Has the optimum time for faecal nematode egg count reduction testing in sheep in New Zealand changed?

Abstract

AIM: To determine what, if any, changes have taken place in the optimum time, for undertaking faecal egg count reduction tests (FECRT) in sheep in New Zealand.

METHODS: A comparison was made between the numbers and types of nematode genera adequately represented for testing purposes (faecal nematode egg count (FEC) of >50 epg) in initial FECRT case submissions to a veterinary laboratory in New Zealand, during two 4-year periods, in 1992–1995 and 2006–2009.

RESULTS: Although there were some minor differences between them, the seasonal patterns of occurrence remained basically the same for all parasite genera in both datasets, with their individual peak periods of representation occurring during February to May in all instances. Not surprisingly, this period of maximum seasonal occurrence for each parasite genus also coincided with those months of the year when the greatest numbers of worm genera were adequately represented for faecal nematode egg count reduction (FECR) testing.

CONCLUSIONS: The results of this study indicate that the optimum time for conducting FECRT in sheep in New Zealand continues to be during the late summer-autumn months of February to May. However, they also reaffirmed that even during this optimal period there are still likely to be many occasions when relatively few nematode genera may be sufficiently well represented for satisfactory FECR testing. Accordingly, veterinary practitioners ought to be aware that, in order to obtain a complete picture of the resistance status of all worm genera on a particular property, such testing may need to be carried out on more than one occasion.     

Failure of young goats to acquire resistance to Haemonchus contortus

Two experiments were carried out to investigate the acquisition by goats of resistance to Haemonchus contortus. In Experiment 1, five Saanen wethers reared worm-free and averaging 51/2 months of age at the start of the experiment, were dosed with 200 H. contortus infective larvae three times per week for 10 weeks (approximately 23 infective larvae/kg mean initial liveweight/week) and then given anthelmintic treatment. Each goat and an equal number of worm-free controls were then challenged with 10,000 infective larvae. Post mortem worm counts were carried out 30 days later. In Experiment 2, eight worm-free Saanen wethers, 14 months old at the start of the experiment, were dosed with 825 infective larvae per week for 14 weeks (approximately 23 infective larvae/kg mean initial liveweight/week) except for one week when only 300 larvae were given and one week when no larvae were given. After anthelmintic treatment, each received, together with seven worm-free control animals, a challenge dose of 15,000 infective larvae. Post-mortem worm counts were carried out 28 days later. There were no significant dii- ferences in post-mortem worm counts between previously infected and uninfected groups in either experiment. In both experiments, serum pepsinogen values rose significantly as a result of infection but there was no significant (p>0.5) correlation between worm counts and pepsinogen values on the day of slaughter.     

Field studies investigating anthelmintic resistance in young cattle on five farms in New Zealand

AIM: To investigate the efficacy of pour-on anthelmintics against field strains of parasitic nematodes in young cattle on five farms in New Zealand.

METHODS: Faecal nematode egg count (FEC) reduction (FECR) tests were carried out on five calf-rearing farms using pour-on formulations of levamisole, ivermectin, eprinomectin, and the simultaneous administration of levamisole and ivermec- tin. Faecal samples were collected per rectum before treatment and about 7, 14, 21 and 28 days after treatment, for FEC and faecal nematode larval culture.

RESULTS: Resistance (i.e. <95% reduction in FEC) of Cooperia oncophora to ivermectin and eprinomectin was identified on all five farms. There was limited evidence of possible emerging resistance in Ostertagia spp to ivermectin but not eprinomectin, in short-tailed larvae of Cooperia spp to ivermectin and eprinomec- tin, and in Trichostrongylus spp to ivermectin, eprinomectin and levamisole used separately. Levamisole was effective against C. oncophora, but had variable efficacy against Ostertagia spp in the calves in this study. Simultaneous treatment with levamisole and ivermectin pour-on formulations were effective against all genera on all farms.

CONCLUSIONS: To effectively manage roundworm parasites in their calves farmers need to be aware of the resistance status of the parasites on their farms. Levamisole is likely to be an effective anthelmintic on most farms at times of the year when the impact of Ostertagia spp is not high. Simultaneous administration of levamisole and ivermectin pour-on anthelmintics to cattle is likely to control both ML-resistant C. oncophora and stages of Ostertagia spp that are not controlled by levamisole alone.     

Physiological Predictors in Calves of Dairy Breeds: Part 1. Genetic Parameters of Basal and Induced Growth Hormone Secretion

Abstract

Genetic variation in plasma growth hormone (GH) concentration before and after GRF (growth hormone releasing factor) stimulation was studied in young bulls (N=284) and heifers (N=212), the progeny of 53 sires of four dairy and dual-purpose breeds (Danish Jersey, Red Dane, Danish Friesian and Danish Red and White). Male and female calves were reared, fed and tested on separate experimental stations; thus sex, station and feeding were completely confounded effects. The animals were tested at about 9 months of age, after a 24 h fast. GH concentration was measured in serial plasma samples collected for 1 h before and 1 h following intravenous administration of 2.0 ug synthetic GRF(1–29)NH₂/kg live weight^>0.75. Prior to statistical analysis, concentrations were log_e-transformed. Response variables were BASELINE (mean GH in -15, -5 and 0 min samples) and PEAK (mean GH in 10, 15 and 20 min samples). A statistical model taking at least three generations of ancestral relationships into account was used to estimate variance and covariance components for traits in male and female calves by use of restricted maximum likelihood methods.

