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1.
AIM: To evaluate and compare the effects of a variety of diets on the resistance of young, lightweight Merino lambs to repeated low-dose infections of Trichostrongylus colubriformis.

METHODS: Ninety-six 12-week-old lambs were fed balanced or unbalanced diets, and given primary (at 19 weeks of age) or both primary (at 12 weeks) and secondary (at 19 weeks) infections of T. colubriformis. Suboptimal diets were low in total intake, rumen undegradable protein, total protein, readily available carbohydrate or minerals, or supplemented with cod liver oil. Liveweight was monitored fortnightly, protection was assessed from worm counts at the end of the study (25 weeks) and faecal nematode egg counts (FEC) conducted weekly, and mast-cell response assessed at the conclusion of the study from concentration of mast-cell protease in the jejunum. Concentrations of glucose in plasma were measured at 21 weeks.

RESULTS: Diets unbalanced for total protein, readily available carbohydrate, Mo or cod liver oil each increased the worm counts after 6 weeks of secondary infection (at 25 weeks of age) and FEC during secondary infection. Low intake of a highnutrient diet restricted liveweight gain but did not affect the development of resistance, as indicated by worm counts and FEC. Defi ciency of available carbohydrate resulted in reduced liveweight gain and reduced concentration of glucose in plasma. There was a reduction in jejunal mast-cell protease concentration in sheep fed unbalanced rations.

CONCLUSIONS: The parasitology results and reduction in the concentration of jejunal mast-cell protease observed in sheep fed unbalanced rations suggest that the nutrient defi ciencies and the fi sh-oil supplement may have acted via inhibition or retardation of the host's acquired immune response. Diets unbalanced for a range of components adversely affected the acquired protective response to T. colubriformis to a similar extent and appeared to involve a similar mechanism as each other. The quality of the diet was more important than quantity for the development of resistance, and soluble carbohydrate was an essential component.  相似文献   

2.
Vaccination with irradiated Trichostrongylus colubriformis larvae produced a high level of immunity, as judged by faecal egg counts and worm burdens following challenge with normal larvae, in nine of ten sheep aged 10 months. In lambs aged 3 months, vaccination was less effective. Some lambs developed partial immunity, but others did not respond.Serum levels of antibodies to T. colubriformis acetylcholinesterase reflected the extent of antigenic exposure rather than the degree of immunity acquired, and there was no evidence that the unresponsiveness of the lambs was due to a deficiency in antibody production.Unresponsiveness was not associated with the numbers of circulating lymphocytes, monocytes or granulocytes, or with the numbers of mast cells, eosinophils and neutrophils at the site of infection. However, there were many globule leucocytes in the intestinal mucosa of adult sheep which were resistant to challenge infection. On the other hand, few of these cells were found in vaccinated lambs which generally gave a poor response to challenge.  相似文献   

3.
Merino wether lambs were individually confined and fed a basal diet of oaten chaff containing essential minerals which was untreated or contained 3% urea. Within each dietary group animals were orally infected with either 200 H. contortus (H), 1000 T. colubriformis (T) or both species (H + T) thrice weekly or remained uninfected (C). Weight gain, wool production, and parasite burden were measured over a 19-week period. Sheep on the diet containing urea gained more weight, consumed more feed and grew more wool of higher fibre diameter than their counterparts given no urea. On both diets uninfected sheep consumed more feed than infected sheep and the sheep given no urea and infected with both H and T worm species consumed the least feed. Parasitised sheep gained less weight than uninfected control sheep. Sheep with urea in their diet had lower faecal egg counts when infected with H alone or with H and T but there was no effect of urea on egg count of sheep infected with T alone. In contrast, T numbers after slaughter were reduced in sheep fed diets containing urea whereas H numbers were not affected by diet. It was concluded that supplementation with urea can increase resilience to parasitism thereby improving production and also enhance resistance mechanisms against worms in young sheep on low quality roughage diets. These responses can be partly attributed to stimulation of feed intake, presumably due to enhanced ruminal digestion, but also to elevated rumen NH3-N levels which would be expected to have increased rumen microbial protein synthesis and availability to the intestines.  相似文献   

