首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
An experiment was conducted to examine the effect of dietary protein on the pathophysiology iof acute haemonchosis in Finn Dorset/Dorset horn lambs.

Erythrokinetic and metabolic studies using 51Cr-red cells, 59Fe-trasferrin and 125I-albumine and digestive efficiency and nitrogen balance measurements wer conducted between 19 and 39 days after infection. Identical radioisotopic and nutritional studies were conducted later on pair-fed control lambs.

The results demonstrated that lambs on a law protein diet (88 g crude protein (CP) kg−1 dry matter (DM)) were less able to withstand the pathyphysiological consequences of infection with 350 Haemonchus contortus larvae kg−1 body weight than lambs given a high protein (170 g CP kg−1 DM) diet, despite similar worm budens.

Erythrokinetic studies indicated that abomasal blood loss was similar in both groups of infected lambs, and circulating red cell volumes were reduced and plasma volumes were expanded to a similar degree in both groups. The majority of infected lambs in both dietary groups responded equally well to the gastric haemorrhage by increasing the rate of red cell production and their absorption of dietary iron was greater than in the control lambs. Albumin catabolism was increased in both groups of infected lambs, particularly in those given the low protein diet.

Within each dietary group there were no differences in the digestibilities of the various proximate fractions of the experimental diets and no differences in the urinary of faecal nitrogen losses between infected lambs and their pair-fed control. However, loss of appetive was a major feature of the disease, particularly in the lambs given the low protein diet and this feature appeared to be crucial in determining the ability of the infected sheep to withstand the pathophysiological effects of the parasite.  相似文献   


2.
An experiment was conducted to examine the influence of dietary protein on parasite establishment and pathogenesis of Haemonchus contortus in lambs of two breeds. Finn Dorset and Scottish Blackface. The lambs were introduced to high protein (170 g crude protein (CP) kg-1 dry matter (DM) or low protein (88 g CP kg-1 DM) diets at three months old and infected one month later with 125 larvae (kg bodyweight)-1. Blood and faecal samples were collected for analysis and bodyweights recorded weekly. The lambs were killed 20 weeks after infection. A second experiment was conducted in Blackface lambs solely to determine the influence on parasite establishment of the high and low protein diets following infection with 125 larvae kg-1. These lambs were killed five or 14 weeks after infection. Results showed that in Scottish Blackface lambs dietary protein did not significantly influence the establishment of H contortus. However, in Finn Dorset lambs dietary protein may have influenced parasite establishment since lambs on the low protein diet had a higher faecal egg output four weeks after infection and more severe clinical signs than infected lambs of the same breed on a high protein diet.  相似文献   

3.
A benzimidazole-resistant strain of Ostertagia circumcinta (HFRO) was used experimentally to infect lambs. The level of resistance, measured by an egg hatch assay, was studied throughout each infection and also after treatment of the lambs with fenbendazole. The HFRO strain was highly resistant to benzimidazoles. There was day-to-day variation in the level of resistance throughout a single infection with a high level of resistance in the early part of the infection, around Day 27 post-inoculation of infective larvae, falling to a lower level later in the infection. Egg hatch assays on the 3 days immediately post-treatment with fenbendazole showed the resistance level was high then resistance fell to the pre-treament level after 7 days. Selection for benzimidazole resistance using fenbendazole treatment at the normal dose rate of 5 mg kg−1 over five passages of the HFRO strain in lambs failed to increase the resistance level. Storage of larvae over a 5-months period at 4°C, prior to infection of lambs, did not produce any alteration in the resistance Level. The possible reasons for the variations in resistance found with the HFRO strain are discussed along with the implications for sheep parasite control and further development of benzimidazole resistance.  相似文献   

