Rice bran oil and flaxseed oil contain omega-3 fatty acids with the potential to reduce post-exercise inflammation and muscle damage. This study measures plasma interleukin-1β and creatine kinase and fatty acid profiles in lightly worked, young horses (Equus caballus) undergoing an exercise test after 60 days (d) of oil consumption, where the oil replaced 25% of concentrate calories. Treatments consisted of CON (no oil), FLAX (flaxseed oil blend), and RICE (crude rice bran oil). Blood was collected pre-exercise, and again at 1 min, 30 min, 24 h, 48 h, and 72 h post-IET. Data were analyzed by repeated measures ANOVA. Plasma creatine kinase activity was not different in CON during the study, greater (p < 0.05) in RICE from pre-exercise to 30 min post-exercise across all exercise tests, and lesser (p < 0.05) in FLAX at 30 min post-exercise on d 30 compared to d 0. Plasma interleukin-1β was greater (p < 0.01) in CON on d 60, but no differences were observed in FLAX and RICE throughout the study. Plasma alpha-linolenic and linoleic acids were greatest (p < 0.05) in FLAX after 30 d of inclusion, while CON horses had greater (p < 0.05) EPA across all exercise tests and DHA after 60 d. These results indicate that 60 d of inclusion of crude rice bran oil or a flaxseed oil blend may benefit lightly worked, young horses by reducing training-program-related increases in interleukin-1β, while a flaxseed oil blend may reduce exercise-induced increases in creatine kinase. Additionally, the flaxseed oil blend has the potential to increase plasma omega-3 and omega-6 fatty acids. Replacing 25% of concentrate calories with flaxseed or rice bran oil has potential benefits for young horses in training.

Horses experience a post-exercise inflammatory response to damaged tissues that is part of the mechanism of recovery and is indicated by heat and muscle soreness (MS). Further, old horses (OH) are at a greater risk of prolonged MS, lameness, and injury than are young horses (YH). Therefore, the objective of this study was to compare heat and MS of unconditioned young (14-16 months) and old (19-24 years) Quarter Horses after the completion of an incremental exercise test (IET: counterclockwise at 3 min at 6.44 kph, 10 min at 16.09 kph, 2 min each at 19.31 and 22.53 kph). MS evaluations were performed on neck, shoulder, back, and hip for both sides at pre, 12, 36, 60, and 84 hours post IET. FLIR images of the shoulder, forearm, back, hip, and gaskin were taken on the left side at day 0, pre-IET, 15 min, and 12, 24, 48, 72 h post-IET. Data were analyzed by repeated measures ANOVA using the MIXED procedure of SAS. There was a main effect of age on gaskin temperature, whereby YH (32.3±17.5°C) had higher temperatures than OH (31.4±17.5°C; P = 0.043). There was a tendency for an interaction of age and time for shoulders (P = 0.063) and an interaction for forearm (P = 0.03) and back (P = 0.046). At 12 h post IET, YH shoulders were higher (34.6±17.1°C) than OH (31.8±17.1°C), YH forearms were higher (34.1±17.3°C) than OH (30.4±17.1°C), and YH backs (33.4±17.3°C) were higher than OH (32±17.3°C). Necks were sorer on the right side 36 h post-IET compared to pre-exercise (P = 0.033) and 60 hours compared to 12 hours post IET (P = 0.033). Muscle soreness increased in the right hip from pre-IET to 36 h post-IET (P = 0.037). No other differences were observed. Our results suggest that YH have higher surface temperatures than OH but this was not associated with MS.

Rice bran (RICE) and flax (FLAX) oils contain omega-3 fatty acids with the potential to reduce post-exercise muscle damage. This study compared plasma essential fatty acid profiles, creatine kinase (CK) activity, and lactic acid (LA) concentrations in lightly worked young horses undergoing a 16 min incremental exercise test (IET; 16.1, 19.3, 22.5, and 25.7 kph) after 60 d of supplementation. Treatments consisted of none (CON; n = 4), FLAX (n = 4), or RICE (n = 4) oil. Horses received their energy requirement as 40% from concentrate and 60% from hay, with oil replacing 25% of concentrate calories. Blood was obtained before, 1, and 30 min post-IET. Data were analyzed by repeated measures ANOVA. On d60, alpha-linolenic acid was greater in FLAX (2.3±0.2 g/100g) than RICE (1.5±0.2 g/100g; P = 0.01), and docosahexaenoic acid was higher in CON (1.4±0.3 g/100g) and RICE (0.9±0.3 g/100g) than FLAX (0±0.3 g/100g; P &lt; 0.01). In CON horses, CK activity was increased on both IET days at 30min post (1.9±0.4 U/L; P &lt; 0.01). In FLAX and RICE horses, CK activity increased 30 min post IET on d0 only (FLAX=2.2±0.1 U/L; P=0.02; RICE=1.9±0.06 U/L; P = 0.01), with no increase on d60 (P &gt; 0.06). For CON, LA concentrations were not different at 1 min post-IET between d0 and 60 (P &gt;0.7) but were different at 30min post (d0=1.0±0.1 mmol/L; d60=0.4±0.1 mmol/L; P = 0.04), In FLAX, LA was greater at 1min post-IET on d60 (2.8±0.1 mmol/L) than d0 (1.5±0.1 mmol/L; P = 0.057), with no differences between days at 30min post-IET (P &gt;0.07). In RICE horses, LA was not different at 1min post IET across days (P &gt;0.1), however was lower at 30min post-IET on d60 (d0=1.7±0.1 mmol/L; d60=0.2±0.1 mmol/L; P &lt; 0.01). Sixty days of rice oil supplementation may benefit lightly worked horses by reducing post-exercise lactic acid concentrations, CK activity, and increasing docosahexaenoic acid.