Effects of early or conventional weaning on beef cow and calf performance in pasture or drylot environments

Performance of cows and calves during 63-d early or conventional weaning periods was evaluated. Spring-calving beef cows (n = 167) of similar age, body condition score (BCS), and body weight (BW = 599 ± 54.5 kg), and their calves (initial BW = 204 ± 26.7 kg; 153 ± 15 d of age) were assigned randomly to 1 of 4 weaning treatments: weaning at 153 d of age followed by 56 days of limit feeding in confinement (E-D), confinement of cow and calf for a 56-d period of limit feeding followed by weaning at 209 d of age (C-D), weaning at 153 d of age followed by a 56-d grazing period (E-P), and a 56-d grazing period for both cow and calf followed by weaning at 209 d of age (C-P). Cows and calves assigned to pasture treatments grazed native range pastures without supplement. Cows and calves assigned to drylot treatments were fed complete diets. Calves assigned to E-D were fed a concentrate-based diet at 2.5% of BW, whereas cows assigned to E-D were fed a forage-based diet at 1.6% of BW. Cows assigned to C-D were offered the diet fed to E-D cows at 2.0% of BW. Calf average daily gain (ADG) was influenced by diet and weaning treatments (diet × weaning, P ≤ 0.03). Cows and calves assigned to all treatments were limit fed common diets for 7 d at the end of our study to equalize gut fill. In general, calves managed in confinement and fed concentrate-based diets (i.e., E-D and C-D) had greater ADG than non-supplemented calves maintained on pasture (i.e., E-P and C-P). Cow BW and BCS change (days 0 to 63) were influenced by both diet and weaning status (P ≤ 0.05). Non-lactating cows maintained on pasture had lesser BW loss than other treatments, whereas non-lactating cows fed in confinement had lesser BCS on day 63 and greater BCS loss from days 0 to 63 than other treatments. Conversely, rump-fat depth on day 63 was greater (P < 0.01) for non-lactating cows maintained on pasture than for lactating cows in either pasture or drylot environments. Similarly, change in rump-fat depth was greatest (diet × weaning, P < 0.01) for non-lactating cows on pasture and least for lactating cows in either pasture or drylot environments. Results were interpreted to indicate that early-weaning spared cow BW and rump fat compared to weaning at conventional ages. Performance of cows appeared to be similar when limit-fed under drylot conditions or maintained in a pasture environment. Conversely, calf performance was generally greater in confinement than on pasture.

Effects of weaning method on post-weaning performance by early weaned beef calves

Health and performance of early-weaned steers was evaluated during a 56-d weaning period, a 56-d feedlot receiving period and a 165-d feedlot finishing period. Steers (n = 239; 128 ± 14 d of age) were assigned to a 56-d weaning treatment: drylot weaning (D) or pasture weaning (P). Pasture steers grazed mature, native tallgrass range (89.2% DM, 9.08% CP) without supplementation. A concentrate-based diet (18.7% CP and 1.15 Mcal NEg/kg) was fed to D steers. Later, all steers were transitioned to a receiving, then a finishing diet and fed to a common endpoint. Body weight after and ADG during weaning were greater (P &lt; 0.01) for D than for P. Incidence of undifferentiated fever during weaning tended to be greater (P = 0.10) for D steers than for P steers. Conversely, incidence of keratoconjunctivitis was greater (P &lt; 0.01) for P than for D during weaning (40.2% vs. 0%, respectively) and receiving (P &lt; 0.01; 14.3% vs. 1.6%, respectively). At the start and end of receiving, D steers had greater (P &lt; 0.01) BW compared with P steers. Drylot steers had greater (P = 0.03) ADG compared with P steers during receiving. Pasture steers tended to have greater DMI (P = 0.09) during receiving than D steers. In contrast, gain:feed (G:F) was improved (P &lt; 0.01) for P steers than for D steers during receiving. Incidence of undifferentiated fever was not different (P = 0.99) between D and P steers during receiving. At start of finishing, D steers were heavier (P &lt; 0.01) than P steers; however, finishing ADG was greater (P &lt; 0.01) for P compared with D. Conversely, hot carcass weight of P steers was less (P &lt; 0.01) compared with D steers. Drylot steers had greater DMI (P &lt; 0.01) than P steers during finishing, whereas P steers had improved G:F (P &lt; 0.01) compared with D steers. There were no differences (P ≥ 0.19) between treatments in DOF, carcass characteristics or USDA yield grade. Growth and health during a 56-d weaning period and a 56-d receiving period were improved when steers were weaned in a drylot environment and fed a concentrate-based diet compared with non-supplemented steers weaned in a pasture environment. We interpret these data to suggest that, under the conditions of our experiment, steers preconditioned on mature, native, warm-season pasture for 56 d without supplementation were unable to compensate for previous nutrient restriction during finishing.

