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1.
Studies were conducted during the summer of 2 successive years (1971 and 1972) to determine the effects of gastrointestinal nematode parasitism on performance failure of stocker beef steers grazed at high stocking rates on Coastal bermudagrass pastures. During each of the 2 years, 3 groups of steers were rotated at 7- to 10-day intervals on sets of three 1.63-ha pastures from mid-May to late October. (Each group was maintained on a given set of pastures.) In the 1971 program, from mid-May to early August (phase 1) each group consisted of 48 steers for a stocking rate of 29.6 steers/ha. From early August to late October (phase 2) the number of steers per group was reduced to 36 (stocking rate of 22.2 steers/ha) to improve the plane of nutrition. In the 1972 program, 2 groups were stocked at 48 steers per group (29.6 steers/ha) and a 3rd group was temporarily stocked with 58 steers (10 additional steers) to provide 2 animals each month for necropsy evaluation of worm burdens. With exception of the monthly removal of 2 steers from the 3rd group, the stocking rate in 1972 remained intact for the entire grazing season. In 1971, the 3 groups (groups 1, 2, and 3) were treated with thiabendazole (2 doses, 16 days between doses) before grazing. Parasite burdens and levels of pasture contamination were low initially and body weight gains were good during the 1st 3 months of grazing (phase 1). In the 2nd half (phase 2) of the grazing program, 1 group of steers given free-choice supplemental feed (1% of body weight/steer each day) and treated with anthelmintic (thiabendazole; 2 doses, 18 days between doses, during August) and another group, given supplemental feed only, had significantly better weight gains than did the 3rd group, not given supplemental feed nor treated with anthelmintic. There was no weight gain advantage derived from the reduced stocking rate in phase 2. Tracer calves, which were allowed to graze on pastures, developed an increased level of infection after August. Fecal egg counts in the principal steers and recovery of infective larvae from pasture paralleled the infection level in tracer calves. Necropsy evaluation of steers from groups 1, 2, and 3 at the end of the 1971 program indicated a similarity in total worm counts, but in the group not given supplemental feed nor treated with anthelmintic there was more generalized inflammation and a greater number of lesions in the abomasum (Ostertagia) and the caudal portion of the intestine (Oesophagostomum). Steers in the 3rd group also were in poorer condition. Initial worm burdens in the 3 steer groups (groups 4, 5, and 6) were low at the start of the 1972 program. One group was given freechoice supplemental feed (0.5% of body weight/steer each day) and treated with anthelmintics (thiabendazole in the 1st dose, levamisole in the 2nd dose, 12 days between doses, in May and August) and another group was given supplemental feed throughout the summer; the 3rd group was treated with anthelmintics (in May and August)...  相似文献   

