Evaluating the effects of feeding management practices and ruminal acidosis on the development of liver abscesses in beef × dairy crossbred steers

Abstract

Objective

We assessed the effects of feeding manage-ment practices, ruminal acidosis, and inoculant concentra-tions of Fusobacterium necrophorum ssp. necrophorum and Salmonella enterica serovar Lubbock on liver abscess (LA) prevalence in beef × dairy steers.

Materials and Methods

Beef × dairy steers (n = 40, initial BW = 88 ± 2.2 kg) were assigned randomly to 1 of 4 treatments: NCON = a high-concentrate diet represen-tative of a standard finishing diet (STD); PCON = a high-concentrate acidotic diet (AD) in which steers were cycled 3-times between AD and a low-concentrate diet (LC) plus 3 intraruminal inoculations of F. necrophorum and S. en-terica (each at 1 × 10⁷ cfu/mL; 100 mL/steer,); STDF = a high-concentrate diet (STD) and 3 intraruminal in-oculations of F. necrophorum; and STDFS = STD and 3 intraruminal inoculations of F. necrophorum and S. en-terica. Steer was the experimental unit. Continuous data were analyzed using mixed models, and categorical data were analyzed using binomial proportions with treatment, time, and their interaction as fixed effects. Hematology was evaluated on d −12 (pre-study), 0 (inoculation), 10, 22, and the day before harvest on d 33 to evaluate signs of systemic infection.

Results and Discussion

Prevalences of LA were 0%, 22%, 33%, and 44% for NCON, PCON, STDF, and STDFS, respectively, but did not differ among treatments. No differences among treatments were observed for ru-menitis or lung health scores. No correlation was observed between LA presence and other variables, including feed disappearance, blood hematology, and rumen, lung, colon, or ileum scores. Ultrasonography as a method to detect LA showed increased sensitivity, specificity, and accuracy as days after the intraruminal inoculation increased, sug-gesting the need for further research on detection strate-gies and techniques.

Implications and Applications

An important find-ing of this study is the ability to induce LA in steers fed a standard high-concentrate finishing diet followed by in-traruminal inoculation of F. necrophorum ssp. necropho-rum and S. enterica. This experiment confirms that rumi-nal acidosis is not required to induce LA, and the presence of the etiologic agent in the rumen is sufficient to induce LA.