A study evaluating effects of metaphylaxis and milk replacer additives on health and growth was conducted with Holstein bull calves (n = 52; mean BW = 42.28 +- 3 kg) < 7 d of age. Calves were randomly assigned to receive tilmicosin phosphate (TIL), ceftiofur crystalline free acid (CEF), or saline (CON). All calves received a commercial milk replacer powder (25% CP, 20% fat), and within metaphylaxis treatment, were randomly assigned to receive milk replacer with: 1) 4 g/d for 7 d and then 2 g/d for the next 14 d of an egg-based additive (PR); 2) 2 g/d of 96% betaine (BE); 3) both PR and BE (BP); or 4) no additives (NA). Calves were housed in individual fiberglass hutches with ad libitum access to a commercial calf starter and water. Body weight was recorded twice weekly and fecal scores (1=firm, 4=watery) were recorded daily for 54 d. Number of treatments per calf for scours, incidence of respiratory symptoms, and febrile events were recorded on a daily basis, and the cumulative incidence of each response was used as an index of morbidity. All data were analyzed as a completely randomized design with a 3 X 4 factorial treatment arrangement. Neither metaphylaxis, additives, nor their interaction affected ADG (P>0.60); overall, calves gained .45 kg/d. Fecal scores were reduced by 39% for CEF compared to CON (P&lt;0.01), but were not affected by additives. Metaphylaxis influenced neither the incidence of fever (P&gt;0.3), or respiratory symptoms (P&gt;0.2), nor were they reduced by additives. Overall, calves were treated an average of only 0.39 times for respiratory symptoms and 0.66 times for fever. Scours were not influenced by metaphylaxis (P&gt;0.6), additives (P&gt;0.5), nor their interaction (P&gt;0.8). Other than fecal score, metaphylaxis did not enhance productivity or reduce morbidity in this study, but disease challenge may have been mild. Feed additives influenced neither measures of health and performance nor did the metaphylaxis and feed additive interaction.

The objectives of this study were to evaluate the effects of: (1) metaphylactic antibiotic administration (none or Excede on arrival); and (2) receiving diet crude protein levels (17.1 % or 11.9 % CP) on respiratory disease incidence, mortality, and growth performance of beef calves received into a stocker system as well as the influence of stocker treatment on feedlot and carcass performance. For the stocker phase, steers (n = 244) were stratified by BW and randomly assigned to 20 pens. Treatments were randomly assigned in a 2 x 2 factorial study design. At the conclusion of the stocker phase, 76 steers were sent to Tri County Steer Carcass Futurity in Lewis, IA. Metaphylactic treatment reduced the incidence of BRD and increasing CP in the receiving ration to 17.1 % resulted in greater ADG. Health, nutrition, and management during the stocker phase can impact feedlot and carcass performance.

