Feeding diets high in soluble carbohydrates to growing horses has been implicated in the development of orthopedic diseases; as a result, substitution of dietary fat for soluble carbohydrates has received attention. Because IGF-I is integral to growth and cartilage development and because it is influenced by nutrition, we evaluated the effect of dietary fat substitution on metabolic endpoints and circulating GH and IGF-I in growing horses. Twelve Quarter Horse weanlings, four female and eight male, 151 to 226 d old, were blocked by sex and age and assigned to two treatment groups. Group one (CARB; n = six) was fed a concentrate containing 2.21% fat and 33.9% starch; group two (FAT; n = six) was fed a concentrate containing 10.3% fat and 24.0% starch. Both concentrates contained 3.0 Mcal/kg of DE and 16% CP. Brome hay also was fed. Diets were fed at 0800 and 1600 for 60 d. On d 0, 30, and 60, blood samples were obtained via a jugular catheter from 1 h before until 5 h after the morning feeding. Serum was analyzed for glucose, insulin, GH, IGF-I, NEFA, and total cholesterol (CHOL). Neither ADG (0.85 +/- 0.04 and 0.84 +/- 0.04 kg) nor concentrate DMI (4.04 +/- 0.12 and 4.03 +/- 0.12 kg/d) differed between treatments. There were consistent increases in glucose and insulin in response to feeding on d 0, 30, and 60 for both groups. On d 30, the glucose response to feeding was less (P = 0.07) over time in FAT vs. CARB; however, there were no significant treatment x time effects on d 0 or 60. On d 60, the insulin response to feeding was less (P < 0.05) over time in FAT compared with CARB; however, there was no treatment x time effect on d 0 or 30. Serum CHOL concentrations did not differ between groups on d 0. Horses in the FAT group had increased CHOL concentrations on d 30 and 60 compared with CARB (P < 0.01). Although treatment x time interactions were noted for GH on d 30 and 60 (P < 0.05), only transient and inconsistent differences in the secretory profiles between CARB and FAT treatments were evident at those sampling times. Serum NEFA and IGF-I did not differ between treatments on d 0, 30, or 60. These results suggest that dietary energy source, at least at the level used in this study, did not affect foal growth performance or serum IGF-I and NEFA concentrations. Fat substitution increased serum CHOL and variably affected serum GH, glucose, and insulin concentrations in response to feeding.

Six pairs of full-sibling Quarter Horse foals were produced by non-surgical embryo transfer and immediate rebreeding of donor mares. Each pair of donor/recipient mares consisted of one multiparous (donor) and one nulliparous (recipient) mare of similar body type and size. Milk yield was determined within 2 d of 8, 15, 22, 29 d (early lactation); 45, 60 d (midlactation); and 90, 120 d (late lactation) postpartum by the weigh-suckle-weigh method. On the following day, milk samples were collected, and foals were weighed and measured for wither height, heart girth, metacarpal length, metatarsal length, carpus height, tarsus height, and hip height. Mean gestation length was longer (P < .05) in nulliparous mares than multiparous mares (343 vs 333 d). Daily milk production was greater (P < .05) during early lactation (12.1 vs 10.8 kg) and tended to be greater (P = .08) during midlactation (11.7 vs 10.4) in multiparous mares but was similar between groups in late lactation. Milk composition was similar between groups throughout lactation. Foals produced by multiparous mares weighed more (P < .03) throughout early lactation (70.4 vs 63.1 kg), but no differences in weights occurred between foals from multiparous and nulliparous mares through mid- and late lactation. Average daily weight gain (ADG) was similar between foal groups through early and midlactation. During late lactation, ADG tended to be greater (P = .07) in foals from nulliparous mares (1.05 vs .92 kg/d). These data suggest that nulliparous and multiparous mares of the same breed and similar body type and size produce foals with no differences in size and weight by 4 mo of age.

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Nineteen weanling horses (average age = 147 d) were divided into exercised (EX; n = 10) and nonexercised (NEX; n = 9) groups, with age, sex and breed represented as equally as possible. The EX group was exercised on an automatic walker at a medium trot for up to 20 min, 5 d each week. Both groups were fed to meet 100% of their protein and 110% of their energy requirements (NRC, 1978). The EX group's diet was supplemented, on exercise days, with corn starch to meet the additional energy requirements for exercise. The experiment was conducted over a 111-d period. Body weight was measured at 10-d intervals, and height at the withers and metacarpal circumference was measured at 20-d intervals. Radiographs of the distal radius, metacarpal joint and the proximal and distal ends of the third metacarpal were taken at 147, 218 and 255 d of age to determine bone density and to observe any possible bone abnormalities. There were no differences between groups in weight or wither height gain; however, gain in third metacarpal circumference was greater (P less than .01) in the EX group than in the NEX group from 167 to 215 d of age. Bone density in the EX group increased by a greater amount (P less than .06) than in the NEX group by the end of the trial. There were no lameness problems or bone abnormalities observed in either group. Exercise training of horses during the weanling to yearling age period was shown to improve the stress-bearing characteristics (radiographic bone density and metacarpal circumference) of the third metacarpal without affecting the quantity of body growth.

When the decision was made to euthanatize an acutely laminitic Thoroughbred broodmare, graduate students from the Department of Animal Sciences and Industry reconstructed the skeleton for use as a teaching tool. The reproductive and gastrointestinal tracts were removed and preserved in formalin. The hide, muscle, tendons, ligaments, and organs were removed, and the bones were boiled in water for > or = 48 h to remove all remaining tissue. After boiling, the bones were soaked in gasoline to remove fat from the marrow cavities and then soaked in a bleach/detergent mixture as a final cleaning step. The bones were allowed to dry for several weeks, then a semi-gloss clear lacquer was applied to aid in preservation. The bones were connected with 17-gauge wire and supported by two 1.91-cm galvanized steel rods on a mobile platform. The vertebral column was aligned on flexible copper tube with a 1.27-cm diameter. Additional support was provided for the head and neck by aluminum and steel rods extending from the front support. The final product is a complete, mobile skeleton that will be used as a teaching aid in equine classes. The skeleton serves a function for all levels of the cognitive learning domain. Examples of applications include memorization, identification, and location of bones; use in case studies for synthesis and demonstration of brainstorming efforts; and evaluation of joint ailments for more advanced levels of learning.