Partitioning variances of growth in ultrasound longissimus muscle area measures in Angus bulls and heifers

The objective of the study was to estimate variance components, heritability, and repeatability of ultrasound longissimus muscle area (ULMA) measures. Data included 4,653 serial ULMA measures from 882 purebred Angus bulls and heifers. Animals were born over a 4-yr period from 1998 to 2001. Each year, bulls and heifers were ultrasonically scanned four to eight times, with a 4- to 6-wk interval between scans. Initially, data were subdivided by scan session across years and were analyzed in a multitrait model (MTM). Data pooled across years and scan session were then analyzed using random regression models (RRM) to estimate trends in genetic parameter estimates. Additive direct genetic variance increased with advancing scan session ranging from 8.67 cm4 at the first scan (mean age = 35 wk) to a maximum of 19.48 cm4 at the sixth scan (mean age = 56 wk). Heritability of ULMA increased from 0.35 at first scan to a maximum of 0.48 at the fourth scan (mean age = 50 wk). Additive direct genetic variance and heritability values at about 1 yr of age (fifth scan) were 18.24 cm4 and 0.45, respectively. Estimates from RRM also showed an increase in sigma(a)2 and h2 with age. Trends in sigma(pe)2 estimates, although tending to fluctuate, also increased with age. Additive direct genetic variance at 1 yr of age ranged from 15.8 cm4 to 17.0 cm4 for the different models. Heritability of yearling ULMA measures ranged from 0.40 to 0.42 and repeatabilities ranged from 0.80 to 0.84. For the range of ages used in the current study, both MTM and RRM showed close to maximum heritability values at around 1 yr of age. Therefore, phenotypic differences in yearling ULMA between Angus cattle are better indicators of genetic differences than earlier measurements. Angus breeders could, therefore, use ULMA measures made at around 1 yr of age to select next generation parents.     

Cloning and structural analysis of partial acetylcholine receptor subunit genes from the parasitic nematode Teladorsagia circumcincta

Nematode nicotinic acetylcholine receptors (nAChRs) are the sites of action for the anthelmintic drug levamisole. Recent findings indicate that the molecular mechanism of levamisole resistance may involve changes in the number and/or functions of target nAChRs. Accordingly, we have used an RT-PCR approach to isolate and characterise partial cDNA clones (tca-1 and tca-2) encoding putative nAChR subunits from the economically important trichostrongyloid, Teladorsagia circumcincta. The predicted tca-1 gene product is a 248 aa fragment (TCA-1) which contains structural motifs typical of ligand-binding (alpha-) subunits, and which shows very high sequence similarities (98.8 and 97.2% amino acid identities) to the alpha-subunits encoded by tar-1 and hca-1 from Trichostrongylus colubriformis and Haemonchus contortus, respectively. Sequence analyses of partial tca-1 cDNAs from one levamisole-resistant and two susceptible populations of T. circumcincta revealed polymorphism at the predicted amino acid level, but there was no apparent association of any particular tca-1 allele with resistance. tca-2 encodes a 67 aa fragment (TCA-2) containing the TM4 transmembrane domain and carboxyl terminus of a putative nAChR structural (non-alpha) subunit. The deduced amino acid sequence of TCA-2 shows highest similarity (75% amino acid identity) to ACR-2, a structural subunit involved in forming levamisole-gated ion channels in Caenorhabditis elegans, but low similarity (43% identity) to the corresponding regions of TAR-1 and HCA-1. tca-2 is the first nAChR subunit gene of this type to be isolated from parasitic nematodes, and it provides a basis for further characterisation of structural subunits in trichostrongyloids.     

The role of molecular biology in veterinary parasitology

The tools of molecular biology are increasingly relevant to veterinary parasitology. The sequencing of the complete genomes of Caenorhabditis elegans and other helminths and protozoa is allowing great advances in studying the biology, and improving diagnosis and control of parasites. Unique DNA sequences provide very high levels of specificity for the diagnosis and identification of parasite species and strains, and PCR allows extremely high levels of sensitivity. New techniques, such as the use of uniquely designed molecular beacons and DNA microarrays will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies of veterinary parasites. The ability to use genome data to clone and sequence genes which when expressed will provide antigens for vaccine screening and receptors and enzymes for mechanism-based chemotherapy screening will increase our options for parasite control. In addition, DNA vaccines can have desirable characteristics, such as sustained stimulation of the host immune system compared with protein based vaccines. One of the greatest threats to parasite control has been the development of drug resistance in parasites. Our knowledge of the basis of drug resistance and our ability to monitor its development with highly sensitive and specific DNA-based assays for 'resistance'-alleles will help maintain the effectiveness of existing antiparasitic drugs and provide hope that we can maintain control of parasitic disease outbreaks.     