Cattle classified as having low residual feed intake (RFI) phenotypes are those that consume less feed than expected based on body weight and growth performance. Mechanisms contributing to the variation in RFI are not fully understood. Previous studies have shown that cattle of divergent RFI phenotypes have different levels of energy expenditures, which are associated with heat increment, basal metabolism, thermoregulation responses, and physical activity. The objectives of this experiment were to characterize residual feed intake (RFI) in growing heifers and to determine if variation in whole-animal energy expenditure contributes to differences in RFI. Brangus heifers (n =120) were individually fed a roughage-based diet (1.93 Mcal ME/kg DM) diet twice daily and feed refusals measured weekly. Heifers were weighed once weekly for 70 d and RFI calculated as the difference between actual and expected DMI from linear regression of DMI on ADG and mid-test BW0.75. Immediately following the 70 d study, oxygen pulse rate (mL O2/heart beat) and 48-h heart rates were measured on 8 high and 8 low RFI heifers to estimate energy expenditure. Daily heart rates and oxygen pulse rates were higher (P < 0.05) in heifers with high RFI compared to those with low RFI. As a result, energy expenditure (kcal/BW0.75) was estimated to be 17.4 percent greater (P < 0.05) in high-RFI heifers then low-RFI heifers. Mortality and morbidity losses caused by bovine respiratory disease (BRD) continue to negatively impact the net revenues of the beef cattle industry. Stress can predispose calves arriving at feedlots to BRD by impairing their immune system with calves having more excitable temperaments possibly having a greater risk. The objectives of the second study was to examine the effects of metaphylactic treatment and temperament on performance, feed intake, feed efficiency, and feeding behavior traits in steers. Santa Gertrudis steers (n =119) were weighed and randomly to control (CON; no antimicrobial treatment) or metaphylactic (MET; 1.5 mL/45 kg BW of ceftiofur crystalline free acid) treatments. Steers were weighed at 14-d intervals and individual intakes and feeding behavior traits measured using a GrowSafe sytems while fed a roughage-based diet (2.21 Mcal ME/kg DM). Objective (relative exit velocity; REV) and subjective (chute score; CS) measurements of temperament were measured on arrival and on day 28 of the study. Steers with higher REV weighed less, grew slower, consumed less feed, spent less time consuming feeding, had more feeding bouts per meal, had less backfat, smaller longissimus muscle area, and higher cortisol levels. Steers treated with MET had higher ADG than those receiving CON. Cattle with higher REV that received MET had less of a decrease in ADG, DMI, time spend consuming feed, and less of an increase in feeding bouts compared to high REV steers receiving CON. Results from this study suggest that process-control strategies, which quantify and manage inter-animal variation in calf temperament may facilitate more judicious use of antimicrobial products and provide more consistent and predictable responses to metaphylactic strategies.

Bovine respiratory disease (BRD) is the leading cause of morbidity in feeder and stocker cattle, resulting in large impacts on economics of stocker and feedlot operations. One of the most effective means of controlling BRD is the mass administration of antimicrobials (AM) at arrival or “metaphylaxis”, potentially leading to increased antimicrobial resistance (AMR). Mannheimia haemolytica (MH), the most commonly isolated bacterial pathogen in BRD cases in feedlot cattle, has been shown to have integrative-conjugative elements (ICE), which are mobile genetic elements that have the ability to integrate themselves in the host genome. Notably, these ICE have been shown to contain multiple antimicrobial resistance genes (ARG) conferring resistance to antimicrobial classes used for BRD treatment. ICE have also been shown to be transferred between different genera. Since these ICE contain genes for resistance to multiple AM classes, administration of one AM could increase pressure for bacteria to transfer ICE for resistance to multiple drug classes; therefore, mass administration of AM may lead to increased isolation of multidrug resistant (MDR) MH and increase presence of resistance genes in the metagenome. Many NGS studies to date have used low numbers of cattle or pooled samples due to cost. Pooling is an acceptable strategy to increase number of units sampled, however sequencing depth per individual sample is decreased, and there is little evidence comparing pools to individual samples. In a trial involving high risk stocker cattle, tulathromycin metaphylaxis was associated with increased isolation of MDR MH, and this was associated with ICE related genes. Using pooled DNA extracted from NPS in these animals, which were shown to be acceptable for group level comparisons, metaphylaxis also increased ARG richness and diversity in these heifers; however, BRD treatment and time had a greater effect on the mircrobiome and resistome. Further work is needed to improve MH strain classification. These finding highlight the complexity of AMR research, because though tulathromycin had a clear effect on odds of isolation of MDR MH, metaphylaxis’ effects on the resistome and microbiome were more complex, and time and BRD contributed to greater change.

