The effectiveness of a single dose of doramectin pour-on in the control of gastrointestinal nematodes in yearling stocker cattle

Three field studies were conducted to determine the efficacy of a single dose of doramectin pour-on in the control of gastrointestinal nematode infections in yearling stocker calves on pasture. These 140-day studies were carried out between October 1995 and March 1996 in Tennessee (TN), between January and June 1997 in Louisiana (LA), and between May and September 1997 in Wisconsin (WI). Calves with patent nematode infections were equally allocated to treatments (doramectin pour-on, at 500 microg/kg body weight or untreated control) and pastures as randomized complete-block designs (LA and TN studies) or completely at random (WI study). There were six pasture replicates per treatment at each site, with each pasture replicate accommodating six calves at the TN site (36 calves per treatment), five calves at the LA site (30 calves per treatment), and seven calves at the WI site (42 calves per treatment). Fecal samples for nematode egg counts were collected on Day 0, and at 28-day intervals thereafter. Body weights were recorded on Day 0 and at 28-day intervals until study termination. Nematode egg output of the doramectin-treated groups was reduced over the entire grazing period compared to those in the untreated control groups, resulting in average daily weight-gain advantages of 0.055 kg (p < or = 0.05) for the TN study, 0.208 kg (p < or = 0.05) for the LA study, and 0.116 kg (p < or = 0.05) for the WI study.     

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

Productivity of cow-calf pairs grazing tall fescue pastures infected with either the wild-type endophyte or a nonergot alkaloid-producing endophyte strain, AR542

The nonergot alkaloid-producing endo-phyte, AR542, has been shown to improve the persistence and yield of tall fescue pastures without causing the animal disorders commonly associated with tall fescue toxicosis. A 3-yr grazing study was conducted to compare effects of AR542-infected tall fescue pastures with wild type endophyte-infected (E+) tall fescue pastures on cow-calf performance. Replicated 7.3-ha pastures of each treatment were grazed by cow-calf pairs (16 pairs per pasture replication) each year from March to weaning in September. The cows were exposed to breeding on their respective pasture treatments from April 1 through June 15. The treatment groups were compared for reproductive performance, ADG, BCS, calf growth rate, and weaning weight. Blood samples were also collected for serum prolactin (PRL) analysis. There were no significant differences in calving rate (P = 0.98) or calving interval (P = 0.62) between pasture treatments. Cows that grazed the AR542 pastures subsequently gave birth to calves that were heavier (P < 0.05) than calves from cows that had grazed the E+ pastures. Cows grazing the AR542 pastures had higher (P < 0.05) BCS at the end of the grazing period, and had higher ADG during the grazing period. Calves raised on the AR542 pasture had higher (P < 0.05) ADG and weaning weights than calves of the same sex raised on the E+ pastures. Serum PRL concentrations were decreased (P < 0.05) in both cows and calves on the E+ pastures compared with serum PRL concentrations in cows and calves grazing the AR542 pastures. The results indicate that grazing tall fescue pastures infected with the AR542 endophyte may give significant advantages in cow-calf growth rates and BCS over grazing E+ pastures. However, there did not seem to be any benefit in reproductive performance in this trial. There was a small, but significant increase in birth weight in cows grazing AR542 pasture.     

Effect of a single strategically timed dose of fenbendazole on cow and calf performance

A 168-day study was conducted to evaluate the effect of a strategically timed treatment with fenbendazole on anthelmintic efficacy and performance of beef cows and calves. Eight groups of 10 Angus cow/calf pairs were allotted on 7 May 1987 to eight similarly managed 4.86-ha pastures (bermudagrass/tall fescue) on the basis of cow age, and calf sex and weight. At that time, four groups of cows received a dose of fenbendazole (5 mg kg-1) with their calves receiving fenbendazole at the same dosage 28 days later. Treated calf average daily gain (ADG) was 0.04 kg greater (P less than 0.05) than control calves (0.82 vs. 0.78 kg) during the 168-day study. Treated cow ADG was 0.09 kg greater (P less than 0.05) than control cows (0.40 vs. 0.31 kg). Although there was a reduction (P less than 0.05) in fecal egg counts following treatment of the cows, the numbers of eggs generally were low compared with egg counts of calves. From Day 28 through Day 112 post-treatment, fecal egg counts of treated calves were lower (P less than 0.05) than those of control calves. However, fecal egg counts from treated calves increased post-treatment until there were no differences (P greater than 0.05) between treated and control calves at the end of the study. The pregnancy rate tended to be higher (P = 0.12) for treated cows (98%) than for untreated control cows (75%). The actual calving rate was higher (P = 0.03), for treated cows (90%) than for untreated control cows (68%). Results indicated that a strategic anthelmintic treatment can improve cow and calf performance, but that calves born in late winter or early spring may need more than one therapeutic dose during the nursing period on pasture.     

Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.     

Influence of Urea Alone or Combined with Fish Meal and Solubles in Liquid Supplements on Performance of Grazing Cow-Calf Pairs

Experiments were conducted for 84 d, beginning on July 1, with cow-calf pairs grazing summer grass to determine the effects of feeding molasses containing urea or urea, fish solubles, and fish meal on BW gains, milk production, and blood metabolites. The four treatments based on a 16% CP urea-molasses mixture were no supplement, 97.8% base mixture plus 2.2% urea for cows and calves, 80% base mixture plus 10% fish solubles and 10% fish meal for cows and calves, and the supplement with fish solubles and fish meal as a creep feed for calves. The mixture contained 23% CP as fed. In Exp. 1, 60 crossbred cows with Angus-sired calves were allotted according to sex and birth date to 12, 2-ha pastures. Three pastures each with five cow-calf pairs were assigned to each treatment. In Exp. 2, 48 Hereford X Brahman F₁ cows with Angus- or Belgian Blue-sired calves were allotted as in Exp. 1 to 24, 1-ha Alicia bermudagrass pastures. Three pastures with two cow-calf pairs were assigned to each treatment for each sire breed of calf. Cows were machine-milked, and jugular blood samples were collected initially and on d 28 and 56. Cows and calves were weighed, and cows were condition-scored after a 16-h shrink at the beginning and end of both experiments. Both supplements were consumed at similar levels (1.75 kg/d) by cow-calf pairs in both experiments. Cows in Exp. 1 and calves in both experiments gained more (P<0.05) BW when cow-calf pairs had access to the supplement containing fish solubles and fish meal. Milk yield was numerically higher on d 28 (P<0.18) and d 56 (P<0.11) when cows received fish solubles and fish meal in the supplement. The decline in milk yield from initial milking tended to be less (P<0.10) on d 28 and was less (P<0.05) on d 56 when cows received this supplement. Plasma ammonia N concentrations were higher (P<0.05) when cows were fed supplement containing only urea, and both supplements increased (P<0.05) plasma urea N when compared with no supplement. Supplements containing molasses, urea, fish solubles, and fish meal appear beneficial for cow-calf pairs grazing summer forage.     

Cow and calf performance on Coastal or Tifton 85 Bermudagrass pastures with aeschynomene creep-grazing paddocks

Cow and calf performance was determined in a 2-yr, 2 x 2 factorial, grazing experiment using Coastal or Tifton 85 (T85) replicated Bermudagrass pastures (4 pastures each; each pasture 4.86 ha), without or with aeschynomene creep-grazing paddocks (n = 4, 0.202 ha each, planted in May of each year, 13.44 kg/ha). On June 10, 2004, and June 8, 2005, 96 winter-calving beef "tester" cows and their calves were grouped by cow breed (9 Angus and 3 Polled Hereford/group), initial cow BW (592.9 +/- 70.1 kg, 2-yr mean), age of dam, calf breed (Angus, Polled Hereford, or Angus x Polled Hereford), calf sex, initial calf age (117 +/- 20.1 d, 2-yr mean), and initial calf BW (161.3 +/- 30.4 kg) and were randomly assigned to pastures. Additional cow-calf pairs and open cows were added as the forage increased during the season. Forage mass was similar for all treatment pastures (P > 0.70; 2-yr mean, 6,939 vs. 6,628 kg/ha, Coastal vs. T85; 6,664 vs. 6,896 kg/ha, no creep grazing vs. creep grazing). Main effect interactions did not occur for performance variables (P > 0.10; 2-yr means), and year affected only the initial and final BW of the calves and cows. The 91-d tester calf ADG was greater for calves grazing T85 than Coastal (0.94 vs. 0.79 kg; P < 0.01), and for calves creep grazing aeschynomene compared with calves without creep grazing (0.90 vs. 0.82 kg; P < 0.03). Calf 205-d adjusted weaning weights were increased for calves grazing T85 compared with Coastal (252.9 vs. 240.3 kg; P < 0.01) and for calves with access to creep grazing (249.9 vs. 243.3 kg; P < 0.05). The IVDMD of esophageal masticate from pastures had a forage x creep grazing interaction (P < 0.05; Coastal, no creep grazing = 57.4%; Coastal, creep grazing = 52.1%; T85, no creep grazing = 59.1%; T85, creep grazing = 60.0%), and IVDMD was greater (P < 0.05) for T85 than for Coastal pastures. Cows were milked in August 2004, and in June and August 2005, with variable milk yields on treatments, but increased milk protein (P < 0.05) for cows grazing T85 compared with Coastal pastures in August each year, contributing to increased calf gains on T85 pastures. These results complement previous research with T85 and indicate increased forage quality and performance of cattle grazing T85 pastures. Calf gains on T85 pastures and for calves on creep-grazed aeschynomene paddocks were high enough to influence the efficiency of cow-calf operations.     