Phenotypic relationships between docility and reproduction in Angus heifers

The objective of this study was to elucidate the phenotypic relationships between docility and first-service AI conception rate in heifers. Data ( = 337) collected from 3 cooperator herds in Kansas at the start of synchronization protocol included exit velocity (EV), chute score (CS), fecal cortisol (FC), and blood serum cortisol (BC). Data were analyzed using logistic regression with 30-d pregnancy rate as the dependent variable. The model included the fixed effect of contemporary group and the covariates FC, BC, EV, CS, BW, and age. Correlation coefficients were calculated between all continuous traits. Pregnancy rate ranged from 34% to 60% between herds. Blood cortisol positively correlated with EV ( = 0.22, < 0.01), negatively correlated with age ( = -0.12, < 0.03), and tended to be negatively correlated with BW ( = -0.10, = 0.09). Exit velocity was positively correlated with CS ( = 0.24, < 0.01) and negatively correlated with BW ( = -0.15, < 0.01) and age ( = -0.12, < 0.03). Chute score negatively correlated with age ( = -0.14, < 0.01), and age and BW were moderately positively correlated ( = 0.42, < 0.01), as expected. Older, heavier animals generally had better temperament, as indicated by lower BC, EV, and CS. The power of our test could detect no significant predictors of 30-d pregnancy for the combined data from all ranches. When the data were divided by ranch, CS ( < 0.03) and BW ( < 0.01) were both significant predictors for 30-d pregnancy for ranch 1. The odds ratio estimate for CS has an inverse relationship with pregnancy, meaning that a 1-unit increase in average CS will reduce the probability of pregnancy at ranch 1 by 48.1%. Weight also has a negative impact on pregnancy because a 1-kg increase in BW will decrease the probability of pregnancy by 2.2%. Fertility is a complex trait that depends on many factors; our data suggest that docility is 1 factor that warrants further investigation.

Effects of dietary protein and bacterial lipopolysaccharide infusion on nitrogen metabolism and hormonal responses of growing beef steers

Purified lipopolysaccharide (LPS) infusion in cattle induces clinical and metabolic responses similar to gram-negative bacterial infection. Effects of LPS and dietary protein on rectal temperature, serum hormones, haptoglobin, plasma urea N and AA, and N balance were evaluated in 24 steers (250 +/- 2.8 kg of BW). Treatments were a 2 x 3 factorial of LPS (0 vs. 1.5 microg/kg of BW; -LPS vs. +LPS) and diets containing (DM basis) 1) 14.5% CP, 11.6% ruminally degradable protein (RDP), and 2.9% ruminally undegradable protein (RUP; CP14.5CON); 2) 16.3% CP, 13.4% RDP, and 2.9% RUP (CP16RDP); and 3) 16.1% CP, 11.2% RDP, and 4.9% RUP (CP16RUP). Diet RDP and RUP were altered using casein, fish meal, and corn gluten meal. Steers were adapted to diets (1.1 Mcal/kg of NE(g); DM fed at 1.8% BW) for 14 d and were infused (intravenously 1 mL/min) with LPS (in 100 mL of saline) on d 15. Rectal temperature and serum cortisol, prolactin, haptoglobin, and insulin increased, glucose initially increased and then declined, and serum thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x hour; P < 0.01). Serum IGF-I was less (P < 0.01) for +LPS vs. -LPS steers. Plasma urea N increased in response to LPS (LPS x hour; P = 0.02) and was greater for +LPS steers fed CP16RDP and CP16RUP vs. CP14.5CON, but greater in -LPS steers fed CP16RUP vs. CP16RDP and CP14.5CON (LPS x diet; P = 0.04). Plasma Met, Thr, Leu, Ile, Phe, Trp, Gly, Ser, Asn, and Tyr decreased, and plasma Ala increased in response to LPS (LPS x hour; P < 0.01). Plasma Orn initially increased and then decreased in +LPS vs. -LPS steers (LPS x hour; P < 0.01). No LPS x diet interactions (P > or = 0.15) occurred for DM, OM, NDF and N intake, fecal excretion, or apparent digestibility. Dietary DM, OM, NDF, and N intake, and retained N were less (P < 0.01) for +LPS than -LPS steers. Total N intake, apparent N digestibility, and retained N were greater (P < or = 0.05) for steers fed CP16RDP and CP16RUP vs. CP14.5CON. An LPS x diet interaction (P = 0.05) occurred for N retention (% N intake) because N retention was less for +LPS than -LPS steers when fed CP14.5CON, but not different between +LPS and -LPS steers when fed CP16RDP and CP16RUP. These results demonstrate that LPS infusion alters serum hormones, plasma AA, and N balance in cattle and imply that growing steers exposed to LPS may require greater dietary protein concentrations to account for altered intake and metabolic AA demand.

