Health evaluation of immune-stimulated and hay-supplemented feedlot receiving calves as assessed by blood gas analysis

Abstract Text: This study evaluated blood parameters, health, and performance of immune-stimulated and hay-supplemented feedlot receiving calves. Heifers (n = 705; 179 ± 0.58 kg BW) were blocked by 6 truckloads and assigned to 48 pens and 4 treatments in a randomized complete block design. Treatments were a factorial arrangement of hay (+HAY vs. -HAY) and immunostimulation (+IMMUN vs. -IMMUN). Pens assigned +HAY received supplemental alfalfa hay to the receiving ration for the first 14 d. Calves assigned +IMMUN received a DNA immunostimulant on d 0. On d 0, 14, and 28, BW, rectal temperatures, and venous blood were collected. Health was recorded throughout the 56-d study, and pen weights on d 56. No HAY × IMMUN interactions occurred (P ≥ 0.18). During the first 14 d, calf ADG was greater (P < 0.01) for +HAY than -HAY, but d 14 to 28 ADG was lower (P < 0.01) for +HAY than -HAY. Calf ADG was lower (P ≤ 0.01) for +IMMUN than -IMMUN from d 28 to 56 and from d 0 to 56. Total DMI was greater (P < 0.01) for +HAY than -HAY from d 0 to 14, but lower (P ≤ 0.04) from d 14 to 28 and from d 28 to 56. Gain efficiency of +HAY calves was greater (less negative; P < 0.01) from d 0 to 14, but lower (P < 0.01) from d 14 to 28 when compared to -HAY. Gain efficiency was lower (P ≤ 0.02) for +IMMUN than -IMMUN calves from d 28 to 56 and d 0 to 56. Calf morbidity, mortality, and blood parameters (pH, glucose, lactate, hemoglobin saturated with oxygen [sO₂]) were not affected (P ≥ 0.18) by treatments. Blood sO₂ was lower (P < 0.01) on d 0 than d 14 and 28, and glucose was greater (P < 0.01) on d 28 than d 0 and 14. Blood sO₂ correlated (P < 0.05) with glucose (R² = 0.09), lactate (R² = -0.12) and mortality (R² = 0.08). Glucose correlated with lactate (R² = 0.61), and first (R² = -0.22) and second (R² = -0.13) medical treatment. Lactate correlated (P < 0.05) with first medical treatment (R² = -0.12) and mortality (R² = -0.12). In conclusion, hay supplementation and immune stimulation did not affect calf health, performance or blood gas parameters. Changes in calf health can be observed in measures of blood parameters.

Keywords: calves, hay, immunostimulant