Evaluation of the parasitological and production responses of a cow/calf operation to an anthelmintic program with ivermectin

The efficacy of a treatment schedule using ivermectin, given subcutaneously at the rate of 200 micrograms kg-1, to control gastrointestinal parasitism and its effect on liveweight gains was assessed. Two herds with a total of 466 Hereford X Brangus cow/calf pairs were used. Each herd was on six pasture plots of comparable size, stocking rate, and quality and quantity of forage. Pasture groups were paired across the two herds. Pasture groups from one herd were randomly assigned to nonmedicated control and the other three to ivermectin treatment. Treatment assignments per pasture group were reversed in the other herd. The control group contained 118 cows and 112 calves and the medicated group 121 cows and 115 calves. Cows were treated in early July and the calves in late July or early August. Cattle from one herd were weighed on Days -28, 0 (day of cow treatment), 30 (day of calf treatment), 58, and 86, while the other herd was weighed on Days -29, 0 (day of cow treatment), 27 (day of calf treatment), 61, and 89. Day 0 was not the same calendar day for the two herds. Fecal samples for parasite egg counts were obtained from the rectum on weight days from five cows and six calves from each pasture; in most cases the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves between day of treatment for cows and the end of the trial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ivermectin on performance of beef cattle on Georgia pastures

A total of 469 cows and calves from 2 herds, each on 6 pastures, was used to evaluate the anthelmintic efficacy and animal-performance benefits of ivermectin given subcutaneously at a dosage of 200 micrograms/kg to nursing beef calves and their dams during a grazing season. Pastures were paired across the 2 herds. Three pasture groups from 1 herd were randomly assigned to either a nonmedicated control or to a medicated group. Treatment assignments were reversed in the other herd. The control groups comprised 110 cows and 108 calves, whereas 127 cows and 124 calves were treated with ivermectin (200 micrograms/kg). The cows were treated once, in late spring, and the calves were treated twice, once in late spring and again in midsummer. Cattle from one herd were weighed on days - 12, 21, 49, 77 (day of 2nd treatment for calves), and 105, and the other herd was weighed on days - 6, 23, 57, 86 (day of 2nd treatment for calves), and 113. Rectal fecal samples for nematode egg counts were obtained from approximately 25% of the cattle in each pasture on weighing days; usually, the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves up to the 2nd treatment date and up to the termination of the study. There was no significant difference between treated and control cows, with regard to weight gain over either interval. Treated calves had fewer positive fecal egg counts (P less than 0.01) and passed fewer eggs (P less than 0.05) after both treatments than did control calves. There were no differences in either number of eggs or number of negative cows between treatment groups. Adverse reactions attributable to treatment were not seen.     

