G.D. Potter

Physiologic and metabolic response of exercising horses to added dietary fat

Summary Six mature Quarter Horse-type geldings were used in a replicated 3 × 3 Latin square experiment to determine the effects of adding 5 or 10% feed-grade rendered animal fat to the concentrate diet fed to performance horses. The experiment was conducted over a 14-day pre-trial period to acquaint horses to the experimental apparatus, a 28-day conditioning period and 3 diet treatment periods of 21 days, each conducted in a Latin square arrangement. The horses were exercised on a dirt track and diet effects were evaluated during and following a submaximal exercise test (SET) on an equine treadmill. Physiological responses to the SET were determined following each experimental period. Relative to the control, the horses required 21% and 25% less of the concentrate feed (P

Locomotor, vocal and other behavioral responses to varying methods of weaning foals

Abstract Behavioral responses to weaning were studied in 21 foals assigned to one of five treatments: (1) abrupt, total separation of mare and foal, no pre-weaning creep feed (TSNC); (2) total separation but with creep feed (TSC); (3) partial separation of mare and foal allowing fence-line contact, no pre-weaning creep feed (PSNC); (4) partial separation but with creep feed (PSC); (5) control (CON), no separation of mare and foal with creep feed. Foals were observed for 5 h immediately after weaning. Vocalization frequency and times of the following behaviors were recorded: lying down; standing still; walking; trotting; cantering. The TSNC foals spent more time walking than PSNC, PSC or CON foals, and spent less time standing still than foals on all other treatments. The TSC, PSNC, PSC and CON foals spent more time standing still than walking. There were no significant treatment effects on times spent lying down or cantering, but TSNC foals tended ( P P P P > 0.05) vocalization frequency during weaning. All weaned foals exhibited aggression toward other foals, pawing and non-nutritional sucking of other foals. Non-nutritional sucking started within 2 h post-weaning and was observed up to 2 weeks post-weaning. Results of this study showed that foals weaned by means of a partial separation management system exhibited fewer signs of stress than those weaned by abrupt separation.

Physiological responses in foals weaned by abrupt or gradual methods

Summary Physiological responses to weaning procedures were studied in 21 foals assigned to one of five treatments: (1) abrupt, total separation of mare and foal, no preweaning creep feed (TSNC); abrupt, total separation with preweaning creep feed (TSC); partial separation of mare and foal allowing fenceline contact, no preweaning creep feed (PSNC); (4) partial separation with creep feed (PSC); and (5) control (CON) no separation of mare and foal, foals creep fed. Changes in adrenal response to exogenous ACTH, basal and peak plasma cortisol concentrations, plasma triiodothyronine (T3) and thyroxine (T4) concentrations, weight gains and feed consumption were measured. Foals on the total separation treatments had higher adrenal responses (P .05) in any cortisol response. No treatment differences were found in thyroid hormone concentrations in this study. On partial separation treatments, creep-fed and non-creep-fed foals consumed similar amounts of feed during the first week postweaning. On total separation treatments, non-creep-fed foals consumed more feed (P

Changes in the third metacarpal bone and frequency of bone injuries in young quarter horses during race training - observations and theoretical considerations

Summary Fifty-three Quarter Horses were put into race-training at 18 mo of age. Changes in the third metacarpal were monitored by radiographic densitometry initially at 83 days prior to the commencement of training and at days 0, 62, 104 and 244 of training. A normal increase in density of the third metacarpal due to growth and mineralization was seen from the first set of radiographs until the horses began training at day 0 (P

Characterization of changes related to mineral balance and bone metabolism in the young racing Quarter Horse

Summary This study was conducted to determine physiologic responses reflective of bone metabolism during the onset of training and to relate those responses to the mineral requirements of young racehorses. Ten previously untrained Quarter Horse geldings were put into race training. They were fed a diet balanced to meet NRC recommendations for young horses in training. Feed, feces and urine were collected, weighed and analyzed over the experiment to determine mineral balance. Radiographs were taken of the left front leg to determine mineral content of a cross-sectional area of the third metacarpal. Blood samples were taken to determine osteocalcin, parathyroid hormone, 25-hydroxyvitamin D, Ca and inorganic P concentrations. Horses were gentled to ride, trained to gallop on the track and maintained in training for four 28-day periods. Blood serum was collected every 14 day, while radiographs and 72-hr total collections of urine and feces were taken every 28 d. Radiographs demonstrated that mineral content was lowest at day 56 in the dorsal, palmar and medial cortices of the third metacarpal. Urinary Ca declined dramatically from day 0 to day 28, then remained constant to day 56, before decreasing at day 84. Fecal Ca peaked at day 28 and remained elevated above day 0 amounts until day 112. calcium retention was negative at day 0, became slightly positive by day 28 and increased through day 112. Phosphorus and Mg balance remained relatively unchanged throughout the duration of the study. This study demon-strated changes in the mineral content of the third metacarpal and Ca balance during early training and suggests that further studies be performed.

