Comparison of a combination of oxfendazole and fenthion versus ivermectin in feedlot calves

A trial involving 6,169 feedlot calves was conducted under commercial feedlot conditions in western Canada to compare the relative efficacy of treatment with a combination of oxfendazole and fenthion (O/F) versus ivermectin (I) with respect to the outcome variables, final weight, gain, days on feed (DOF), dry matter intake (DMI), average daily gain (ADG), dry matter intake to gain ratio (DM:G), and morbidity, mortality, and carcass grade parameters.

There were no significant differences (p ≥ 0.05) between the treatment groups for final weight, gain, DOF, DMI, ADG and DM:G. In addition, there were no significant differences (p ≥ 0.05) in the carcass grading parameters between the treatment groups. The bovine respiratory disease (BRD) relapse rates, the overall mortality rates, and the cause specific mortality rates were not significantly different (p ≥ 0.05) between the treatment groups. The BRD treatment rate in the O/F group was significantly lower (p ≤ 0.05) than in the I group, but this difference was not economically important.

These data indicate that a combination of oxfendazole and fenthion is comparable to ivermectin with respect to performance, animal health, and carcass grade parameters.

     

Comparison of two formulations of oxytetracycline given prophylactically to reduce the incidence of bovine respiratory disease in feedlot calves

A trial involving 1,803 feedlot calves was conducted under commercial feedlot conditions in western Canada to compare the relative effectiveness of a new oxytetracycline formulation, administered either intramuscularly (BMI) or subcutaneously (BMS), to a currently available oxytetracycline formulation, administered intramuscularly (LAB), for the prevention of bovine respiratory disease (BRD) in feedlot calves. All experimental treatments were administered upon arrival at the feedlot and again on the third day after arrival.

Over the entire feeding period, there were no significant differences (p≥0.05) in the BRD treatment rates or the BRD relapse rates between either the BMI or BMS groups compared to the LAB group. Similarly, there were no significant differences (p≥0.05) in the BRD treatment rates in the BMI or BMS groups from days 8-14, days 15-90, or days 1-90 of the feeding period compared to the LAB group. However, during the first seven days of the feeding period the BRD treatment rate in the BMI group was 1.55 times (p<0.05) higher than in the LAB group. From days 1-90 and day 1 to the end of the feeding period, the overall mortality rates, BRD mortality rates, and BRD case fatality rates were two to six times lower in the BMS and BMI groups as compared to the LAB group; however, these differences were not statistically significant (p≥0.05).

These data indicate that both the intramuscular and subcutaneous administration of a new oxytetracycline formulation are comparable to the intramuscular administration of a currently available oxytetracycline formulation when given to calves upon arrival at the feedlot.

     

Use of treatment records and lung lesion scoring to estimate the effect of respiratory disease on growth during early and late finishing periods in South African feedlot cattle

Growth, morbidity, and slaughter data from 2,036 calves in 2 South African feedlots were used to estimate the effect of bovine respiratory disease (BRD) and of lung lesion type and extent on growth during the early (processing to d 35) and late (d 35 to slaughter) finishing periods. Calves were weighed at processing (d 5 after arrival), on d 35, and at slaughter after a mean of 137 d on feed. All calves were monitored twice daily and were treated for BRD if rectal temperature was > 40 degrees C or if other specific signs of BRD were present. After slaughter, the occurrence and extent of parenchymal bronchopneumonic lesions and pleural adhesions were recorded. Subclinical BRD (never treated but with lung lesions at slaughter) occurred in 29.7% and clinical BRD in 22.6% of calves. Lung lesions were present in 43% of calves at slaughter; 8.6% had parenchymal lesions and 38.8% had pleural adhesions. Using a combined case definition (treated for BRD and/or lung lesions present at slaughter), the incidence of BRD was 52.5%. During the early finishing period, clinical BRD reduced ADG by 216 g (P < 0.001), subclinical BRD reduced ADG by 91 g (P < 0.001), and the combined effect of BRD was a 143 g reduction in ADG (P < 0.001). After d 35, animals treated for BRD tended to grow faster than those with subclinical BRD (P = 0.11), indicating that treatment was generally successful in reducing economic losses. The extent of bronchopneumonic lesions at slaughter was not associated with reduced growth during the early finishing period (P = 0.27), but extensive lesions reduced ADG by 88 g during the late period (P = 0.02). In contrast, the extent of pleural adhesions was not associated with reduced growth rate during the late finishing period (P = 0.37) but was strongly associated with reduced ADG before d 35; there was a 101 g reduction (P < 0.001) and a 220 g reduction (P = 0.01) for adhesions involving < 50% and > 50% of the pleural surfaces, respectively. Thus, although the presence of bronchopneumonic lesions and pleural adhesions at slaughter were both associated with reductions in overall ADG, they were indicative of production losses having occurred at different times during the finishing period. The overall effect of BRD was a 24 g reduction in ADG (P = 0.02) and a 5.1 d increase in days on feed (P < 0.001). The hidden cost of reduced growth rate due to BRD amounted to $3.41 per calf with clinical or subclinical BRD, or $1.79 per animal entering the feedlot.     