Differences in susceptibility to gastrointestinal nematode infection between Angus and Brangus cattle in south Louisiana

Breed susceptibility to nematode infection was evaluated in Angus (Bos taurus) and Brangus (B. indicus crossbreed) cattle. A cow-calf herd and a yearling replacement heifer herd were monitored during one grazing season. Calves were born in March and were weaned in October. Individual rectal fecal samples were collected monthly from the two herds and processed for fecal egg counts (FEC) and coprocultures. Cow and calf FEC increased from April, reaching maximum values during the summer. Angus cows and calves had significantly (p<0.05) greater FEC than Brangus cows and calves, and Haemonchus and Cooperia were the predominant genera. Replacement heifer FEC showed a similar pattern with maximum levels during late summer/fall, and Haemonchus was the predominant genus. No significant differences were seen between breeds, however, infection levels were consistently lower in Brangus heifers. Ostertagia was present in cows and heifers only in fall/winter, which is consistent with summer inhibition. The data suggested that cows were an important source of pasture contamination for their susceptible calves and that the Brangus breed was relatively more resistant to infection. The use of B. indicus crossbreeds may help in alleviating reliance on chemical control by reducing the rate of pasture contamination and subsequent infection losses.     

Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures

A 3-yr study used 16 cows and their spring-born calves (yr 1) and 48 first-calf heifers (yr 2, n = 24; yr 3, n = 24) and their spring-born calves in a completely randomized design. All cows and heifers were Angus x Beefmaster, and calves were sired by Angus bulls. Cow-calf pairs were assigned randomly to one of two management systems: 1) an early-weaning system, in which steer and heifer calves were weaned at 108 d of age and fed a postweaning growing diet (EW), or 2) a normal weaning system, in which calves were weaned at 205 d without supplementation (NW). Before early weaning and within each management system, calves and their dams were maintained in two 1.4-ha, endophyte-infected tall fescue pastures for 35 d (yr 1) or 14 d (yr 2 and 3). Early-weaned calves and cow-calf pairs were then randomly allotted to 1.4-ha, endophyte-infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow-calf pairs per pasture (four pastures per management system). Cow weights and BCS changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG from early to normal weaning did not differ (P = 0.32). Similar to ADG, BW of calves at normal weaning were not different (P = 0.11). Forage intake was greater (P < 0.01) by NW calves during Periods 2 and 3 of yr 1 and Periods 1 and 2 of yr 2 and 3; however, total DM and CP intakes were greater (P < 0.01) for EW calves in Periods 2 and 3 of each year. Intakes of NDF tended (P = 0.11) to be greater by EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2; however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05) than those consumed by EW calves. These results show the condition of cows with EW calves was improved by early weaning and gains by calves weaned at 108 d to pasture plus a commercial grower diet were comparable to those by calves continuing to nurse dams until weaned at 205 d.     

Strategic deworming for spring-calving beef cow/calf herds

Strategic application of an anthelmintic was tested during the 1982 grazing season as part of the continued study of the epidemiology of beef cattle parasitism in central Missouri. Forty Hereford and Hereford X Simmental cow/calf pairs were assigned to 2 treatment groups. The 20 cow/calf pairs in group 1 were nonmedicated controls. After calving in mid-March, the 20 cows in group 2 were drenched with a 10% suspension of the anthelmintic fenbendazole (10 mg/kg of body weight). Ten cow/calf pairs were placed on each of four 20-acre fescue or orchard grass pastures in mid-May. Cows and calves in treatment group 2 were drenched with the 10% fenbendazole suspension (5 mg/kg) in mid-July. Body weights and fecal specimens were obtained monthly. Nematode egg counts in cow and calf fecal specimens collected monthly were significantly (P less than 0.05) lower in treatment group 2 than in treatment group 1. Numbers of larvae cultured for speciation revealed that Ostertagia ostertagi was the predominant nematode species. Developmental arrest of O ostertagi was found to be significantly (P less than 0.05) greater than zero from mid-May to mid-July. An important significant difference (P less than 0.01) was shown in body weights of calves, with the calves in treatment group 2 having a higher mean weight gain of 22.5 kg in adjusted 205-day weaning weights, and a higher mean daily gain of 0.11 kg. Weight maintenance of cows was not affected significantly by anthelmintic treatment. Nematode egg counts in monthly cow and calf fecal specimens were not significantly different between those animals on different pastures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of vaccination and treatment in controlling naturally occurring infectious bovine keratoconjunctivitis.

