Some negative effects of heat stress in feedlot heifers may be mitigated via yeast probiotic supplementation

Authors: Broadway, Paul; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; CRAVEY, MATT - Phileo Lesaffre Animal Care; CORLEY, JIMMY - Phileo Lesaffre Animal Care

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2020
Publication Date: 1/23/2020
Citation: Broadway, P.R., Carroll, J.A., Sanchez, N.C., Cravey, M.D., Corley, J.R. 2020. Some negative effects of heat stress in feedlot heifers may be mitigated via yeast probiotic supplementation. Frontiers in Veterinary Science. 6:515. https://doi.org/10.3389/fvets.2019.00515.
DOI: https://doi.org/10.3389/fvets.2019.00515

Interpretive Summary: Heat stress is an issue that negatively impacts livestock production by reducing production efficiency as well as influencing animal health and well-being. There are very few intervention strategies that can be implemented to reduce the negative impacts of heat stress beyond access to shade and water. Therefore the objective of this study was to determine if feeding a yeast based probiotic to cattle during heat stress could alleviate some of the negative repercussions of heat stress. In this study one group of cows were fed a diet without yeast supplements, and the other group was supplemented with a yeast product for approximately 1 month. These cattle monitored for 2 days in thermoneutral temperatures, then were subjected to a moderate heat stress for 4 days by manipulating temperature and humidity in an enclosed barn. Results from this study show that animals fed yeast had increased water intake during the heat stress. Yeast supplemented animals also displayed decrease respiration rates, and also had decreased body temperature. There were no differences in blood parameters measured. Overall, supplementing cattle with a yeast supplement during a heat stress event may help alleviate some of the negative symptoms associated with heat events.

Technical Abstract: Heat stress (HS) in feedlot cattle can be detrimental to performance, health and profitability; however, utilization of feed additives has the potential to mitigate some of these negative effects. Therefore, this study was designed to determine if supplementation of a combination live yeast and yeast cell wall product in feed could mitigate the negative impacts associated with HS. Crossbred, phenotypically similar beef heifers (n = 32; BW = 385±43 kg) were divided into 2 pens in which one pen was fed a standard finishing ration (CON), and the other was fed the same ration supplemented with a combination of a live yeast (1.5 g/hd/d) and yeast cell wall product (2.5 g/hd/d; YEAST; Phileo Lesaffre Animal Care, Milwaukee, WI). After 50 d of supplementation, heifers were transported to an environmentally-controlled facility and placed in individual bleeding stalls after indwelling jugular catheters and vaginal temperature (VT) loggers were inserted. Heifers were kept in thermoneutral (TN) conditions for 48 h [temperature-humidity index (THI) ~67; d1 to 2] then were subjected to HS for 4 d (THI ~80; d 3 to 6). From d 2 to 6, hourly blood samples were collected for serum isolation from 1400-1800 h and again from 2200-0200 h which represented the daily targeted peak and nadir of THIs. A whole blood sample was collected twice daily at 1400 and 2200 h for complete blood counts (CBC). Data collected included BW, water intake, respiration rate (RR; measured at 1600 and 2400 h daily) and serum cortisol, glucose and NEFA concentrations. There was no change in BW (P = 0.14) or ADG (P = 0.53) between the treatments during HS. Yeast-supplemented heifers exhibited reduced VT during HS compared to CON heifers (P < 0.01). There was no difference in water intake during the TN phase (P = 0.25); however, YEAST heifers consumed more water/h (P < 0.01) and had increased drinking bouts (P<0.01) during HS compared to CON heifers. Respiration rates were similar (P = 0.21) during TN, but YEAST heifers tended (P = 0.09) to have decreased RR during HS compared to CON heifers. There were no differences between treatments when evaluating CBC parameters (P > 0.05). There was a tendency (P = 0.08) for greater cortisol in the CON than YEAST heifers during HS; however, glucose (P = 0.38) and NEFA (P = 0.70) concentrations did not differ. In summary, supplementation of live yeast and yeast cell wall products to feedlot heifers may mitigate some of the negative effects associated with HS in feedlot cattle as observed in decreased RR and VT and increased water intake.