Rider Energy Expenditure During High Intensity Horse Activity.

Despite the fact that horseback riding is a popular sport, there is little information available on horseback riding as a physical activity. The objective of this experiment was to quantify energy expenditure of participants (n=20) during three riding tests: a 45min walk-trot-canter ride (WTC), a reining pattern ride and a cutting simulation ride while wearing a telemetric gas analyzer. Total energy expenditure (tEE), mean and peak metabolic equivalents of task (MET), heart rate (HR), respiratory frequency (RF), relative oxygen consumption (relVO2), and respiratory exchange ratio (RER) were assessed. Mean MET and HR responses were greater (P < .05) for riders during the long trot portion of the WTC (6.19 ± 0.21 MET, 152.14 ± 4.4 bpm) and cutting (4.53±0.21 MET, 146.88 ± 4.4 bpm) vs the overall WTC (3.81 ± 0.16 MET, 131.5 ± 4.2 bpm). When WTC was evaluated by gait, mean MET increased as gait speed increased. As expected, METs were greater (P < .05) for riders during long trot (6.19 ± 0.21 MET) and canter (5.95 ± 0.21 MET) than during the walk (2.01 ± 0.21 MET) or trot (3.2 ± 0.21 MET). Previous horseback riding studies have not reported METs, but the peaks of all three activities in the present study were similar to METs measured during activities like jogging, playing soccer and rugby. Riders engaged in cutting and reining experienced more intense exercise in short durations, while, as expected on the basis of the duration of the activity, WTC provided a greater overall total energy expenditure. These results suggest that it is possible for health benefits to be achieved through accumulated horseback riding exercise, particularly if riding at the more intense gaits.

Skeletal response to whole body vibration and dietary calcium and phosphorus in growing pigs.

The quality and strength of the skeleton is regulated by mechanical loading and adequate mineral intake of calcium (Ca) and phosphorus (P). Whole body vibration (WBV) has been shown to elicit adaptive responses in the skeleton, such as increased bone mass and strength. This experiment was designed to determine the effects of WBV and dietary Ca and P on bone microarchitecture and turnover. A total of 26 growing pigs were utilized in a 60-d experiment. Pigs were randomly assigned within group to a 2 × 2 factorial design with dietary Ca and P concentration (low and adequate) as well as WBV. The adequate diet was formulated to meet all nutritional needs according to the NRC recommendations for growing pigs. Low Ca, P diets had 0.16% lower Ca and 0.13% lower P than the adequate diet. Pigs receiving WBV were vibrated 30 min/d, 3 d/wk at a magnitude of 1 to 2 mm and a frequency of 50 Hz. On days 0, 30, and 60, digital radiographs were taken to determine bone mineral content by radiographic bone aluminum equivalency (RBAE) and serum was collected to measure biochemical markers of bone formation (osteocalcin, OC) and bone resorption (carboxy-terminal collagen crosslinks, CTX-I). At day 60, pigs were euthanized and the left third metacarpal bone was excised for detailed analysis by microcomputed tomography (microCT) to measure trabecular microarchitecture and cortical bone geometry. Maximum RBAE values for the medial or lateral cortices were not affected (P > 0.05) by WBV. Pigs fed adequate Ca and P tended (P = 0.10) to have increased RBAE max values for the medial and lateral cortices. WBV pigs had significantly decreased serum CTX-1 concentrations (P = 0.044), whereas animals fed a low Ca and P diet had increased (P < 0.05) OC concentrations. In bone, WBV pigs showed a significantly lower trabecular number (P = 0.002) and increased trabecular separation (P = 0.003), whereas cortical bone parameters were not significantly altered by WBV or diet (P > 0.05). In summary, this study confirmed the normal physiological responses of the skeleton to a low Ca, P diet. Interestingly, although the WBV protocol utilized in this study did not elicit any significant osteogenic response, decreases in CTX-1 in response to WBV may have been an early local adaptive bone response. We interpret these data to suggest that the frequency and amplitude of WBV was likely sufficient to elicit a bone remodeling response, but the duration of the study may not have captured the full extent of an entire bone remodeling cycle.

Development of a mathematical model for predicting digestible energy intake to meet desired body condition parameters in exercising horses.