EFFICACY OF A FAT-SUPPLEMENTED DIET ON MUSCLE GLYCOGEN CONCENTRATIONS IN EXERCISING THOROUGHBRED HORSES MAINTAINED IN VARYING BODY CONDITIONS

Abstract In a switchback experiment, twelve mature Thoroughbreds were randomly divided into three groups; each group was fed to achieve moderately low (ML), moderate (M) or moderately high (MI-I) body-fat content. Following a 28-day aerobic conditioning period, two horses from each group were fed a conventional, control diet and the other two were fed a fat-supplemented diet for a 21-day adaptation period. During the adaptation period, aerobic work continued as before, and the horses were also worked at a level to achieve anaerobiosis twice per week. After the adaptation period, horses performed a standardized exercise test consisting of four, 600-m sprints. Muscle biopsies were obtained from the biceps femoris before and after the test, and blood samples were taken before, during and throughout recovery from the test. Then, the horses were switched to opposite diets and the procedures were repeated. Muscle biopsies were obtained from biceps femoris before and after the exercise test, and blood samples were taken before, during and throughout recovery from the test. Pre-test muscle-glycogen concentrations were similar (P .05) in horses on all treatments. Thus, adapting Thoroughbred horses to a fat-supplemented diet inereased utilization of muscle glycogen, which may enhance performance that requires anaerobic energy production.

Lactation and reproductive performance of mares fed added dietary fat during late gestation and early lactation

Summary Eighteen pregnant mares were randomly allotted to one of two treatment groups. The control group was fed a conventional concentrate and the fat group was fed a concentrate containing 5% feed-grade rendered fat. Both concentrates had the same nutrient:calorie ratio and were fed in amounts required to maintain zero change in percent body fat of the mares. During the study, which began 60 d prior to expected foaling date and ended 60 d postpartum, mares were monitored for feed intake, body weight, rump fat thickness, ration digestibility, plasma glucose and lipid concentrations, milk composition and reproductive efficiency. Birth weight, growth rate, and plasma glucose and lipid concentrations were also measured in foals. Mares fed fat consumed less concentrate (P

Response of young horses in training to varying concentrations of dietary calcium and phosphorus

Summary This experiment was conducted to determine if additional mineral supplementation during early training would increase mineral retention and improve the strength of bone as indicated by the mineral content of the third metacarpal. Twelve previously untrained Quarter Horse geldings were randomly divided into two groups, broke to ride, trained to gallop on the track and maintained in training for four 28-day periods. One group of four horses served as controls and was fed a ration averaging 28.3 g of Ca/day and 21.9 g P/day while in training. Eight other horses were fed a ration averaging 34.9 g Ca/day and 26.4 g P/day while in training. Feed, feces and urine were analyzed to determine mineral balance. Radiographs were taken of the left front leg to examine bone density as indicated by radiographic bone aluminum equivalence (RBAE). The high mineral treatment group retained more Ca than controls (P

The significance of small vs large intestinal digestion of cereal grain and oilseed protein in the equine

Abstract Mature ponies fitted with permanent ileal cannulas were used in two 3×3 Latin square experiments to quantify prececal, postileal and total tract digestion of N. In trial 1, corn, oats and sorghum were each fed with coastal Bermuda grass hay in 75:25 ratios. Apparent prececal digestibilities were similar (P>.05) and averaged 46.6%. By-difference procedures were employed to calculate digestibility of the cereal grain N only and apparent prececal N digestibility averaged 57.1%. In trial 2, a basal corn and hay diet was supplemented with cottonseed meal and soybean meal. Apparent total tract N digestibilities were similar (P>.05) across treatments, and prececal digestibility averaged 45.6%. By-difference calculations were used to determine digestibility of SBM and CSM N alone. Apparent prececal digestibility of SBM was 52.5% and was lower (P

Growth and feed utilization by yearling horses fed added dietary fat

Summary Twenty-four yearlings were used to evaluate the efficacy of feeding feed-grade fat to growing horses. All horses were started on trial at 13-months-of-age and were fed for 112 days. The experimental diets, containing similar nutrient-to-calorie ratios, were: 1) control (no added fat; 2) 5% added fat and; 3) 10% added fat. There was a trend for yearlings fed the 10% added fat diet to grow faster and eat less feed than those on the control diet. Data from this study indicate that feed-grade fat can be safely fed to growing horses. Feeding fat to yearlings stimulated growth and efficiency of feed utilization initially, but these effects were not maintained as the yearlings grew toward maturity.