4.
OBJECTIVE; To show that low bodyweight is a predisposing cause of high Trichostrongylus colubriformis and Haemonchus contortus burdens and egg counts in Merino lambs. DESIGN: A comparison was made, among lambs of different bodyweights, on the effect on immunity of a primary or secondary viable infection with T colubriformis or H contortus larvae. PROCEDURE: Sixty-one Merino lambs, 1 or 6 months of age, were penned indoors and given primary, or both primary and secondary, infection of T colubriformis or H contortus. Faecal egg counts, worm counts and parasite-specific immunoglobulin concentrations were examined for their relationships with bodyweight. RESULTS: Bodyweight at the start of a primary infection was correlated with worm burden, worm fecundity and jejunal IgA antibody concentration. Merino lambs weighing less than 23 kg at the time of first exposure to T colubriformis or H contortus had impaired ability to develop protective mucosal immunity and to resist homologous challenge. CONCLUSION: If the goal is to ensure that lambs develop immunity before weaning, then every endeavour should be made to achieve the combination of critical bodyweight and exposure to moderate levels of nematode infection as soon as possible.  相似文献   

5.
Four Merino wethers were fed ad libitum on a roughage diet comprised of equal parts of chopped lucerne hay and oaten chaff. The sheep received continuous infusions of DL-methionine into the rumen; the daily dose increasing from 0 g (control treatment) up to 30 g in 3 g amounts at weekly intervals.
Dry matter intake (DMI) fell below the control level when 24 g/day of more of the amino acid was infused, while plasma free methionine levels increased substantially when 30 g/day was given.
There was no effect of DL-methionine supplementation on the bodyweight of the animals. However, when 30 g/day of DL-methionine was infused one animal died and the acute condition of 2 others necessitated their slaughter. Significant lesions included acute nephrosis and haemolytic anaemia, with milder changes in the liver and pancreas.
This report indicates that sheep are unlikely to show the kind of chronic methionine toxicity seen in other species.  相似文献   

6.
The study was conducted at Sinana Agricultural Research Center, Ethiopia to assess the supplementation of graded levels of vetch (Vicia dasycarpa `lana’) and lucerne (Medicago sativa,’ Hunter river’) hay on feed intake, digestibility and body weight (BW) change of Arsi-Bale sheep fed urea treated barley straw (UTBS). A 7 day- digestibility and a 90 day- feed intake trials were conducted using 28 and 35 sheep, respectively. The experimental design was a randomized complete block design with seven dietary treatments that consisted of feeding UTBS (T1) as the control treatment, UTBS plus 150, 250 and 350 g dry matter (DM) per day of vetch for T2, T3, T4, respectively and UTBS plus 150, 250 and 350 g DM per day of lucerne for T5, T6 and T7, respectively. Intake of UTBS was not affected (P > 0.05) by inclusion of lucerne hay at 25–35% of daily DM intake. The supplements increased daily intake of total DM, organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF) and metabolizable energy (ME) (P < 0.001) as well as apparent digestibility of DM, OM (P < 0.001), NDF (P < 0.01), ADF, crude protein (CP) (P < 0.05) and daily BW gain (P < 0.001). Supplementation with lucerne than vetch hay promoted higher (P < 0.001) CP and ME intakes and daily BW gain. Feeding with the UTBS without supplementation was enough to meet the maintenance requirements of the sheep and allow small BW gain. The results of the study showed that urea treatment of barley straw in conjunction with supplementation of lucerne or vetch hay could serve as a useful strategy in improving smallholder sheep production in the tropics.  相似文献   

7.
Selection of sheep for resistance to gastrointestinal nematodes has been considered as one option to control nematode infection. It is essential to understand the influence of selection on the diversification of protein metabolism in individual tissues. In this experiment we examined fractional protein synthesis rate (FSR) and polyamine (putrescine, spermidine and spermine) and histamine concentrations in tissues of Merino sheep selected for low faecal worm egg count (parasite resistance) and control sheep. Sixty 18-month-old Merino rams, 40 from the resistant flock and 20 from the control line, were kept in individual pens of an animal house and fed ad libitum. Half of each genotype group were dosed orally with infective larvae of Trichostrongylus colubriformis and Ostertagia circumcincta thrice weekly to deliver 10,000 larvae from each species per week for 18 weeks. At the end of week 18, FSR was measured using a flooding dose of l-[ring-d5]phenylalanine, and polyamine concentrations were determined in all the sheep. Regardless of sheep genotype, the nematode infection significantly increased FSR in the mesenteric lymph nodes (37.0% vs. 32.6%/day, P < 0.01) and abomasal lymph nodes (28.8% vs. 16.0%/day, P < 0.001) and the bone marrow (5.12% vs. 3.96%/day, P < 0.01), but reduced FSR in skin (17.4% vs. 20.6%/day, P < 0.001), muscle (2.46% vs. 2.73%/day, P < 0.05) and liver (24.1% vs. 25.8%/day, P < 0.05). Nematode infection did not affect FSR in the jejunum. Polyamine concentrations in the tissues were generally increased by the infection (P < 0.05) except for a decline in spermine concentration in the muscle (P < 0.01). Overall there was no significant effect of selection for nematode resistance on tissue FSR or the concentration of amines. It was concluded that nematode infection resulted in a divergence of protein synthesis between tissues, and selection for nematode resistance in Merino sheep did not result in significant change in tissue protein synthesis compared with control sheep.  相似文献   

