The effects of whole cottonseed on performance, carcass characteristics, and shedding characteristics of Escherichia coli O157 by finishing beef steers
Cranston, Jacob John
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One hundred twenty crossbred beef steers (initial body weight = 230.3 ± 18.0 kg) were used to determine the effects of whole cottonseed (WCS) supplementation on performance, carcass characteristics, and the prevalence of Escherichia coli 0157 in the feces and on hides at slaughter of finishing beef steers. The three dietary treatments included: (1) a standard finishing diet (STD); (2) a diet containing 15.10% whole cottonseed (WCS): and (3) a whole cottonseed equivalent diet (EQU) formulated to contain percentages of fat and neutral detergent fiber (NDF) equal to those in the WCS diet. Cattle were on feed for an average of 120 d. A randomized complete block design was used with pen as the experimental unit (eight pens/treatment). Results reported here are for the period from d 0 to slaughter. A difference among treatments was detected for dry matter intake (DMI; P = 0.056). Steers fed the WCS diet consumed more feed than steers fed the STD or EQU diets (P < 0.091). No differences were detected among treatments for average daily gain (ADG; P = 0.521), carcass-adjusted ADG (P = 0.305), or feed efficiency, expressed as feed:gain. (P = 0.225); however, a difference was detected among treatments for carcass-adjusted feed efficiency (P = 0.009). Separation of the treatment means revealed that cattle fed the STD treatment used feed more efficiently (P < 0.01) on a carcass-adjusted basis than steers fed the WCS or EQU diets. No differences (P > 0.10) were detected among treatments for hot carcass weight, fat thickness at the 12"' rib, longissimus muscle area, percentage of kidney, pelvic, and heart fat, liver abscess score, and USDA yield and quality grades. Differences were detected among treatments for dressing percent (P = 0.061) and marbling score of the longissimus muscle (P = 0.058). Steers fed the STD diet had higher dressing percents (P < 0.058) than steers fed the WCS and EQU diets. Additionally, steers fed the STD diet had higher marbling scores (P < 0.081) than steers fed the WCS and EQU diets. No differences were detected (P > 0.229) among treatments for the presence of £. coli 0157 detected at any sampling period during the study. These results indicate that unless an adjustment is made for total dietary fiber, finishing cattle fed a diet containing supplemental WCS will likely consume more feed and gain similarly to cattle fed a standard finishing diet. These data also indicate that WCS will likely have no effect on the prevalence of £. coli 0157 in beef cattle.