4.
Field trials were undertaken to compare nematode population dynamics, lamb productivity and levels of breech soiling in experimental flocks of Romney lambs selectively bred for increased resistance or susceptibility to nematode infection. In each year of the 2 year study, spring-born ewe lambs derived from Wallaceville Animal Research Centre's divergent nematode-resistant and nematode-susceptible breeding lines were grazed as separate flocks on matched farmlets from weaning (at 3 months old) until they were approximately 10–11 months old. Allocation of farmlets was reversed between Years 1 and 2 of the study to account for any possible paddock-related effects. Within each year both flocks were subjected to identical management conditions, including anthelmintic treatment (which was administered only when the overall mean faecal worm egg count measured across both genotypes reached 1500 eggs g−1). In both years, by mid-autumn (April) nematode larval infestation levels on pasture were approximately 5–6-fold greater on the farmlet grazed by susceptible (S) genotype lambs than on that grazed by their resistant (R) counterparts (Year 1: 2506 cf. 544 larvae Kg−1 herbage; Year 2: 431 cf. 74 larvae kg−1 herbage). This led to 51-fold and 56-fold differences in faecal egg count between R and S lambs by late autumn (May) and winter (July) in Years 1 and 2, respectively. Although mean growth rates were similar in the R and S lambs over summer (while pasture infestation levels on the farmlets were still in the process of diverging), significantly higher growth rates occurred in the R than in the S lambs over autumn-winter in both years of the study (P < 0.01). In contrast, no significant differences in growth rate occurred in either year between male lambs derived from the nematode-resistant and nematode-susceptible breeding lines which were grazed together on another area of the Wallaceville farm from weaning until late autumn. Despite the substantially lower pasture infestation levels encountered by the R ewe lambs, they nevertheless temporarily suffered more breech soiling (dags) than their S counterparts (P < 0.01) in both years. Yearling fleece-weights of the R and S genotypes did not differ significantly in either year. Although the results of our study confirmed that there are potentially significant epidemiological benefits to be derived from breeding sheep for resistance to nematode infection, these benefits did not appear to be associated with large advantages in animal performance. Further work is needed to establish how these results should be interpreted with respect to anthelmintic drench requirements of genetically resistant animals.  相似文献   

5.
Medicinal plants have been investigated for their anthelmintic properties and shown to be effective against eggs and larvae of gastrointestinal nematodes. The aim of this study was to evaluate the efficacy of the Lippia sidoides essential oil (LsEO) on sheep gastrointestinal nematodes. Initially, 44 naturally infected sheep were divided and treated with 200 μg kg−1 ivermectin and 230 and 283 mg kg−1 LsEO, respectively, plus the control. Fecal samples were collected from each animal to determine epg at 7, 14 and 21 days after treatment. In another test, 21 sheep were distributed and treated with 200 μg kg−1 ivermectin, 283 mg kg−1 LsEO and the control, respectively. Seven days after treatment, they were euthanized and necropsied to count and identify the nematodes from the abomasum, small and large intestines. In the first test, the efficacy of 230 and 283 mg kg−1 LsEO and ivermectin was 38%, 45.9% and 40.2%, respectively, 7 days after treatment, and 30%, 54% and 39.6%, respectively, 14 days after treatment. In the second experiment, the respective efficacy of 283 mg kg−1 LsEO and ivermectin was 56.9% and 34.4% against Haemonchus spp., and 39.3% and 63.6% against Trichostrongylus spp.  相似文献   

6.
The relation between the faecal egg count and the worm burden was investigated in 104 steers of three breeds, 9–24 months of age, which were subjected to natural infection with nematode larvae from pasture at The National Cattle Breeding Station near Rockhampton in central Queensland. The worm species found were Cooperia spp., Haemonchus placei, Trichostrongylus axei, Oesophagostomum radiatum and small numbers of Bunostumum phlebotumum.

The faecal egg count was found to be a reliable measure of the size of the worm burden. Steers slaughtered at 24 months of age had 90% fewer worms and 96% fewer eggs g−1 faeces (P < 0.001) than those slaughtered at 9 months of age. Adjusted for age, the estimated faecal egg count increased 14 times (95% confidence limits 7.2, 35) for each 10-fold increase in estimated worm numbers.

The proportion of each species of larvae obtained from faecal culture (larval differential count) was related to the composition of the worm burden as measured by the proportion of worms in selected maturity categories and in selected length categories for each species (P < 0.001).  相似文献   


7.
Mixed-sex groups of three-month-old Finn Dorset and Dorset Horn lambs were given complete diets containing either high or low protein. A trickle infection with Haemonchus contortus of 200 larvae, given three times a week, began one month later for a 17 week period. Erythrokinetic, metabolic, digestibility and balance studies were conducted with the male lambs during weeks 12 to 14 of the infection. Clinical signs of haemonchosis became evident only in the low protein diet group. The infection was characterised by severe macrocytic anaemia, hypoproteinaemia, hypoalbuminaemia, reduced survival, high egg counts and a significantly greater worm burden. In the high protein diet group many lambs developed resistance to further infection in contrast to the low protein group in which no resistance developed. Live-weight gain was not affected by infection in the high protein diet group but decreased in the lambs given the low protein diet compared with uninfected controls. However, infection did not appear adversely to affect the digestive efficiency, nitrogen retention or iron absorption in either dietary group although loss of appetite occurred in the low protein group. Examination of a sample joint from the carcases showed infection was associated with a marked reduction in muscle mass in lambs given the low protein diet relative to the control animals.  相似文献   

