Yeast cell wall supplementation alters the performance and health of newly received crossbred heifers
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Many natural feed additives have been evaluated to determine their effectiveness on improving cattle health and performance. One such feed additive is yeast and yeast by-products. Yeast and yeast cell wall supplementation have been reported to improve immune function of host animals, as well as offer advantages in performance traits such as ADG and DMI. The objective of the first study was to determine the effects of supplementing yeast cell wall (YCW) on heifer performance during a 56-d receiving period, as well as performance following a mild endotoxin, lipopolysaccharide (LPS), challenge along with heat stress. A second study was designed to determine the effect of feeding YCW products on the physiological and acute-phase responses of heifers to a LPS challenge. Finally, a third experiment was held in conjunction with the second experiment to evaluate the effects of YCW on the metabolic response of heifers during an LPS challenge. Cattle in Experiment 1 were sorted by source on arrival. A source x treatment interaction was detected, and data were interpreted accordingly. Results from Source 1 showed that supplementation of YCW- C improved ADG from d 0 to 28 and d 0 to 42. The DMI was increased in YCW-C heifers from d 0 to 42, as well as d 14 to 28 and d 28 to 42. Within Source 2, a linear effect for YCW-A and -AA was detected for d 14 BW, d 0 to 14 ADG, and d 0 to 14 G:F. Following the LPS challenge, YCW C was superior in terms of ADG as well as feed efficiency wtihin Source 1. These results suggest that supplementation of YCW-C may be advantageous during the receiving period, as well as during times of immune challenges and heat stress. The linear effects of YCW-A and -AA in Source 2 would suggest the higher dose of 5 g•head•d may be more beneficial during the first 14 d on feed. In experiment 2, heifers receiving YCW-C maintained lower vaginal temperature post-LPS than control (CON) heifers as well was YCW A heifers. Sickness behavior scores (SBS) increased post-LPS but were not affected by treatment. Cortisol concentrations were greatest in CON heifers post LPS compared with YCW-A and -C. Concentrations of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) increased post-LPS but were not affected by treatment. Serum interleukin-6 (IL-6) concentrations increased post-LPS and were greater in CON heifers than in YCW-A and -C heifers. Together these data indicated that YCW supplementation can decrease the acute-phase and physiological response of heifers to an endotoxin challenge. Experiment 3 revealed differences in metabolism of heifers in response to the LPS challenge. Post-LPS, glucose increased and was less in YCW-A than in CON and YCW-C heifers. Post-LPS, insulin also increased and was greater in YCW-A and YCW-C than in CON. Post-LPS, non-esterified fatty acid (NEFA) concentrations were lower in YCW-C heifers compared with CON and YCW-A. Pre-LPS, blood urea nitrogen (BUN) concentrations were greater in YCW-A heifers than in CON, and post-LPS concentrations greater in YCW-A than in CON and YCW-C. These data indicate that YCW products can enhance the metabolic response of heifers during an immune challenge without mobilizing body tissue for energy. Overall, it is evident that YCW supplementation can alter performance, immune response, and metabolism of stressed cattle. Thus, YCW may be a valuable tool for cattle feeders in today’s industry.