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    Implications of Feed Additives in the Mitigation of Heat Stress in Cattle

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    Author
    Vander Poel, Matthew Jonathon
    Issue Date
    2019
    Keywords
    Cattle
    Cows
    Feed additives
    Heat Stress
    Yeast Culture
    Advisor
    Diaz, Duarte
    
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    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Nutritional supplements have been used to mitigate heat stress in cattle. A series of experiments were conducted under controlled environment conditions in the Animal Research Complex (ARC) to evaluate the value of nutritional intervention on mitigation of heat stress (HS) in cattle. Previous research and literature have shown mixed results in terms of performance benefits. In the first study, we evaluated the use of a proprietary yeast cell extract to help mitigate the effects of hyperthermia on growth development by improving metabolic and immune functions. Twelve crossbred Hereford steers (250 ± 100 kg) were randomly assigned to one of two dietary groups: control group (CON) received 56.7 g of placebo/hd/day; the feed additive group (BA) received 56.7 g of BA/hd/day. Steers were randomly assigned to one of two tie stall rooms with 6 steers per room and 3 steers per treatment/room. Rooms were exposed to cyclical daily temperature humidity index (THI) of 70 - 81 and 27 – 39 for HS and the thermoneutral (TN) rooms respectively for a total of 15 days. Average daily water consumption and average daily gain were calculated at the end of the experimental period. Heat stress increased water consumption (P<0.001), respiration rate (P<0.001), and skin temperature (P<0.001) and tended to increase rectal temperature (P<0.06). Supplementation with BA tended to reduce rectal temperatures (P<0.06) in heat stressed cattle. Exposure to heat stress lowered serum glucose (P<0.01) and insulin (P<0.01) while increasing NEFAS (P<0.01) and TAG (P<0.01). Supplementation with BA lowered TAG (P<0.05) and glucose (P<0.05). HS and BA supplementation had no effect on serum cortisol levels. Results of this study suggest that HS exposure for 15 days had performance and metabolic impacts in crossbred Hereford steers. Supplementation with the dietary BA alleviated some of the daily metabolic effects associated with heat exposure. The objective of the second study was to evaluate the effect of feeding a dietary supplement (PMI Nutritional Additives, Arden Hills, MN) on the HS response in multi-parturient dairy cows in mid lactation. Two pens of cows at a commercial dairy were fed either control (CON) or additive (YB) at 113 g/cow per d for two weeks prior to arrival. Study cows (n=12) were balanced in days in milk (DIM), milk production, and parity (111.91±4.85 d, 33.67±0.96 kg/d, and 2.25±0.18). Cows were randomly selected from both groups (6 TRT and 6 CON) and housed in environmentally controlled chambers for 18 d and fed appropriate diet. Cows were subjected to 7 d of TN conditions, 7 d of HS, and 4 d of recovery (REC) under TN conditions. HS increased RT (P<0.0001), RR (P<0.0001), BUN (P<0.0001), insulin (P=0.04), neutrophil (P=0.009), and water intake (P=0.0005). HS decreased lymphocyte (P=0.0008), DMI (P=0.0007), energy corrected milk (ECM, P=0.01), and 4% fat corrected milk (FCM, P=0.02). YB decreased the feed efficiency ratio (P=0.03). YB had no effect on blood parameters. There was a treatment x environment interaction with cows fed YB having lower feed efficiency (P=0.02) during peak thermal loads than CON. Results of this study suggest that HS exposure had performance and metabolic impacts in mid lactation cows. Supplementation with YB alleviated some of the performance effects associated with HS. The research results support that feed additives have the potential to mitigate the negative effects of heat stress but doesn’t undermine the importance of other nutritional and management strategies that are in use.
    Type
    text
    Electronic Thesis
    Degree Name
    M.S.
    Degree Level
    masters
    Degree Program
    Graduate College
    Animal Sciences
    Degree Grantor
    University of Arizona
    Collections
    Master's Theses

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