P.G. Gibbs

Digestion of soybean meal proteinin the equine small and large intestine at various levels of intake

Summary Four mature pony geldings weighing an average of 134 kg and fitted with ileal cannulas were used in a 4×4 Latin square experiment to determine the digestibility of soybean meal (SBM) protein in different segments of the equine digestive tract at various levels of protein intake. A complete basal corn-based diet was supplemented with SBM to formulate four diets with increasing crude protein. The diets, labeled A (basal), B, C and D, contained 4.9%, 9.5%, 14% and 16.5% crude protein (as fed), and provided nitrogen, per feeding, at approximately 44.8, 84.3, 123.9 and 146.3 mg/kg of body weight, respectively. Chromic oxide was fed to measure ileal flow and fecal excretion. Digestion and absorption of nitrogen was determined from changes in nitrogen: chromium ratios, and true digestion of nitrogen was computed by regression analysis. True total tract digestion of nitrogen was 95.7%. True digestibility of nitrogen in the small intestine over the range of linearity was 72.2%, while true digestibility of nitrogen reaching the large intestine was 89.8%. These data indicate that the protein in SBM was almost completely digested in the equine digestive tract. Furthermore, approximately 75% of the digestible protein was digested prececally when nitrogen intake was less than approximately 125 mg/kg of body weight per feeding.

Markers of Inflammation in Arthritic Horses Fed Omega-3 Fatty Acids

Sixteen mature horses with arthritis in the knee, fetlock, hock, or stifle joints were blocked by severity of arthritis, affected joints, and age, and randomly divided into 2 groups. The control group (n = 8) received a commercial 12% CP feed at 1% BW per day. Treated horses (n = 8) received the same mixed feed with the addition of 2 n-3 fatty acid supplements to supply an additional 15 g/d of eicosapentaenoic acid and 19.8 g/d of docosahexaenoic acid. Both groups had access to coastal bermudagrass hay at approximately 1.3% of BW. Horses received respective dietary treatments for 90 d. Synovial fluid was collected from at least one affected joint of each horse on d 0, 30, 60, and 90. Blood samples were collected every 15 d beginning on d 0. Compared with control horses, treatment horses experienced a greater decrease (P< 0.05) in synovial fluid white blood cell concentration and plasma prostaglandin E2 A trend (P = 0.076) toward lower normalized plasma fibrinogen concentration was observed in treated horses compared with control horses throughout the entire trial. When data were analyzed from d 30 through 90, fibrinogen concentrations between groups were significantly different (P < 0.05). Force plate data from 7 horses were obtained to determine potential changes in weight distribution. No significant increase in weight placed on arthritic limbs (P = 0.12) was seen. These data provide further evidence that supplemental long-chain n-3 fatty acids in the equine diet could be advantageous for horses with existing arthritis.

Response of serum biochemical markers of bone metabolism totraining in the juvenile racehorse

Summary Sixteen Quarter Horse-type geldings were used to examine the response of biochemical markers of bone metabolism to forced exercise prior to and during race training. The study began when the average age of the horses was 15 months. Horses were exercised on a high-speed treadmill for 14 weeks, and were subsequently placed into race training. Serum was collected and assayed for concentrations of osteocalcin (BGP), the carboxyterminal telopeptide of type I collagen (ICTP) and the carboxyterminal propeptide of type I procollagen (PICP). When data were normalized from the onset of race training, ICTP and PICP concentrations were higher in the pre-exercised horses (P

Absorption and Retention of Trace Minerals in Adult Horses

Absorption and retention of Cu, Mn, and Zn were compared when feeding diets supplemented with oxide, sulfate, or organic-chelated forms of the minerals. Six mature Miniature Horses were used in the replicated 3 × 3 Latin square-designed experiment. The experiment was conducted in three 17-d periods, consisting of 10 d of diet adaptation followed by a 7-d total fecal and urine collection. Horses were fed a diet of 40% coastal Bermudagrass and 60% concentrate formulated to meet the energy, protein, Ca, and P requirements for maintenance of mature horses. Copper, Mn, and Zn were supplemented to provide 140 to 180% of the NRC (1989) recommended dietary concentrations for these minerals and were supplied in oxide, sulfate, and organic-chelate forms. Following total collections of feces and urine, feed, fecal, and urine samples were processed and analyzed for Cu, Mn, and Zn concentrations by atomic absorption spectrophotometry. Absorption of Cu, Mn, and Zn in all forms was low compared with previous studies, but systemic retention of these minerals was high. The cause of this disparity is unknown, although experimental error is unlikely. There were no differences in the absorption or retention of Cu, Mn, and Zn among the three forms of mineral supple