8.
The persistent efficacy of four commercially available macrocyclic lactones (ML) in maintaining reduced faecal egg counts in cattle grazing naturally infested pastures was evaluated in 44 zebu animals aged 1–2 years in Zambia. The study started in February (rainy season) when the strongyle egg output was increasing. Four days before the start of the trial, all animals were treated with a double dose of oxfendazole. They were then divided into five groups which were again treated on day 0. Groups A, D, I and M received 0.2 mg kg−1 of abamectin, doramectin, ivermectin and moxidectin, respectively. Animals of group C received albendazole (7.5 mg kg−1). Faecal samples were collected twice a week for egg counts and larval differentiation. Faecal egg counts in the C group increased from day 21 onwards and plateaued from day 42 between 180 and 380 eggs per gram. The main genera found in cultures were Cooperia (90%) and Haemonchus (7%). Faecal egg excretion in groups M, A, D and I started on day 35, 42, 42 and 45, respectively. subsequently and until day 84, average counts in these four groups were always significantly lower than in group C. Compared with albendazole, all four ML gave over 95% reduction in cumulative faecal egg counts for 42 days after treatment. The percentage efficacy was still over 84% by day 84 when an average cumulative egg count of 11 320 eggs per gram faeces was calculated in group C. In addition, there was no significant difference in efficacy between the four ML groups at any of the sampling dates. During the trial no significant difference in weight gain between any of the groups was observed.  相似文献   

9.
The effect of xylo-oligosaccharides (XOS), a probiotic culture of Saccharomyces cerevisiae (SC) and the combined administration of XOS and SC on the piglet intestinal microbiota was investigated. Twenty four weaned piglets were fed during 4 weeks with one of the following diets: (BD) basal diet; (BD + XOS) basal diet supplemented with xylo-oligosaccharides (20 g kg− 1); (BD + SC) basal diet supplemented with S. cerevisiae (6 × 109 CFU kg− 1); and (BD + XOS + SC) basal diet supplemented with xylo-oligosaccharides and S. cerevisiae. Samples from the ileum, caecum and colon were collected and analysed for total anaerobes growing in XOS or glucose, xylose and arabinose (GXA) containing media. Specific primers were used to evaluate differences in Bifidobacterium and Lactobacillus populations and ERIC PCR to fingerprint the intestinal microbiota.

The lowest number of culturable bacteria was obtained from the ileum of animals fed BD + XOS. The highest PCR titres with Lactobacillus group-specific primers in BD and BD + SC were obtained in the caecal contents. In XOS-supplemented diets the PCR titres were increased or maintained, from the caecum to the colon. Bifidobacteria were not detected in any samples using genus-specific primers. In the dendrogram from ERIC PCR, the piglets fed with XOS diets presented the highest similarity between samples and probiotic reference strains.  相似文献   


10.
Sheep in five age groups (two weeks, 10 weeks, 18 weeks, six months and four years old) were immunised systemically, twice, with ovalbumin or Brucella abortus (live or killed) and antibody responses in blood were measured. The animals were also infected with the nematode parasites Trichostrongylus colubriformis and Haemonchus contortus and faecal egg counts and serum antibody responses to larval antigens were measured. The experiments were designed so that, as far as possible, the effect of age per se could be dissociated from the combined effects of age and prior exposure to antigen. The effects of the age of sheep were more marked for antibody responses to Brucella abortus lipopolysaccharide than to ovalbumin. Older animals had much greater resistance to infection with internal parasites, as shown by the magnitude of the faecal egg count. In contrast to older lambs, neonatal lambs (infected with H contortus at two weeks old) had consistently declining concentrations of anti-H contortus antibody in their serum, mounted no detectable autogenous anti-H contortus antibody response in blood and appeared to develop no resistance to the parasite. Post natal ontogeny of immune responses was different for the various antigens/pathogens.  相似文献   

