High deoxynivalenol and ergot alkaloid levels in wheat grain: effects on growth performance, carcass traits, rumen fermentation, and blood parameters of feedlot cattle

This study was designed to assess the impacts of a mixture of deoxynivalenol (DON) and ergot alkaloids (EAs) on growth performance, rumen function, blood parameters, and carcass traits of feedlot cattle. Forty steers (450 ± 6.0 kg) were stratified by weight and randomly allocated to 1 of 4 treatments; control-low (CON-L), control-high (CON-H) which contained low or high wheat screenings that lacked mycotoxins at the same level as the mycotoxin-low (MYC-L; 5.0 mg/kg DON, 2.1 mg/kg EA), and mycotoxin-high (MYC-H: 10 mg/kg DON, 4.2 mg/kg EA) diets that included wheat screening with mycotoxins. Steers were housed in individual pens for a 112-day finishing trial. Intake was 24.8% lower (P < 0.001) for MYC steers compared to CON steers. As a result, average daily gains of MYC steers were 42.1% lower (P < 0.001) than CON steers. Gain to feed ratio was also lower (P < 0.001) for MYC steers compared to CON steers. Platelets, alanine aminotransferase, globulins, and blood urea nitrogen were lower (P ≤ 0.008), and lymphocytes, glutathione peroxidase activity (GPx), and interleukin-10 (IL-10) were elevated (P ≤ 0.002) in MYC steers compared to CON steers. Hot carcass weights and backfat thickness were reduced (P < 0.001) in MYC steers, resulting in leaner (P < 0.001) carcasses and higher (P < 0.007) meat yield compared to CON steers. Results suggest that a mixture of DON and EAs negatively impacted health, performance, and carcass traits of feedlot steers, with the majority of this response likely attributable to EAs. However, more research is needed to distinguish the relative contribution of each mycotoxin to the specific responses observed.

Economic impacts of lameness in feedlot cattle

Lameness is an important health issue in feedlot cattle; however, there is a paucity of information regarding its economic impact. Decision tree models are excellent tools for assessing costs of disease such as the net return (net return = benefit – cost). Models were developed using expert opinion, literature and retrospective feedlot data provided by Vet-Agri Health Services (VAHS, Airdrie, Alberta, Canada) collected from 2005 to 2015 on individually treated cattle (n = 30,940) from 28 feedlots. The objective was to estimate net return of various lameness diagnoses and impacts of cattle type, season of treatment, and extreme high and low cattle prices. Cattle were diagnosed as lame according to the following categories: foot rot, foot rot in heavy cattle (BW > 363 kg at treatment), injury, lame with no visible swelling, and joint infection. Records consisted of arrival and treatment weight, cost of treatment, and cattle deaths. Records included cattle types classified as: fall calves (heifer and steer), winter calves (heifer and steer) and yearling cattle (heifer and steer). Lastly, variables ADG, days on feed (DOF), and Season (spring, summer, fall, and winter) were created. Models estimated net return using cattle slaughter prices for healthy cattle that reached a slaughter weight of 635 kg and for three possible outcomes for each diagnosis after final treatment: cattle that recovered after treatment and reached a slaughter weight of 635 kg; cattle that were removed before they reached slaughter weight; or cattle that died. Compared to undiagnosed cattle with 1.36 kg/d ADG, cattle diagnosed with foot rot and foot rot heavy cattle had the highest ADG until first treatment (1.14 and 1.57 kg/d, respectively) and differed significantly (P < 0.05) compared to cattle diagnosed with injuries (0.87 kg/d), lame with no visible swelling (0.64 kg/d), and joint infections (0.53 kg/d). Yearling steers had the most positive returns compared to all other cattle types. Cattle with lighter arrival weight had lower ADG and increased economic losses after treatment compared to heavier weighted cattle on arrival. Based on average slaughter prices over a 10-yr period for healthy cattle, return was $690. Return after final treatment for cattle with foot rot was $568, foot rot in heavy cattle was $695, and injury was $259. However, joint infections and lame with no visible swelling had negative returns of –$286 and –$701, respectively.