8.
The epidemiology of H. contortus was studied for 21 months in 80 set-stocked Merino ewes and their grazing in an endemic area in Kenya. Observations included faecal egg counts (weekly), worm burdens (monthly), haematological indices and clinical signs. The levels of infective larvae on the pasture were estimated using tracer sheep.The classical acute form of haemonchosis was seen with equal intensity in both ewes and lambs during periods of high rainfall and self-cure was confirmed as a flock phenomenon which occured simultaneously on one occasion in sheep of all ages.Not previously recognised were the uniformity of the faecal egg counts in both ewes and lambs over long periods when the worm burdens fluctuated greatly, the marked decrease in worm burdens without the occurence of classical self-cure during periods when the intake of infective larvae was low, and the inverse relationship between the individual worm-weight and the total worm population. It was also concluded that one of the most significant features of haemonchosis is not the acute syndrome so characteristically associated with the disease, but the fact that a moderate infection of a few hundred worms persisting over a period of several months will produce chronic anaemia and, ultimately, severe loss of bodily condition and deathes in ewes and lambs grazing on poor quality pasture.  相似文献   

9.
An experiment was undertaken between July and November 1985 in East Gippsland, Victoria, to determine the efficacy of an intra-ruminal controlled-release albendazole capsule against naturally acquired worm burdens and larval challenge in Merino hoggets. Two groups of 20 sheep, one group untreated, the other dosed with a capsule were grazed together; 5 sheep from each group were slaughtered for total worm counts 30 and 101 d after capsules were administered. Serum anthelmintic concentrations, faecal egg counts and body weights were monitored. Most capsules were exhausted within 91 d of administration. During the estimated 80 d for which they remained active the capsules were highly effective against the benzimidazole-susceptible worm populations. Faecal egg counts were reduced to zero and total worm populations were reduced by over 97% 30 d after administration. By 101 d egg counts were increasing and worm counts indicated that sheep were becoming reinfected. Sheep treated with the capsules grew faster than those not treated.  相似文献   

10.
为明确燕麦干草与青贮玉米不同组合对绵羊生产性能和消化代谢的影响,选用9只体重和体况相似并已安装永久性瘤胃瘘管的杂种(美利奴♂×蒙古羊♀)公羊为试验动物,按燕麦干草占粗饲料百分比配制3组饲粮,A1组(100%青贮玉米),A2组(50%青贮玉米+50%燕麦干草)和A3组(100%燕麦干草)。试验采用3×3拉丁方设计,饲粮精粗比为35∶65,研究不同燕麦干草和青贮玉米组合对饲料转化率、消化代谢、表观消化率及氮存留率的影响。结果表明:(1)饲粮中添加燕麦干草对绵羊干物质采食量无显著影响(P0.05),但添加燕麦干草后绵羊日增重显著提高(P0.05),绵羊采食添加50%燕麦干草的饲粮其饲料转化率得到显著提高(P0.05);(2)饲粮中添加燕麦干草对绵羊消化代谢影响显著,添加50%燕麦干草后绵羊的DM、OM、NDF、ADF和N的表观消化率以及N存留率均显著提高(P0.05),添加100%燕麦干草组与100%青贮玉米组各指标之间差异不显著(P0.05)。3个处理组中,以A2组效果最佳,显著提高了绵羊的生产性能,改善了其消化代谢。  相似文献   