Master of Science / Department of Animal Sciences and Industry / Christopher D. Reinhardt / Three experiments were conducted to examine nutritional and management strategies for different segments of the beef industry. The first experiment examined the effects of feeding traditional step-up diets (STEP) vs. limit-feeding (LIMIT) the finishing diet to adapt cattle to high-concentrate diets. When all cattle reached ad libitum intake of the finishing diet there was a trend (P = 0.09) for DMI to be different between treatments. During week 1, STEP cattle had higher total VFA concentrations (P = 0.02), while LIMIT cattle had higher valerate absorption (P = 0.02) and disappearance (P = 0.08). During week 4, LIMIT cattle had higher total VFA concentrations (P = 0.03) and lower valerate disappearance and absorption (P = 0.05) than STEP cattle. These results indicate that limit-feeding the finishing diet may inhibit nutrient absorption from the rumen or this method may cause increased production of valerate by lactate utilizing bacteria due to a more acidotic rumen environment. The second experiment examined the effects of feeding 5% (DM basis) dried, full-fat corn germ (GERM) on feedlot performance and carcass characteristics of naturally raised yearling steers and heifers. Carcass-adjusted ADG was higher for GERM cattle (P = 0.04). There were no other differences in performance or carcass characteristics. Total incidence of liver abscesses and the incidence of severe liver abscesses were decreased by 12 and 8.2% (P = 0.01 and 0.02, respectively) when GERM was added to the diet. Corn germ can be added to finishing diets at 5% without affecting performance and carcass characteristics. Producers raising natural cattle may also be able to benefit from the reduced incidence of liver abscesses. The third experiment examined concurrent metaphylactic treatment of high-risk calves with tulathromycin and chlortetracycline. Calves were placed on 1 of 3 treatments: 1) no top-dress pellets; 2) diet top-dressed with pellets containing chlortetracycline; or 3) diet top-dressed with pellets containing no chlortetracycline. There were no differences in the performance or health of these calves (P > 0.25). There are no additive benefits of concurrent metaphylaxis using both tulathromycin and chlortetracycline. This information could assist producers when designing receiving health protocols for high-risk calves.

Master of Science / Department of Clinical Sciences / Daniel U. Thomson / Bovine Respiratory Disease (BRD) continues to be one of the largest animal health concerns in the cattle industry. BRD is a multifaceted group of pathogens, both viral and bacterial, that take advantage of an immune compromised calf to cause disease. This study took aim at comparing metaphylactic treatments for BRD in both the feedlot and pasture setting. In the feedlot study, heifers (n=579, 403.7 ± 27.4 lbs) from Southwest Texas were identified as being high risk for BRD and shipped to the Clayton Livestock Research Center in Clayton, NM. Cattle were randomly allocated within truck load lots into 18 to 20 head treatment pens (30 pens; 3 treatments; 10 reps). Cattle were given one of three metaphylactic treatments based on the randomly assigned treatment for their pen within a replicate. The three antibiotic treatments administered at initial processing were: 1) Tulathromycin (2.5 mg/kg), 2) Tilmicosin (13.3 mg/kg), and 3) Gamithromycin (6.0 mg/kg). Cattle were fed a typical commercial starter diet for the first 56-60 d with a step-up ration change at day 28. At the end of the feeding period, pens were weighed and body weights recorded. Dry Matter Intake, morbidity, and mortality were recorded by CLRC personnel daily. Cattle administered tulathromycin had higher daily gains than cattle administered gamithromycin by 0.29 lbs/d (P<.01) and tended (P=0.09) have higher daily gains than cattle that received tilmicosin by 0.18 lbs/d. Tulathromycin treated cattle tended (P = 0.12) to have improved feed efficiency compared to gamithromycin treated cattle. Cattle that received tulathromycin (5.2%) had lower morbidity rates (P < .02) than tilmicosin (14.6%) and gamithromycin (12.79%) treated cattle. There were no treatment differences in dry matter intake or mortality in cattle. For the wheat pasture study, heifers (n=120, 393.2 ± 28.6 lbs) from the same origin and risk were shipped to the CLRC and processed before being trailed to a nearby wheat pasture. Cattle were randomly assigned into three treatment groups (3 treatments, 40 reps), and were given one of three metaphylactic treatments. The three antibiotic treatments administered at initial processing were: 1) Tulathromycin (2.5 mg/kg), 2) Tilmicosin (13.3 mg/kg), and 3) Gamithromycin (6.0 mg/kg). Cattle were allowed to graze on wheat for 54 days with free-choice Hi-Pro mineral mixed with Lasalocid, an ionophore. After 54 days on wheat pasture, the cattle were trailed back to the CLRC facilities and final individual weights were recorded. Morbidity and mortality were recorded daily by CLRC personnel. No differences were identified for ADG (P=0.98), morbidity (P=0.46) or mortality (P=0.36) among the three treatment groups.