2.
To evaluate the effect of gastrointestinal parasites on grazing behaviour, herbage intake and milk production in spring calving dairy cows, 12 naturally infected control cows were compared with 12 similar animals treated on three occasions (June, July and September) with eprinomectin. The cows were blocked according to calving date, parity, live weight and milk yield during week 2 after turnout and then allocated to the treatments. The grazing area was sub-divided into two sets of 12 replicated paddocks of equivalent size and topography. Pairs of either control or treated animals were randomly assigned to graze each paddock over the duration of the study. Within each plot, the pair of cows grazed a series of 1-day paddocks, of areas calculated to provide 72 kg of herbage dry matter measured to ground level. Faecal samples were collected from each cow in April, prior to allocation, and every 28 days thereafter. Samples were submitted for counts of nematode eggs (sensitivity 1 epg) and the presence of Dictyocaulus viviparus larvae. Additional faecal samples were taken on each occasion for culture and nematode identification. Pasture samples for direct larval counts were collected at the same time as faecal sampling. Behaviour measurements on all cows were made during three periods, once before the first treatment with eprinomectin and thence after the 2nd and 3rd treatments. During each behaviour measurement period, grazing and ruminating behaviour were recorded over two 24-h periods and measurements of components of short-term intake rate were made during a morning and a late afternoon grazing meal. Milk yield was recorded daily and milk quality was recorded weekly. Live weight and body condition score were recorded on the day of allocation, the day of initial treatment and thereafter at weekly intervals until the end of the trial. The parasitological results showed low levels of faecal egg output throughout the study with group arithmetic means ranging from 0 to 6.8 epg. Faecal culture yielded predominantly larvae of the genus Ostertagia, but the following genera were also identified: Cooperia, Oesophagostomum and Trichostrongylus. Pasture larval levels were also low with peak values of 135 and 58 L3/kg DM herbage (7 August) in the paddocks grazed by the control and treated cattle, respectively. Thereafter, larval counts on paddocks grazed by treated cows declined to undetectable levels by October, while control paddocks remained at approximately 40 L3/kg DM. There was no effect of treatment on components of grazing or ruminating behaviour recorded over 24 h or on short-term intake rates. There were significant differences between components of short-term intake rates measured during the morning and afternoon grazing meals. The overall milk yield response to treatment with eprinomectin was +1.68 kg/day solids-corrected milk (SCM) (P=0.026). The overall response included significant (P<0.050) increases in mean daily SCM yield following each of the three treatments, indicating a positive response to repeated treatments at several different stages of lactation. There were no significant differences in the overall percentages of fat, protein or lactose between control and treated groups. The differences in live weight were not significant, although there was a consistent pattern throughout for the treated cows to be heavier than the controls.  相似文献   

3.
To evaluate non-chemical strategies to control pasture-borne parasites in first-season grazing (FSG) cattle, a 3-year grazing trial was conducted during 2002-2004 on naturally infected pastures on a commercial beef cattle farm in Sweden. A uniform pasture was divided in 4 equal 2 ha paddocks onto each of which 10, 5-9 months old dairy breed steer calves were allocated at turn-out in May each year. Two strategies were evaluated: (1) turn-out onto pasture which had been grazed the previous year by second-season grazing (SSG) steers, followed by a move to aftermath in mid-July (RT) and (2) supplementation with concentrate and roughage for 4 weeks from turn-out (FD). Comparisons were made with an untreated (UT), and an anthelmintic treated control group (DO). Animal parasitology and performance were monitored monthly throughout the 20 weeks grazing period. Additional sampling occasions were performed on day 9 (for coccidia) and 10 weeks after turn-out (mid-July). Due to clinical parasitic gastro-enteritis (PGE), salvage treatments were performed on all animals in group FD approximately 7 weeks after turn-out in 2003 and of three animals in group UT 5 weeks after turn-out in 2004. In 2003, the geometric mean oocyst excretion 9 days after turn-out was approximately 150,000 opg of mainly Eimeria alabamensis in group FD, and in 2004 approximately 180,000 opg in group UT. Apart from the DO group, geometric mean faecal egg counts (FEC) were between 80 and 400 epg 4 weeks after turn-out. Mean serum pepsinogen concentrations (SPC) of approximately 3.6 U tyrosine were recorded in the FD and UT groups from late August 2002. In 2003 and 2004, mean concentrations in these groups were between 4.1 and 7.2 U tyrosine 8 weeks after turn-out. By the end of the three grazing seasons the average weight gain difference compared to the DO group was for FD -29, -38 and -5 kg and for RT -4, -21 and +14 kg, and compared to the UT group -18, +2 and +22 for FD and +7, +19 and +41 kg for group RT. In conclusion, the rotation control strategy showed promising results, whereas the strategic feeding was poor from a parasite control standpoint.  相似文献   