11.
Worm egg counts of yearling Angora or Merino wethers grazing in mixed flocks at either 4/ha or 8/ha were observed over a 5 month period. Based on faecal egg counts infection levels in the sheep increased for the first 3 months and then decreased as the animals developed resistance. Egg counts in the goats did not decrease during the experiment. Post mortem worm counts indicated that there was a significant host species--stocking rate interaction on worm burdens of Haemonchus contortus adults and Ostertagia circumcincta adults and larvae. Goats had more H. contortus and O. circumcincta adults than sheep at the 8/ha stocking rate. At 4/ha goats had fewer O. circumcincta fourth stage larvae than sheep. There was no stocking rate effect on the numbers of Trichostrongylus axei or T. colubriformis. Sheep had more T. axei and fewer T. colubriformis than goats.  相似文献   

12.
This study aimed to quantify production loss due to larval challenge in sheep administered a controlled release albendazole capsule (CRC) and thus determine the suitability of CRC treated sheep as a proxy for worm-free sheep in grazing experiments. The experiment used an incomplete 2 × 3 latin square design with 81 Merino wethers. Sheep were either infected (INF) with mixed oral infection of albendazole-susceptible Haemonchus contortus, Trichostrongylus colubriformis, and Teladorsagia circumcincta (initial bolus then thrice weekly maintenance) or remained uninfected (UINF). Worm control treatments were with a CRC (CRCT), threshold treatment with a short-acting anthelmintic when worm egg count (WEC) exceeded 1500 epg (TT) or untreated (UT). The experiment was conducted in two 63-day periods (separated by a 14 day washout period) with infection treatments swapped between periods. A subset of animals was killed at the end of each period for worm counts and tissue sampling. Faecal worm egg count in UINF-UT reached 10,204 and 6078 epg at day 63 in periods 1 and 2, respectively, and remained 0 throughout in the CRT treatments. There was no difference in live weight gain or wool growth of INF-CRCT sheep (67 and 70 g/d) relative to UINF-CRCT (67 and 76 g/d). Live weight gain was significantly lower in INF-UT (27 g/d) and INF-TT (55 g/d) than UINF-UT (88 g/d) or UINF-TT (81 g/d) treatments. During the first infection period, greasy fleece weight growth was significantly lower in INF-UT (6.33 g/d) and INF-TT (6.37 g/d) than UINF-UT (7.80 g/d) or UINF-TT (7.32 g/d) treatments. The effects of infection on production persisted in INF-UT, but not INF-TT sheep for several weeks after termination of infection. Eosinophil counts were elevated in all infected groups and the antibody response to T. colubriformis was greater in INF-CRCT and INF-TT groups compared to uninfected sheep. Together, these results indicate that larval challenge in sheep with a CRC is mildly immunogenic but is not associated with production loss. The results also showed that the CRC itself reduced live weight gain and that anthelmintic treatment at a WEC threshold of 1500 epg reduces production loss during infections and prevents persistence of adverse effects following infection.  相似文献   

13.
Objective Develop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by leaving some adult sheep untreated, would delay development of anthelmintic resistance without compromising nematode control. Procedures Compare model predictions with field observations from a breeding flock in Armidale, NSW. Simulate the impact of leaving 1–10% of adult sheep untreated in diverse sheep‐grazing systems. Results Predicted populations of Tr. colubriformis and T. circumcincta were less than those observed in the field, attributed to nutritional stress experienced by the sheep during drought and not accounted for by the model. Observed variation in faecal egg counts explained by the model (R2) for these species was 40–50%. The H. contortus populations and R2 were both low. Leaving some sheep untreated worked best in situations where animals were already grazing or were moved onto pastures with low populations of infective larvae. In those cases, anthelmintic resistance was delayed and nematode control was maintained when 1–4% of adult stock remained untreated. Conclusions In general, the model predicted that leaving more than 4% of adults untreated did not sufficiently delay the development of anthelmintic resistance to justify the increased production risk from such a strategy. The choice of a drug rotation strategy had an equal or larger effect on nematode control, and selection for resistance, than leaving 1–10% of adults untreated.  相似文献   