Maintaining optimal body condition is an important concern for horse owners and managers as it can affect reproductive efficiency, athletic ability, and overall health of the horse; however, information regarding dietary requirements to maintain or alter BCS in the horse is limited. A recently developed model had high accuracy in predicting the energy required to alter BCS in the horse. However, the model was restricted to sedentary mares, while many horses are subject to physical work. The objective of this study was to expand the scope of that model to include exercising horses by incorporating previously published estimates of exercise energy expenditure and then testing the expanded model. Stock type horses (n = 24) were grouped by initial BCS (3.0 to 6.5) and assigned to treatments of light (L), heavy (H), or no-exercise control (C). Horses were fed according to the model recommendations to increase (I) or decrease (D) two BCS within 60 d. Thus, six treatments were obtained: HD, HI, LD, LI, CD, CI. Mean DE intake Mcal/d for each group was HD = 19.3 ± 0.90, HI = 29 ± 0.84, LD = 13.2 ± 0.54, LI = 23.1 ± 1.39, CD = 12.1 ± 0.79, and CI = 21.9 ± 0.94. BCSs were evaluated by three independent appraisers, days 0 and 60 values were used to calculate the average BCS change for HD = -0.88 ± 0.24, HI = 1.13 ± 0.24, LD = -1.5 ± 0.29, LI = 0.88 ± 0.38, CD = -1.38 ± 0.13, and CI = 1.35 ± 0.14. Statistical comparison of final observed and model predicted values revealed acceptable precision when predicting BCS and BW respectively in control horses (r2 = 0.91, 0.98) but less precision when predicting body fat (BF) (r2 = 0.51). Model precision for BCS, BW, and BF respectively in lightly (r2 = 0.29, 0.85, 0.57) and heavily (r2 = 0.04, 0.84, 0.13) exercised horses was low. Model accuracy was acceptable across all treatments when predicting BW (Cb = 0.97, 0.96, 0.98). However, accuracy varied when predicting BCS (Cb = 0.82, 0.89, 0.41) and BF (Cb = 0.80, 0.55, 0.87) for the control, light, and heavy exercise groups, respectively. These results indicate that the revised model is acceptable for sedentary horses but the predictability of the model was insensitive to the exercising horse, therefore the exercise energy expenditure formulas incorporated into the model require revision. Packaging this model in a format that facilitates industry application could lead to more efficient feeding practices of sedentary horses, generating health, and economic benefit. Further investigation into energy expenditure of exercising horses could yield a model with broader applications.

Effects of repeated arthrocentesis on systemic cytokine expression and leukocyte population in young horses challenged with intra-articular lipopolysaccharide.

Osteoarthritis (OA) is a prevalent and economically costly source of lameness in the athletic horse. Previous studies investigating OA pathology have focused on localized trauma to the articular cartilage of a joint, largely ignoring the systemic immune status of the animal. In this study, yearling Quarter Horses were used to evaluate systemic cytokine gene expression and circulating leukocytes following a localized intra-articular inflammatory insult of the endotoxin, lipopolysaccharide (LPS). Treatments for the 35-d experiment included an intra-articular injection of 0.25 ng (n = 7) or 0.50 ng (n = 6) of LPS obtained from Escherichia coli O55:B5 or sterile lactated Ringer's solution (n = 6; control) into the radial carpal joint. Blood and synovial fluid samples were collected at preinjection hour 0 and 2, 6, 12, and 24 h postinjection. Synovial fluid was obtained for a companion study. Total RNA was isolated from plasma leukocytes and real-time PCR was used to determine relative gene expression of the cytokines interleukin (IL)-1beta (ß), IL-6, IL-8, IL-10, and tumor necrosis factor-alpha (TNF-α). Total leukocyte subpopulations and differentials were performed using a cell counter. Data were analyzed using the PROC MIXED procedure of SAS. Gene expression of all cytokines were unaffected by intra-articular treatment. However, IL-1ß increased above baseline beginning at hour 6 and remained elevated to 24 h (P = 0.04). In contrast, IL-6 decreased from hours 6 to 12 and then increased to 24 h (P = 0.02). Levels of TNF-α increased at 6 and 12 h (P = 0.01) postinjection. Only IL-8 exceeded a 2-fold change in expression (P = 0.01), peaking at 12 h and indicating greater responsiveness to arthrocentesis when compared with other cytokines. No treatment effects on the leukocyte population were observed; however, total circulating leukocytes increased over time (P = 0.04), peaking at 6 h postinjection. Similarly, an increase over time was observed in monocytes (P = 0.02) and in platelets (P = 0.01) at 24 h postinjection. The results indicate that regardless of treatment, a mild immune response was elicited, which may be due to repeated arthrocentesis. Future experiments should consider the effects of arthrocentesis and potential systemic inflammatory response, even in control animals, when administering intra-articular LPS to young horses.