Heritability of BASELINE was low (0.04 ± 0.12) in males but high in females (0.60 ± 0.16). The heritability of PEAK was high in both sexes (males, 0.42 ± 0.16; females, 0.60 ± 0.16). Genetic correlations between the same trait measured in males and females were low for BASELINE (r _g = 0.32±0.55) but high for PEAK (r _g = 0.82±0.15). Within sex, BASELINE and PEAK were both highly genetically correlated (males, r _g=0.62 ± 0.40; females, r _g= 1.00 ± 0.07).

We conclude that growth hormone concentration is a highly heritable trait in juvenile cattle of both sexes, and that GRF stimulation is benificial to the uncovering of genetic differences among animals.     

Intermittent Stress in Pigs: Behavioural and Pituitary-Adrenocortical Reactivity

Abstract

Ninetysix pigs, half females and half castrated males from 12 litters, were housed in 24 groups of 4 litter mates (2 females, 2 castrates). The pigs were weaned at 4 weeks of age and from the age of 115 days half of the groups were subjected to a schedule of unpredictable, inescapable electroshocks for 33 days, and half served as control. The adrenocortical reactivity to ACTH stimulation and to an emotional stressor (the procedure associated with initiation of blood collection) was measured in females, whereas the behavioural and pituitary-adrenocortical reactivity to an open field test was measured in castrates, as was the behavioural reactivity in a social test. Intermittent stress increased adrenocortical reactivity to ACTH stimulation significantly. This effect was present within the first week of intermittent stress (p < 0.06), but no difference was found after 4–5 weeks of stress. In contrast, the adrenocortical reactivity to additional emotional stressors was unaffected by stress after one week of intermittent stress, but increased after 4–5 weeks. In the open field test, centre location increased after one week of intermittent stress, whereas exploration decreased and walking and ambulation increased after 4–5 weeks of stress. In addition, 4–5 weeks of intermittent stress decreased aggressiveness in a social test. In conclusion, the change in reactivity to an additional acute stressor during intermittent stress appeared in different variables and contexts at different times during the course of intermittent stress. Thus, assessment of stress based on changed reactivity has to include several distinct measures of behavioural and hormonal reactivity.     

杂交早稻品比试验

引进7个杂交早稻品种,以T78优2155为对照进行品比试验,结果表明：金优028、中优2155、金优2689表现产量高、抗性好、综合性状优良,可作为当家品种推广.     

胡萝卜新品种比较试验

以坂田七寸为对照品种,对9个胡萝卜新品种进行品种比较试验,结果表明：红星、佳美红和文兴七寸3个新品种综合表现较好,分别比对照品种增产8.39％、1.67％和0.56％,建议进一步扩大示范.     

甘蔗汁饮料配方的优化

从甘蔗中榨取甘蔗原汁并加入柠檬酸、白砂糖和蒸馏水进行调配,设计正交试验考察柠檬酸和白砂糖的用量以及甘蔗原汁和蒸馏水的配比对甘蔗汁饮料口感、色泽、气味和组织状态等感官品质的影响,优化甘蔗汁饮料配方.结果表明,柠檬酸用量对甘蔗汁饮料感官品质的影响最大,其次是甘蔗原汁与蒸馏水的体积比,白砂糖用量的影响最小.优化的配方为柠檬酸用量0.5 g/L、白砂糖用量15 g/L、V甘蔗原汁∶V水=1.0∶2.0.     

5种药剂对金银花尺蠖室内毒力及田间药效研究

[目的]明确常用杀虫剂对金银花尺蠖的防治效果。[方法]选用5种药剂(敌敌畏、辛硫磷、溴氰菊酯、毒死蜱和高效氯氰菊酯)的原药和乳油分别对金银花尺蠖幼虫进行了室内毒力测定和田间药效试验。[结果]5种药剂中,高效氯氰菊酯的毒力最大,48 h的LC50为0.019 3μg/ml;其他依次为毒死蜱、敌敌畏、辛硫磷和溴氰菊酯,48 h的LC50分别为0.027 6、0.050 5、0.053 3和0.056 3μg/ml。5种药剂在药后7 d的防效均达到80%以上,其中4.5%高效氯氰菊酯乳油和48%毒死蜱乳油的效果最好,其药后7 d的防效均为100%。[结论]5种药剂对金银花尺蠖幼虫均具有较高的毒力和田间防效。     

新疆煤田灭火区植被恢复无土基质配比试验研究——以乌鲁木齐松树头煤矿为例

以乌鲁木齐松树头煤矿为研究对象,采用无土基质配比方法,针对研究区土壤特点,选取选用粘合剂（A）、保水剂（B）、复合肥（C）和秸秆（D）为试验因素,进行无交互作用的正交试验,并对结果进行极差、方差分析影响.结果表明,粘合剂对植物高度、盖度均有显著影响,复合肥对植物盖度有极显著影响,同时也是生物量指标的主要影响因子.各因素主次顺序为C（复合肥）＞B（保水剂）＞A（粘合剂）＞D（秸秆）.基质最优配比方案为A2B1C1D1,即当粘合剂用量为16 g/m2,保水剂为5 g/m2,复合肥为30 g/m2,秸秆为90g/m2时,可获得最佳的植被恢复效果.