14.
Effects of protein supplementation and of nematode control on production responses in young grazing sheep and on nematode population dynamics were assessed. Young Merino wether sheep (n = 270) were allocated to one of three supplementation (Su) treatments and one of three regimes of nematode control (drench, Dr) in a factorial design. Each of the nine treatments was replicated three times in a randomised complete block. Animals received no supplement (SuO) or were given supplements at a level equivalent to 200 g day−1, fed three times a week. The supplements contained 25% lucerne meal with either 75% sunflower meal (Su1) or 75% formaldehyde-treated sunflower meal (Su2). Nematode control regimes were: not drenched unless survival of individual animals was threatened (DrO); drenched according to a strategic drenching programme (Dr1); treatment with a controlled-release albendazole capsule (Dr2). Infections with Haemonchus contortus were suppressed by use of closantel. Due to drought conditions and lack of pasture growth, lucerne hay was fed to all sheep from Week 14 onwards (350 g per head per day, fed twice a week). Supplementation reduced the need for ‘survival drenching’ in Dr0 sheep considerably. Live-weight gain was increased significantly by supplementation with Su1 or Su2 during the 36-week experiment. Undrenched animals given Su1 or Su2 tended to grow faster than unsupplemented animals in the Dr1 and Dr2 groups. Greasy wool production and fibre diameter were increased by supplementation and anthelmintic treatment. Faecal worm egg counts (FEC) in undrenched sheep were significantly lower for Su1 and Su2 sheep than for Su0 sheep. There were no effects of supplementation on FEC in Dr1 or Dr2 sheep. Worm burden was generally unaffected by supplementation, while the drenching treatments Dr1 and Dr2 reduced worm burden at Week 16 and to a lesser extent at Week 27. Trichostrongylus colubriformis was the predominant nematode species, with smaller numbers of Nematodirus spp., Trichostrongylus vitrinus, Trichostrongylus axei and Ostertagia circumcincta also present. It was concluded that supplementary feeding with protein meal substantially reduced production losses attributable to nematode infections in young grazing sheep. This appears to be due to an enhanced resilience of the host, rather than any major changes in development of protective immunity.  相似文献   

15.
Nonconventional agro-industrial by-products such as traditional liquor residues (locally called katikala atella) are widely used by livestock farmers in Ethiopia. The objective of this experiment was to evaluate the supplementary value of katikala atella and malt sprout (MS) on performance of sheep fed a basal diet of Rhodes grass hay. Thirty intact yearling male sheep with an average initial body weight of 17.4?±?0.74 kg (mean?±?SD) were assigned to the treatments in a completely randomized block design: atella alone (T1), 75 % atella?+?25 % malt sprout (MS) (T2), 50 % atella?+?50 % MS (T3), 25 % atella?+?75 % MS (T4), MS alone (T5), and Rhodes grass hay alone (T6). Grass hay was fed ad libitum to all treatments. The total dry matter (DM) and organic matter (OM) intakes of sheep fed T4, T5, and T3 diets were the highest (P?<?0.05), while sheep receiving T6 had the lowest DM intake. The highest (P?<?0.05) total crude protein (CP) intake was for sheep fed T5 diet, while the lowest was for those fed T6 diet. Sheep receiving T3 diet had higher (P?<?0.05) DM, OM, CP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibility as compared with those fed T1, T2, and T6 diets. Sheep supplemented with 50–100 % malt sprout had similar (P?>?0.05) DM, OM, CP, NDF, and ADF digestibility. The highest (P?<?0.05) average daily gain was for sheep fed T3, T4, and T5 diets, while sheep in T6 lost body weight. Sheep fed T5 diet had the highest (P?<?0.05) nitrogen retention, while those fed T6 diet had the lowest. The study has shown that a mixture diet consisting of equal parts of katikala atella and malt sprout (T3) are found to be superior in most of the required nutrient characteristics.  相似文献   

16.
Eleven native sheep, 1–2 years old, of both sexes were randomly divided into two groups, 6 sheep being allocated to the experimental group and 5 serving as controls. The sheep in the experimental group were fed 80% Tribulus terrestris and 20% alfalfa hay and wheat straw, while the control sheep were given a mixture of 40% alfalfa hay and 60% wheat straw. Clinical signs of hepatogenous photosensitivity were observed from day 11, including reddening and crust formation on the muzzle, nose, ears and eyelids, depression, weight loss, icterus, conjunctivitis, and yellow discoloration of the urine. Laboratory findings on weekly samples indicated significant differences (p<0.05) in white blood cell count, total plasma protein and fibrinogen, total and direct bilirubin, blood urea nitrogen and creatinine concentrations, and aspartate aminotransferase and alkaline phosphatase activities. There were no significant differences in the packed cell volume, in the neutrophil, lymphocyte or eosinophil counts, or in the serum calcium, phosphorus, potassium, sodium or chloride concentrations. At necropsy of the experimental animals, there were various degrees of generalized icterus and the livers were swollen and discolored by bile pigment. Histopathological examination revealed varying amounts of crystalloid material in the bile ducts and renal tubules, hepatocellular degeneration, biliary fibrosis and proliferation, renal tubular necrosis and focal necrosis of cardiac muscle.  相似文献   