A vaccination study for infectious bovine keratoconjunctivitis was conducted on 108 newborn Hereford calves in the US Department of Agriculture Meat Animal Research Center cattle herd at Clay Center, Nebraska. Groups were allocated so that age of calf, sex of calf, and age of dam were equally distributed between the 54 vaccinated (group I) and the 54 nonvaccinated (group 2) control calves. The dams of both groups of calves were monitored as group 3 controls. An autogenous Moraxella bovis bacterin (formalin-killed, whole cells) was given IM at birth and at approximate intervals of 2 weeks for a total of 3 doses. Bacterial isolation rates for the cattle in groups 1, 2, and 3 during the summer were 92.6%, 92.6%, and 54.1%, respectively, and disease rates were 100%, 96.3%, and 70.6%. The rates were significantly (P less than 0.05) different between calves and cows. Vaccination of calves at birth permitted serum antibodies to develop before the calves were extensively exposed to infection; however, immunity to the disease did not develop. In a treatment study of other animals in the same herd, but in another pasture, the same criteria were used for allocation of 107 cow-calf pairs. Eye spray was applied to treated principals (group 4, 52 calves; and group 6, 53 cows) each week after examination and sample collection. Controls consisted of 54 calves (group 5) and 54 cows (group 7) that were examined and cultured bacteriologically in the same manner. The bacterial isolation and disease rates were less (P less than 0.05) in the treated calves (group 4) than in the nontreated controls (group 5). The differences in bacterial isolation rates between groups 6 and 7 were not significant, but group 6 had less (P less than 0.05) grade III lesions than did group 7. Weekly treatment appeared to be more effective in reducing the incidence of disease than did vaccination.     

Creep grazing and early weaning effects on cow and calf productivity

One hundred fifty Simmental-Hereford cows and calves were used in a 3-yr study to evaluate three creep grazing treatments and an early weaning treatment on cow and calf performance during midsummer (July to September). Calves were approximately 150 d of age and averaged 178.6 kg when treatments were initiated. Tifleaf pearl millet (Pennisetum Americanum L. Leeke) was used as the forage for two of the creep treatments, representing two cow stocking intensities of .466 (TLM1) and .239 (TLM2) ha of base hill land pasture/cow, and as pasture for early weaned calves. A red clover (Trifolium pratense L.)-Kentucky bluegrass (Poa pratensis L.) mixture was used as the other creep forage. Hill land pastures were similar for the mature cow units in all creep treatments. Calf average daily gains ranged from .93 to 1.10 kg and were not influenced (P greater than .05) by treatment. Calf gains per hectare were similar for the control, red clover and TLM1 treatments. The TLM2 and early weaning treatments resulted in increases of 105.4 and 39.1 kg of calf gain/ha (P less than .05) compared with the control. When calves were allowed to creep graze millet, decreasing the forage area from .466 to .239 ha per cow-calf unit resulted in an increase of 97.7 kg of calf gain/ha with no reduction in calf gain. Cows on the more intensively grazed millet creep treatment (TLM2) lost more weight (P less than .05) during midsummer than those on the TLM1 treatment, but they gained 18.5 kg more (P less than .10) weight than TLM1 cows between weaning and the start of winter feeding.     

Toxocara vitulorum in suckling calves in The Netherlands

A Dutch farmer with beef cattle and suckling calves noticed one of the calves suffering from diarrhoea and observed large white worms near the perineum. In the faeces of this calf, eggs of Toxocara vitulorum were found. The majority of the cows in the herd were of the Piemontese breed previously imported from southern France. Treatment with albendazole was successful. Two other calves had positive faecal egg counts. One month after treatment of these calves with doramectin, no eggs were found. To prevent further infections on the farm and dissemination of this uncommon infection to other farms, the farmer decided to have all his cattle slaughtered.     

The persistent efficacy of doramectin pour-on against biting and sucking louse infestations of cattle

A repeated-exposure challenge model was used to evaluate the pour-on formulation of doramectin in preventing the establishment of louse infestations in cattle. Twenty calves cleared of preexisting biting and sucking louse infestations were randomly and equally allocated to either a doramectin-treated or untreated control group, with five replicates per group. Doramectin pour-on was administered topically at a dose rate of 500 microg/kg body weight. Every 14 days, from a pool of seeder calves with infestations of at least 50 biting and 50 sucking lice each, 10 calves were selected and 1 was placed in each replicate pen. Every week during the 112-day study, 9 predilection sites on the doramectin-treated and untreated calves were examined to estimate the louse population density. A calf met the infestation criterion for a louse species when two or more live lice were counted on two or more body regions for two consecutive count days. Because only 4 of 10 untreated calves acquired Solenopotes capillatus infestations, the persistent efficacy of doramectin against S. capillatus was not evaluated. Bovicola bovis and Linognathus vituli infestations in the untreated calves developed shortly after exposure to infested seeder calves. The acquisition of B. bovis and L. vituli infestations in the doramectin-treated group was delayed for 77 days and 105 days, respectively.     

