| dc.description.abstract | Seventeen yearling Quarter Horses were used in a randomized complete block design for a 56 d trial to determine ability of dietary conjugated linoleic acid (CLA) to reach circulating levels in plasma and mitigate joint inflammation and cartilage turnover. Horses were blocked by age, sex and BW and randomly assigned to treatments consisting of a commercial concentrate offered at 1% BW (as-fed) supplemented with either 1% soybean oil (CON; n = 6), 0.5% soybean oil and 0.5% CLA (LOW; n = 5; Lutalin®, BASF Corp.), or 1% CLA (HIGH; n = 6; 55% purity) top-dressed daily. Horses were fed individually every 12 h and offered 1% BW daily (as-fed) coastal bermudagrass (Cynodon dactylon) hay.
This study was separated into two phases: phase 1 determined incorporation of CLA to circulating levels in plasma; phase 2 evaluated the potential of CLA to mitigate induced intra-articular inflammation and cartilage metabolism stimulated by lipopolysaccharide (LPS). Phase 1 comprised the first 41 d. Phase 2 began on d 42 and extended to d 56. Weekly, beginning at d 0, physical growth measurements were recorded and blood samples were collected and analyzed for fatty acid concentrations.
On d 42, an LPS challenge was conducted. Carpal joints within each horse were randomly assigned to receive intra-articular injections of 0.5 ng LPS derived from Escherichia coli 055:B5 or sterile lactated Ringer’s solution as a contralateral control. Synovial fluid samples were obtained via arthrocentesis at pre-injection h 0 and 6, 12, 24, 168 and 336 h post-injection, and subsequently analyzed by ELISA for prostaglandin E2 (PGE2), carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C). Vitals were monitored at 0, 6, 12 and 24 h; and carpal circumference and surface temperatures were also recorded. All data were analyzed using PROC MIXED procedure of SAS.
All physical measurements increased (P < 0.01) over time with no influence of CLA supplementation. Isomers of CLA were detectable in plasma by d 14, and HIGH horses had greatest concentrations (P < 0.04). Horses fed CON had undetectable levels of CLA. Arachidonic acid levels were lower (P < 0.06) in HIGH horses compared to both LOW and CON. Vitals were not different across dietary treatments (P > 0.13) and remained within normal.
Synovial PGE2 was not affected by dietary treatment (P = 0.15). Synovial C2C responded to dietary treatment (P = 0.05) with HIGH horses having lower C2C than LOW. There was an effect (P < 0.01) of time with C2C values peaking between h 12 and 24, and decreasing by h 336. Levels of CPII tended to be influenced by dietary treatment (P = 0.10) with LOW horses having greater CPII compared to CON, and HIGH horses were intermediate with no difference from CON or LOW. Regardless of diet, CPII increased to h 24 (P < 0.01) and decreased to h 336. In conclusion, dietary CLA reached circulating levels in plasma prior to the LPS challenge. Dietary CLA supplementation did not influence PGE2; however, horses receiving CLA had lesser C2C and greater CPII, indicating less degradation and greater synthesis of cartilage in response to an acute inflammatory condition. | en |
