mares and their foals were f...
Influence of chromium tripicolinate on growth and glucose metabolism in yearling horses. Thoroughbred and Quarter Horse yearlings (n = 24; 335+/-7 d of age) were used in a 112-d feeding trial to determine whether chromium (Cr) supplementation would alter growth, development, and energy metabolism of growing horses on high-concentrate diets. The horses were assigned at random within breed and gender subgroups to one of four treatment groups: A) basal concentrate; B) basal plus 175 microg of Cr/kg concentrate; C) basal plus 350 microg of Cr/kg concentrate; and D) basal plus 700 microg of Cr/kg concentrate. Chromium was provided via Cr tripicolinate (Prince Agri Products, Quincy, IL)...
Responses of horses to trailer design, duration, and floor area during commercial transportation to slaughter. Nine trailer loads of horses (n = 306) transported to slaughter facilities with distances ranging 596 to 2,496 km were studied to characterize the type of horses used in commercial markets and the physiological responses and number of injuries due to transportation under summer environmental conditions. Slaughter horse candidates were middle-aged (11.4+/-.4 yr), possessed moderately fleshy body condition, weighed 432+/-3.3 kg, and were of Quarter Horse or Thoroughbred breeding. The mean weight loss during commercial transport was 4%. The percentage of injured horses was greater (P < .05) fo...
Voluntary intake, digestibility, and subsequent selection of Matua bromegrass, coastal bermudagrass, and alfalfa hays by yearling horses. Matua bromegrass (Bromus willdenowii Kunth. cv. Grasslands Matua) was introduced in 1973, but little information exists concerning its potential as a hay for horses. Thus, voluntary intake and apparent digestibility of OM, CP, and fiber components of Matua by 18 Quarter Horse yearlings (mean initial BW 354 kg; SE 5.8) were compared with alfalfa (Medicago sativa L.) and coastal bermudagrass (Cynodon dactylon L.) as hays in a randomized block design. A 15-d adjustment period was followed by a 5-d collection period during which the hays were consumed ad libitum. Voluntary intake of DM was greater...
Effects of recombinant equine somatotropin on wound healing, carbohydrate and lipid metabolism, and endogenous somatotropin responses to secretagogues in geldings. The primary purpose of this experiment was to assess the possible beneficial effects of recombinant equine somatotropin (reST) administration on wound healing in adult geldings. The effects of the 21-d reST treatment on carbohydrate and lipid metabolism and on endogenous ST characteristics were monitored as well. Single, full-thickness skin incisions (7.62 x 7.62 cm) were made in the pectoral region of all geldings on d 0. Treated geldings received reST at 20 microg/kg BW i.m., and control geldings received vehicle (10 mM sodium borate) at equivalent volumes daily from d 0 (immediately after s...
The influence of betaine on untrained and trained horses exercising to fatigue. Because exercise fatigue has been associated with the accumulation of lactic acid, factors that influence lactate metabolism during exercise can potentially enhance performance. The objective of this study was to examine the effects of supplemental betaine on eight mature Thoroughbred horses before and after 8 wk of conditioning. The effects of betaine were tested in two cross-over design experiments, allowing each horse to receive both the control and betaine treatments at each fitness level. Ingestion of 80 mg of betaine/kg of BW for 14 d before exercise testing did not alter plasma lactate,...
Diurnal variation and age differences in the biochemical markers of bone turnover in horses. Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and ...
Sarcoplasmic reticulum responses to repeated sprints are affected by conditioning of horses. Sarcoplasmic reticulum (SR) responses to repeated sprints and to physical conditioning were studied in 10 Quarter Horses. Exercise tests (four repeated sprints on a treadmill) were conducted before and after 12 wk of sprint conditioning. Muscle samples from the middle gluteal muscle were taken before and after each exercise test, and SR vesicles were isolated. Calcium uptake was determined spectrophotometrically using antipyrylazo III, and Ca2+-ATPase activity was determined using an enzyme-linked optical assay. Conditioning increased calcium uptake rate and Ca2+-ATPase activity by 14 and 38%,...