4.
Generally, grazing endophyte-infested tall fescue (Festuca arundinace Schreb.) in the late spring and summer is not recommended because of the effects of fescue toxicosis on cattle weight gains, which can be extreme. For steers conditioned to graze tall fescue in the early spring, stocking rate (3, 4, 5, and 6 steers/ha) effects were evaluated for two methods designed to avoid poor cattle performance during the late spring and summer (compensation period). The evaluation was conducted in 1997 and 1998. During the compensation phase, one replicate of each stocking rate was randomly assigned to 1-ha pastures of eastern gamagrass (Tripsacum dactyloides L.), and the other replicate of each stocking rate remained on tall fescue; the steers were fed a 1:1 mixture of broiler litter and corn at 2.27 kg as fed/steer per d. Average daily gain for steers fed eastern gamagrass during the compensation phase declined linearly (P<0.05) as stocking rate increased, but ADG for steers fed tall fescue plus the broiler litter-corn mixture tended to increase (P<0.10) as stocking rate increased. As a result, ADG and live weight gain (kilograms per hectare) with heavier stocking rates were higher for steers fed tall fescue plus the broiler litter-corn mixture, whereas the responses at a lighter stocking rate were higher for steers fed eastern gamagrass. At the conclusion of the compensation phase in 1998, steers fed tall fescue plus the broiler litter-corn mixture had lower (P<0.05) serum prolactin levels, and a higher (P<0.05) proportion of steers fed tall fescue had rough hair coats compared with those fed eastern gamagrass. Results of this study show that, for steers grazing tall fescue pastures, either eastern gamagrass or supplementation with a broiler litter-corn mixture can provide acceptable performance, but responses are affected by grazing pressure. Symptoms of fescue toxicosis can still occur, however.  相似文献   

5.
Investigations were carried out over three grazing seasons with parasitized and treated (control) steers on irrigated and non-irrigated upland and dikeland pastures. The stocking rate in each paddock was adjusted by either adding or removing animals so as to maintain as uniform a sward and rate of grazing as possible. Animals were weighed on and off the pastures and fortnightly during the grazing seasons.

During the first grazing season clinically normal steers shedding low numbers of gastrointestinal worm eggs contaminated the parasite-free pastures sufficiently to give rise to large residual pasture infections and clinical parasitic gastroenteritis in grazing stock during the second grazing season. Worm burdens of 100,000 to 200,000 Ostertagia ostertagi and Cooperia oncophora were established in several steers showing marked clinical signs. In spite of treatments with high dosages of thiabendazole in attempts to keep worm burdens at a minimum, there was a slow but gradual buildup of pasture infections in the paddocks grazed by the control steers over the three year period.

During the second and third grazing seasons there were significant differences in the daily rate of gain between the parasitized and control animals on both upland and dikeland pastures. The parasitized groups of steers had daily rates of gain ranging from 0.29 to 0.80 pounds less than their comparable control groups.

Under Maritime conditions, irrigation did not have a consistent effect on weight gains and development of parasitism.

  相似文献   

6.
Sub-clinical parasitism in spring-born single suckled beef calves was investigated from the middle of their first grazing season until weaning or housing later the same year. The study was conducted on four beef suckler herds in southern England over a 3-year period and involved a total of 334 spring-born beef suckler calves and their dams. The animals were grazed extensively on pastures naturally infected with nematode larvae. At the start of each period of observation, faecal samples were taken from calves and cows and subjected to routine worm egg counts; calves were re-sampled at the end of the grazing season.In July in each year and at each location the calves were ranked by initial weight within sex, paired according to rank and randomly allocated to either an untreated control group or a group in which the calves were each treated with an ivermectin sustained-release (SR) bolus. The calves in both trial groups, and their dams, were grazed together until weaning or housing. The calves were weighed at the initial allocation and at the end of the study. The adult cows were not treated with any anthelmintic during the study.The faecal nematode egg counts (FECs) conducted in July showed that the suckler cows were excreting worm eggs at low concentrations: range 0-100 eggs per gram (epg), with one individual count of 500epg, 88% of the cows sampled had counts of <50epg. Similarly, the counts from the calf samples were fairly low in July: range 0-250epg, 73% of the calves sampled had counts of <50epg. By the end of the grazing season, the faecal samples from the untreated control calves showed higher values: range 0-650epg, with only 58% having an epg of <50.The average rate of daily liveweight gain in the untreated heifer calves was 0.79kg per day, the corresponding figure for the heifer calves treated with the ivermectin SR bolus in mid-summer was 0.88kg per day; the difference of 90g per day was significantly different (P=0.0118). The average rate of daily liveweight gain in the untreated bull calves was 0.91kg per day, the corresponding figure for the bull calves treated with the ivermectin SR bolus in mid-summer was 1.01kg per day; the difference was significantly different (P=0.0169).  相似文献   

