Osteochondrosis — a big word that has all but dropped out of the swine industry's vocabulary — has resurfaced in a small study conducted by swine veterinary consultant E. Wayne Johnson, DVM, at the University of Illinois.
Johnson says the condition, often called OCD, occurs in the articular cartilage and the growth plate (see Figure 1). The cartilage cells of the growth plates and articular ends of the bones divide and grow, and can change to bone through ossification. A good blood supply is essential to bring oxygen and nutrients to the cartilage and bone. The pressures of rapid body weight gain can damage the tiny blood vessels and the rapidly dividing and differentiating cells, resulting in abnormal cartilage and bone and often in pain and lameness.
“In animals that develop OCD, we think that at least part of the problem is poor cross-linkage among the extracellular matrix components, such that the pressure is concentrated at one point rather than being distributed over a unified cartilage surface. A joint is like touching two balls together. The pressure is concentrated in a fairly small spot,” Johnson explains.
The cartilage may buckle or tear into a flap that can come loose and float in the joint. The damaged tissue can heal, but often with scarring of the normally smooth, slippery joint surface
“Often, animals start out with OCD, which later turns into arthritis because the joint is irregular and it's grinding all of the time,” Johnson says.
Johnson's interest in OCD piqued when a client called about “a horrible lameness problem” in a group of Durocs and Yorkshires. After examining the pigs for injury and basic skeletal structure, he suspected OCD.
Drawing on some long-recognized work in plants that confirmed the importance of adequate boron for structural stabilization of plant cell walls by cross-linkage, Johnson wondered if the mineral could improve the strength and durability of cartilage in pig joints. A preliminary boron treatment of the pigs proved promising.
Later, he set up a field test with 56 fast-growing, heavily muscled pigs (35 Durocs, 21 Yorkshires). Pigs, averaging 42 lb., were divided into three straw-bedded pens. One pen, serving as the “control” group, was fed a typical 18% crude protein commercial diet. Another received the commercial diet plus 25 ppm boron. The third group received the commercial diet plus 10 ppm boron and 250 ppm ascorbic acid.
During a three-month trial, pigs were individually weighed and evaluated for lameness, then were sacrificed and had joints scored for OCD lesions. In this test, 61% of the non-supplemented pigs became lame, compared with only 3% of the pigs receiving boron. Lameness rate did not differ between breeds, and growth rate did not differ across treatments. Ascorbic acid had no effect on the variables measured.
“From these results, it may be concluded that OCD in swine apparently is a boron-responsive disease,” Johnson observes. OCD may be one manifestation of pandemic boron deficiency in swine fed low-boron, grain-based diets without boron supplementation.
Here's the catch — the Food and Drug Administration has not approved boron in any form for use in animal feeds.
“We know that animals that grow faster are more likely to get OCD. Further research should determine dose and other biological effects,” he says.
Johnson believes OCD is a major cause of lameness and culling, and that boron supplementation could help alleviate OCD-related problems in growing pigs and breeding animals.