A longitudinal study of Neospora caninum infection on a dairy farm in New Zealand

A 600-cow New Zealand dairy herd experienced an abortion storm in 1997 and was monitored (blood sampling at about 3-month intervals) from May 1997 until January 1999. Abortion risk reached 9% in 1997 and was highest in heifers at 19%. The abortion risk decreased in 1998 to 3.2% (still somewhat higher than during the years prior to the outbreak). The serological reaction pattern for Neospora caninum showed an association with abortion risk only around the time of the 1997 outbreak when seropositive cows were 4.2 times more likely to abort than negative ones. Over the whole study period, only 27% of cows that were sampled on all nine visits always tested negative. Offspring from dams which had positive tests for Neospora caninum were 2.4 times more likely to abort than those from dams testing consistently negative. Controlling for age and breed, seropositive cows produced more milk than those that were consistently negative. Infection might have been present endemically within this herd prior to the epidemic, but in 1997 an additional factor appeared to have triggered the outbreak.     

Regulation of Corpus Luteum-function in the Bitch

Functional lifespan of the corpus luteum (CL) in non-pregnant dogs exceeds that of pregnant animals and may last for more than 80 days. Prolactin and LH act luteotropic, however, luteolytic mechanisms are poorly understood. Other than in life stock there is no uterine luteolysine and it was postulated that local paracrine/autocrine mechanisms might play a major role. In following this hypothesis the present investigations have clearly demonstrated that up-regulation of prostaglandin synthesis in the CL as indicated by the expression of cyclo-oxygenase II occurs with its formation and not regression, pointing towards a luteotropic rather than luteolytic action. Throughout dioestrus luteal and other cells of the CL express the oestrogen (ERalpha) and progesterone receptor (PR). While ERalpha expression was not cycle-related, PR concentrations were high in the early and late-luteal phase and a regulatory role of both steroids on CL-function is assumed. As in other species also in the dog the immune system seems to participate in the mechanisms regulating CL-function as an increased presence of lymphocytes within the CL could be detected at the beginning [CD4- CD8-, major histocompatibility complex (MHC)II-antigen expressing cells] and during the latter half of dioestrus (CD8- and MHCII-antigen expressing cells). Thus, leucocyte-derived cytokines may be important and the expression of the mRNA for interleukin (IL)8, IL10, IL12, tumour necrosis factor (TNF)alpha and transforming growth factor (TGF) beta1 was observed throughout dioestrus. Electron microscopy confirmed the slow process of luteolysis; first distinct signs of degeneration were seen on day 60, accompanied by some apoptotic events. From these data it is concluded that luteal regression as monitored by the gradual decrease of systemic progesterone concentrations in the dog is not an actively regulated but rather a permissive process. Immune-mediated events may play a key role. Changes in the vascular supply, as indicated by the expression of endoglin, seem to be of lower importance.     

In vitro Evaluation of in vivo Fertilizing Ability of Frozen Rabbit Semen

The present work studied different spermatozoa parameters and the ability of frozen rabbit spermatozoa to fertilize, in vitro, in vivo‐matured oocytes, as a test to predict their in vivo fertility and prolificacy. Semen from rabbit bucks was frozen using two freezing protocols [in a freezer at ?30°C or in liquid nitrogen vapour (LNV)]. For the in vivo trial, females were inseminated with frozen‐thawed spermatozoa. Oocytes used for in vitro testing were recovered 14 h after ovulation induction from donors and co‐incubated with 2 × 10⁶ frozen‐thawed spermatozoa during 4 h at 37°C in Tyrode's medium under an atmosphere of 5% CO₂ in air with maximal humidity. After co‐incubation period, presumptive zygotes were cultured in TCM199 supplemented with 20% foetal bovine serum (FBS), under the same conditions described above. Although no statistical differences were observed between freezing protocols in seminal parameters [motility rate: 40 and 35%, VCL: 35 and 46 μm/s, amplitude of lateral head displacement (ALH): 1.7 and 2.4 μm, for semen frozen at ?30°C and in LNV, respectively], significant differences were noted in the fertilizing ability in vivo and in vitro. Semen frozen at ?30°C showed the highest fertilizing ability in vitro (26.7% vs 6.2 and 8.7% for semen frozen at ?30°C, in LNV and fresh semen, respectively) and the lowest fertility rate in vivo (21.7% vs 64.2% and 70.6% for semen frozen at ?30°C, in LNV and fresh semen, respectively). Sperm frozen at ?30°C seemed to be more capacitated.     