Microbial respiration and substrate weight loss—II: A model of the influences of chemical composition

Three models of the influences of chemical composition on microbial respiration and substrate weight loss are presented. The three approaches represent different means of incorporating influences of temperature and moisture upon chemical-specific respiration rates. Although influences of temperature and moisture dominate microbial respiration patterns, chemical-specific respiration rates do exist with ethanol soluble substrate components respiring about 5–10 × as rapidly as nonethanol soluble components (depending upon temperature). Simulation models are utilized to project and relate the laboratory measures of microbial respiration to field measures of substrate weight loss. Utilizing chemical-specific respiration rates, simulated rates of weight loss from ethanol soluble and non-ethanol soluble substrate components are 48% and 12% per yr. Measured rates are 49% and 11%. After the initial period of relatively high leaching, changes in substrate weight and chemical composition result largely from changing microbial respiration rates which are chemical-specific and independently influenced by temperature and moisture.     

A comparison of catch rates of artificial lures from an automated handline fishery at Shetland,UK

Automated handlining (jig fishing) has recently been trialled in waters around Shetland, UK. Although different types and colours of artificial lures are commercially available there is a paucity of information available on the effects of either lure design or lure colour on resulting catches. We compared the catch rates of (1) five colours of rubber eel tube lures; and (2) five different designs of artificial lure commonly used in handline fisheries. Lure colour did not significantly affect catches of pollack (Pollachius pollachius), saithe (Pollachius virens), cod (Gadus morhua), ling (Molva molva) or tusk (Brosme brosme). Cod showed a preference for lower hooks on the six hooks per reel set-up when lures were black and pollack showed a preference for lower hooks when the lures were blue. There were no significant differences in catches of saithe, cod, ling or tusk between the five lure types. However, catches of pollack on a novel ‘sonar’ lure were lower than on other lures. No evidence of a preference for any hook position on the reels was found with any of the lure types.     

THE UTILIZATION OF DRIED GRASS BY EARLY WEANED LAMBS

Three groups of 8 Polled Dorset Iambs were weaned at 8 weeks of age and were fed dried grass, a 50–50 mixture of dried grass and protein-supplemented barley and protein-supplemented barley. All rations were completed. Digestibility trials were also conducted and the effect of level of feed intake on nutrient digestibility investigated. The dried grass resulted in rates of gain comparable to those produced by the pelleted barley ration. Feed conversion efficiency was lowest for the grass and highest for the barley ration. An interaction between the dried grass and barley was observed in nutrient digestibility. Increasing the level of feeding from approximately maintenance to appetite tended to result in slight depressions in the digestibility of energy and protein of all rations. The results suggest that dried grass can be used successfully for intensive feeding of early weaned lambs and little nutritional advantage appears to be gained from combining dried grass with barley.     

Haemoparasite prevalence and Theileria parva strain diversity in Cape buffalo (Syncerus caffer) in Uganda

Cape buffalo (Syncerus caffer) are considered to be an important reservoir for various tick-borne haemoparasites of veterinary importance. In this study we have compared the haemoparasite carrier prevalence in buffalo from four geographically isolated national parks in Uganda [Lake Mburo National Park (LMNP), Queen Elizabeth National Park (QENP), Murchison Falls National Park (MFNP) and Kidepo Valley National Park (KVNP)]. Differences were seen in haemoparasite prevalence in buffalo from the four national parks. All the buffalo sampled in LMNP were carriers of Theileria parva however, buffalo from MFNP and KVNP, which are both located in the north of Uganda, were negative for T. parva. Interestingly, 95% of buffalo in the northern part of QENP were T. parva positive, however all buffalo sampled in the south of the park were negative. A high multiplicity of infection was recorded in all the buffalo found to be carrying T. parva, with evidence of at least nine parasite genotypes in some animals. Most of the buffalo sampled in all four national parks were carriers of T. mutans and T. velifera, however none were carriers of T. taurotragi, Babesia bovis, Babesia bigemina, Ehrlichia bovis or Ehrlichia ruminantium. All the buffalo sampled from LMNP were positive for T. buffeli and T. sp. (buffalo) however, buffalo from the parks in the north of the country (KVNP and MFNP) were negative for these haemoparasites. Anaplasma centrale and Anaplasma marginale were circulating in buffalo from all four national parks. T. parva gene pools from two geographically separated populations of buffalo in two of the national parks in Uganda (LMNP and QENP) were compared. The T. parva populations in the two national parks were distinct, indicating that there was limited gene flow between the populations. The results presented highlight the complexity of tick-borne pathogen infections in buffalo and the significant role that buffalo may play as reservoir hosts for veterinary haemoparasites that have the potential to cause severe disease in domestic cattle.