7.
In a 3-yr study, 135 crossbred steers (330 ± 10 kg) were used in a randomized complete block design to evaluate corn dried distillers grains plus solubles (DDGS) fed to yearling steers as a substitute for forage and N fertilizer and its effect on N use efficiency in yearling steers grazing smooth bromegrass pastures. Steers were initially stocked at 6.8 animal unit months (AUM)/ha on nonfertilized smooth bromegrass pastures (CONT), at 9.9 AUM/ha on smooth bromegrass pastures fertilized with 90 kg of N/ha (FERT), or at 9.9 AUM/ha on nonfertilized smooth bromegrass pastures with 2.3 kg (DM) of DDGS supplemented daily per steer (SUPP). Paddock was the experimental unit, with 3 replications per treatment per year for 3 yr. Paddocks were strip-grazed, and put-and-take cattle were used to maintain similar grazing pressure among treatment paddocks during the 160-d grazing season. Steers consumed less forage (P < 0.01), but total N intake for SUPP was greater (P < 0.01) per steer and per hectare than for FERT, and both were greater (P < 0.01) than for CONT. Nitrogen retention for steers in the SUPP treatment was increased (P < 0.01) by 31% compared with N retention in the CONT and FERT treatments. Nitrogen retention per hectare for SUPP was 30 and 98% greater (P < 0.01) than N retention per hectare for FERT and CONT, respectively. Nitrogen excretion per steer and per hectare were also greater (P < 0.01) for SUPP than FERT, and both were increased (P < 0.01) compared with CONT. Animal N use efficiency was similar (P = 0.29) for steers in the CONT, FERT, and SUPP treatments. However, system-based N use improved (P < 0.01) by 144% for SUPP compared with FERT. The DDGS increased N intake and N excretion in yearling steers. However, because of improvements in BW gain and increases in stocking rate of pastures, DDGS can be a useful tool to increase the efficiency of N use in smooth bromegrass grazing systems.  相似文献   

8.
Reduced efficacy of anthelmintics in young compared with adult horses   总被引：3，自引：0，他引：3  
Studies on a Thoroughbred breeding farm in Ohio from 1982 to 1988 demonstrated the value of three anthelmintic pastes (ivermectin, oxibendazole, pyrantel pamoate) in controlling benzimidazole resistant cyathostomes (small strongyles) in adult horses. However, a comparison of drug efficacy in suppressing faecal egg counts for the full period between treatments showed a significant reduction in efficacy of all drugs in yearling horses compared with adults. Mean faecal egg counts of adult horses were generally kept below 100 eggs per gram (epg) of faeces when using oxibendazole or pyrantel pamoate at four to five week intervals and ivermectin at eight week intervals. By contrast, mean counts of young horses rose as high as 655 epg (oxibendazole), 729 epg (pyrantel pamoate) and 852 epg (ivermectin) within the same time period after treatment. Individual counts of treated yearlings sometimes exceeded 3,000 epg. Three distinct mechanisms appeared to be involved in the poor results in young horses. These were 1) anthelmintic refuge, 2) anthelmintic resistance, and 3) anthelmintic avoidance.  相似文献   