Feeding behavior and ruminal pH of corn silage, barley grain, and corn dried distillers' grain offered in a total mixed ration or in a free-choice diet to beef cattle

Seventy-nine continental crossbred beef heifers (524.4 ± 41.68 kg BW), 16 of which were ruminally cannulated, were used in a 53-d experiment with a generalized randomized block design to assess the effects of barley grain (BG), corn silage (CS), and corn distillers' grain (DG) offered in a free-choice diet on feeding behavior and ruminal fermentation. Treatments were total mixed ration (TMR) consisting of 85% BG, 10% CS, and 5% supplement or free-choice (i.e., self-selection) diets of BG and CS (BGCS), BG and corn dry DG (BGDG), or CS and corn DG (CSDG). Heifers were housed in groups of 9 or 10 in 8 pens and weighed 2 h before feed delivery at d 0, 21, 42, and 52 of the study. Pens were equipped with an electronic feed bunk monitoring system enabling feed intake and feeding behavior to be continuously monitored. Each of these pens was randomly allocated 2 cannulated heifers equipped with indwelling pH probes for continuous measurement of ruminal pH during wk 1, 2, 4, and 7. Blood and rumen contents were taken from cannulated heifers 2 h after feed delivery on d -3, 0, 7, 8, 42, and 49. Cattle fed either TMR or free-choice diets had similar (P > 0.10) ruminal fermentation, blood profile, and growth performance, with the exception of the CSDG diet, for which ruminal pH levels were consistently greater (P < 0.01) and performance was lower (P < 0.01). When DG was a component in free-choice diets, heifers reduced its inclusion in the diet (P < 0.05) over the experiment without affecting growth rate or ruminal fluid pH. Finishing feedlot cattle fed BG and CS separately selected a diet with a greater proportion of BG (85% DMI) compared to the TMR with no signs of acidosis. When cattle were given free-choice access to corn dry DG as an alternative to CS, they consumed levels up to 30% of their total daily DMI. Under the conditions of our experiment cattle can effectively self-select diets without increasing the risk of subclinical acidosis and still maintain similar levels of growth and feed efficiency compared with a TMR.

Effect of backgrounding and transition diets on fecal concentration and strain types of commensalEscherichia coliin beef cattle

Su, R., Munns, K., Beauchemin, K. A., Schwartzkopf-Genswein, K., Jin-Quan, L., Topp, E. and Sharma, R. 2011. Effect of backgrounding and transition diets on fecal concentration and strain types of commensal Escherichia coli in beef cattle. Can. J. Anim. Sci. 91: 449–458. The aim of the study was to assess the effect of four different backgrounding diets [55% corn silage in combination with 40% of either temper rolled barley-grain, wheat dried distillers' grain, corn dried distillers' grain or millrun (dry matter basis)] and a transition diet containing increasing amount of concentrate (60 to 90%) on fecal Escherichia coli in feedlot heifers. Heifers were fed backgrounding forage based diets for 91 d and then were shifted to a transition diet for an additional 18 d. Strain characterization of E. coli (n=224) was carried out at time time points over 109 d and indicated that heifers fed the barley–grain diet shed higher (P<0.001) total and tetracycline-resistant (Tetr) E. coli in the backgrounding phase. Of the total E. coli examined (n=224), 70.3% showed resistance to one or more of the 14 antimicrobials examined, which increased to 82.3% by day 109. Among the recovered E. coli, 23 phenotypes and 154 pulsed field gel electrophoresis patterns grouped into 38 clusters indicative of extensive E. coli diversity in heifers. Although supplementation of 40% barley-grain was correlated to higher total E. coli shedding in the backgrounding phase, the backgrounding diets did not influence strain clustering. Strains collected during the transition phase clustered more closely than those collected during the backgrounding phase. This increased strain clustering with high concentrate inclusion in the transition diet was observed within 18 d of the transition phase. Our study indicated variations in E. coli shedding rates and strain clustering in relation to time and diet.