Comparative feeding value of a cubed alfalfa:Corn plant product as an exclusive diet for exercising horses

Summary In a switchback experiment, six mature Quarter Horse and Thoroughbred geldings weighing approximately 495 kg and in average body condition score of 5.4 were fed two diets and exercised daily. Horses were randomly assigned to a conventional diet or alfalfa:corn plant cubes as an exclusive diet. During the 21-day adaptation period, level of work increased daily digestible energy requirements to approximately 1.75 times maintenance. Sweat production was estimated on days 0, 7, 14 and 21. A 4-day digestion trial was conducted on days 17, 18, 19 and 20. Horses performed a standardized exercise test on day 21 by galloping 18 minutes at a heart rate of 150 beats per minute followed by 2 minutes at 200 beats per minute. Venous blood samples, heart rates, respiration rates and rectal temperatures were taken before exercise, immediately after and throughout recovery from the test. Then, the horses were abruptly switched to opposite diets and the procedures were repeated. No noticeable digestive disturbances occurred as a result of the abrupt introduction of diets to horses. Furthermore, no “cribbing” problems or apparent cases of choking were observed throughout the study. Horses consumed the cubed diet slower (P .1) between diets. Only slight increases (P>.05) in body condition were observed at the end of each period. Heart rate, respiration and rectal temperature increased (P

Variances in Reproductive Efficiency of Mares in Fat and Moderate Body Conditions Following Parturition

An increase in time to ovulation after parturition could result in economic loss if the mare does not successfully conceive within a short time after foaling. To evaluate whether a difference exists in reproductive efficiency between mares of either fat (BCS of 7 to 8) or moderate body condition (BCS of 5 to 6), 24 mares were allotted to and maintained in their respective group from late gestation until pregnancy was confirmed after breeding on the second postpartum estrus. No differences were found between the groups in the number of days to foal heat ovulation (14.4 vs. 16.2 d), interovulatory interval (22.9 vs. 24.3 d), and conception rates (91.7 vs. 83.3%; P > 0.05) for fat- and moderately conditioned mares, respectively. This suggests that mares maintained in a fleshy body condition (BCS 7 to 8) are not prone to reproductive dysfunction or lowered levels of fertility. Nevertheless, mares in a moderate body condition did lose a greater percentage of body fat after foaling as compared with fleshier mares (0.82% vs. 0.35%; P < 0.05). The significance of these results reassures breeders that mares in a fleshier body condition are not prone to demonstrate subfertility, but does allude to the fact that mares benefit by foaling at a BCS of at least 6 to avoid diminished reproductive capability that may result from the loss of body fat that occurs at parturition and in early lactation.

Biochemical Markers of Bone Modeling and Remodeling in Juvenile Racehorses at Varying Mineral Intakes

In this study, blood-borne biochemical markers were used to track comparative rates of bone turnover in horses fed differing amounts of Ca, P and Mg. Bone turnover was tracked by serum osteocalcin; bone resorption by the carboxyterminal telopeptide of type I collagen (ICTP); and bone formation by the carboxyterminal propeptide of type I procollagen (PICP). Twenty-one longyearling Quarter Horses were blocked by gender and age, randomly assigned to one of four diets and subjected to 128 d of race training. The study was conducted in 32-d periods, each consisting of 28 d of race training followed by a 4-d fecal and urine collection, or a 4-d rest period. Blood samples were taken weekly during the training period. Serum and plasma samples were analyzed for biochemical markers of bone activity using RIA procedures. Onset of training resulted in elevated blood concentrations of ICTP, PICP and osteocalcin. Concentrations of ICTP and PICP were greater during the first 64 d of training, indicating increased bone activity during the first half of the training period. Horses with the greatest intake of minerals exhibited greater concentrations of PICP (bone formation marker) and lesser concentrations of ICTP (bone breakdown marker). Further, ICTP, PICP and osteocalcin concentrations decreased dramatically following 4-d of confinement and relative inactivity. Therefore it appears that feeding minerals at levels greater than current NRC recommendations provided a protective effect on the developing skeleton of the young racehorse. Additionally, the biochemical markers used in this study were sensitive enough to track daily changes in bone activity resulting from daily changes in stress to the skeleton.

