BEEF SPECIES–RUMINANT NUTRITION CACTUS BEEF SYMPOSIUM: Energy and roughage levels in cattle receiving diets and impacts on health, performance, and immune responses1

Abstract

Transition of newly received feedlot cattle from a forage- to grain-based diet is challenging, and the appropriate roughage level in receiving diets is debatable. Nutritionists must consider the paradox of dietary transition and roughage level to mitigate ruminal acidosis, yet concomitantly low feed intake presents difficulty in achieving nutrient requirements when metabolic demand is increased due to inherent stress and disease challenge during the receiving period. Previous research suggests that performance is improved at the expense of increased morbidity for newly received cattle consuming diets with less roughage and greater starch concentration. The clinical signs of bovine respiratory disease (BRD) and acute acidosis are analogous; therefore, it is probable that acidotic cattle are incorrectly diagnosed with BRD in both research and production settings. Additional research efforts have attempted to elucidate alterations in microbial populations and digestion, physiological response to inflammatory challenge, and immunological response to infectious bovine rhinotracheitis virus challenge in cattle consuming diets of various roughage levels. Furthermore, our understanding of the rumen microbiome is improving rapidly with culture-independent assays, products such as direct-fed microbials are available, and increased availability and use of fibrous byproduct ingredients requires further attention. Beef cattle nutritionists and producers should consider that the health benefit of receiving diets containing greater levels of roughage and lower energy may not compensate for the reduction in performance compared with feeding receiving diets with lower roughage and greater energy.

Effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on clinical health, growth performance, and carcass traits of high-risk cattle during the feedlot receiving and finishing periods1

“…Dry matter intake is characteristically low within the first 2 wk of feedlot arrival and is coupled with immunosuppression and negative energy balance induced by traditional beef marketing channels ( Nagaraja et al, 1998 , Richeson et al, 2019 ). Sowell et al (1999) observed that steers diagnosed with BRD spent 30% less time eating than healthy cohorts, especially within the 4-d following feedlot arrival.…”

“…Consequently, cattle experience immunosuppression and a negative energy balance upon feedlot arrival. Feed intake is concomitantly low during this time, averaging 1.5% of body weight (BW) in the first 2 wk following arrival, which further exacerbates immunosuppression due to inadequate nutrient intake ( Nagaraja et al, 1998 ; Richeson et al, 2019 ). As observed by Sowell et al (1998) , steers diagnosed with BRD spent 30% less time at the feed bunk than healthy cohorts, with differences in dry matter intake (DMI) being most pronounced within the initial 4 d following arrival ( Sowell et al, 1998 , 1999 ).…”

Effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on serum chemistry, complete blood count, and fecal Salmonella spp. count in high-risk cattle during the feedlot receiving and finishing periods1,2

“…This is likely a defense mechanism, as the overall function is to reserve plasma glucose for maximal brain function during a stress event by promoting gluconeogenesis but reducing glucose utilization by skeletal muscle and white adipose tissue ( Kuo et al, 2015 ). Marketing, transportation, and feedlot arrival of high-risk cattle is a stressful event ( Richeson et al, 2019 ), and the stress-induced production of glucocorticoid and subsequent increase in total white blood cell count supports the observed decrease in treatment for BRD in CHR-fed cattle ( Smock et al, 2020 ). Furthermore, CHR did not influence receiving period performance but did decrease performance during the finishing period ( Smock et al, 2020 ).…”

“…As a result of limited or no feed and water access and inflammation during marketing and transportation, high-risk cattle arrive at the feedlot in a catabolic and chronically stressed state ( Richeson et al, 2019 ). The observed serum chemistry day effects ( Table 1 ) clearly indicate the metabolic disruption high-risk cattle possess at feedlot arrival and how they return to homeostasis later in the receiving period.…”

“…Auction-derived feeder cattle are considered high risk because a variety of predisposing factors lend them especially susceptible to digestive disturbances and bovine respiratory disease (BRD) associated morbidity and mortality. Stress and pathogen exposure induced by weaning, marketing, and shipment results in compromised immune function, alteration of and likely negative state of energy and protein metabolism, reduced appetite and growth performance, and compromised digestion and rumen function ( Loerch and Fluharty, 1999 ; Richeson et al, 2019 ). Cattle feeders employ a variety of pharmacological interventions to address these challenges, such as antimicrobial metaphylaxis and BRD treatments.…”