A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM: To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS: Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000?cells/mL at the first herd test after calving.

RESULTS: Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000?cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000?cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40–1.30).

CONCLUSIONS AND CLINICAL RELEVANCE: In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.     

Acute cortisol responses of calves to scoop dehorning using local anaesthesia and/or cautery of the wound

Objective To measure plasma cortisol responses in calves dehorned using a scoop after administration of local anaesthesia and/or cautery of the wounds.
Design A physiological study with controls.
Procedure There were six treatments: control handling with and without local anaesthesia, dehorning, dehorning after local anaesthesia, dehorning followed by wound cautery, and dehorning after local anaesthesia followed by wound cautery. Blood samples were taken before and after dehorning.
Results Dehorning caused an increase in plasma cortisol concentrations, which decreased a little to plateau values and then declined to pretreatment values 3 to 4 h after dehorning. The peak was smaller after local anaesthesia was administered but when its effects wore off, cortisol concentrations increased and thereafter were similar to those in the dehorned animals. The combination of local anaesthesia and cautery resulted in a plasma cortisol response similar to those in control calves with or without local anaesthesia.
Conclusions If plasma cortisol concentrations reflect the distress being experienced by the calves, then local anaesthesia reduces the acute distress for about 3 h after dehorning but not during the subsequent 3 to 4 h. Combining local anaesthetic and cautery prevented the significant increase in plasma cortisol following dehorning and may eliminate the acute distress caused by scoop dehorning.     

Epidemiology and pathogenesis of Mycobacterium bovis infection of red deer (Cervus elaphus) in New Zealand

AIMS: This study was initiated to investigate aspects of the epidemiology, pathogenesis and transmission of tuberculosis in wild red deer, with the aim of determining whether this species may be considered a reservoir host of Mycobacterium bovis in New Zealand. METHOD: One hundred and six wild red deer (Cervus elaphus) carcasses from the Castlepoint and Hauhungaroa Range areas, which are endemic for bovine tuberculosis, were examined for the presence of M. bovis infection. Samples were also examined from 46 skin test-positive farmed deer killed at two deer slaughter premises. Where possible, a standard set of tissues and excretion site samples was collected for mycobacteriological examination. RESULTS: Fifty-eight infected deer were identified, and of these 28% showed no gross lesions. The prevalence of tuberculosis confirmed by culture in the wild deer was 32%. Only one of 18 deer younger than 1 year was infected. Mature deer (>2 years) were 12 times more likely to be infected than those under 1 year of age. Infected older deer were less likely to show typical gross lesions than younger animals. Mycobacterium bovis was isolated from the oropharyngeal tonsil of 34 of 56 (61%) of the infected deer, and this was the most commonly infected site. Gross lesions were found in 18 of the 34 infected tonsils and only one of these showed a purulent tonsillitis. Mycobacterium bovis was recovered from four of 53 nasopharyngeal tonsils, four of 53 oropharyngeal swabs, one of 53 tracheal and nasal swabs, and one of 46 faecal samples, but not from any urine specimens. CONCLUSION: These findings suggest that significant bacillary excretion from infected deer was uncommon, and is more likely to occur in severely affected animals. This study has confirmed the importance of mucosa-associated lymphoid tissues (MALT), particularly the oropharyngeal tonsil, in the pathogenesis of tuberculosis in deer. The findings justify investigation of the hypotheses that the prevalence of tuberculosis in wild deer in New Zealand is high due to transmission of infection from possums, and that in the absence of an infected possum population, the prevalence of tuberculosis in deer is likely to be low, and spatially patchy. CLINICAL RELEVANCE: The results suggest that about one quarter of infected deer show no detectable gross lesions. This implies that many infected carcasses may enter the food chain unrecognised and that the estimated sensitivity and specificity of diagnostic tests may be erroneous if there is a difference in test performance between those conducted on deer with or without gross lesions. Diagnostic sensitivity following slaughter may be improved by routine culture of oropharyngeal tonsils and careful examination of lungs for adhesions and small subpleural tubercles.     