Calcium absorption and bone density in immature horses fed two levels of crude protein

Research in other animal models indicate that high protein diets increase urinary calcium (Ca) excretion and may lead to a negative Ca balance and reduced bone density. This study was undertaken to determine the effects of two common levels of dietary protein intake on physiological parameters, Ca absorption, and bone density in immature horses. Sixteen 10-month old horses were blocked by age and sex into two dietary treatments. The control diet (C) was formulated using common ingredients to provide 100% of the National Research Council (NRC) for crude protein (CP), while the high protein diet (H) was formulated at 150% of NRC recommendations. Lower than expected dietary intake resulted in mean protein intake of 769±16 g/d in C and 978±18 g/d in H, equivalent to 91% and 116% of NRC, respectively. Blood, urine, and faeces were collected during the 112-day study to determine pH and mineral balance. Radiographs of the left third metacarpal were used to estimate bone density via radiographic bone aluminum equivalence (RBAE). Although urine pH decreased over time (P<0.001), no change in blood or urine pH was observed due to diet. Faecal pH, normalised to day 0, was significantly lower in H (P<0.02). Faecal Ca loss was greater in H (P<0.005); while Ca absorption and absorption as a percent of intake were lower for H (P<0.02). RBAE of dorsal and palmar cortices increased over time (P<0.001), but no differences were observed between diets. While excess dietary protein decreased faecal pH, increased faecal Ca excretion, and decreased Ca absorption, there appeared to be no effect on bone density over the course of this study.

Utilizing Body Temperature to Evaluate Ovulation in Mares

Although reproductive technology has added many dimensions to the horse breeding industry, less invasive and more efficient methods of evaluating follicular development and ovulation would be beneficial to both the commercial breeder and private horse owner. Because of the highly variable estrous cycle of the mare, it is difficult for breeders to coordinate insemination with ovulation, and much time is invested in evaluation via palpation, ultrasound, and teasing. In both dairy cattle and women, a significant change in body temperature has been measured during the hours immediately prior to ovulation. Research exploring the relationship of body temperature and ovulation in horses has been limited to one study in which no relationship between temperature and ovulation was identified. The current study utilized 38 mature mares and was conducted during the physiologic breeding season. Each mare was implanted in the nuchal ligament with a microchip capable of reporting body temperature, and rectal temperatures were obtained using a digital thermometer. Once an ovulatory follicle was detected using ultrasonography and the mare was exhibiting signs of estrus, the follicle size and temperature were recorded approximately every 6 h until ovulation. No difference was found in rectal temperature in relation to the presence or absence of a follicle. Under specific circumstances, temperatures obtained using the microchip were higher (P < 0.05) prior to ovulation compared with those temperatures collected immediately following ovulation.

Does Pre-Conditioning Improve Bone Quality in the Juvenile Racehorse?

Abstract Sixteen Quarter Horse-type geldings were used to determine the effectiveness of a pre-conditioning program on altering bone density in young horses prior to race training. The pre-conditioning program began when the average age of the horses was 15 mo. Horses were exercised on a high speed treadmill for 14 wk and were subsequently placed into race training. Changes in density of the third metacarpal bone were determined via radiographic densitometry throughout preconditioning and the race training regimen. Gain in total bone volume was greater in the group exercised during the pre-conditioning phase. Also, the pattern of bone density in different locations indicated that the exercised group might have been preferentially laying down more bone in the dorsal and medial cortices and less bone in the palmar cortex to achieve altered bone shape. Initiation of race training appeared to limit gains in bone density in comparison with the pre-conditioning phase.