Suppression of bloodfeeding by Ochlerotatus dorsalis and Ochlerotatus melanimon on cattle treated with python ear tags

Adult mosquitoes were collected by drop traps to compare bloodfeeding rates between cattle treated with 2 Python ear tags (10% zeta-cypermethrin and 20% piperonyl butoxide) per animal and animals that were untreated. Mosquitoes were collected both 2 and 4 wk after application of the ear tags. Bloodfeeding by Ochlerotatus dorsalis was reduced by 79 and 77%, respectively, and bloodfeeding by Ochlerotatus melanimon was reduced by 84 and 81%, respectively, at 2 and 4 wk. Based on chi-square analysis, differences in bloodfeeding rates due to treatment were significant. The effect of the treatment appeared to be repellency, because no mosquito mortality was observed at the time of collection and no mortality was observed among bloodfed mosquitoes that were collected and held for 24 h.

Persistent efficacy of doramectin topical solution against induced infestations of Bovicola bovis and Solenopotes capillatus

A study was conducted in two locations, Wyoming and Wisconsin, USA, to evaluate the persistent efficacy of doramectin topical solution at a dose rate of 500 microg/kg body weight against artificially induced infestations of Bovicola bovis and Solenopotes capillatus on cattle. At each location, lice-free beef calves were individually housed and randomly allocated to treatment. Both B. bovis and S. capillatus were transferred from untreated donor animals to doramectin-treated cattle at the end of 35, 63, 91 or 126 day post-treatment periods. Cattle treated with a saline pour-on served as the control. Based on the geometric means of lice counts 2 weeks following transfer, the persistent efficacy of a single treatment with doramectin topical solution against induced infestations of B. bovis was 100.0, 100.0, 99.5, and 100.0% at post-treatment days of 35, 63, 91, and 126, respectively. Persistent efficacy against induced infestations of S. capillatus, for the same intervals, were 100.0, 94.9, 86.3, and 74.9%.

Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from Hereford cattle and ponies treated with permethrin

The blood feeding of mosquitoes and black flies from Hereford cattle and ponies treated with commercial formulations of permethrin was evaluated using an animal enclosure trap sample system that allowed comparison of insect blood-feeding levels between treated and nontreated animals. Blood feeding of both Aedes dorsalis Meigen and A. melanimon Dyar from heifers treated with pour-on concentrate and whole body spray treatments was reduced significantly by 79-88% at 4 d posttreatment, with apparent but not significant reductions of 61-68% at 11 d posttreatment. Simulium bivittatum Malloch and S. griseum Coquillett blood feeding was reduced significantly by 96% to >99% at 4 d posttreatment, but apparent reductions of 30-87% at 11 d posttreatment were not significant. Blood feeding of S. bivittatum from ponies treated with a permethrin fly wipe was reduced significantly by 98 and 87% at 1 and 7 d posttreatment, respectively. No evidence of treatment-induced mortality was observed for recently blood-fed female mosquitoes or black flies captured from treated animals and held for 24 h. The potential benefit of using permethrin to protect livestock from insect-transmitted pathogens was estimated with a model based on level of host attack, pathogen infection rate in the vector, and suppression of blood feeding. Suppression of blood feeding by 90% is predicted to prevent the exposure of a host to a pathogen for up tolO d at 1,000 insect feedings per d when the vector population infection rate is one insect per 1,000. If insect feedings are lower (100/d) and the insect infection rate remains at one per 1,000, protection is predicted for 100 d. In contrast, a 90% suppression of blood feeding is predicted to provide protection for less than 1 d at 1,000 feeding per day and a vector infection rate of one insect per 100.