Comparison of three serological tests and an interferon-gamma assay for the diagnosis of paratuberculosis in experimentally infected sheep

OBJECTIVE: To compare the diagnostic performance of a complement fixation test, an agar gel immunodiffusion test, an enzyme-linked immunosorbent assay, and a whole-blood interferon-gamma assay for paratuberculosis in 14 sheep experimentally infected with Mycobacterium avium subsp paratuberculosis. EXPERIMENTAL DESIGN: Longitudinal study. RESULTS: The IFN-gamma assay detected more experimentally infected sheep, and earlier, than any of the serological tests. None of the antibody assays was able to detect all sheep with histologically confirmed paratuberculosis. CONCLUSIONS: The superior performance of the IFN-gamma assay in detecting infected sheep in this small experimental population warrants its further evaluation in a larger population of sheep naturally exposed to M a paratuberculosis.     

Performance characteristics of an enzyme-linked immunosorbent assay performed in milk for the detection of liver fluke (Fasciola hepatica) infection in cattle

AIM: To determine the performance characteristics of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against liver fluke (Fasciola hepatica) in bovine milk. METHODS: Serum and milk from liver fluke infected and non-infected cattle was assayed in a commercially available enzyme-linked immunosorbent assay. Serum test results were used to determine the "gold standard" infection status of cattle and milk ELISA results assessed by ROC analysis. RESULTS: ROC analysis suggested changes to the ELISA protocol, arriving at milk dilutions assayed considerably higher than those suggested by the manufacturer. With those changes, the ELISA performed with high sensitivity and specificity, 95 and 98.2%, respectively, for individual bovine milks (relative to sera). For bovine tank milks, sensitivity was lower, with bulk milks only testing positive if 60% or more of cattle milking in the herd were infected. CONCLUSIONS: The analysis of the ELISA's performance when used on individual bovine milks demonstrated high sensitivity and specificity. ROC analyses optimised the assay conditions and cut-off point suggested by the manufacturer for this commercial diagnostic assay. This would help with the identification and control of fasciolosis, enabling simpler sample collection.     

Effect of clenbuterol on growth,carcase and skeletal muscle characteristics in broiler chickens

1. Male and female broiler chickens (144 in total) were given diets supplemented with clenbuterol (CB) at 0 (control) and at 1 mg/kg between 28 and 49 d of age to study the effect of CB on growth, carcase and skeletal muscle.

2. CB improved growth in males by increasing daily weight gain and final live weight and by lowering food conversion ratio. In females it changed the carcase composition by reducing abdominal fat pad and by increasing the proportion of protein. Consequently, carcase protein gain was increased in both sexes (11% and 16%, respectively).

3. Skeletal muscle weights were enhanced by between 6% and 22%. Muscle fibre diameters were increased in extensor hallucis longus (EHL) but not in gastrocnemius (GAS) muscle. This increase was more pronounced in females. EHL total muscle fibre number remained unchanged. The proportion of fast‐twitch glycolytic fibres was increased at the expense of fast‐twitch oxidative fibres in males only. Nuclear/cytoplasm and DNA/protein ratios tended to be decreased by CB.

4. From the elevated EHL muscle RNA/DNA, unchanged protein/RNA and translation activity it is suggested that CB stimulated protein synthesis at the pretranslational level. Reduced protein degradation is deduced from decreased neutral calcium‐dependent proteolytic activity.

5. It is concluded that broiler chickens respond to long‐term CB treatment as has been shown in various mammals. However, the sex‐specific response in growth, carcase composition and skeletal muscle cellularity is more clearly apparent in broiler chickens.