Supplementing organic-complexed or inorganic Co,Cu, Mn,and Zn to beef cows during gestation: postweaning responses of offspring reared as replacement heifers or feeder cattle

One hundred and ninety nonlactating, pregnant beef cows (¾ Bos taurus and ¼ Bos indicus; 138 multiparous and 52 primiparous) were assigned to this experiment at 117 ± 2.2 d of gestation (day 0). Cows were ranked by parity, pregnancy type (artificial insemination = 102, natural service = 88), body weight (BW) and body condition score, and assigned to receive a supplement containing: (1) sulfate sources of Cu, Co, Mn, and Zn (INR; n = 95) or (2) an organic complexed source of Cu, Mn, Co, and Zn (AAC; Availa4; Zinpro Corporation, Eden Prairie, MN; n = 95). The INR and AAC provided the same daily amount of Cu, Co, Mn, and Zn, based on 7 g of the AAC source. From day 0 to calving, cows were maintained in a single pasture and segregated 3 times weekly into 1 of 24 individual feeding pens to receive treatments. Calves were weaned on day 367 (200 ± 2 d of age), managed as a single group for a 45-d preconditioning period (days 367 to 412), and transferred to a single oat (Avena sativa L.) pasture on day 412. Heifer calves were moved to an adjacent oat pasture on day 437, where they remained until day 620. Heifer puberty status was verified weekly (days 437 to 619) based on plasma progesterone concentrations. Steer calves were shipped to a commercial feedlot on day 493, where they were managed as a single group until slaughter (day 724). Plasma cortisol concentration was greater (P = 0.05) in AAC calves at weaning but tended to be less (P = 0.10) on day 370 compared with INR calves. Mean plasma haptoglobin concentration was greater (P = 0.03) in INR vs. AAC calves during preconditioning, and no treatment effects were noted (P = 0.76) for preconditioning average daily gain (ADG). Puberty attainment was hastened in AAC heifers during the experiment (treatment × day; P < 0.01), despite similar (P = 0.39) ADG between treatments from days 412 to 620. Expression of myogenin mRNA in the longissimus muscle was greater (P = 0.05) in INR vs. AAC heifers on day 584. No treatment effects were detected (P ≥ 0.24) for steer ADG from day 412 until slaughter, nor for carcass quality traits. Hepatic mRNA expression of metallothionein 1A was greater (P = 0.02) in INR vs. AAC steers on day 586. In summary, supplementing Co, Cu, Zn, and Mn as organic complexed instead of sulfate sources to beef cows during the last 5 mo of gestation did not improve performance and physiological responses of the steer progeny until slaughter, but hastened puberty attainment in the female progeny reared as replacement heifers.     

Lung and pleural lesions of veal calves at slaughter and their relationship with carcass weight

Summary

At slaughter the lungs of 2138 veal calves (13 transport groups, mainly from different farms) were examined. Lung and pleural lesions were classified by degree of extension and pathomorphological features, and the accompanying carcass weights were measured. Seventeen percent of the calves had extensive lung lesions, extensive pleural lesions or both, and their mean carcass weight was reduced by 4.3 kg (p<0.05). The percentage of calves with extensive lesions varied between transport groups from 4% to 33%. All pleural lesions were adhesive. Most lung lesions (93%) were classified as cuffing/exudative pneumonia. Slaughterhouse inspection of lungs can be used as a non‐clinical parameter of respiratory disease in veal calves.     