11.
The efficacies of ivermectin, nemadectin and moxidectin were evaluated when administered orally to lambs infected with either a susceptible laboratory strain of Haemonchus contortus or a strain reported to be resistant to ivermectin. Groups of 24 Dorset cross Cheviot cross Suffolk lambs were infected with either the susceptible or resistant strain of H contortus and allocated to treatment groups according to their faecal egg counts 27 days after infection. One day later the lambs were dosed orally with one of the three anthelmintics at 0.2 mg/kg bodyweight, and they were killed and surviving worms were recovered 13 or 14 days after treatment. Against the ivermectin resistant strain, ivermectin did not significantly reduce the egg count or the numbers of adult H contortus; however, both nemadectin and moxidectin reduced the nematode egg counts and the numbers of H contortus by 99 and 100 per cent, respectively. Against the susceptible strain, all the anthelmintics reduced the egg counts by 100 per cent as early as four days after treatment and reduced the numbers of susceptible H contortus by 100 per cent. No adverse reactions to any of the drugs were observed.  相似文献   

12.
36 intact male and 69 female lambs of two breeds (n = 63 Merinoland; n = 42 Rh?n) aged 12 weeks were orally infected with 5000 infective-stage larvae, L3, of the nematode Haemonchus contortus. After 4 and 8 weeks faecal egg counts (FEC), haematocrit values and plasma testosterone levels were determined. All lambs were slaughtered at 20 weeks of age. The gastrointestinal tracts were examined for the presence of adult stages of H. contortus. Male lambs showed significantly higher log FEC (p < 0.001), higher mean establishment rates (p < 0.05), higher worm burdens (p < 0.01) and lower haematocrit values (p < 0.001) when compared with female lambs. Correlations between economically important traits (body weight, daily weight gain) and parasitological parameters were significantly higher in male animals. Testosterone level was 4 weeks after infection significantly positive correlated with worm burden. The results suggest that female lambs are more resistant against an experimental H. contortus infection when compared with male lambs. Testosterone seems to play an important role in resistance. This approach can be of importance if parasite resistance is incorporated into breeding programs and the estimated breeding values for rams are only based on male offspring information. Therefore male breeding values are probably not representative for the whole population.  相似文献   

13.
Two experiments were conducted to study the effects of growth hormone-releasing factor (GRF) and thyrotropin-releasing factor (TRF) administration on hormone concentrations in dairy cows. In the first trial, 12 cows were used on 5 consecutive days to determine the effect of four sc doses of GRF (0, 1.1, 3.3 and 10 μg•kg−1 BW) and three sc doses of TRF (0, 1.1 and 3.3 μg•kg−1 BW) combined in a factorial arrangement. GRF and TRF acted in synergy (P = .02) on serum growth hormone (GH) concentration even at the lowest dose tested and GH response to the two releasing factors was higher than the maximal response observed with each factor alone. TRF increased (P<.01) prolactin (Prl), thyrotropin (TSH), triiodothyronine (T3) and thyroxine (T4) concentrations similarly at the 1.1 and 3.3 μg•kg−1 doses and GRF did not interact (P>.40) with TRF on the release of these hormones. In the second trial, the effect of GRF (3.3 μg•kg−1 BW, sc) and TRF (1.1 μg•kg−1 BW, sc) was tested at three stages (18, 72 and 210 days) of lactation on serum Prl and TSH concentrations. Eighteen cows (n = 6 per stage of lactation) were used in two replicates of a 3 × 3 latin square. The TRF and GRF-TRF treatments were equipotent (P>.05) in increasing Prl and TSH concentrations. Prl and TSH responses were similar (P>.40) throughout lactation. In summary, GRF at doses ranging from 1.1 to 10.0 μg•kg−1 and TRF at doses ranging from 1.1 to 3.3 μg•kg−1 act in synergy on GH release and do not interact on Prl, TSH, T3 and T4 concentrations in dairy cows. Furthermore, Prl and TSH response to TRF are not affected by stage of lactation.  相似文献   

14.
In 2004, an experiment was carried out to evaluate the effect of biological control through feeding spores of Duddingtonia flagrans on parasitic gastroenteritis in lambs, kept under an evasive grazing system. In total 66 lambs were used. Forty naturally infected 3-month old ram lambs were weaned in mid June, and divided into four groups of 10 lambs. On 21 June, G1–G4 were moved to four separate virtually clean plots, they were moved after 4 and 8 weeks to similar plots, and housed after 12 weeks to be necropsied 16 days later. The other 26 lambs had been raised helminth-free, and were used as pairs of tracer lambs. All but one of these pairs, were grazed during the last 2 weeks on each plot. The remaining pair (TA) was grazed during the last 2 weeks on pasture (30 August to 13 September) on the plot that had been grazed by G3 between 19 July and 16 August, to study inhibited development in Haemonchus contortus. All lambs were fed 200 g of concentrates daily throughout the whole period, and those of G1 and G2 were also fed 500,000 spores of D. flagrans/kg bodyweight daily.

