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The objective of this experiment was to determine the effect of yeast supplements on performance and health of steers during the receiving period . Weaned crossbred steers (n = 184 ; initial BW = 203 ± 1 kg ) were blocked by BW and randomly assigned to pen (4 pens /block ; 5 -6 hd /pen ) . Pens within a block were randomly assigned to one of four treatments (9 pens /treatment ) : 1 ) control (CON ; no yeast additive ) , 2 ) live yeast (LY ; 5 g .hd -1 .d -1 BIOSAF , Lesaffre Feed Additives , Milwaukee , WI ) , 3 ) yeast cell wall (YCW ; 5 g .hd -1 .d -1 Pronady 500 , Lesaffre Feed Additives ) , 4 ) live yeast + yeast cell wall (LY+YCW ; 5 g .hd -1 .d -1 live yeast and 5 g .hd -1 .d -1 yeast cell wall ) . Daily DMI was recorded and individual BW was collected every 14 d for 56 d . Data were analyzed using a randomized complete block design using the fixed effect of treatment and random effect of block (SAS Inst . Inc . , Cary , NC ) . A subset of 24 steers was utilized after 38 d on feed to determine the effect of yeast supplementation on the response to a lipopolysaccharide (LPS ) challenge . Calves were fitted with jugular catheters and indwelling rectal temperature measuring devices that measured rectal temperature at 1 -min intervals , and were moved into individual stanchions . On d 39 , blood samples were collected at 30 -min intervals from -2 to 8 h and then at 24 h relative to administration of LPS (0 .5 μg /kg BW ) at 0 h . Blood samples were used to determine serum interleukin -6 (IL -6 ) , tumor necrosis factor -α (TNF -α ) , interferon -γ (IFN -γ ) , cortisol concentrations , and neutrophil :lymphocyte (N :L ) ratios . Data were subjected to analysis of variance specific for repeated measures using Statview (SAS Inst . Inc . ) with sources of variation including treatment , time and their interactions . Specific time point comparisons within treatment group were conducted using a Paired t -test to compare pre -challenge values with specific time points post -challenge . Steers receiving LY or YCW showed a 7 % numerical increase (P = 0 .59 ) in ADG and a 7 .7 ± 4 .7 kg increase in BW at d 56 . Cumulative DMI increased (P = 0 .05 ) for the LY , YCW , and LY+YCW treatments compared to CON (5 .47 , 6 .02 , 5 .96 , and 5 .89 kg /d ; CON , LY , YCW , and LY+YCW , respectively ) . Steer morbidity and mortality were not affected by yeast supplementation (P ≥ 0 .10 ) . In response to LPS challenge , basal RT prior to LPS tended (P ≤ 0 .06 ) to differ among groups with CON calves having higher RT compared to LY+YCW (P ≤ 0 .01 ) and LY (P ≤ 0 .04 ) calves . After the LPS challenge , RT remained higher in the CON calves compared to other treatments (P ≤ 0 .05 ) . By 10 h post -LPS , RT were still greater (P ≤ 0 .05 ) in CON calves compared to all other calves , and remained numerically greater throughout the study . Serum cortisol increased in all groups post -LPS with peak concentrations observed at 1 h . Peak cortisol concentrations were 26 .5 ng /mL greater (P ≤ 0 .04 ) in CON calves compared to LY+YCW calves . Interferon -gamma (IFN -γ ) concentrations tended (P ≤ 0 .06 ) to be greater in CON calves compared to YCW calves prior to LPS exposure . Collectively , these data indicated that the use of yeast additives increased total feed consumed by the steers during the first 56 d of the feeding period , and improved health , thus allowing for enhanced performance . |
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