Effects of dietary energy and protein on induction of dyschondroplasia in foals

Summary Thirty mixed‐bred foals aged 2.5–6.5 months (mean 4.6 ± 1.0 months) with no clinical or radiographic signs of dyschondroplasia (DCP) were fed one of four diets for 16–18 weeks. Twelve foals were fed a Control diet which comprised ˜100% of the NRC recommendations for dietary energy (DE) and crude protein (CP). Six were fed a diet with ˜126% of NRC levels for CP and 12 foals were fed a diet with 129% of NRC levels for DE. The diets comprised 3 different formulations of rice‐based pellets with added maize oil for the High DE diet, and oaten chaff. Average daily gain, humeral length and wither height were slighly, but not significantly, different in the foals on the High DE diet than in those fed the Control or High CP diet. Clinical and radiographic signs of DCP were seen in 6 out of 12 foals fed the High DE diet. Not one of the foals fed High CP or Control diets showed any clinical and radiographical signs of DCP. The number and severity of DCP lesions found at post‐mortem examination were much greater in the High DE foals than in the Control and High CP foals. Multiple lesions of DCP were detected in 11 foals fed the High DE diet, in 1 foal fed the High CP diet and in 1 foal fed the Control diet. Histological lesions of DCP were confirmed in 18 foals; in all 12 of the High DE foals, 4 of the 6 High CP foals and 2 of the 12 Control foals. The number of histological lesions of DCP were significantly greater in the High DE foals than in the Control group (P < 0.0001). The incidence of lesions of DCP in the foals fed High CP was not significantly different from that in the Control foals (P = 0.11).