Alleged Predisposing Factors in Diets Fail to Increase the Incidence of Osteochondrosis Lesions in Growing Pigs at 12 and 24 Weeks of Age

Early lesions of osteochondrosis (OC) are exhibited by regions of cartilage retention along the growth plate. Progression of OC lesions may lead to fractures and impaired locomotion. Little is known about the disease etiology, but diet is commonly implicated as a predisposing factor. In this study nutrient concentrations and physical form of diets were altered in an attempt to induce the formation of OC lesions under controlled conditions. At 6 wk of age 96 crossbred (1/4-Landrace X 1/4-Large White X 1/2-PIC Line 19) gilts (initial BW = 17.4 + 0.36 kg) were randomly assigned to 1 of 4 corn-SBM based dietary treatments (4 pens/diet, 6 pigs/pen) to assess effects of diet on number and volume of OC lesions. Diets included a standard meal diet (Ctl); Ctl plus 20% glucose (Glc); a meal diet formulated to supply 120% of requirements for lysine, Ca, and P (+CaP); and the +CaP diet pelleted (PEL). Pigs were killed at either 12 or 24 wk of age and femurs were collected. Based on mixed model analysis with pen as the experimental unit, treatments did not affect final BW (129.3 + 3.8 kg) or ADG (1.00 + 0.03 kg/d). As expected, pigs fed PEL and Glc diets were more efficient (P < 0.05) in feed conversion compared with Ctl and +CaP. Using femur as the experimental unit, at 12 wk, bone mineral content, determined by dual-energy x-ray absorptiometry scans, was greater (P < 0.05) in pigs fed +CaP and PEL diets than Ctl or Glc, but only +CaP group differed (P < 0.05) at 24 wk. Computed tomography scans of the femurs were analyzed by multiple observers using Mimics (Materialize software 17.0) to detect incidence and volume of lesions in distal growth plates. At 12 wk, pigs fed Ctl had fewer lesions (P< 0.05), but no differences were detected in total lesion volume across the entire growth plate. Pigs had fewer lesions at 24 than 12 wk, but differences were not detected among treatments. However, at 24 wk pigs fed Ctl diet had the greatest lesion volume among diets. In conclusion, none of the pigs exhibited symptoms of lameness regardless of dietary treatment or OC lesion traits.

Lesion Traits		Treatment
	Week	Ctl	Glc	+CaP	PEL	SEM
Number	12	4.06A	6.94B	7.00B	6.88B	0.89
	24	2.97A	1.78A	2.56A	3.16A	0.63
Total Volume, mm3	12	30.16A	66.89A	55.16A	54.36A	13.39
	24	7.05A	2.33B	3.75AB	4.21AB	1.92