PSV-27 - Serum mineral and vitamin concentrations in central performance tested Rambouillet rams with and without angular limb deformities

Abstract: Angular limb deformities (ALD) have historically affected 3-18% of Rambouillet ram lambs enrolled in central performance tests in the Northern great plains. Osteochondrosis, the underlying pathology of ALD, results in varying degrees of abnormal ossification in long bones and limits ram welfare and performance under extensive rangeland conditions. The objective of this research was to quantify serum mineral and 25-hydroxyvitamin D differences in rams with and without (non-affected) ALD. A total of 25 ram lambs (age = 189 ± 19 d; n = 13 ALD, n = 12 non-affected) were evaluated. Serum and body weight (BW) were collected on d 0, 28, 56, 83, and 112 of the test. Serum concentrations of 25-hydroxyvitamin D, macrominerals (Ca, Cl, K, Mg, Na, P, and S), and microminerals (Co, Cr, Cu, Fe, Mn, Mo, Se, and Zn) were quantified. Traits were analyzed as repeated measures with fixed effects of ALD status, sampling timepoint, and their interaction. An autoregressive type-I covariance structure with heterogenous variance was used to model the random ram effect. The ALD status x sampling timepoint interaction was significant (P ≤ 0.03) for serum 25-hydroxyvitamin D and Mg concentrations. Rams with ALD had greater 25-hydroxyvitamin D concentration at d 83 and 112 and greater Mg concentration at d 28 and 112 (P ≤ 0.05). The main effect of ALD status was significant for serum Cl and greater for ALD than non-affected rams (3672 ± 38.8 vs. 3500 ± 38.3 mg/L; P < 0.001). Ram BW and serum concentration of all other minerals were similar between ALD and non-affected. Sampling timepoint affected several serum mineral concentrations as Ca generally increased with time, Co peaked at d 28, and Na decreased with time (P ≤ 0.03). Not surprisingly, BW also increased over time (P < 0.001). The range in serum mineral concentrations and percentage of rams deficient were: 25-hydroxyvitamin D (non-affected 32 – 241 mmol/L, 17%; ALD 35 – 160 mmol/L, 15%), Mg (non-affected 10.7 – 44.1 mg/L, 14%; ALD 11.7 – 45.0 mg/L, 14%), Cl (non-affected 3,066.3 – 4024.5 mg/L, 21%; ALD 3,068.4 – 4,072.5 mg/L, 12%). While ALD and non-affected rams differed in key serum vitamin and mineral element concentrations, it’s a multifaceted disorder in which perinatal, endocrine, genetic, and nutritional conditions need to be researched to fully understand the etiology and mitigate its incidence.