饲料铜水平对生长猪部分生化指标的影响

使用硫酸铜作为铜源,在生长猪饲料中添加铜,对照组铜添加浓度为0mg/kg,试验各组铜添加浓度为100mg/kg、150mg/kg、200mg/kg、250mg/kg和300mg/kg。试验开始时采血,之后每隔20d采血一次。测定有关血液生化指标。试验结果如下:试验组平均血清尿素氮(SUN)在20、40、60和80d时,分别降低10.3%、12.0%、9.7%和5.6%;60d时200mg/kg和250mg/kg铜组降幅分别达8.7%(P<0.01)和8.4%(P<0.05)。总蛋白(TP)和白蛋白(ALB)试验组比对照组均有不同程度提高,TP在40、60和80d时分别提高5.4%、7.2%和3.2%;ALB在20、40、60和80d时分别提高14.6%、15.5%、16.9%和0.23%。甘油三脂(TG3)、胆固醇(CH)、采食量未见有显著性变化(P>0.05)。本试验结果表明:日粮铜水平对血液相关生化指标的影响随饲料铜浓度的差异呈现明显的阶段性差异,其差异的显著性与铜的促生长效应基本是一致的。     

叶酸水平对断奶仔猪生长性能及血清组织中蛋白质代谢的指标影响

试验旨在研究日粮中添加不同剂量的叶酸对断奶仔猪生长性能及血清和组织中蛋白质代谢相关指标的影响。试验选择25日龄断奶仔猪160头(80头纯种大白和80头纯种长白,公、母各半),随机分为5个处理组,每个处理4个重复,每个重复8头猪,进行28 d的饲养试验。5种日粮分别在基础日粮上添加0、0.5、2.5、5 mg/kg和10 mg/kg叶酸。结果表明:添加2.5 mg/kg叶酸仔猪的全期日增重较基础日粮组有显著提高(P<0.05),提高了血清蛋白质浓度(P<0.05),降低了血清尿素氮浓度(P<0.01),并提高了肝脏DNA、RNA和蛋白质的含量(P<0.05)以及肌肉RNA/DNA和RNA/蛋白质值(P<0.05),而添加更高水平叶酸时却使仔猪生长性能下降。本试验结果显示,仔猪日粮中叶酸适宜添加量为2.5 mg/kg,叶酸不足或者过高都将影响动物的生长。     

不同铜源对仔猪生长性能、腹泻率及血清免疫和抗氧化功能的影响

试验旨在研究日粮中添加不同铜源(柠檬酸铜、硫酸铜或碱式氯化铜)对仔猪生长性能、腹泻率及血清免疫和抗氧化功能的影响。选用21日龄断奶、健康、平均体重(6.41±0.32)kg的杜×长×大仔猪64头,按单因素试验设计原则,随机分为4个处理,每个处理4个重复,每个重复4头猪(公、母各半)。对照组不额外添加铜,试验在基础日粮中分别添加90 mg/kg硫酸铜、90 mg/kg碱式氯化铜或90 mg/kg柠檬酸铜(均以铜计)。预试期3 d,正试期28 d。结果表明:与对照组相比,添加柠檬酸铜组仔猪平均日增重提高了25.89%(P0.05),仔猪腹泻率降低了66.79%(P0.05),仔猪血清丙二醛含量降低了21.38%(P0.05);但仔猪平均日采食量、耗料增重比、血清IgA、IgG、IgM和铜蓝蛋白含量均无显著差异(P0.05);与对照组相比,添加硫酸铜或碱式氯化铜对仔猪生长性能、腹泻率及血清免疫和抗氧化指标均无显著影响(P0.05);与硫酸铜组和碱式氯化铜组相比,添加柠檬酸铜使仔猪腹泻率降低66.79%和63.82%(P0.05),但对仔猪生长性能及血清免疫和抗氧化指标无显著影响(P0.05)。综上,在仔猪日粮中添加90 mg/kg柠檬酸铜可以提高平均日增重、降低腹泻率和降低血清丙二醛含量。     