Predicting bovine respiratory disease outcome in feedlot cattle using latent class analysis

Bovine respiratory disease (BRD) is the most significant disease affecting feedlot cattle. Indicators of BRD often used in feedlots such as visual signs, rectal temperature, computer-assisted lung auscultation (CALA) score, the number of BRD treatments, presence of viral pathogens, viral seroconversion, and lung damage at slaughter vary in their ability to predict an animal’s BRD outcome, and no studies have been published determining how a combination of these BRD indicators may define the number of BRD disease outcome groups. The objectives of the current study were (1) to identify BRD outcome groups using BRD indicators collected during the feeding phase and at slaughter through latent class analysis (LCA) and (2) to determine the importance of these BRD indicators to predict disease outcome. Animals with BRD (n = 127) were identified by visual signs and removed from production pens for further examination. Control animals displaying no visual signs of BRD (n = 143) were also removed and examined. Blood, nasal swab samples, and clinical measurements were collected. Lung and pleural lesions indicative of BRD were scored at slaughter. LCA was applied to identify possible outcome groups. Three latent classes were identified in the best model fit, categorized as non-BRD, mild BRD, and severe BRD. Animals in the mild BRD group had a higher probability of having visual signs of BRD compared with non-BRD and severe BRD animals. Animals in the severe BRD group were more likely to require more than 1 treatment for BRD and have ≥40 °C rectal temperature, ≥10% total lung consolidation, and severe pleural lesions at slaughter. Animals in the severe BRD group were also more likely to be naïve at feedlot entry and the first BRD pull for Bovine Viral Diarrhoea Virus, Bovine Parainfluenza 3 Virus, and Bovine Adenovirus and have a positive nasal swab result for Bovine Herpesvirus Type 1 and Bovine Coronavirus. Animals with severe BRD had 0.9 and 0.6 kg/d lower overall ADG (average daily gain) compared with non-BRD animals and mild BRD animals (P < 0.001). These results demonstrate that there are important indicators of BRD severity. Using this information to predict an animal’s BRD outcome would greatly enhance treatment efficacy and aid in better management of animals at risk of suffering from severe BRD.     

Epizootiologic Studies of Shipping Fever of Cattle: I. The Microbial Agents Isolated

Nineteen strains of Pasteurella spp., but no viruses cytopathogenic for bovine embryonic kidney cells were isolated from pneumonic lesions present in “normal” veal calves at slaughter.

In studies on two herds of native cattle and six lots of western feeder calves, Pasteurella spp. were isolated from nasal swabs from healthy cattle and those with shipping fever. Viruses of the psittacosis-lymphogranuloma group were isolated from nasal swabs from animals in five groups. Viruses provisionally identified as bovine enteroviruses were isolated from nasal swabs of calves in two lots.

There was serologic evidence of a temporal association of myxovirus para-influenza 3 (PI3) with shipping fever in three lots of calves. From two of these three lots, strains of PI3 were isolated from ten animals, four of which had clinical shipping fever at the time of virus isolation.

     

Behavioral and performance response associated with administration of intravenous flunixin meglumine or oral meloxicam immediately prior to surgical castration in bull calves

The objective of this study was to determine the effects of flunixin meglumine or meloxicam on behavioral response and performance characteristics associated with surgical castration in crossbred bulls. Intact male Bos taurus calves (n = 252; averaging 176 kg) were randomly allocated into one of three treatment groups within pen: control (CON), flunixin meglumine (FLU; 2.2 mg/kg intravenous injection), or meloxicam (MEL; 2.0 mg/kg per os). The individual animal was the experimental unit. Calves were individually weighed on days 0 and 14 of the trial to evaluate performance outcomes. On study day 0, treatments were administered, according to their random allocation, immediately prior to surgical castration using the Henderson tool method. Visual analog scale (VAS) assessment and categorical attitude score (CAS) were collected on days −1, 0 (6 h post-castration), 1, 2, 3, and 4 in the study. The VAS was assigned using a 100 mm horizontal line with “normal” labeled at one end of the line and “moribund” at the other end of the horizontal line. The masked observer assigned a mark on the horizontal line based upon the observed severity of pain exhibited by that individual animal. The CAS was assigned by the same observer using five different categories with a score of 0 being “normal”. Average daily gain tended (P = 0.09) to be associated with the treatment group, and MEL had a greater (P = 0.04) average daily gain through day 14 compared with CON. A significant (P < 0.01) treatment by day interaction was indicated for VAS score, and MEL had lower VAS scores on days 0, 1, 2, and 3 post-castration compared with CON; FLU had lower VAS scores on days 0 and 1 compared with CON. A significant treatment by day interaction was not present (P = 0.25) for CAS. The FLU had lesser percent CAS ≥1 (17.5%; P = 0.05) compared with CON (29.4%); MEL has lesser percent CAS ≥1 observations (14.9%; P = 0.01) compared with CON. The median VAS increased as CAS was more severe. Results indicated MEL and FLU calves temporally improved behavioral responses following surgical castration with positive numerical trends for a 14 d average daily gain (ADG). The VAS system appeared to be an effective method of subjective evaluation of pain in beef calves in this study. Route of administration, duration of therapy, and low relative cost make oral meloxicam a reasonable analgesic treatment in calves when administered at the time of surgical castration.     

