The effects of zinc amino acid complex on biomarkers of gut integrity, inflammation, and metabolism in heat-stressed ruminants

Authors: OPGENORTH, JULIE - Iowa State University; ABUAJAMIEH, MOHANNAD - Iowa State University; HORST, ERIN - Iowa State University; MOHANNAD, SARA - Iowa State University; Johnson, Jay; MAYORGA, EDITH - Iowa State University; SANZ FERNANDEZ, VICTORIA - Iowa State University; AL-QAISI, MOHAMMED - Iowa State University; DEFRAIN, JEFF - Zinpro Corporation; KLEINSCHMIT, D - Zinpro Corporation; GORDEN, PATRICK - Iowa State University; BAUMGARD, LANCE - Iowa State University

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2020
Publication Date: 1/23/2020
Citation: Opgenorth, J., Abuajamieh, M., Horst, E., Mohannad, S., Johnson, J.S., Mayorga, E., Sanz Fernandez, V., Al-Qaisi, M., Defrain, J., Kleinschmit, D., Gorden, P., Baumgard, L. 2020. The effects of zinc amino acid complex on biomarkers of gut integrity, inflammation, and metabolism in heat-stressed ruminants. Journal of Dairy Science. https://doi.org/10.3168/jds.2020-18909.
DOI: https://doi.org/10.3168/jds.2020-18909

Interpretive Summary: Heat stress jeopardizes animal health and this in part is mediated by reduced intestinal health. During heat stress, blood is diverted to the skin to maximize heat dissipation. However, a negative outcome of this survival strategy is that blood and nutrient delivery to the intestine is decreased, leading to intestinal damage. To combat this effect, researchers have determined that supplementing pigs with zinc in the form of an amino acid complex can reduce the impact of heat stress on intestinal health, but it was unknown whether this nutritional supplement would have similar effects in cattle. Therefore, the study objective was to evaluate the effectiveness of supplementing heat-stressed cattle with zinc in the form of an amino acid complex on improving intestinal health in response to a heat stress challenge. It was hypothesized that supplemental zinc would help to maintain intestinal health and reduce markers of inflammation in cattle exposed to heat stress. It was determined that zinc supplementation had some beneficial effects on reducing body temperature, improving intestinal architecture, and decreasing biomarkers of intestinal damage in heat stressed cattle and thus may be an effective nutritional strategy to reduce the negative effects of heat stress in cattle.

Technical Abstract: Study objectives were to evaluate the effects of replacing 40 mg/kg of dietary Zn from Zn sulfate (ZS) with Zn amino acid complex (ZA) on inflammation and intestinal integrity in heat-stressed and nutrient-restricted ruminants. Forty Holstein steers (173.6 ± 4.9 kg) were randomly assigned to 1 of 5 dietary-environmental treatments: 1) thermoneutral (TN) ad libitum with 75 mg/kg (ZSCON), 2) TN pair-fed with 75 mg/kg ZS (ZSPF), 3) TN pair-fed with 40 mg/kg ZA and 35 ppm ZS (ZAPF), 4) heat stress (HS) ad libitum with 75 mg/kg ZS (ZSHS), and 5) HS ad libitum 40 mg/kg ZA and 35 ppm ZS (ZAHS). Prior to study initiation, calves were fed their respective diets for 21 d. Following the pre-feeding phase, steers were transferred into environmental chambers and were subjected to 2 successive experimental periods (P). During P1 (5 d), all steers were fed their respective diets ad libitum and housed in TN conditions (20.2 ± 1.4°C, 30.4 ± 4.3% relative humidity). During P2 (6 d), ZSHS and ZAHS steers were exposed to cyclical HS conditions (27.1 ± 1.5°C to 35.0 ± 2.9°C, 19.3 ± 3.5% relative humidity), whereas the ZSCON, ZSPF, and ZAPF steers remained in TN conditions and were fed ad libitum or pair-fed to their ZSHS and ZAHS counterparts. Overall, steers exposed to HS had markedly increased rectal temperature (0.83°C), respiration rate (26 bpm), and skin temperature (8°C) relative to TN treatments. Rectal temperature from ZAHS steers was decreased (0.24°C) on d 4-6 of HS relative to ZSHS steers. Regardless of diet, HS decreased DMI (18%) relative to ZSCON steers. Circulating glucose from HS and PF steers decreased (16%) relative to ZSCON steers. Heat stress and nutrient restriction increased circulating NEFA 2- and 3-fold, respectively, compared to ZSCON steers. Serum amyloid A increased ~2-fold in PF relative to ZSCON and HS steers. There was no treatment effect on blood pH; however, ZAHS steers had increased HCO3 relative to ZSHS. Relative to ZSHS, ZAHS steers had increased jejunum villi height (25%), a tendency for increased ileum villi height (9%), and decreased duodenal villi width (16%). In summary, ZA supplementation has some beneficial effects on thermal indices, intestinal architecture characteristics, and biomarkers of leaky gut in heat-stressed steers indicative of an ameliorated heat load, and thus may be a nutritional strategy to minimize negative consequences of HS.