刺五加多糖对断奶仔猪生长性能和免疫指标的影响

本试验旨在探讨饲粮中添加刺五加多糖(Acanthopanax senticosus polysaccharide,ASPS)对断奶仔猪生长性能和免疫指标的影响。试验选用96头(28±3)日龄、平均体重为(7.13±0.67)kg的"长白×约克夏"二元杂交仔猪,随机分成6组,每组4个重复,每个重复4头猪。对照组饲喂基础饲粮,试验组饲喂在基础饲粮中分别添加150、300、500、800和1 000 mg/kg ASPS的试验饲粮,试验期21 d。结果表明:饲粮中添加500和800 mg/kg ASPS提高了仔猪的末重和平均日增重(P<0.01),降低了仔猪的腹泻率(P<0.01),但对平均日采食量和料重比无显著影响(P>0.05)。随ASPS添加水平的提高,末重、平均日增重和腹泻率均呈二次曲线变化(P<0.01),料重比呈线性改善(P<0.05)。饲粮中添加800 mg/kg ASPS提高了仔猪外周血淋巴细胞转化率(P<0.01),降低了仔猪血清皮质醇水平(P<0.05),二者随ASPS添加水平的提高均呈线性变化(P<0.01)。由此可见,饲粮中添加ASPS可以显著提高断奶仔猪的平均日增重,显著降低腹泻率,改善血液免疫指标,缓解仔猪应激反应,其中以添加量为800 mg/kg效果最好。     

饲粮铜水平对生长猪部分生化指标的影响

使用硫酸铜作为铜源,在生长猪饲粮中添加铜,对照组铜添加浓度为0mg/kg,试验各组铜添加浓度为100、150、200、250和300mg/kg。试验开始时采血,之后每隔20d采血一次。测定有关血液生化指标。试验结果,试验组平均血清尿素氮(SUN)在20、40、60和80d时,分别降低10.3%、12.0%、9.7%和5.6%;60d时200和250mg/kg铜组降幅分别达8.7%(P<0.01)和8.4%(P<0.05)。总蛋白(TP)和白蛋白(ALB)试验组比对照组均有不同程度提高,TP在40、60和80d时分别提高5.4%、7.2%和3.2%;ALB在20、40、60和80d时分别提高14.6%、15.5%、16.9%和0.23%。甘油三脂(TG3)、胆固醇(CH)、采食量未见有显著性变化(P>0.05)。试验结果表明,饲粮铜水平对血液相关生化指标的影响随饲粮铜浓度的差异呈现明显的阶段性差异,其差异的显著性与铜的促生长效应基本是一致的。     

中草药制剂对断奶仔猪生长性能、血清生化和免疫的影响

文章旨在评估日粮添加中草药添加剂对断奶仔猪生长性能、血清生化和免疫指标的影响。试验选择21d断奶、平均体重为(5.90±0.03)kg的仔猪450头,随机分为3组,每组5个重复,每个重复30头。对照组饲喂基础日粮,抗菌肽组饲喂基础日粮+45mg/kg抗菌肽,中草药组饲喂基础日粮+200mg/kg中草药添加剂,试验共进行42d。结果:对照组断奶仔猪在1~21d日增重较其他两组分别显著降低3.57%和5.86%(P<0.05),而中草药组仔猪在22~42d的日增重较对照组和抗菌肽组分别显著提高3.64%和3.37%(P<0.05),同时该组1~42d日增重较对照组显著提高4.54%(P<0.05)。与对照组相比,中草药组仔猪在1~21d和1~42d的料重比分别显著降低5.52%和3.47%(P<0.05)。对照组仔猪死亡率较其他两组分别显著提高137.75%和126.21%(P<0.05)。中草药组仔猪血清胆固醇含量较对照组和抗菌肽组分别显著降低35.78%和33.43%(P<0.05),但该组血清甘油三酯浓度分别显著提高19.09%和11.96%(P<0.05)。中草药组仔猪血清IgG浓度较对照组显著提高12.74%(P<0.05),而对照组和中草药组血清IL-6浓度较抗菌肽组分别显著提高34.04%和23.89%(P<0.05)。结论:在本试验条件下,日粮添加200mg/kg中草药添加剂可以改善断奶仔猪生长性能、血清性状及免疫反应。     