Effects of duration of zilpaterol hydrochloride feeding and days on the finishing diet on feedlot cattle performance and carcass traits

British and British x Continental steers (n = 560; initial BW = 339.4 +/- 1.76 kg) were used in a serial slaughter study with a completely random design to evaluate effects of zilpaterol hydrochloride (ZH; 8.33 mg/kg of dietary DM basis) on performance and carcass characteristics. Treatments were arranged in a 4 x 4 factorial (112 pens; 7 pens/treatment; 5 steers/pen) and included duration of ZH feeding (0, 20, 30, or 40 d before slaughter plus a 3-d ZH withdrawal period) and days on feed (DOF) before slaughter (136, 157, 177, and 198 d). No duration of ZH feeding x slaughter group interactions were detected for the performance measurements (P > 0.10). Final BW did not differ (P = 0.15) between the 0-d group and the average of the 3 ZH groups, but ADG was greater for the average of the 3 ZH groups during the period in which ZH diets were fed (P < 0.01) and for the overall feeding period (P = 0.05). As duration of ZH feeding increased, DMI decreased (P = 0.01) and G:F increased linearly (P < 0.01). With the exception of KPH (P = 0.022), no duration of ZH feeding x slaughter group interactions (P > 0.10) were detected for carcass characteristics. Regardless of the duration of ZH feeding, cattle fed ZH had greater HCW (P < 0.01), greater dressing percent (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.03), and lower yield grade (P < 0.01) than the 0-d cattle. The 0-d group had greater marbling scores (P < 0.01) than cattle fed ZH diets, with a tendency for a linear decrease in marbling score (P = 0.10) as duration of ZH feeding was extended. A greater percentage of carcasses in the 0-d group graded USDA Choice or greater (P < 0.01) than in the 3 ZH groups, whereas the percentage of Select carcasses was greater (P = 0.01) for the 3 ZH groups. From d 0 to end (P = 0.04) and during the last 43 d on feed (P < 0.01), ADG responded quadratically to DOF before slaughter. No differences were detected among slaughter groups for DMI for the entire trial period; however, a quadratic response (P = 0.02) was observed for the final 43 d before slaughter. A quadratic response was also detected for the final 43 d before slaughter (P < 0.01) and from d 0 to end (P = 0.02) for G:F. Final BW, HCW, dressing percent, and 12th-rib fat increased linearly (P < 0.01) as DOF before slaughter increased. Our results indicate that no substantial effects on performance and carcass measurements were observed when ZH was fed for 30 or 40 d as opposed to 20 d, and that effects of ZH generally did not interact with DOF before slaughter.     

Bovine respiratory disease in feedlot cattle: phenotypic, environmental, and genetic correlations with growth, carcass, and longissimus muscle palatability traits

Bovine respiratory disease (BRD) is the most costly feedlot disease in the United States. Selection for disease resistance is one of several possible interventions to prevent or reduce the economic loss associated with animal disease and to improve animal welfare. Undesirable genetic relationships, however, may exist between production and disease resistance traits. The objectives of this study were to estimate the phenotypic, environmental, and genetic correlations of BRD with growth, carcass, and LM palatability traits. Health records on 18,112 feedlot cattle over a 15-yr period and slaughter data on 1,627 steers over a 4-yr period were analyzed with bivariate animal models. Traits included ADG, adjusted carcass fat thickness at the 12th rib, marbling score, LM area, weight of retail cuts, weight of fat trim, bone weight, Warner-Bratzler shear force, tenderness score, and juiciness score. The estimated heritability of BRD incidence was 0.08 +/- 0.01. Phenotypic, environmental, and genetic correlations of the observed traits with BRD ranged from -0.35 to 0.40, -0.36 to 0.55, and -0.42 to 0.20, respectively. Most correlations were low or negligible. The percentage of carcass bone had moderate genetic, phenotypic, and environmental correlations with BRD (-0.42, -0.35, and -0.36, respectively). Hot carcass weight and weight of retail cuts had moderate, undesirable phenotypic correlations with BRD (0.37 and 0.40, respectively). Correlations of BRD with LM palatability and ADG were not detected. Low or near zero estimates of genetic correlations infer that selection to reduce BRD in feedlot cattle would have negligible correlated responses on growth, carcass, and meat palatability traits or that selection for those traits will have little effect on BRD susceptibility or resistance.     