9.
Factors associated with fat necrosis in cows and tall-fescue summer toxicosis in steers were studied. In the cow study, fescue pastures were fertilized, using 3 rates of N: high N (703 to 483 kg and 0 kg of N/ha/year from broiler litter in 1972 to 1974 and 1975, respectively), moderate N, and low N (224 and 74 kg of N/ha/yr from NH4NO3, 1972 to 1975, respectively). Bermuda grass pastures were fertilized at 2 rates of N: moderate N and low N (280 and 20 kg of N/ha/year from NH4NO3, 1972 to 1975, respectively). Fat necrosis developed only in cows grazing tall fescue, with an occurrence of 60%, 8%, and 3% for high-N, moderate-N, and low-N pastures, respectively. Cows grazing the high-N fescue, and to some extent those grazing the moderate-N fescue, had clinical signs of summer fescue toxicosis. Plasma cholesterol concentrations were lowest in cattle grazing the high-N fescue, averaging 114 mg/dl, followed by 134 and 127 mg/dl in cattle grazing the moderate-N and low-N fescue, respectively. In the steer grazing study, 24 paddocks of 0.49 ha each were seeded with tall-fescue lines G1-307 or G1-306 or with tall-fescue cultivars, KY-31 or Kenhy. All paddocks were fertilized with 170 kg of N/ha/year. Serum cholesterol concentrations were lower in steers grazing on G1-307 than in steers grazing on G1-306 or cultivars. Serum total lipids followed a similar trend, with a positive correlation (r = 0.49) between cholesterol and total lipids.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
Levamisole, morantel, fenbendazole, or ivermectin was administered at 2-week intervals from May 1 through Sept 14, 1985, to breeding ewes (20 ewes/drug) infected with various gastrointestinal nematodes. All ewes had fewer gastrointestinal nematode eggs per gram of feces (epg) after 2 treatments, compared with pretreatment epg counts. Ewes administered ivermectin continued to have a low mean epg (0 to 3) throughout the study. The mean epg counts of ewes treated with levamisole increased from 3 to 483 during the study. This increase was similar to that of ewes treated with morantel (7 to 485 epg). The mean epg count of fenbendazole-treated ewes increased from 4 to 192 during the study. By the end of the study, the mean epg counts when expressed as a percentage of the pretreatment epg counts were 4% (ivermectin), 249% (fenbendazole), 627% (levamisole), and 630% (morantel). With the exception of the ivermectin-treated ewes, the epg count increased almost linearly in the ewes after the 2nd anthelmintic treatment. These data indicate that the gastrointestinal nematodes (including Haemonchus contortus) may have developed more resistance to levamisole and morantel than to fenbendazole. On the basis of the epg counts, resistance to ivermectin did not develop during the 4.5-month treatment period. The percentage of ewes shedding eggs after 2, 4, and 6 anthelmintic treatments was lowest for ewes treated with ivermectin (20%) and was similar (40%) for ewes treated with 1 of the other 3 anthelmintics. At the conclusion of the study, most of the ewes (90%) were shedding at least a small number of eggs, regardless of the anthelmintic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

11.
Four groups of 17 crossbred beef weaners were used in an experiment which extended from 14 November 1985 to 8 October 1986 (328 days). All groups began grazing on separate, contaminated pastures at a stocking rate of 5.3 cattle ha-1 and the different treatments were: Group 1, ivermectin (IVM) injectable X 1 (200 micrograms kg-1) on 14 November only, with provision for individual salvage treatment; Group 2, IVM X 3 on 14 November, 4 February and 2 July; Group 3, IVM X 2 on 14 November and 2 July; Group 4, fenbendazole (FBZ) paste X 2 (5 mg kg-1) on 14 November and 2 July. Pairs of parasite-free tracer calves were grazed on all group pastures for 1 month at the beginning of the experiment (13 November-12 December and in spring (1 April-1 May). Yearling cattle from each group were randomly selected and removed from pasture during spring (n = 2 per group, 3 April) and at the end of the experiment (n = 3 per group, 8 October) for slaughter analysis of worm population characteristics and observation of gross pathology in the abomasum and intestinal tract. At monthly intervals, all cattle were weighed and fecal egg counts, pasture larval counts and plasma pepsinogen values were determined. The results of this investigation demonstrated that three IVM treatments of weaner-yearling beef cattle during year-long grazing, were more effective than a single IVM treatment or two treatments with IVM or FBZ in the enhancement of productivity and protection from the effects of infection with nematode parasites.  相似文献   