Ultrasonic evaluation for the time of ovulation in ewes treated with norgestomet and norgestomet followed by pregnant mare’s serum gonadotropin. Progestogens and follicular stimulants have proved reasonably successful for estrus synchronization, but time of ovulation relative to removal of the progestogen is not clearly established. We monitored time of ovulation in ewes following synchronized estrus. Ovaries of 40 Dorset and Rambouillet x Dorset ewes were evaluated during the spring and fall (20/replicate). Ewes were randomly assigned to one of two treatment groups (n = 20/group): implant-only (I) ewes received a norgestomet implant for 10 d; and implant + PMSG (PI) ewes received a norgestomet implant for 10 d with an i.m. injection o...
Calculation of fecal kinetics in horses fed hay or hay and concentrate. Marker methods are needed for estimating fecal output by grazing animals in studies of nutrition and environmental impact. In addition, estimates of prefecal mass and turnover time are relevant to exercise performance and certain digestive disorders. As a first step in developing marker methods for field use, a chromic oxide model of fecal kinetics was developed and tested in the context of a digestion balance experiment with stall-fed horses. The model consists of removal of feces at a constant rate from a single compartment, the prefecal mass. Four horses were fed hay, and another four were ...
Deconditioning reduces mineral content of the third metacarpal bone in horses. Diet and exercise are two management factors that affect bone density and strength. We proposed that bone density and calcium status would be affected by deconditioning for 12 wk and by dietary Ca concentration. Eleven highly conditioned Arabian horses were taken out of training and placed in stalls for 12 wk. Horses were walked on a mechanical walker in two 30-min sessions, 7 d/wk. Diets were designated CC (.36% Ca) and HC (.62% Ca). Data were collected every 21 d. Serum or plasma were analyzed for total and ionized Ca, parathyroid hormone, osteocalcin, hydroxyproline, electrolytes, and blood...
Immunocytochemical localization of luteinizing hormone and follicle-stimulating hormone in the equine pituitary. Gonadotropin-specific primary antisera and gold-conjugated secondary antibodies were used to immunocytochemically localize gonadotropins in the anterior pituitary of intact pony mares. Electron microscopy was then used to characterize the ultrastructure and immunoreactive staining characteristics of equine gonadotropes. Cells containing LH were morphologically indistinguishable from those containing FSH. Gonadotropes were relatively large and commonly had eccentric nuclei. The rough endoplasmic reticulum was well developed and dilated. Secretory granules were present in two morphologically dis...
Illegal use of beta-adrenergic agonists: European Community. The use of veterinary medicinal products within the European Community is governed by a series of directives and regulations that describe the requirements for safety, quality, and efficacy of these products. Veterinary therapeutic use of beta-agonists has only been approved in the case of clenbuterol for bronchodilatation in horses and calves and for tocolysis in cows. No beta-agonists have been permitted in the European Community for growth-promoting purposes in farm animals. Surveillance for the presence of residues of veterinary agents in food-producing animals and meat is regulated by the...
Immunocytochemical localization of prolactin and growth hormone in the equine pituitary. The ultrastructural and immunoreactive staining characteristics of cells containing prolactin (lactotropes) and growth hormone (GH; somatotropes) in the anterior pituitaries of gonadally intact pony mares were studied at the electron microscopic level. Lactotropes included two morphological subsets: Type I cells were larger and contained large, dense, polymorphic granules that were scattered throughout the cytoplasm; Type II cells were smaller and contained small, dense, polymorphic granules that were predominantly found in peripheral areas of the cytoplasm. Lactotropes constituted 5 to 16% of...
Vitamin A repletion in thoroughbred mares with retinyl palmitate or beta-carotene. Forty-five Thoroughbred mares used in an 8-mo depletion study were kept for an additional 20 mo on the same three forage diets (15 mares each): 2-yr-old orchardgrass hay and vitamin A-free concentrate on a drylot (HC); pasture, orchardgrass/alfalfa hay, and vitamin A-free concentrate (PHC); or pasture and orchardgrass/alfalfa hay only (PH). Each diet group was divided into three subgroups, and mares (n = 5) in each group were given either retinyl palmitate (A) at twice the NRC (1989) recommended daily intake, the equivalent amount of vitamin A in the form of water-dispersible beta-carotene (B)...
