Evaluation of chromium propionate on growth performance and immune response in weaned beef calves

Weaning is a stressful period for beef calves, and these stresses might affect the immune system and increase infection risks. This study investigated the effects of Chromium Propionate (CrP) supplementation on growth performance and immune responses of weaned beef calves. A total of 12 pens (n = 12; 6 pens/group, 10 calves/pen), were assigned to two treatment groups (Control: 0 ppm; Treated: 0.5 ppm on a dry matter basis from KemTRACE® Cr propionate, 0.4 %) in a completely randomized design with subsampling, with six pens allocated to each treatment group. Calves were fed free-choice bermudagrass hay, water, mineral blocks, and a 50:50 mix of soybean hulls and corn gluten meal for 60 days. Calves’ body weights were measured on days 0, 30, and 60. Blood was sampled from calves from a subset of four pens (n = 4; 2 pens/group) to perform complete blood counts, serum biochemistry analysis, cytokine levels (IL-2, IL-4, IL-6, TNF-alpha), and serum IgG antibody titers measurements. Cell-mediated immunity was evaluated by using phytohemagglutinin (PHA) and humoral immune response was assessed by chicken ovalbumin (cOVA) injections. Average daily gain from day 30–60 was significantly increased (P < 0.05) by Cr supplementation. Cytokine concentration of IL-2 was significantly higher (P < 0.05) in the Cr-treated beef calves, indicating immune modulation and a shift towards a Th1-type immune response. Neutrophil-to-lymphocyte ratio (NLR), an indirect indicator of cortisol, was significantly reduced (P < 0.05), supporting that Cr supplementation may lower physiological stress and improve immune homeostasis. Moreover, IL-4 and TNF-alpha tended to be lower (P < 0.1), suggesting a potential for regulated inflammatory immune response. These findings suggest that Cr supplementation in beef calves’ feed may improve their growth performance and immune function.