12.
OBJECTIVE: To compare two strategies for the preparation of pastures that have reduced trichostrongylid infections during winter and spring for Merino weaners. DESIGN: A replicated field experiment was conducted over two successive years. A 'standard' strategy, comprising set-stocked wethers given anthelmintic treatments in late October and early February, was compared with a 'new' one in which intensive grazing for 1 month after each treatment and destocking for 1 or 2 months was integrated with the anthelmintic treatments. Paddocks prepared according to these strategies were set-stocked at 15 Merino weaners/ha from April to October inclusively. RESULTS: Contamination of pastures prepared according to the new strategy was substantially reduced compared to those of the standard strategy. Worm counts showed that on new strategy paddocks the numbers of trichostrongylid larvae, except Nematodirus spp, were reduced by 50 to 95% compared to standard strategy paddocks. Worm egg counts from the set-stocked weaners were reduced by about 50% on new strategy paddocks from April to October. Weaners grazing the new strategy paddocks grew significantly more clean wool (254 g, P = 0.01) and were significantly heavier in October (3.2 kg, P = 0.01) than weaners in the standard strategy paddocks. The improved production was attributable partially to better pasture growth early in winter and partially to reduced parasitism. CONCLUSION: The new strategy is a simple, practical and widely applicable example of the integration of grazing management with strategically timed anthelmintic treatments to reliably reduce trichostrongylid infections in weaners grazing during winter and spring.  相似文献   

13.
A worm control programme in which heifers were treated with anthelmintic on three occasions during autumn, was tested in the Mediterranean-type climatic environment of south-west Western Australia. The experiment aimed to determine if the treatments would prevent the heifers contaminating their pastures with worm eggs during autumn, thereby improving their growth performances the following winter. An attempt was made to measure the availability of infective larvae of abomasal worms on the heifers' pastures during early winter by counting the worms in steers, previously of low worm status, that grazed with the heifers from late autumn until the start of mating in mid-winter.

The anthelmintic treatments reduced the contamination of pasture for most of autumn. The treated heifers that grazed these pastures grew faster, and by the start of mating two months after the last treatment were about 22 kg heavier, than untreated heifers grazing contaminated pasture. At the end of mating six weeks later the difference was 45 kg in favour of the treated heifers. At this time half the heifers grazing contaminated pasture were treated with anthelmintic. The following month these heifers grew faster than those left untreated, but by late November they had not attained the wieght of the heifers grazing uncontaminated pasture.

The heifers that grazed uncontaminated pasture produced more calves the following autumn than did those grazing contaminated pasture. The abomasal worm counts of the steers, with a mean of about 46 000 worms, failed to reveal any difference between treatments in the availability of larvae of abomasal worms on pasture. However, it was concluded that the treatments probably exerted their effect on growth rates by reducing the number of infective larvae ingested by heifers grazing the uncontaminated pasture during winter.  相似文献   


14.
The effect of previous pasture management and ivermectin treatment on gastrointestinal parasitism, weight gain and carcase composition of steers was studied in the semiarid Pampeana region of Argentina from April 1986 to April 1987. Three groups, each of 15 weaned calves, were grazed on separate lucerne pastures. Group 1 control calves, which grazed paddocks previously grazed by nematode-infected weaners and yearlings with a high nematode egg output, were only medicated when heavy parasitism was recorded. Group 2 calves, which grazed paddocks previously infected by steers at least two and a half years old with low nematode egg output, were treated strategically with ivermectin. Group 3 calves, which grazed on 'clean' paddocks, were treated monthly with ivermectin. Group 1 calves showed heavy parasitism and parasitological parameters were higher than in groups 2 and 3. The liveweight gain responses of groups 2 and 3 were significantly greater than those of group 1 (P less than 0.001) during autumn, winter and early spring. At the end of the study when cattle reached market condition, the liveweight gains of groups 2 and 3 were 74.1 and 81.9 kg, respectively, greater than group 1. Carcase analyses showed significantly greater weight and killing-out percentages in groups 2 and 3 than in group 1. Reduced total bone, muscle and fat weights were observed in group 1.  相似文献   