γ-氨基丁酸对热应激肉种鸡产蛋性能和繁殖性能的影响

本试验旨在研究γ-氨基丁酸(GABA)对热应激条件下肉种鸡产蛋性能和繁殖性能的影响,并从血清抗氧化和免疫功能及肝功能相关酶活等方面探讨其作用机理。选取360只28周龄岭南黄肉种鸡,随机分为4组,每组3个重复,每个重复30只鸡,分别在基础饲粮添加0(对照)、25、50、75 mg/kg GABA。预试期14 d,正试期56 d。结果显示:与对照组比,1)添加75 mg/kg GABA显著提高了肉种鸡产蛋率、平均蛋重和料蛋比(P<0.05),并显著提高了种蛋的受精率、孵化率、雏鸡初生重(P<0.05)及出雏率(P<0.01);添加25和50 mg/kg GABA也显著提高了种蛋孵化率和出雏率(P<0.05),添加25 mg/kg GABA还显著提高了雏鸡初生重(P<0.05)。2)添加75 mg/kg GABA显著提高了血清免疫球蛋白A(IgA)和免疫球蛋白M(IgM)及补体C4含量(P<0.05);添加25 mg/kg GABA也显著提高了血清IgM含量(P<0.05)。3)添加75 mg/kg GABA显著提高了血清超氧化物歧化酶活性和血清谷胱甘肽过氧化物酶活性(P<0.05)及总抗氧化能力(P<0.01),降低了血清丙二醛浓度(P<0.01);添加25 mg/kg GABA也显著降低了血清丙二醛浓度(P<0.05)。结果提示,饲粮中添加GABA具有提高热应激条件下肉种鸡产蛋性能和繁殖性能的作用。     

伊利石对仔猪生长性能、抗氧化和免疫功能及肠道形态的影响

本试验旨在研究饲粮中添加伊利石对断奶仔猪生长性能、养分消化率、血清抗氧化和免疫功能、肠道形态及粪便氮素排放的影响。选取144头28日龄健康"杜×长×大"断奶仔猪[平均体重(7.27±0.89)kg],按完全随机区组设计分为3组,每组8个重复,每个重复6头猪(公母各占1/2)。对照组饲喂玉米-豆粕型基础饲粮,试验组分别在基础饲粮中添加2 000和4 000 mg/kg伊利石(替代等量的玉米)。试验期28 d。结果表明,与对照组相比:1)试验第1~14天和第1~28天,4 000 mg/kg伊利石添加组仔猪平均日增重和增重耗料比显著提高(P<0.05);试验第1~14天,4 000 mg/kg伊利石添加组仔猪腹泻率显著降低(P<0.05)。2)4 000 mg/kg伊利石组仔猪干物质、粗蛋白质和总能表观消化率在试验第1~14天显著提高(P<0.05),粗蛋白质表观消化率在试验第15~28天显著提高(P<0.05)。3)试验第14天,4 000 mg/kg伊利石添加组仔猪血清免疫球蛋白A和免疫球蛋白G含量、超氧化物歧化酶活性和总抗氧化能力(T-AOC)显著提高(P<0.05),血清丙二醛含量则显著降低(P<0.05);试验第28天,4 000 mg/kg伊利石添加组仔猪血清T-AOC显著提高(P<0.05)。4)4 000 mg/kg伊利石添加组仔猪空肠和回肠绒毛高度/隐窝深度(V/C)值显著升高(P<0.05),试验组回肠绒毛高度(P=0.07)和十二指肠V/C值(P=0.06)有升高的趋势。5)4 000 mg/kg伊利石添加组仔猪每千克体增重粪氮排放量在试验第1~14天显著降低(P<0.05),试验组仔猪在试验第15~28天每千克体增重粪氮排放量有降低的趋势(P=0.06)。综上,饲粮添加4 000 mg/kg伊利石可显著提高断奶仔猪机体抗氧化和免疫功能,改善肠道形态,降低腹泻率,提高养分消化率,减少粪便氮素排放,促进仔猪生长。     

载铜硅酸盐纳米微粒对仔猪生长性能和血清生化指标的影响

试验用128头体重(7.5±0.3)kg“杜长大”三元杂交仔猪研究玉米-豆粕型基础日粮含铜10mg/kg的情况下,以载铜硅酸盐纳米微粒(CSN)形式添加铜60和80mg/kg和硫酸铜形式添加铜250mg/kg对仔猪生长性能、血清生化指标的影响。结果表明:添加不同水平的CSN使仔猪日增重显著(P<0.05)提高,饲料转化率显著(P<0.05)降低;血清总蛋白、白蛋白含量显著(P<0.05)提高;血清尿素氮含量、碱性磷酸酶活性显著(P<0.05)降低;血清谷丙转氨酶、谷草转氨酶活性无显著(P>0.05)影响。添加硫酸铜使谷丙转氨酶活性显著(P<0.05)升高,谷草转氨酶活性极显著(P<0.01)升高。     