Effect of removal and remixing of lightweight pigs on performance to slaughter weights

Two experiments were conducted to determine the effect of lightweight pig removal and remixing on performance to slaughter. Experiment 1 was a growing-finishing trial utilizing a total of 900 pigs (26.2+/-0.1 kg initial weight) that were sorted and remixed at a mean replicate BW of 72 kg. Experiment 2 was a wean-to-finish trial (17 d mean wean age; 4.8 kg +/- 0.1 BW) utilizing 225 barrows with sorting and remixing occurring 3 wk after weaning. Treatments were 15 pigs/ pen from initial weight to slaughter (15S), 20 pigs/pen from initial weight to time of sort and remix and then reduced to 15 pigs/pen (20/15), and 15 pigs/pen from time of sort and remix to slaughter comprised of the five lightest pigs from each of three 20/15 pens per replicate (15M). Space allocation was 0.56 m2/pig from 26 to 70 kg and 0.74 m2/pig thereafter in Exp. 1. In Exp. 2, pen size was fixed at 2.44 x 4.27 m. In Exp. 1, there was no effect (P > 0.20) of treatment on performance prior to 70 kg. Least squares means for ADG from time of sort and remix to first pig removal from a pen for slaughter at 113 kg were 0.93, 0.87, and 0.91 kg/d for the 20/15, 15M, and 15S treatments, respectively (P < 0.05). When comparing the population represented by the 20/15 + 15M treatments vs the 15S population, there was no difference (P > 0.20) in ADG, ADFI, feed conversion, or carcass lean content. In Exp. 2, pigs in the 20/15 treatment grew slower (P < 0.05) than 15S pigs for the first 21 d (0.20 vs 0.22 kg/d, respectively) with a lower ADFI (P = 0.06) and no difference in feed conversion. When comparing the population represented by the 20/15 + 15M treatments vs the 15S population after sorting and remixing, there was no effect (P > 0.15) of experimental treatments on ADG, ADFI, feed conversion efficiency, carcass lean content, or daily lean gain. These results suggest that removal of lightweight pigs and remixing of the removed pigs into pens of similar-weight pigs is ineffective in improving the overall performance of a population of pigs during the postweaning period.     

Comparative efficacy of tulathromycin versus florfenicol and tilmicosin against undifferentiated bovine respiratory disease in feedlot cattle

Four studies conducted at feedlots in Greeley and Wellington, Colorado; Nebraska; and Texas compared the efficacy of tulathromycin to florfenicol or tilmicosin for the treatment of cattle with undifferentiated bovine respiratory disease (BRD) and subsequent feedlot performance and carcass characteristics. In each study, 100 calves with BRD were treated with tulathromycin given SC at 2.5 mg/kg body weight. At the Greeley, CO, and Nebraska study locations, 100 calves were treated with florfenicol given SC at 40 mg/kg body weight, and at the Wellington, CO, and Texas study locations, tilmicosin was given SC at 10 mg/kg body weight. Cure rate, a derived variable that included assessments of mortality, rectal temperature, and attitude and respiratory scores from day 3 to day 28 and day 3 through harvest, was the primary assessment of BRD efficacy. Cure rates of calves treated with tulathromycin were significantly (P < or = .009) higher than those calves treated with florfenicol. At Wellington, CO, the cure rate of calves treated with tulathromycin was significantly higher (P < or = .018) compared with tilmicosin-treated calves. The differences in cure rates between tulathromycin and tilmicosin treatment groups in the Texas study were not significantly different (P > .05). Tulathromycin was more efficacious in the treatment of undifferentiated BRD compared with florfenicol and, in one study, compared with tilmicosin.     

Comparison of a multivalent viral vaccine program versus a univalent viral vaccine program on animal health,feedlot performance,and carcass characteristics of feedlot calves