Productivity and hay requirements of beef cattle in a Midwestern year-round grazing system

Our objective was to evaluate a replicated (n = 2) Midwestern year-round grazing system's hay needs and animal production compared with a replicated (n = 2) conventional (minimal land) system over 3 yr. Because extended grazing systems have decreased hay needs for the beef herd, it was hypothesized that this year-round system would decrease hay needs without penalizing animal production. In the minimal land (ML) system, two replicated 8.1-ha smooth bromegrass-orchardgrass-birdsfoot trefoil (SB-OG-BFT) pastures were rotationally stocked with six mature April-calving cows and calves and harvested as hay for winter feeding in a drylot. After weaning, calves were finished on a high-concentrate diet. Six mature April-calving cows, six mature August-calving cows, and their calves were used in the year-round (YR) grazing system. During the early and late summer, cattle grazed two replicated 8.1-ha SB-OG-BFT pastures by rotational stocking. In mid-summer and winter, April- and August-calving cows grazed two replicated 6.1-ha, endophyte-free tall fescue-red clover (TF-RC) and smooth bromegrass-red clover (SB-RC) pastures, respectively, by strip-stocking. In late autumn, spring-calving cows grazed 6.1-ha corn crop residue fields by strip-stocking. Calves were fed hay with corn gluten feed or corn grain over winter and used as stocker cattle to graze SB-OG-BFT pastures with cows until early August the following summer. First-harvest forage from the TF-RC and SB-RC pastures was harvested as hay. Body condition scores of April-calving cows did not differ between grazing systems, but were lower (P < or = 0.03) than those of August-calving cows from mid-gestation through breeding. Preweaning calf BW gains were 47 kg/ha of perennial pasture (P < 0.01) and 32 kg/cow (P = 0.01) lower in the YR grazing system than in the ML system. Total BW gains ofpreweaning calf and grazing stocker cattle were 12 kg/ha of perennial pasture less (P = 0.07), but 27 kg/cow greater (P = 0.02) in pastures in the YR grazing system than in the ML system. Amounts of hay fed to cows in the ML system were 1,701 kg DM/cow and 896 kg DM/cow-stocker pair greater (P < 0.05) than in the YR grazing system. Extended grazing systems in the Midwest that include grazing of stocker cattle to utilize excess forage growth will decrease stored feed needs, while maintaining growing animal production per cow in April- and August-calving herds.     

Endemic avian toxoplasmosis on a farm in Illinois: clinical disease, diagnosis, biologic and genetic characteristics of Toxoplasma gondii isolates from chickens (Gallus domesticus), and a goose (Anser anser)

This study evaluated potential relationships between parasite egg/oocyst outputs in cow-calf beef herds located within the United States Northern Great Plains and herd longitude and latitude. Management of study herds was typical of herds from this region. Parasite egg/oocyst counts were measured from 10 cows and 5 calves selected from each herd near the end of the traditional grazing season (October 1993). The types and numbers of eggs and oocysts recovered from both cows and spring-born calves were consistent with those described in other studies. No significant relationship between fecal egg/oocyst counts and latitude was observed in calves or cows. Monezia egg output exhibited no significant correlation with longitude for calves or cows. In cows, a significant negative correlation was detected between coccidian oocyst counts and herd longitude but not between helminth egg counts and longitude. In calves, Nematodirus, trichostrongyle and Trichuris egg output and coccidian oocyst output were all negatively correlated with longitude. This negative correlation suggests that nematode populations within the study area decreased slightly from an east to west direction.     