饲粮铁、铜水平对早期断奶仔猪生长发育及组织铁、铜含量的影响

本试验就饲粮铁、铜水平对早期断奶仔猪(30日龄)生长发育及组织中铁、铜含量的影响进行了研究。结果指出:在含铁70mg/kg及含铜10mg/kg的基础饲料中以硫酸亚铁形式添加35及70mg/kg铁和以硫酸铜形式添加125及200mg/kg铜时,对仔猪生长性能、组织器官的发育以及品骨、肾脏中的铁含量没有影响,但饲粮铁水平的增加可导致肝脏和脾脏铁含量的增加。在饲粮中添加35mg/kg及70mg/kg的铁时,可使肝脏铁含量增加14.6％和55.0％(P<0.01),使脾脏铁含量增加15.1％(P<0.05)及22.9％(P<0.01)。在仔猪饲粮中添加200mg/kg铜,可使仔猪日增重和采食量分别提高9.7％和16.2％,使肾脏和肝脏铜含量分别增加104.6％(P<0.01)和434.0％(P<0.01),使肝脏铁含量降低19.4％(P<0.05)。添加125mg/kg铜,使肾脏和肝脏铜增加27.9％和93.4％(P<0.01),使肝脏铁降低9.4％。     

白术、微米白术和白术多糖对断奶仔猪生长性能和肠道形态及微生态区系的影响

试验选用96头平均体重14.82 kg左右的杜×长×大断奶仔猪,随机分成4组,每组3栏,每栏8头(公母各半)。对照组饲喂基础日粮,试验1、2、3组分别添加1%80目白术、0.2%白术多糖和1%微米白术。试验期30 d。结果表明:在生长性能方面,与对照组相比,1%微米白术添加组可显著提高日增重(P0.05)、降低饲料增重比和腹泻率,而且效果优于1%80目白术组和0.2%白术多糖组,在肠道形态和肠道微生态区系方面,与对照组相比,日粮添加1%80目白术、0.2%白术多糖、1%微米白术均可不同程度的提高十二指肠和空肠的绒毛高度,加深十二指肠和空肠的隐窝深度,并且增加肠道微生态区系的多样性,其中以1%微米白术添加组的效果最佳。     

Prevalence and seasonal incidence of nematode parasites and fluke infections of sheep and goats in eastern Ethiopia

Sissay, M.M., Uggla, A. and Waller, P.J., XXXX. Prevalence and seasonal incidence of nematode parasites and fluke infections of sheep and goats in eastern Ethiopia. Tropical Animal Health and Production, XXXX. A 2-year abattoir survey was carried out to determine the prevalence, abundance and seasonal incidence of gastro-intestinal (GI) nematodes and trematodes (flukes) of sheep and goats in the semi-arid zone of eastern Ethiopia. During May 2003 to April 2005, viscera including liver, lungs and GI tracts were collected from 655 sheep and 632 goats slaughtered at 4 abattoirs located in the towns of Haramaya, Harar, Dire Dawa and Jijiga in eastern Ethiopia. All animals were raised in the farming areas located within the community boundaries for each town. Collected materials were transported within 24 h to the parasitology laboratory of Haramaya University for immediate processing. Thirteen species belonging to 9 genera of GI nematodes (Haemonchus contortus, Trichostrongylus axei, T. colubriformis, T. vitrinus, Nematodirus filicollis, N. spathiger, Oesophagostomum columbianum, O. venulosum, Strongyloides papillosus, Bunostomum trigonocephalum, Trichuris ovis, Cooperia curticei and Chabertia ovina), and 4 species belonging to 3 genera of trematodes (Fasciola hepatica, F. gigantica, Paramphistomum {Calicohoron} microbothrium and Dicrocoelium dendriticum) were recorded in both sheep and goats. All animals in this investigation were infected with multiple species to varying degrees. The mean burdens of adult nematodes were generally moderate in both sheep and goats and showed patterns of seasonal abundance that corresponded with the bi-modal annual rainfall pattern, with highest burdens around the middle of the rainy season. In both sheep and goats there were significant differences in the mean worm burdens and abundance of the different nematode species between the four geographic locations, with worm burdens in the Haramaya and Harar areas greater than those observed in the Dire Dawa and Jijiga locations. Similar seasonal variations were also observed in the prevalence of flukes. But there were no significant differences in the prevalence of each fluke species between the four locations. Overall, the results showed that Haemonchus, Trichostrongylus, Nematodirus, Oesophagostomum, Fasciola and Paramphistomum species were the most abundant helminth parasites of sheep and goats in eastern Ethiopia.     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Internal Parasites and Haematological Values in Cattle Slaughtered in Buea Subdivision of Cameroon