The faecal cultures demonstrated a high reduction in yield as a result of fungal application. However, no differences between groups were seen in weight gain, faecal egg counts, pasture larval counts, worm counts and tracer worm counts. H. contortus was the dominant species, and it is obvious that the moves at 4-week intervals prevented the development of severe haemonchosis. This is in particular demonstrated by the much higher worm counts in the two TA tracer lambs grazed. Nevertheless, increases to high faecal egg counts 3 weeks after the first and second moves, indicated acquisition of infection before these moves and at least subclinical haemonchosis. This was supported with the worm counts of lambs and tracer lambs. A higher proportion of inhibited early L4 than in other tracers and than in the permanent lambs were found in the pair of TA tracer lambs. This indicates that moves to new pastures in late summer and autumn delays the onset of inhibition.  相似文献   


15.
Fifteen worm-free lambs (two-and-a-half to three months or four to four-and-a-half months old) were infected with 3500 or 4000 Ostertagia ostertagi larvae on five days each week for six weeks, and their performance compared to that of controls. Eleven lambs were killed after eight weeks and four were challenged with O circumcincta to determine whether any cross resistance had developed. A feature of the O ostertagi infection was the considerable variation in response. Overall liveweight gain was lowered by 24 per cent in the two-and-a-half to three-month-old infected lambs, mainly due to reductions of 27 to 40 per cent in four of the seven lambs. There was no consistent effect in the older lambs. The worm populations consisted mainly of early fourth stage larvae and developing worms, but a small percentage reached sexual maturity and these produced a low faecal egg count (1 to 63 eggs per gram). Numerous intraluminal refractive crystals were present in the gut of both adult worms and developing stages, possibly reflecting degenerative changes. Hypertrophy of the abomasal mucosa with patchy loss of differentiation was a feature of the infection, and in four lambs serum pepsinogen concentrations were elevated. Exposure to O ostertagi did confer some protection against challenge with O circumcincta in that worm counts were reduced to about 60 per cent of those in controls, although no increase was observed in the numbers of arrested larvae. The successful passage of O ostertagi through young lambs could be important in mixed or alternate grazing systems by providing a reservoir of infection for the alternate host.  相似文献   

16.
Six-month-old red Maasai lambs were more resistant than Dorper lambs to repeated infections at one to two week intervals with 1000 Haemonchus contortus infective larvae. Resistance after infection was assessed by means of faecal egg counts, packed cell volumes, eosinophil counts, total serum protein concentrations and mortality rates. The weight gains of the infected animals were only marginally lower than those of their uninfected controls, most probably because of their significantly higher feed consumption, and evidently the infected lambs were not utilising all of the extra feed for growth. This absence of anorexia in spite of the infection was probably due to the palatability of the high protein diet fed to the lambs.  相似文献   

17.
Gastrointestinal nematode infections cause substantial economic losses in pasture-based sheep farming worldwide. Host nutritional status has been identified as a key component of immune function. While vitamin E supplementation is known to have broad-spectrum effects on immune function in livestock, to our knowledge, there are no reports on the effect of vitamin E supplementation on trichostrongylid parasite infections in lambs. This study evaluated the effect of parenteral vitamin E supplementation on naturally acquired parasite infection in lambs. Twenty-seven spring lambs were sequentially assigned to receive injections of vitamin E (15 or 30 IU D-α-tocopherol/kg body weight (BW) or placebo, every two weeks, from birth to 28 weeks of age. Blood was collected at weeks 0, 2, 4, 8, 12, 16, 20, 24, and 28 to determine serum α-tocopherol concentration. Once the youngest animal reached 15 weeks of age all lambs were dewormed and grazed together on a pasture known to be contaminated with trichostrongylid larvae. Fecal egg count and blood packed cell volume (%) were determined on each lamb immediately prior to deworming and for the first seven weeks of pasture infection. Lambs were euthanized when they reached 28 weeks of age for determination of parasite worm burdens. Vitamin E supplementation at 30 IU/kg BW increased serum α-tocopherol over that of placebo (P<0.001) however, there was no effect of vitamin E supplementation on liver (P=0.804) or muscle (P=0.16) α-tocopherol content. There was no effect of vitamin E supplementation on fecal egg counts, packed cell volume, worm burden or nematode species distribution. Nematode genera identified were Haemonchus (30%), Trichostrongylus (42%), Nematodirus (27%), Strongyloides sp. (<1%), and Aonchotheca sp. (<1%). These results indicate that biweekly injections of vitamin E at 15 and 30 IU d-α-tocopherol/kg BW, had no effect on parasitological parameters used in the study to assess gastrointestinal nematode infection.  相似文献   

