Zinc source and concentration altered physiological responses of beef heifers during a combined viral-bacterial respiratory challenge

Authors: Broadway, Paul; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; WORD, ALYSSA - Texas Tech University; ROBERTS, SHELBY - West Texas A & M University; KAUFMAN, EMILY - West Texas A & M University; RICHESON, JOHN - West Texas A & M University; BROWN, MIKE - Global Animal Products, Incorporated; RIDENOUR, KEN - Global Animal Products, Incorporated

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2021
Publication Date: 3/1/2021
Citation: Broadway, P.R., Carroll, J.A., Sanchez, N.C., Word, A.B., Roberts, S.L., Kaufman, E.L., Richeson, J.T., Brown, M.S., Ridenour, K. 2021. Zinc source and concentration altered physiological responses of beef heifers during a combined viral-bacterial respiratory challenge. Animals. 11(3):646. https://doi.org/10.3390/ani11030646.
DOI: https://doi.org/10.3390/ani11030646

Interpretive Summary: Bovine respiratory disease (BRD) is one of the most costly animal health issues faced by beef cattle producers. Due to consumer pressures and increased scrutiny placed on the use of antibiotics in livestock production, alternatives products are being utilized that may confer a health benefit. Zinc is an important mineral for cattle health and immune function; however, there are differences in the types of zinc supplemented and their biological activity. Therefore, the objective of this study was to determine if supplementing zinc from two different sources at various levels could lessen the severity of illness and expedite the recovery of cattle during a respiratory disease challenge. To accomplish this study, 32 beef calves were supplemented with either 100 or 200 mg of inorganic zinc or 80 mg of organic zinc each day for 30 days prior to exposure to BRD. Organic zinc reduced body temperature during the challenge and there was a slight reduction in stress hormones in the organic zinc treatment. Other blood parameters also indicated that organic zinc reduced the severity of the disease. However, it appears that the 200 mg dose of inorganic zinc may have been detrimental to the health of the cattle. Finally, the severity of lesions in the nostrils of organic zinc supplemented calves was reduced compared to other treatments. Overall, it appears that organic zinc may be beneficial for the overall health and well-being of beef cattle when supplemented prior to a respiratory disease event, and it may be possible to overdose zinc to cattle and be detrimental to animal health.

Technical Abstract: Three treatments were evaluated in feedlot heifers to determine the effects of zinc supplementation on the immune response to a combined viral-bacterial respiratory disease challenge. Thirty-two beef heifers (255±15 kg) were subjected to a 30-d period of Zn depletion, then randomly assigned to one of three treatment diets fed for 30 d before the challenge: 1) Supplementation with 100 mg of Zn from Zn sulfate/kg of DM (Zn100), 2) Supplementation with 200 mg of Zn from Zn sulfate/kg of DM (Zn200), and 3) Supplementation with 80 mg of Zn/kg of DM from zinc methionine (ZinMet® Global Animal Products, Inc., Amarillo, TX) and 20 mg of Zn from Zn sulfate/kg of DM (ZinMet). After the 30-d supplementation period, all heifers were fitted with indwelling vaginal temperature (VT) devices and intra-nasally challenged with 1x108 PFU bovine herpesvirus-1 on d -3, and then allowed to rest in outdoor pens for 3 d. On d 0, each heifer was challenged intra-tracheally with an average dose of 2.38 x 107 CFU Mannheimia haemolytica (MH), fitted with an indwelling jugular catheter, and then moved into individual stalls in an environmentally-controlled enclosed barn. Whole blood samples were collected at 1-h (serum) and 2-h (complete blood counts) intervals from 0 to 8 h, and at 12, 24, 36, 48, 60, 72, 168 and 360 h relative to MH challenge. Data were analyzed using the MIXED procedure of SAS specific for repeated measures with fixed effects of treatment, time and their interaction. There was a treatment effect (P < 0.01) for VT such that Zn200 heifers had greater VT than Zn100 and ZinMet heifers. There was a trend (P=0.10) for a serum cortisol treatment effect with Zn100 heifers having greater cortisol than ZinMet heifers. Total leukocytes and lymphocytes were greater (P=0.008) in Zn100 heifers than Zn200 and ZinMet heifers, while monocytes were less (P=0.05) in ZinMet heifers than Zn100 and Zn200 heifers. Concentrations of IL-6 were greater (P=0.02) in ZinMet heifers than Zn100 and Zn200 heifers. Concentrations of IFN-' were greater in Zn200 heifers than ZinMet heifers at 0h, and Zn100 heifers from 0 to 12 h post-MH challenge (treatment x time P=0.02). Serum haptoglobin was not affected by treatment or treatment x time (P=0.36), but increased over time (P<0.001) in all groups. There was a trend (P=0.11) for ZinMet heifers to have less severe nasal lesion scores than Zn100 heifers. The observed differential physiological responses in this study indicate that zinc source and concentration may alter the response to a bovine respiratory challenge in heifers.