A field study was conducted under commercial feedlot conditions at 2 sites in western Canada to determine the relative effects of a univalent viral vaccine (MLV 1) program versus a multivalent viral vaccine (MLV 4) program on animal health; feedlot performance; and carcass characteristic variables of fall-placed, auction market derived, feedlot calves. Five thousand one hundred and sixty-three calves were processed and randomly allocated to 1 of 2 experimental groups as follows: MLV 1, which received a modified live infectious bovine rhinotracheitis (IBR) virus vaccine upon arrival at the feedlot and again at approximately 70 days on feed (DOF); or MLV 4, which received a modified live IBR virus, parainfluenza-3 virus, bovine viral diarrhea virus, and bovine respiratory syncytial virus vaccine upon arrival at the feedlot and again at approximately 70 DOF. A total of 20 pens (10 pens at the site located near High River, Alberta and 10 pens at the site located near Vegreville, Alberta) were allocated to the study. On both a live and carcass weight basis, final weight, weight gain, and average daily gain (ADG) were significantly (P < 0.05) improved in the MLV 4 group as compared with the MLV 1 group. However, there were no significant (P > or = 0.05) differences in DOF, daily dry matter intake, dry matter intake to gain ratio (DM:G) live, or DM:G carcass between the experimental groups. In addition, there were no significant (P > or = 0.05) differences between the experimental groups in any of the carcass characteristic variables measured. The initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) lower in the MLV 4 group as compared with the MLV 1 group. There were no significant (P > or = 0.05) differences in the other measures of health between the experimental groups. In the economic analysis, there was a net advantage of $0.74 CDN per animal in the MLV 4 group as compared with the MLV 1 group due to lower initial UF treatment and improved ADG, even though the cost of the vaccine program was higher in the MLV 4 group.     

The effect of milk intake on forage intake and growth of nursing calves

Thirty-nine Holstein steer calves were assigned to one of five treatments at birth and individually fed for 200 d with milk replacer reconstituted to equal the fat and protein concentration of beef cow milk. Treatment levels were the quantities of reconstituted milk fed per day based on lactation curves, which were based on peak milk levels (PML) of 2.72, 5.44, 8.16, 10.88, and 13.6 kg/d, respectively. In addition to reconstituted milk, chopped alfalfa hay was offered ad libitum to allow for maximal voluntary forage consumption. All calves were fed a high-energy diet postweaning until they reached a similar degree of fatness in the 12th rib (4 to 5% chemical fat) as determined by ultrasound. There were differences (P < 0.05) among groups in weaning weight, preweaning ADG, age, and weight at slaughter. During the preweaning phase, there was a linear relationship (P < 0.01) for daily milk and forage DE intake; however, DE intake per unit of BW did not differ across treatments (P = 0.06). Increasing PML resulted in a linear (P < 0.01) decrease in alfalfa hay intake in the preweaning phase, and G:F increased quadratically (P < 0.01). During the postweaning phase, preweaning milk intake had no meaningful effect on postweaning ADG, but overall ADG had a linear relationship (P < 0.01) with preweaning milk level. There was no effect of PML on the 12th-rib lipid percent, marbling score, or quality grade, but protein and fat concentration in the carcass and empty BW increased linearly (P < 0.01) with PML. The group fed at 2.72 kg/d PML was 58 kg lighter (P = 0.03) and required 34 d more (P < 0.01) to reach the predetermined degree of fatness at slaughter than the group fed at 13.6 kg/d PML, suggesting that increased milk production by the dam can decrease the number of days to the slaughter weight at which a similar rib lipid concentration is reached.     

Zinc supplementation strategies in feedlot heifers receiving an extended-release implant or an aggressive re-implant program

Two hundred eight Angus-crossbred heifers (291 ± 23 kg) from four sources were used in a randomized complete block design. The objective of the study was to determine the effects of implant strategy and Zn supplementation on performance, carcass characteristics, muscle fiber diameter, and mineral status of heifers. Heifers were assigned to a 2 × 2 factorial study for 168 d, and factors included Zn and implant (IMP). Heifers were supplemented Zn (mg/kg dry matter [DM]; ZnSO₄) at national (30; NRC) or industry (100; IND) recommendations. Implant strategies (Merck Animal Health, Madison, NJ) included extended-release Revalor-XH on day 0 (REV-XH; 20 mg estradiol + 200 mg trenbolone acetate) containing four uncoated pellets and six coated pellets or the uncoated implant Revalor-200 on day 0 and again on day 91 (REV-200; 20 mg estradiol + 200 mg trenbolone acetate). Heifers were blocked by weight within source to pens of five or six heifers per pen (nine pens per treatment). A corn silage-based diet was fed during the growing period (days 0–55) followed by transition to a corn-based finishing diet. Weights were taken consecutively on days −1/0, 55/56, and 167/168. Liver and muscle from the longissimus thoracis were collected from one heifer per pen on days −5, 14, 105, and 164. Data were analyzed via Mixed Procedure of SAS. Average daily gain (ADG) and liver mineral used Period as the repeated effect. Corresponding to periods of high hormone payout from each implant, days 0–28 and 91–120 ADG were greatest for REV-200, whereas REV-XH numerically peaked during days 56–91 (IMP × Period; P = 0.02). Day 91 IND body weight tended to be heavier (P = 0.06) and day 120 body weight was heavier (P = 0.05) than NRC heifers. No effect of Zn or IMP on final body weight was observed (P ≥ 0.21). Muscle fiber cross-sectional diameter on day 164 was greater (P = 0.05) in IND than NRC. Liver Mn concentrations decreased by day 14 regardless of implant, though days 105 and 164 concentrations were lesser for REV-200 than REV-XH (IMP × Period; P = 0.02). No effects of Zn, IMP, or the interaction were observed for carcass-adjusted gain to feed, days 0–168 DM intake, hot carcass weight, or ribeye area (P ≥ 0.11). The nominal differences in performance between implant strategies suggest that extended-release implants may be an effective implant strategy to replace re-implant programs in heifers, whereas the improved performance of heifers fed IND vs. NRC during times of peak hormone payout suggests a role for Zn in periods of rapid growth.     