17.
The effects of Arctotheca calendula (capeweed) on digestive function in the rumen, caecum and colon of sheep were studied. Three groups of 2-year-old Merino wethers were compared: 13 grazing capeweed-free pasture for 23 days; 8 fed 700 g of lucerne hay daily for 18 days, and 13 fed 6 kg of freshly cut capeweed (dry matter 11.3%) daily for 7 days. Capeweed did not cause diarrhoea and based on measurements of products of fermentation in the rumen, the plants were as nutritious as pasture containing grasses and clovers. The main disadvantage of capeweed in this single feeding trial was that sheep eating it lost body weight due to their inability, or lack of incentive, to consume enough dry matter.  相似文献   

18.
The possible existence of breed differences in the response of sheep to primary infection with Haemonchus contortus was examined by comparing worm establishment and pathogenic effects of the parasite in Awassi and Merino sheep of haemoglobin type B infected with 500 third stage H. contortus larvae per kg body weight. The results showed that the Merino sheep had lower faecal egg counts and worm burdens and suffered less severe clinical disturbances than sheep of the Awassi breed. This suggests that genetic resistance operates primarily at the level of worm establishment.  相似文献   

19.
OBJECTIVE: To assess the efficacy of copper oxide wire particles (COWP) for the control of H contortus infections in grazing sheep. PROCEDURE: In experiment 1, 40 worm-free Merino hoggets (11 to 12 months of age) were divided into four equal groups and allocated to separate 0.8 ha pasture plots. Two groups then received 2.5 g COWP whereas the other two groups were untreated. From 1 week after COWP treatment all lambs received a weekly infection of 2000 H contortus larvae. At week 8, six sheep from the untreated group were then allocated to two groups and treated with either 2.5 or 5.0 g of COWP to establish therapeutic efficacy of treatment. Experiment 2 followed a similar protocol but was conducted with 40 worm-free Merino lambs (3 to 4 months of age) and no assessment of therapeutic efficacy was made. Results: In experiment 1 no significant difference in faecal worm egg counts was observed between treatments and faecal worm egg counts remained less than 3000 epg in all animals. Total worm counts were reduced by 37% by COWP treatment (P = 0.055). Both 2.5 g and 5.0 g doses of COWP at 8 weeks of infection reduced faecal worm egg counts by > 85% with the higher dose giving an earlier response to treatment. In experiment 2, faecal worm egg counts at 4 and 6 weeks were reduced by more than 90% in the COWP treated lambs and worm numbers were 54% lower after 6 weeks when all remaining untreated lambs had to be treated for haemonchosis. Mean faecal worm egg counts in the COWP lambs remained below 3500 epg and clinical disease did not develop in the majority of lambs before the end of the experiment at 10 weeks. CONCLUSION: Treatment with COWPs appears to have the potential to reduce establishment and worm fecundity of Haemonchus spp for an extended period and may offer livestock producers a supplementary means of reducing larval contamination of pasture particularly in areas where anthelmintic resistance is a problem and copper supplementation is likely to be beneficial.  相似文献   

20.
The effects of non-genetic factors on responses to gastrointestinal nematode infections were examined in artificially infected indigenous Horro and Menz lambs in the central highlands of Ethiopia. The experiment involved lambs of two sexes, infection and monitoring regimens (3 levels), dam parity (4 levels) and birth types (2 levels). A total of 152 weaner lambs (103 Menz and 49 Horro) were used. Endoparasite challenge involved three infection periods (primary, secondary and tertiary) each separated by an anthelmintic treatment. Data were collected on faecal egg counts (FEC), packed cell volume (PCV), worm count, and weight gain. Female lambs were found to harbor lower numbers of T. colubriformis counts and had lower (p < 0.01) FEC in tertiary infection compared to males. Younger animals were more susceptible to the nematode infections than older animals as measured by all the parameters studied (p < 0.01). Twins had higher FEC in both secondary and tertiary infections compared to singles. Lambs born to dams of first parity had higher PCV and lower FEC values during the tertiary infection compared to other parities. These results would be used as basic information in designing a more rational control strategy and should also help to advise on better management care for less resistant sheep.  相似文献   

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