EFFECTS OF DIETARY COMPOSITION AND FEEDING MANAGEMENT REGIMEN ON FEEDLOT CATTLE PERFORMANCE

The objective of this study was to evaluate the independent and interactive effects of dietary starch concentration and feeding management regimen on growth performance, carcass outcomes, liver abscess prevalence, and metabolic health in finishing feedlot steers. In a randomized complete block design, crossbred beef steers (n = 720) were assigned to 48 pens that housed 15 steers per pen. Treatments were arranged in a 2 × 2 factorial with the factors being diet and feeding management. Diets varied in starch inclusion; low starch (42.1%; CON) or high (64.4%; HOT) and feeding management was either consistent (REG) or erratic (ERR) in both feed quantity (85% followed by 115% of a 4 d average randomly once a week) and delivery times (randomly delayed 1, 2, 3, or 4 h twice a week on randomized d). Live steer performance (BW, fecal score, and fecal pH) were collected every 56 d until harvest. Within each pen, 3 steers closest to the median body weight (BW) were selected to serve as a subset (n = 144). On d 0, the subset were administered a 3-axis accelerometer ear tag (AllFlex), and an indwelling ruminal pH bolus (SmaxTech). Data from the technologies were collected from d 0 to d 150. At harvest, a tissue sample from the subset was collected from the ventral sac of the rumen, adjacent to the cranial pillar, and from the colon. The tissues were washed with sterile saline and stored separately in polypropylene bottles with approximately 800 mL of 10% buffered formalin until analysis of morphological and histological characteristics. When a liver abscess was present, an additional sample was collected from the ventral sac in addition to the colon and liver, shipped overnight to the laboratory at Kansas State University, and processed for bacteriological using culture and quantitative polymerase chain reaction (qPCR) methods. Continuous data such as performance, non-categorical carcass data, histological and morphological measurements were analyzed using the MIXED procedure of SAS (SAS 9.4, SAS Institute Inc.). Pen served as the experimental unit. The model included the effects of diet, feeding management, and their interaction, and block was included as a random effect. Rumination and ruminal pH were analyzed as repeated measures using PROC MIXED with the main effects of diet, management, time, and their interactions using pen within block as the subject. Categorical data such as quality grade and liver abscess frequency outcomes were analyzed using the GLIMMIX procedure as binomial proportions. Pen served as the experimental unit. The model included the effects of diet, feeding management, and their interaction, and block was included as a random effect. No diet × management interactions were detected for growth performance, carcass characteristics, liver abscess prevalence, ruminal scoring, daily rumination prevalence, fecal characteristics, histological or morphological measurements, or pathogenic bacteria presence or concentration (P ≥ 0.10). Steers consuming HOT had greater liver abscess frequency (55.1% vs. 33.4%) and liver scars (46.7% vs. 34.0%). Additionally, steers fed HOT had less final BW, ADG, DMI, HCW, marbling score, and calculated YG compared to CON (P ≤ 0.05). A diet × day interaction existed for HOT having greater rumination than CON, which primarily occurred after they were transitioned from REC to their respective dietary treatments (P < 0.01). Ruminal pH was less (P = 0.04; diet × day interaction) for cattle consuming HOT compared to CON for most of the feeding period. Steers consuming HOT had fewer normal rumens (P < 0.01), a greater proportion of rumens exhibiting minor damage (P < 0.01), and less rumen scarring (P = 0.05) compared to CON. Steers consuming HOT had greater epithelial thickness in all 3 strata measured (P ≤ 0.05) compared to CON. Steers consuming HOT had 22 μm shorter colon crypt length than CON (P = 0.03), but no difference in colon crypt width was detected (P = 0.22). Steers consuming HOT had a greater number of liver abscesses positive for F. subsp. funduliforme (P = 0.03) and ruminal epithelium positive for Trueperella pyogenes (P < 0.01). Additionally, HOT steers tended to have a greater number of ruminal epithelium samples positive for F. subsp. necrophorum (P = 0.09). The steers consuming HOT had approximately 23 CFU/g more (P = 0.03) F. subsp. funduliforme in liver. Feeding management did not impact growth performance, carcass characteristics, liver abscess frequency, liver scar presence, fecal characteristics, rumination, ruminal pH, or colonic morphological measurements (P ≥ 0.21). The steers receiving ERR tended to have greater (P = 0.09) ruminal epithelial thickness for the outer most layers (stratum corneum) of the epithelium; however, there was no difference in thickness of the stratum granulosum or stratum spinosum/stratum basale layer (P ≥ 0.12) compared to REG. Steers that were fed ERR tended to have a greater percentage of liver abscesses positive for F. subsp. funduliforme (P = 0.06), and ruminal tissue positive for F. subsp. necrophorum (P = 0.07) compared to REG. However, feeding management did not have an impact on the presence of other bacterial in ruminal tissue or any bacteria presence in colonic epithelial tissue (P ≥ 0.48). The ERR treatment tended to have greater concentration of F. subsp. funduliforme in liver abscess tissue (P = 0.06), and F. subsp. necrophorum in ruminal tissue (P = 0.07). Results suggest that decreasing dietary roughage concentration below that typically used in feedlot cattle finishing diets and excluding grain-milling co products to provide high concentrations of readily fermentable starch is an effective strategy to induce liver abscesses in cattle but could have negative implication on liver performance. Also, feeding a diet with high concentrations of readily fermentable starch decreases ruminal and fecal pH, exposes cattle to ruminal and colonic damage. While our study confirms that F. necrophorum subsp. necrophorum is the primary etiologic agent of LA, it also reveals that approximately 20% of abscesses were caused solely by subsp. funduliforme, without the involvement of subsp. necrophorum. A novel and notable finding was the high prevalence of subsp. funduliforme, either alone or in association with subsp. necrophorum, in ruminal epithelial tissues and LA, suggesting a broader role of this subspecies in liver abscess pathogenesis than previously understood. Furthermore, the prevalence of F. necrophorum in colonic tissue suggests that the colon could also be an important reservoir for pathogens related to liver abscess development.

Author dc:creator

• Schneid, Kasi Nicole

Contributors dc:contributor

• Samuelson, Kendall L.
• Lawrence, Ty E.
• Richeson, John T.
• Guerrero, Bridget
• Nagaraja, Tiruvoor

• Feedlot Nutrition

Language dc:language

English

Handle dc:identifier.uri

https://hdl.handle.net/11310/9422

OAI identifier oai:identifier

oai:tdl-ir.tdl.org:11310/9422