Tropical Animal Health and Production -     

Chemotaxis of macrophage in inflammation

Our particular attention in this article was given to natural mediators for macrophages isolated from the sites of tissue injury. A number of chemotactic factors, which may satisfy many criteria making them acceptable as inflammatory leucocyte chemotactic factors, has been separated. Among them, our laboratory has isolated three macrophage (monocyte) chemotactic factors (MCF-a, -b and -c). Their purification, characterization and functional specificity are discussed.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

Y‐chromosomal variation of local goat breeds of Turkey close to the domestication centre

Genetic variations in chromosome Y are enabling researchers to identify paternal lineages, which are informative for introgressions and migrations. In this study, the male‐specific region markers, sex‐determining region‐Y (SRY), amelogenin (AMELY) and zinc finger (ZFY) were analysed in seven Turkish native goat breeds, Angora, Kilis, Hair, Honaml?, Norduz, Gürcü and Abaza. A SNP in the ZFY gene defined a new haplotype Y2C. All domestic haplogroups originate from Capra aegagrus, while the finding of Y1A, Y1B, Y2A and Y2C in 32, 4, 126 and 2 Turkish domestic goats, respectively, appears to indicate a predomestic origin of the major haplotypes. The occurrence of four haplotypes in the Hair goat and, in contrast, a frequency of 96% of Y1A in the Kilis breed illustrate that Y‐chromosomal variants have a more breed‐dependent distribution than mitochondrial or autosomal DNA. This probably reflects male founder effects, but a role in adaptation cannot be excluded.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

Changes in proportion of canine urinary calculi composed of calcium oxalate or struvite in specimens analyzed from 1981 through 2001

The objective of this report was to characterize 20-year changes in proportion of calcium oxalate (CaOx) calculi and struvite calculi in dogs, and associations with breed, age, and sex. In this retrospective study, results of analysis of urinary calculi from dogs were reviewed for specimens received between July 1, 1981, and December 31, 2001. Breed, sex, age, year of submission of the specimen, and mineral type(s) were analyzed statistically. CaOx or Struvite or both were contained in 18,966 of 20,884 (91%) specimens. For both sexes, a 20-year statistically significant increase was observed in the proportion of calculus specimens that contained CaOx. The increase in this proportion was greater in females (1% to 31%) than in males (18% to 82%). From 1998 to 2001, when proportions may have plateaued, the odds of specimens containing CaOx were markedly higher in 18 breeds, markedly lower in 5 breeds, and not significantly different in 13 breeds compared with crossbreds. For both sexes, a 20-year statistically significant decrease was observed in the proportion of calculus specimens that contained struvite. This decrease in proportion was greater for males (79-16%) than for females (97-68%). From 1998 to 2001, when proportions plateaued, the odds of calculi containing struvite were markedly lower in 20 breeds, markedly higher in 1 breed, and not significantly different in 15 breeds when compared with crossbreds. Breed, age, and sex were associated statistically with CaOx or struvite urolithiasis. In conclusion, there appears to have been a long-term increase in the proportion of specimens of canine urinary calculi that contain CaOx as well as a long-term decrease in the proportion of specimens of calculi that contain struvite for both male and female dogs. The rate of change appeared to begin leveling off in the period 1998 to 2001. The recent proportion of dogs with either CaOx- or struvite-associated urolithiasis may depend on breed, age, and sex, and on interactions among these 3 factors.     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.