Effect of wean-to-finish management on pig performance

In each of three trials, 240 crossbred barrows weaned at 17 d of age (5.1 kg BW) were assigned to one of three experimental treatments based on light and heavy weight outcome groups. Experimental treatments were 1) wean-to-finish at 0.69 m2/pig and 15 pigs/pen; 2) wean-to-finish double-stocked at 0.35 m2/pig, 30 pigs per pen for 8 wk and then randomly split into two pens (either stayed in same pen or moved to new pen) for growth to slaughter at 0.69 m2/pig; and 3) nursery facility for 8 wk at 0.35 m2/pig and 15 pigs/pen followed by move to the same grow-finish facility housing wean-to-finish and double-stocked pigs and maintaining pen integrity. Beginning at 38 kg BW, diets were supplemented with either bacitracin methylenedisalicylate at 33 mg/kg to slaughter or tylosin at 44 mg/kg to 59 kg BW and 22 mg/kg thereafter. There were no trial x treatment interactions, even though there was considerable variation in health status among trials. At the end of the 56-d nursery period, wean-to-finish pigs weighed more than nursery (28.7 vs 27.7 kg; P = 0.071) and double-stocked pigs (28.7 vs 26.9 kg; P = 0.002), due to greater ADG (wean-to-finish vs nursery; P = 0.062; wean-to-finish vs double-stocked; P = 0.002) and greater ADFI (wean-to-finish vs nursery; P = 0.024; wean-to-finish vs double-stocked, P = 0.002). There was no effect of treatments (P > 0.1) on ADG, feed conversion, carcass lean percentage, or lean gain during the growing-finishing period. There was also no effect of treatment (P > 0.1) on ADG or ADFI from weaning to slaughter. There was no difference (P > 0.1) between bacitracin methylenedisalicylate and tylosin for ADG, feed conversion, carcass lean percentage, or daily lean gain. These data suggest that housing 5-kg weaned pigs in fully slatted growing-finishing facilities from weaning to slaughter was not detrimental to overall performance. In this experiment, dietary additions of bacitracin methylenedisalicylate or tylosin from 38 kg BW to slaughter weight resulted in similar growth performance.     

Plasma metabolites of receiving heifers and the relationship between apparent bovine respiratory disease, body weight gain, and carcass characteristics

Six hundred sixty-five crossbred beef heifers initially weighing 225 kg were used in a completely randomized design to measure plasma glucose, lactate, and urea N concentrations at time of initial processing, determine the incidence of apparent bovine respiratory disease (BRD) in receiving cattle, and evaluate the effect of apparent BRD on subsequent cattle growth and carcass characteristics. Heifers were processed within 24 h of arrival, and processing included vaccination against common viral and clostridial diseases, recording rectal temperature, and sampling whole blood for subsequent measurement of plasma glucose, lactate, and urea concentrations. Heifers were monitored for clinical signs of apparent BRD, including depression, lethargy, anorexia, coughing, rapid breathing, and nasal or ocular discharge. Heifers exhibiting signs of apparent BRD received antibiotic therapy, and the number of times a heifer was treated for apparent BRD was recorded. Following the 36-d receiving period, heifers were transported to native grass pastures and allowed to graze for 136 d. At the end of the grazing season, heifers were transported to a commercial feedlot where they were adapted to a common finishing diet offered for ad libitum consumption. Following the 124-d finishing period, heifers were slaughtered and carcass data were collected. Heifers treated for apparent BRD had decreased plasma glucose (linear, P < 0.01), lactate (linear, P < 0.01), and urea N concentrations (linear, P < 0.06) measured at time of initial processing. Rectal temperature measured at time of initial processing tended to be greater (linear, P < 0.11) for heifers treated for apparent BRD. Heifers treated for apparent BRD during the receiving period had decreased overall ADG (linear, P < 0.10), final BW (linear, P < 0.01), HCW (linear, P < 0.01), fat thickness (linear, P < 0.01), and marbling score (linear, P < 0.03). These data suggest that initial plasma glucose and lactate concentrations might be affected by the health status of receiving cattle and that increased incidence of apparent BRD in cattle decreases ADG and carcass quality.     