Made available in DSpace on 2014-07-29T15:07:38Z (GMT). No. of bitstreams: 1 Dissertacao Marcus L G Rezende.pdf: 1012119 bytes, checksum: 7a1b79b8bc4ccbbdcb5a9578a1fc487f (MD5) Previous issue date: 2010-11-30 / Producing more in less physical space and in less time, increasing the profitability and reducing sanitary and economical risks are some of the challenges of the Brazilian livestock that the intensive breeding aims to supplant. A considerable increase in the number of confining unities as well as in feedlot cattle is already observed, thus, the attention to the control of pathological alterations deriving from the production intensification that can compromise the profitability and the economical viability of such activities should also increase. Considering the context presented herein, this essay aimed to analyze the economical/sanitary viability of the usage of florfenicol (40 mg/kg) in the metaphylaxis of bovine respiratory diseases (BRD) in feedlot cattle in the state of Goiás, where two groups totalizing 125 animals were concurrently monitored during 100 days. The first group, having 32 animals, was maintained under the standard sanitary protocol of the confining groups and it was called control (G1). The second group, having 93 animals, was submitted to metaphylaxis with florfenicol (40 mg/kg) at the beginning of the confinement and it was called metaphylaxis (G2). In the both groups, the sanitary and the productive standards were evaluated and a financial analysis was performed in order to economically validate the method. The animals were examined, weighted and materials for analyses were collected at the beginning and at the end of the confinement, when the occurrence of respiratory problems in the animals was evaluated. The animals submitted to metaphylaxis with florfenicol had a daily weight gain (DWG) superior to the one of the animals pertaining to the control group, and the indexes of BRD demonstrated through the analysis of the method viability (MV) were superior to 2.7%, which justifies the investment in the prevention of BRD. / Produzir mais em menor espaço físico e em menor tempo, incrementando a lucratividade e reduzindo os riscos sanitários e econômicos são alguns dos desafios da pecuária brasileira que a criação intensiva procura suplantar. Já se observa considerável aumento no número de unidades confinadoras, bem como de animais confinados; e do mesmo modo, cresce a atenção ao controle das alterações patológicas decorrentes da intensificação da produção e que possam comprometer a lucratividade e a viabilidade econômica da atividade. Considerando este cenário, o presente trabalho pretendeu analisar a viabilidade econômico/sanitária da utilização do florfenicol (40mg/Kg) na metafilaxia da doença respiratória bovina (DRB) em bovinos confinados no estado de Goiás, onde foram acompanhados concomitantemente durante o período de 100 dias dois grupos com 125 animais. O primeiro grupo foi mantido sob o protocolo sanitário padrão do grupo confinador e com 32 animais foi designado controle (G1). O segundo grupo, com 93 animais foi submetido à metafilaxia com florfenicol (40mg/Kg) a entrada do confinamento e designado metafilaxia (G2). Em ambos os grupos foram avaliados padrões sanitários e produtivos, também foram realizadas análises financeiras para a validação econômica do método. Os animais foram examinados, pesados e colhidos materiais para análise na entrada e saída do confinamento, período em que se avaliou a ocorrência de problemas respiratórios nos animais. Foi observado que os animais submetidos à metafilaxia com florfenicol tiveram um ganho de peso diário (GPD) superior aos animais do grupo controle, e os índices de DRB demonstrados por meio da análise de viabilidade do método (VM) foram superiores a 2,7%, justificando o investimento na prevenção da DRB.