Efficacy of eprinomectin against Hypoderma spp in cattle

OBJECTIVE

To determine the efficacy of a topical formulation of eprinomectin against natural infestations of first (L1)-stage, and second and third (L2/L3)-stage larvae of Hypoderma spp.

ANIMALS

140 approximately 6- to 18-month-old cattle of various breeds.

PROCEDURE

Cattle, selected from herds with high prevalence of Hypoderma infestation, were treated in 4 experiments: within each replicate, 1 animal received eprinomectin at a dosage of 500 micrograms/kg of body weight against first-stage larvae (L1). The second animal received the same treatment against second or third-stage larvae (L2/L3). The third animal served as an untreated control. In a fifth experiment, visible warbles were treated on half of the cattle. Remaining cattle served as vehicle-treated controls. In 1 experiment, warbles were examined from time of treatment until all lesions were resolved. In 4 experiments, emerging Hypoderma larvae were recovered, speciated, and enumerated, and viability was determined.

RESULTS

Eprinomectin (500 micrograms/kg) efficacy was complete against L1. Hypoderma L2/L3 eradication approached 100% efficacy (1 live larva was recorded). Warbles in treated cattle resolved in a significantly shorter time than did those in controls. Adverse reactions related to treatment were not observed in any of the trials.

CONCLUSIONS

Eprinomectin (500 micrograms/kg) applied topically was safe and highly efficacious for treatment of all larval stages of Hypoderma spp in these trials.

CLINICAL RELEVANCE

Attributes of eprinomectin besides antiparasite efficacy allow treatment of all classes of cattle with no need for meat or milk withdrawal.

Doramectin systemic activity against cattle grubs, Hypoderma lineatum and H. bovis (Diptera: Oestridae), and cattle lice, bovicola bovis (Mallophaga: Trichodectidae), Linognathus vituli and Solenopotes capillatus (Anoplura: Linognathidae), and Haematopinus eurysternus (Anoplura: Haematopinidae), in Wyoming

Seven individual trials were conducted in Wyoming to evaluate the therapeutic efficacy of doramectin administered subcutaneously at a dosage of 200 micrograms kg-1 against multiple, natural infestations of cattle grubs or cattle lice. Insect species present and the number of trials that included each species were: Hypoderma lineatum, 2; Hypoderma bovis. 1; Bovicola bovis, 5; Haematopinus eurysternus, 1; Linognathus vituli, 5; and Solenopotes capillatus, 3. Examinations for lice were performed prior to treatment and either weekly or bi-weekly thereafter for 28 days. Examinations for cattle warbles were performed either weekly or every 4 to 5 weeks from time of first appearance through last appearance in the backs of the cattle. No H. lineatum, H. bovis, H. eurysternus, L. vituli, or S. capillatus were found on doramectin-treated animals at any time following treatment. By 28 days following treatment, the number of B. bovis was reduced between 58 and 98%. Treatments applied later in the season, i.e. in March, were more efficacious against B. bovis than those applied in January or February.

In vitro ruminal metabolism of larkspur alkaloids

Larkspur (Delphinium sp) poisoning of range cattle is a serious, recurring problem in the western United States. Numerous stratagems have been recommended to ameliorate larkspur intoxication, but none are completely effective. Previous studies in this laboratory indicated bovine ruminal microflora are capable of chemically modifying Delphinium alkaloids. Research reported herein was undertaken to further evaluate whether differences in ovine and bovine rumen metabolism might explain differences in susceptibility to larkspur intoxication and whether existing metabolic activity can be enhanced by sustained exposure to Delphinium alkaloids. Comparison of ovine and bovine rumen metabolism of Delphinium geyeri alkaloids in vitro failed to demonstrate differences in the rate of alkaloid metabolism. Rumen liquor collected sequentially from a fistulated cow dosed with dried Delphinium geyeri did not vary in ability to metabolize larkspur alkaloids.