Effects of injectable vitamin C at weaning and prior to transit on growth performance of early-weaned beef steers

Beef calves weaned at a younger age may encounter greater physiological or oxidative stress during weaning and transit. This research examined the ability of an injectable vitamin C to affect growth performance and immune function in early-weaned beef calves. Lay Summary Weaning and transit represent the primary stressors for beef calves in the United States and are responsible for increasing inflammation, suppressing the immune system, and decreasing antioxidant status. These adverse physiological responses to stressors may decrease growth and increase morbidity in beef calves. Vitamin C is the primary water-soluble antioxidant in plasma and when provided intramuscularly prior to the stress event, may be able to attenuate aspects of a stress response on growth and immune function. This study evaluated the effects of injectable vitamin C given to early-weaned beef calves prior to weaning on day 0 and a 6-h transit on day 49 after weaning. Basal levels of plasma ascorbate were lower than prior studies in older and larger animals. As expected, injectable vitamin C rapidly increased plasma ascorbate concentrations at 24 h, but concentrations also increased in control calves receiving a saline injection. Treatments did not affect overall growth performance or dry matter intake. Treatments also did not impact the immune response to a booster vaccination provided at weaning. While other research has indicated a positive effect of injectable vitamin C prior to transit, additional research is needed to refine the dosage and physiological need for exogenous antioxidants like vitamin C based on the severity and duration of a stress event in lightweight beef calves. This study investigated the effects of injectable vitamin C (VC) at weaning and prior to transit on growth performance and immune function in early-weaned beef steers. On day 0, 91 Angus x Simmental steers (92 +/- 4 kg) were weaned (65 +/- 11 d of age), given vaccination boosters, blocked by age, and randomly assigned to weaning (WEAN) treatments: intramuscular injections (20 mL per steer) of VC (250-mg sodium ascorbate per mL; 5 g per steer) or saline (SAL). From days 0 to 48, steers were housed at the Dixon Springs Agricultural Center (Simpson, IL) in pens (six pens; N = 14 to 16 steers per pen) equipped with two to three Vytelle bunks to measure individual daily feed disappearance. On day 49, half of the steers in each WEAN treatment were randomly assigned to an additional injection treatment (20 mL per steer) of VC or SAL prior to transport (TRANS). After administering pretransit injections, all steers were loaded onto a commercial livestock trailer with equal representation of treatments across compartments. Steers were transported for 6 h (approximately 480 km) to the Illinois Beef and Sheep Field Laboratory (Urbana, IL). Upon arrival, steers were sorted into pens (six pens; N = 13 to 17 steers per pen) with 2 Vytelle bunks per pen. Steers were weighed on days 0, 1, 14, 48, 49, 64, 78, 106, and 107. Blood was collected (WEAN = 24 steers per treatment; TRANS = 12 steers per treatment) on days 0, 1, 2, 14, 49 (pre- and posttransit), 50, and 51. Data were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of age block, WEAN, TRANS, and WEAN x TRANS. Plasma ascorbate concentrations were greater (WEAN x time P < 0.01) on days 1 and 2 for steers that received VC at weaning. Similarly, for steers that received VC on day 49 pretransit, ascorbate concentrations were greater (TRANS x time P = 0.04) on days 49 posttransit, 50, and 51. Treatments did not affect (P >= 0.13) body weight, average daily gain, or gain to feed throughout the trial. Serum Bovine Viral Diarrhea Virus type 1 and 2 antibody titers on days 14 and 51 were not affected (P >= 0.32) by treatment. Injectable VC administered to early-weaned beef steers at the time of weaning or pretransit increased plasma ascorbate concentrations but did not improve growth performance or antibody response to vaccination booster.