18.
Twenty four Duroc × Landrace male piglets, aged 21 days, were assigned to 1 of 4 experimental diets. Diets 1 and 2 contained 150 g kg− 1 wheat bran and diets 3 and 4 contained 90 g kg− 1 maize cobs as the major fibre source. All diets contained 480 g kg− 1 wheat and 200 g kg− 1 soybean meal. Diets 2 and 4 were supplemented with the following enzyme complex: 800 U/kg cellulase, 1800 U/kg glucanase and 2600 U/kg xylanase.

The replacement of wheat bran by maize cobs increased the acetic (P < 0.05) and decreased the butyric acid production (P < 0.05) in the cecum. Piglets fed diets with maize cobs had lower (P < 0.05) levels of butyric acid in the colon than those fed wheat bran.

The xylanolytic, pectinolytic and cellulolytic enzyme activities were higher (P < 0.05) in the cecum and colon of piglets fed the wheat bran based diets. The supplementation of the diet with the enzyme complex did not significantly affect the levels of short chain fatty acids formed in the small intestine and there was a non significant increase of the levels of acetic, propionic and butyric acids in the cecum and colon of piglets (P < 0.10). No interactions were present between fibre sources and enzyme addition.

The results suggest that the enzyme supplementation of the diet did not bring significant benefits to the animals and that when maize cobs replaces wheat bran in diets it negatively affects butyric acid production and fibre-degrading enzyme activity in the hindgut of piglets.  相似文献   


19.
The effect of Betamethasone treatment on faecal larval production in lambs infected with Dictyocaulus filaria was studied. Four-to-six-month-old male lambs were infected with D. filaria at a dose of 75 larvae per kg body weight (L/kg) and subsequently treated with a total dose of 14 mg of Betamethasone, administered in divided doses, either during the early (day 5–15) or late (day 30–40) stages of infection. Faecal larval yields in treated animals during the period of patency were compared with those of un-treated controls and also with lambs infected with a dose of 150 L/kg.Higher worm establishment, as well as higher percentage survival of infected animals during patency, were associated with infections of 75 L/kg in comparison to 150 L/kg. Treatment with Betamethasone during the early stages of infection resulted in higher worm establishment but similar treatment given during the late stages of infection produced no such effects.The number of larvae per gram of faeces was higher in animals receiving infections of 150 L/kg in comparison to 75 L/kg. Treatment with Betamethasone, whether given during the early or late stages of infection, increased larval output in faeces of infected lambs. However, the output did not reach the levels shown by lambs given infections of 150 L/kg. The total estimated faecal larval yields for the period of patency were higher in the treated animals. The yields were much higher in animals treated during early stages of the infection.  相似文献   

20.
A study was conducted to examine the role of nutrition in the development of gastrointestinal (GI) parasitism, performance and pathophysiology of parasitism in female lambs. Forty-four months old ewe lambs received for 6 weeks 0, 1500 or 7000 L(3) larvae of Teladorsagia circumcincta in two doses per week. The animals were given access to a pelleted diet to meet energy requirements for gaining weight close to their potential (H) or approximately 50% of it (L). The level of protein in the diet was 20-30% above requirements for both planes of nutrition.Measurements of body weight, serum pepsinogen concentration and faecal egg counts were taken at weekly intervals. All animals were slaughtered 2 weeks after the last larval dosing for estimation of worm count, carcass composition and reproductive tract development.Voluntary intake of infected animals decreased by approximately 10%. Both nutrition and infection influenced lamb performance and carcass composition. However, no direct effects on reproductive tract parameters due to the presence of infection were observed.The level of L(3) infection showed a significant effect not only on faecal egg counts and on worm burden, as it could be expected, but also on the proportion of females to males, which increased significantly with the level of infection.While the plane of nutrition did not show a significant effect on faecal egg counts or on worm burden, surprisingly, both female worm size and their fecundity decreased significantly with the level of nutrition. This response was accompanied by a significant increase in the concentration of circulating eosinophils suggesting that the immune response of lambs consuming high levels of energy was enhanced compared to that of lambs kept on a restricted diet.Results herein show that in young female lambs fed on adequate levels of protein, an improvement in energy supply does not only improve carcass characteristics but clearly enhances the development of resistance to GI nematodes infection. This may have decisive management implications for the control of parasitic infections in sustainable production systems.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号