15.
Grazing studies were conducted to determine cattle growth performance, evaluate toxicosis, and compare grazing behavior in stocker cattle grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup, Georgia-5, and Kentucky-31 tall fescue. Replicated 0.81-ha tall fescue paddocks were established at the Central Georgia Branch Station at Eatonton and the Northwest Georgia Branch Station at Calhoun during October 1998 and were stocked with beef cattle for autumn and spring periods from fall 1999 through spring 2002. Mean ergot alkaloid concentrations were higher (P < 0.01) on E+ pastures than the other treatments at both locations. At Calhoun and Eatonton, post-treatment serum prolactin concentrations were decreased (P < 0.01) on E+ compared with AR542, AR502, and E- tall fescue. Cattle on AR542, AR502, and E- pastures had lower (P < 0.05) post-treatment rectal temperatures than cattle grazing E+ tall fescue during spring at Eatonton and Calhoun. Calf ADG was higher (P < 0.05) on AR542, AR502, and E- as compared with E+ tall fescue during autumn and spring grazing at Eatonton, and at Calhoun, cattle on E+ pastures had lower (P < 0.05) ADG in both autumn and spring. Gain/hectare was higher (P < 0.05) on AR542, AR502, and E- than on E+ during autumn at Eatonton and during spring at both locations. In autumn at Calhoun, gain/hectare was greater (P < 0.05) on AR502 and E- compared with E+ tall fescue. During April, May, and June, cattle grazing E+ pastures at Eatonton spent more (P < 0.01) time idling, more (P < 0.01) time standing, and used more (P < 0.01) water than cattle on AR542 and E- tall fescue. Daily prehensions and biting rate were each higher (P < 0.01) on AR542 and E- tall fescue than E+ tall fescue in both grazing seasons. There were no differences among pasture treatments for bite size in either spring (P = 0.50) or autumn (P = 0.34). Steers grazing E+ pastures had lower DMI than steers grazing AR542 and E- pastures during spring (P < 0.10) and lower DMI than steers grazing E- pastures during autumn (P < 0.05). Daily steer water usage was decreased (P < 0.10) in E+ pastures compared with AR542 and E- pastures during late fall. These results indicate that nonergot alkaloid-producing endophyte technology is a promising option for alleviating tall fescue toxicosis in stocker cattle.  相似文献   

16.
Environmental contamination and the egg excretion pattern of the ascarid Parascaris equorum (Nematoda) was investigated in relation to anthelmintic treatment on a Swedish stud farm. Faecal samples from 15 foals, dewormed every 8th-week with a paste formulation of ivermectin at the standard dose rate of 0.2 mg/kg bodyweight, were collected at five sampling occasions between August and November 2006. In addition, soil samples were obtained from four paddocks used by these foals in November 2006. The number of eggs per gram (epg) was counted in both faeces and soil. Egg excretion started when the foals were 3-4 months, and reached the highest levels when they were approximately 5-month-old, and was then followed by a decline. Egg excretion seemed to be unaffected by ivermectin despite these foals were dewormed at regular intervals. In four out of five foals examined 10 days after treatment, epg actually increased. In contrast, when either fenbendazol or pyrantel embonate were used instead of ivermectin, treatments were effective. The number of eggs in soil was significantly higher in the permanent paddock compared to in the temporarily used soil paddock and in the summer paddocks.  相似文献   

17.
A 4-yr study was conducted to determine the effects of two grazing methods (GM) at two stocking rates (SR) on alfalfa pasture plant productivity and animal performance and to ascertain the effect of grazing systems on subsequent performance of steers fed a high-concentrate diet. Eight pasture plots (.76 ha) were seeded in 1988 with alfalfa (Medicago sativa L. var. WL225) and divided into two blocks of four pastures each. Grazing methods consisted of a traditional four-paddock or an intensive 13-paddock system. Pastures were managed to allow a 36-d rest period with an average grazing season of 110 d. The low and high SR were 5.9 vs 11.7, 5.3 vs 10.5, 5.3 vs 7.9, and 5.3 vs 7.9 steers/ha for years 1989 to 1992, respectively. Following the grazing season, steers were placed in a feedlot and fed a high-concentrate diet (81% high-moisture corn, 14% corn silage, 5% protein-mineral supplement) for an average of 211 d. There was no effect of GM on herbage mass, pasture phase ADG, or live weight gain/hectare. Increasing the number of paddocks was beneficial when herbage mass was limited and stocking rate was above 7.9 steers/ha. Increasing SR above 7.9 steers/ha decreased herbage mass and pasture-phase ADG. As forage allowance increased, pasture-phase ADG increased quadratically (R2 = .82, P < .001), reached a plateau, and then decreased. Previous grazing system did not influence the performance of steers in the feedlot or their carcass characteristics. Optimum SR is dependent on herbage mass produced.  相似文献   