Pulsatile release of somatotropin related to meal feeding and somatotropin response to secretagogues in horses. Our goal was to establish a time of day and(or) interval from feeding that would avoid the refractory period after a somatotropin (ST) surge and optimize the responsiveness of horses to ST secretagogues. Two experiments were conducted with eight geldings conditioned to consume grain at 0800 and 1600 daily. In Exp. 1, during a 24-h period, these geldings averaged 3.2 +/- .3 pulses of ST with peak amplitude of 4.2 +/- .4 ng/mL, pulse duration of 55 +/- 6 min, and interpeak interval of 400 +/- 57 min. No ST peaks occurred within 2 h after either grain feeding. In Exp. 2, eight geldings were given...
Digestibility, apparent mineral absorption, and voluntary intake by horses fed alfalfa, tall fescue, and caucasian bluestem. Alfalfa (Medicago sativa L.), low-endophyte (< 5%) tall fescue (Festuca arundinacea Schreb.), and caucasian bluestem (Bothriochloa caucasica [Trin.] C.E. Hubbard) were fed as chopped hay to six Arabian geldings (BW 441 kg; SE 2) in intake and digestibility experiments to determine nutritional value for horses at maintenance. Each experimental design was a replicated Latin square. Alfalfa was higher in DM and CP digestibility, IVDMD, apparent absorption of Ca, K, and S, and voluntary intake than the grasses (P < .05). Caucasian bluestem was higher in Zn but was lower in CP, TNC, Mg, P, K,...
Effect of dietary vitamin E supplementation on the integrity of skeletal muscle in exercised horses. The effect of vitamin E intake on indicators of muscle integrity was studied in exercised horses. Nineteen horses were blocked by sex and then assigned to one of three diets: no supplemental vitamin E (BASAL), BASAL plus 80 IU of supplemental vitamin E/kg DM (80), or BASAL plus 300 IU of supplemental vitamin E/kg DM (300). The BASAL diet contained less than 44 IU of vitamin E/kg DM, but it was adequate in all other nutrients. During the 90-d treatment period, horses were exercised 5 d/wk; in addition, serum and middle gluteal muscle alpha-tocopherol concentrations were measured at 0, 30, and 9...
Acute effects of short-term feed deprivation and refeeding on circulating concentrations of metabolites, insulin-like growth factor I, insulin-like growth factor binding proteins, somatotropin, and thyroid hormones in adult geldings. Two studies were performed with Standardbred geldings 7 to 21 yr of age to determine the sequence of changes in blood plasma concentrations of some hormones and metabolites during feed deprivation for 48 h and for 12 h after refeeding. Plasma hormone and metabolite concentrations were determined with methods validated for horse plasma. Insulin-like growth factor binding proteins (IGFBP) were determined with radioligand analysis following SDS-PAGE electrophoresis. In both experiments, plasma concentrations of triiodothyronine and thyroxine decreased (P < .01) during feed deprivation and incr...
Prolactin, gonadotropin, and hair shedding responses to daily sulpiride administration in geldings in winter. This experiment was designed to determine 1) the efficacy of daily s.c. injections of a dopamine antagonist, sulpiride, for increasing prolactin secretion in geldings in winter and 2) whether increasing prolactin concentrations would hasten the onset of hair shedding or enhance gonadotropin secretion. Five geldings each received vehicle (vegetable oil) or sulpiride (100 mg in vehicle) daily from February 8 through March 29. On February 8 and every 7 d thereafter through March 29, blood samples were drawn around treatment injections and hair samples were collected. On March 30, all geldings rec...
Prolactin administration to seasonally anestrous mares: reproductive, metabolic, and hair-shedding responses. Eight pony mares received 4 mg of recombinant porcine prolactin (rpPRL) daily for 45 d beginning on January 15; eight control mares received vehicle. Reproductive end points and various indicators of metabolism, hair shedding, and thyroid activity were monitored. Prolactin concentrations peaked in mares treated with rpPRL at 94 +/- 19 ng/mL 2 h after injection and were 5.1 +/- 1.7 ng/mL 24 h after injection. Treatment with rpPRL increased (P < .01) hair shedding within 14 d, which peaked at 28 d and then dropped precipitously. Binding of 125I-equine prolactin confirmed that antibodies were ...