Meta-analysis of field trials of antimicrobial mass medication for prophylaxis of bovine respiratory disease in feedlot cattle

One hundred and seven field trials of prophylactic mass medication for bovine respiratory disease (BRD) in feedlot cattle were reviewed. Meta-analysis is the formal quantitative statistical review process that was used to synthesize the data from randomized field trials and draw conclusions concerning the efficacy of prophylactic mass medication in feedlot calves.

The results of the meta-analysis indicated that prophylactic parenteral mass medication of calves with long-acting oxytetracycline or tilmicosin on arrival at the feedlot would reduce BRD morbidity rates (p < 0.001). There were, however, unreliable data on the effects of mass medication on mortality rates and performance, insufficient data on the most effective treatment regimes, and no valid data on the efficacy of feed and water medication for prophylaxis of BRD.

This review highlights the gaps in our knowledge and points out the need for additional well-designed randomized controlled field trials of adequate size to assess the efficacy and socioeconomic impact of prophylactic mass medication for BRD in feedlot cattle.

     

A comparison of trimethoprim-sulfadoxine and ceftiofur sodium for the treatment of respiratory disease in feedlot calves

A field trial was performed to compare trimethoprim-sulfadoxine to ceftiofur sodium in the treatment of bovine respiratory disease (BRD) in feedlot calves. Five-hundred-and-fifty-five recently weaned, crossbred beef calves, with naturally occurring cases of BRD, were randomly assigned to either trimethoprim-sulfadoxine or ceftiofur sodium treatment groups. The effectiveness of the antibiotics was assessed by comparing relapse rates, three day treatment response rates, mortality rates, chronicity rates, and wastage rates. There was no statistical difference in the first or second relapse rates between the two groups. For the initial therapy, first relapses, and overall treatment episodes, a significantly greater proportion of the calves treated with ceftiofur sodium responded to three days of therapy than those treated with trimethoprim-sulfadoxine (p < 0.05). This resulted in a 10% reduction in treatment costs for calves in the ceftiofur group. There were significantly lower mortality and wastage rates attributable to BRD in the ceftiofur sodium group than in the trimethoprim-sulfadoxine group (p < 0.05). However, there were no significant differences in overall mortality, overall chronicity, or overall wastage rates between the treatment groups.     

Effects of percentage Brahman and Angus breeding, age-season of feeding and slaughter end point on feedlot performance and carcass characteristics

Steers (n = 165) of known percentage Brahman (B) and Angus (A) breeding were used to study effects of breed group (A, 3/4A:1/4B, 1/2A:1/2B, 1/4A:3/4B), age-season of feeding (calves fed during the cool season vs yearlings fed during the warm season) and slaughter end point (less than .90, 1.0 to 1.15, 1.27 to 1.40, greater than or equal to 1.5 cm of adjusted fat over the ribeye) on feedlot performance and carcass characteristics. The 1/2B and 3/4B steers had heavier (P less than .05) initial and final feedlot weights than the A and 1/4B steers and higher (P less than .05) unshrunk ADG than the A steers did. Breed types did not differ for feed efficiency. Yearling steers fed in the warm season had higher (P less than .05) unshrunk ADG than calves fed in the cool season, but ADG calculated on an empty-rumen basis did not differ between the two age-seasons of feeding. Calves fed in the cool season were more efficient (P less than .05) than yearlings fed in the warm season when efficiency was expressed on an empty-rumen basis; however, on a live weight basis there was no difference in feed efficiency. No breed group by age-season of feeding interactions on performance were detected. Slaughter end point did not significantly affect feed efficiency on an empty-rumen basis. The 1/2B and 3/4B steers had smaller ribeye areas (REA) per 100 kg hot carcass and lower marbling scores than the 1/4B and A steers. Yearlings fed in the warm season produced heavier carcasses (P less than .05) than calves fed in the cool season. As s.c. fat thickness at slaughter increased, hot carcass weight and numerical yield grade increased, whereas REA per 100 kg of hot carcass decreased. Marbling also increased as fatness increased up to about 1.5 cm subcutaneous fat.