18.
An effort was undertaken to replace a community of sheep endoparasites that had been classified as resistant to levamisole and albendazole with a community of more susceptible parasites using a dilution approach that could be integrated into the management of a commercial flock. For this study, pastures on this sheep farm were divided into two areas: north and south. Strategically timed anthelmintic treatments combined with pasture management reduced to nondetectable levels the endemic community of anthelmintic resistant parasites in this flock and on these pastures by early summer. A group of 102 ewes, lambs, and rams were experimentally infected with third stage larvae from the more susceptible community of parasites. These sheep then seeded the south pastures with the new parasite community, while sheep on the north pastures maintained the endemic resistant community. Despite its insensitivity as a technique for detecting anthelmintic resistance, fecal egg count reduction tests at the end of the grazing season indicated that the more susceptible parasites were present on the south pastures while resistant parasites were present on the north.The following grazing season, similar protocols were used to introduce the more susceptible parasites onto the north pastures. At the end of the grazing season, fecal egg count reduction tests indicated that the new community of parasites had become established on both groups of pastures of the farm.  相似文献   

19.
Dallisgrass (Paspalum dilatatum) is well adapted to the Black Belt physiographic region of the southeastern United States, and information on its productivity and nutritive quality as influenced by grazing management is needed. In a 2-yr grazing experiment, replicate 0.40-ha paddocks in established dallisgrass pasture were continuously stocked, or replicate 0.40-ha paddocks were subdivided into two 0.20-ha (RS2), three 0.13-ha (RS3), or four 0.10-ha (RS4) cells and rotationally stocked with yearling beef steers. Individual cells within the RS2, RS3, and RS4 treatments were stocked for 7 d followed by 7, 14, or 21 d of rest, respectively. In 2007, 3 Angus × Simmental crossbred steers (initial BW, 354 ± 6 kg) were assigned randomly to each paddock on July 16; in 2008, 3 Angus × Simmental crossbred steers (initial BW, 310 ± 6 kg) were assigned randomly to each paddock on July 14. In 2007, there was no effect (P = 0.25) of stocking treatment on ADG. Steers grazing RS4, RS2, and continuously stocked paddocks had 106 (P = 0.01), 86 (P = 0.03), and 83 (P = 0.03) kg greater total BW gain per ha, respectively, than steers grazing RS3 paddocks. In 2008, there were no differences among treatments in ADG (P = 0.43) or total BW gain per ha (P = 0.90). Correlation and regression analyses revealed positive associations between steer performance and forage concentration of CP, areal mass (kg/ha) of forage DM, and areal mass of forage CP. Results indicate that productivity and quality of dallisgrass for stocker cattle production were comparable between continuous and rotational-stocking methods.  相似文献   

20.
Two rotational grazing procedures, a four‐paddock system with a 10‐day period of stay and an eight‐paddock system with a 5‐day period of stay, were compared with continuous grazing on veld. The trial was conducted 40 km south of Bulawayo in Zimbabwe, over the six‐year period 1975–81. Using yearling steers, the treatments were applied at two year‐long stocking rates, 1.8 and 2.5 ha steer?1, and were replicated twice. Fresh groups of steers were used in the trial each year. Steer performance was virtually identical in all treatments, except continuous grazing at the lower stocking rate, in which, during the growing season, mass gains were on average 13% higher than those in the other treatments. Although floristic composition changed over the period of the trial, no differential effects of either grazing procedure or stocking rate were detected on the composition.  相似文献   

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