Feed intake, body weight, body condition score, musculation, and immunocompetence in aged mares given equine somatotropin. Sixteen 20- to 26-yr-old mares were given 0, 6.25, or 12.5 mg/d equine somatotropin (eST) to determine whether aged mares respond to ST with changes in feed intake, body weight, body condition score (based mostly on fat cover), or immunocompetence. Neither dry matter intake, body weight, nor body condition scores were altered during the 6 wk of eST injection. However, based on photographs taken to evaluate musculation before and after treatment (scores 0 to 4), mares given eST developed greater (P < .07) muscle definition (1.8 +/- .6 and 2.5 +/- .6 for 6.25 and 12.5 mg eST/d, respectively) ...
Effect of feeding and feed deprivation on plasma concentrations of prolactin, insulin, growth hormone, and metabolites in horses. Two experiments were conducted to determine 1) the prolactin response to different kinds of feedstuffs in stallions and 2) the effects of total feed deprivation on prolactin secretion in mares and its interaction with the prolactin response to feeding. Experiment 1 was performed with stallions as a 6 x 6 Latin square: A) no feed; B) pelleted feed fed to meet 82.5% of the horses' CP requirements; C) pelleted feed at 25% of the amount in B; D) pelleted feed as in B plus water ad libitum; E) cracked corn at the weight in B; and F) chopped alfalfa at the weight in B. The positive prolactin respons...
Prolactin involvement with the increase in seminal volume after sexual stimulation in stallions. To test the hypothesis that prolactin mediates the increase in seminal volumes induced by sexual stimulation in stallions, semen was collected from six stallions every other day for 26 d. The last eight collection days were treatment days. For each stallion, four treatments were randomly assigned to the first four of the eight treatment collection days, and then repeated in reverse order on the last four collection days; 1) CONTROL: semen collected per normal procedures; 2) Sexually stimulated: stallions were presented to mares in a chute for 10 min before collection; 3) Bromocriptine (dopamin...
Age and breed differences in thyroid hormones, insulin-like growth factor (IGF)-I and IGF binding proteins in female horses. A survey with horses was conducted to determine whether plasma concentrations of triiodothyronine (T3), thyroxine (T4), insulin-like growth factor (IGF)-I and IGF binding proteins (IGFBP) change as horses grow, mature sexually, and age. Jugular blood was sampled from Standardbred fillies and mares at ages 0, 1, 7, and 14 d, at 1, 2, 4, 5, 6, and 9 mo, and at 5 to 8 and 16 to 22 yr (n = 5 to 18). In a second survey, we measured the same variables in eight breeds of horses with markedly different adult body sizes, from Miniatures to Friesians. Plasma T3, T4, and IGF-I were determined by radioimm...
Dietary protein and energy restriction in mares: rapid changes in plasma metabolite and hormone concentrations during dietary alteration. Two diets consisting of bermudagrass hay and a corn-cottonseed hull-based supplement were formulated to provide either 100% (control) or 50% (restricted) of the protein and energy requirements for maintenance for mature mares. Twelve light horse mares were fed the control diet for 7 d, and then at 0800 on d 0, six mares were switched to the restricted diet. All diets were fed as two equally sized meals at 0800 and 1600. At 0800 on d 7, mares receiving the restricted diet were switched back to the control diet. Relative to control mares, mares switched to the restricted diet had reduced plasma ...
Behavior of horses is affected by soy lecithin and corn oil in the diet. To test the hypothesis that dietary fats may improve tractability of horses, the effects of four total mixed diets on behavior were compared. The control diet (CON) contained chopped hay, corn, oats, beet pulp, molasses and a mineral mix; the three test diets contained an additional 10% (by weight) corn oil (CO), soy lecithin-corn oil (SL-CO), or soy lecithin-soy oil (SL-SO). Eight horses were fed each diet in random order for four 3-wk periods. Behavior was observed during the last week of each feeding period. Spontaneous activity was evaluated using a pedometer and was less in horses fed SL-...