Effects of Supplemental Zinc Concentration and Trace Mineral Source on Immune Function and Growth Performance in Weaned Beef Calves Received into a Feedlot

 

During the receiving phase in a feedlot, newly received calves are exposed to stressors such as transportation, lack of feed and water, introduction to unfamiliar feed resources, different environmental conditions, and foreign pathogens.¹ These stressors can lead to reduced dry matter intake.² Trace minerals play important roles in in immune function.³ Thus, during the receiving phase, additional fortification of the diet with trace minerals may prove beneficial. The source of supplemented trace minerals (inorganic or organic) may also be important. Inorganic sources of trace minerals are generally bound to sulfate. Whereas organic sources of trace minerals are bound to an organic material. These materials are generally amino acid complexes, proteinates, chelates, polysaccharide complexes, and propionates. Research has generally shown that organic trace minerals are more bioavailable than inorganic minerals.

 

Research published in 2012 showed that organic trace mineral supplementation improved growth performance of shipping-stressed calves compared with those fed equivalent levels of inorganic sources.⁴ Zinc in particular appears to be critical in receiving cattle diets. Dietary zinc, regardless of source, has been shown to improve growth in cattle during the growing period.⁵ Iowa State university researchers conducted a study to evaluate the effects of supplemental zinc concentration and trace mineral source on immune function, associated biomarkers of immune status, trace mineral status, and growth performance in weaned beef calves being received into a feedlot.⁶

 

In this project, 72 newly received, low-risk weaned Angus-crossbred steers (initial body weight = 626 lb) were enrolled in a 42-day feedlot receiving study. Steers in this study were considered low-risk as they originated from a known source, were weaned, vaccinated, and a complete health history was known. The steers were housed in pens (6 steers per pen) equipped with GrowSafe bunks for determination of individual animal feed disappearance. They were assigned to one of three dietary treatments containing supplemental trace minerals of differing source and concentration that were included as premixes in a common receiving diet: 1) trace minerals from an organic source (Availa4; Zinpro Corp.) at 7 grams/steer/day for the entire 42-day receiving trial (ORG), 2) ORG for entire 42 days plus AvailaZn (Zn amino acid complex, Zinpro Corp.) to provide 1,000 mg Zn/steer/day for the first 14 days (ORG+Z), or 3) inorganic trace mineral sources supplemented at equivalent concentrations as in the ORG treatment for 42 days (ING). In this trial, the cattle Cattle were weighed on day -1, 0, 14, 41, and 42. Whole blood was collected all 72 steers) on day 0, 14, and 42. Liver biopsies were conducted (36 steers; 3 steers per pen) on day 0, 14, and 42.

 

The effects of dietary supplemental zinc concentration and trace mineral source on growth performance are shown in Table 1. During the first 14 days, day 14 body weight (BW), average daily gain (ADG), dry matter intake (DMI), and Gain:Feed ratio were not affected by dietary treatment (P ≥ 0.18). From days 14 to 42 gain efficiency was increased for ORG+Z steers (P = 0.02) compared to ORG and ING. However, no significant response (P ≥ 0.14) was noted for day 42 BW, ADG, or DMI. Overall (days 0 to 42), there was a tendency for improved ADG (P = 0.07) for steers supplemented trace minerals from an organic source where ORG and ORG+Z were increased ~9.0% and ~12.0%, respectively, compared to ING. Final BW did not differ (P = 0.21) and overall DMI intake was unaffected by dietary treatment (P ≥ 0.18). However, overall gain-to-feed ratio was improved (P = 0.01) in steers supplemented with organic trace minerals (ORG and ORG+Z) compared to ING. When compared to ING, overall G:F for steers from ORG and ORG+Z was increased 12.4% and 19.7%, respectively.

 

^a,bWithin a row, means with unlike superscripts differ P ≤ 0.05.

^x,yWithin a row, means with unlike superscripts differ 0.1 ≥ P > 0.05.

Adapted from Smerchek et al., 2023.

 

These researchers noted that at the initiation of the study, the cattle were well within the adequate range of liver and plasma zinc when compared to standard reference ranges. Since the cattle were already eating well at trial initiation and all treatments were fed diets adequate in zinc, liver and plasma zinc concentrations were adequate during the trial.

 

In conclusion, in this study with low stress cattle with adequate liver and plasma trace mineral concentration, supplementation with organic trace minerals tended to improve overall ADG and did improve overall gain efficiency during the 42-day receiving period. Plasma trace mineral concentration was minimally influenced by trace mineral source or concentration. These results also showed that trace mineral supplementation, regardless of source, can alter markers of activation within immune cell populations.

 

¹ Loerch, S. C., and F. L. Fluharty. 1999. Physiological changes and digestive capabilities of newly received feedlot cattle. J. Anim. Sci. 77:1113–1119.

 

² Hutcheson, D. P., and N. A. Cole. 1986. Management of transit-stress syndrome in cattle: Nutritional and environmental effects. J. Anim. Sci. 62:555–560.

 

³ Spears, J. W. 2000. Micronutrients and immune function in cattle. Proc. Nutr. Soc. 59:587–594.

 

⁴ Kegley, E., M. Pass, J. Moore, and C. Larson. 2012. Supplemental trace minerals (zinc, copper, manganese, and cobalt) as Availa-4 or inorganic sources for shipping-stressed beef cattle. Prof. Anim. Sci. 28:313–318.

 

⁵ Spears, J., and E. Kegley. 2002. Effect of zinc source (zinc oxide vs zinc proteinate) and level on performance, carcass characteristics, and immune response of growing and finishing steers. J. Anim. Sci. 80:2747–2752.

 

⁶ Smerchek, D. T, M. E Branine, J. L McGill, and S. L Hansen. 2023. Effects of supplemental Zn concentration and trace mineral source on immune function and associated biomarkers of immune status in weaned beef calves received into a feedlot. J. Anim. Sci. 101.