Evaluation of hay-type and grazing-tolerant alfalfa cultivars in season-long or complementary rotational stocking systems for beef cows

Alfalfa (Medicago sativa L.) persistence and forage and cow-calf production were evaluated on pastures containing smooth bromegrass with or without grazing-tolerant or hay-type alfalfa cultivars rotationally stocked in either a season-long or complementary system. In 1997, six 2.02-ha pastures were seeded with smooth bromegrass, a mixture of a grazing-tolerant alfalfa (Amerigraze variety) and smooth brome-grass, or a mixture of a hay-type alfalfa (Affinity variety) and smooth bromegrass to be used in season-long stocking systems. Four 2.02-ha pastures were seeded with smooth bromegrass on 1.21 ha of each pasture, and mixtures of either the grazing-tolerant or hay-type alfalfa cultivars and smooth bromegrass on the 0.81 ha of each pasture to be used in complementary stocking systems. All 10 pastures were divided into 10 paddocks and rotationally strip-stocked at 1.98 cow-calf units/ha with crossbred cows and calves for 120 and 141 d starting May 18, 1998 (yr 1), and May 6, 1999 (yr 2), respectively. Each year, first harvest forage was harvested as hay from 40% of all 10 pastures, this being the portions of the pasture seeded with the alfalfa-smooth brome-grass mixtures for pastures with the complementary stocking systems. In yr 1 and 2, the remaining 60% of each pasture was grazed for the first 44 and 54 d, and 100% of each pasture was grazed on d 45 to 120 and d 55 to 141, respectively. Proportions of alfalfa in the live dry matter of pastures seeded with the grazing-tolerant and hay-type alfalfa cultivars decreased by 70 and 55% in paddocks stocked season-long and by 60 and 42% in paddocks used for complementary stocking (alfalfa cultivar, P < 0.05; stocking system, P < 0.05) in yr 1, but decreased by 72% across cultivars and stocking systems in yr 2. Total (P < 0.08) forage masses in September of yr 1 and in August of yr 2 were greater in pastures in which alfalfa paddocks were stocked season-long than in those with complementary alfalfa stocking. Grazing of alfalfa in grass mixtures increased calf and total cow/calf weight gains in comparison with grazing of smooth bromegrass, but alfalfa persistence, measured as a proportion of the live dry matter, was not affected by alfalfa cultivar.     

Allocating forage to fall-calving cow-calf pairs strip-grazing stockpiled tall fescue

In a 2-yr study, we evaluated the effect of different forage allocations on the performance of lactating beef cows and their calves grazing stockpiled tall fescue. Allocations of stockpiled tall fescue at 2.25, 3.00, 3.75, and 4.50% of cow-calf pair BW/d were set as experimental treatments. Conventional hay-feeding was also evaluated as a comparison to grazing stockpiled tall fescue. The experiment had a randomized complete block design with 3 replications and was divided into 3 phases each year. From early December to late February (phase 1) of each year, cows and calves grazed stockpiled tall fescue or were fed hay in the treatments described above. Immediately after phase 1, cows and calves were commingled and managed as a single group until weaning in April (phase 2) so that residual effects could be documented. Residual effects on cows were measured after the calves were weaned in April until mid-July (phase 3). During phase 1 of both years, apparent DMI of cow-calf pairs allocated stockpiled tall fescue at 4.50% of BW/d was 31% greater (P < 0.01) than those allocated 2.25% of BW/d. As allocation of stockpiled tall fescue increased from 2.25 to 4.50% of cow-calf BW/d, pasture utilization fell (P < 0.01) from 84 +/- 7% to 59 +/- 7%. During phase 1 of both years, cow BW losses increased linearly (P < 0.02) as forage allocations decreased, although the losses in yr 1 were almost double (P < 0.01) those in yr 2. During phases 2 and 3, few differences were noted across treatment groups, such that by the end of phase 3, cow BW in all treatments did not differ either year (P > 0.40). Calf ADG in phase 1 increased linearly (P < 0.01) with forage allocation (y = 0.063x + 0.513; R(2) = 0.91). However, calf gain per hectare decreased linearly (P < 0.01) as stockpiled tall fescue allocations increased (y = -26.5x + 212; R(2) = 0.97) such that gain per hectare for cow-calf pairs allocated stockpiled tall fescue at 4.50% BW/d was nearly 40% less (P < 0.01) than for those allocated 2.25% of BW/d. Allocating cow-calf pairs stockpiled tall fescue at 2.25% of BW/d likely optimizes its use; because cow body condition is easily regained in the subsequent spring and summer months, less forage is used during winter, and calf gain per hectare is maximized.