Genital pathology of feral male goats

Genitalia from 1000 feral male goats derived from western Queensland and New South Wales were examined after slaughter at an abattoir and the prevalence of abnormalities determined. Ulcerative balanoposthitis, considered due to caprine herpesvirus infection, was observed in 11 animals (1.1%); acidophilic intranuclear inclusions were found in 7 of these. Other conditions included focal hypoplasia of seminiferous tubules in 2 bucks (0.2%), segmental aplasia of the epididymis (one buck, 0.1%), bulbourethral gland cysts with contained aggregations (33 bucks, 3.3%) and haemangiosarcoma of the bulbourethral gland in one animal. The low prevalence of several conditions such as spermatic granuloma, cryptorchidism, and testicular hypoplasia, was attributed largely to the fact that the bucks examined were horned so that the recognised association between genital abnormalities and polledness did not apply.     

Characteristic site disturbance due to harvesting and extraction machinery traffic on sensitive forest sites with peat soils

The effects of wood harvesting and extraction machinery traffic on sensitive forest sites with peat soils were characterised with the objective of quantifying the threshold levels beyond which significant site impacts (compaction and rutting) would occur. The treatments involved running the machines in selected extraction racks (i.e., 3 m wide machine routes) while conducting normal wood thinning and extraction operations comprising one and two passes by the harvester and the forwarder with full payload, respectively. Soil disturbance thresholds were established by testing the level of significance of the difference in induced soil damage and compaction before and after machine traffic treatments. For volumetric soil water content lying between 10.0 and 14.9%, threshold cone penetration resistance levels for two 600/55–30.5 tyres were found to range from 594 to 640 kPa for deep-raised peat soil with initial strength lying between 524 and 581 kPa. In general, the proportion of the total rut depth data in each rack that exceeded the threshold level of 21.5 cm was about 5%. The threshold value corresponds to sinkage equivalent to 15% of the overall wheel diameter of the harvester, above which machine mobility would be hampered considerably. In addition, after harvester traffic the mean rut depth per unit rack length was 10.2×10⁻² cm/m, and it ranged from 0.7 to 24.7×10⁻² cm/m.     

Semen cryopreservation of salmonid fishes: influence of handling parameters on the postthaw fertilization rate

Using the cryopreservation method of Lahnsteiner, Berger, Weismann & Patzner (1995, Aquaculture Research 26 , 801-807) the influence of allowable variations of methodical parameters (storage of semen before cryopreservation, dilution ratios in the extender, equilibration in the extender, cooling rates, storage of deep-frozen semen in liquid nitrogen, storage of frozen/thawed semen, minimal sperm/egg ratio) was investigated under the aspect of routine utilization. Under optimized experimental conditions, fertilization rates were 90-100% of controls in Oncorhynchus mykiss (Walbaum), Salmo trutta L. f. lacustrisSalmo truttaL.f. fario and Salvelinus fontinalis (Mitchill). The following results were obtained: 1. Storage of untreated semen for more than 1 h before cryopreservation decreased the postthaw fertility. 2. Equilibration of semen up to 20 min in the extender did not affect the postthaw fertility. 3. Optimal dilution ratio of semen in the extender was threefold in Oncorhynchus mykiss and Salvelinus fontinalis. Lower dilution ratios decreased the postthaw fertility, higher dilution ratios did not affect the postthaw fertility. In Salmo trutta f. lacustris and Salmo trutta f. fario, which have a higher sperm density, optimal dilution ratio of semen in the extender was fivefold to sevenfold. 4. In Oncorhynchus mykiss, as in Salmo trutta f lacustris and Salmo trutta f. fario, the optimal freezing height was at 1.5 cm above the level of liquid nitrogen (-110 ± 2^oC); in Salvelinus fontinalis it was 2.5 cm above the level of liquid nitrogen (-92 ± 2^oC). Changes in the freezing height of 0.5 cm (about 10^oC) resulted in a significant decrease of postthaw fertility. 5. Storage of deep-frozen semen for up to 370 days in liquid nitrogen had no influence on its postthaw fertilization rate. 6. Storage of frozen/thawed semen for 30 s before insemination significantly decreased its postthaw fertility. 7. Reliable minimal sperm:egg ratio to obtain fertilization rates of 90-100% of control was 3-5 X 10⁵ spermatozoa egg^-1.     

Body measurements of newborn calves and relationship of calf shape to sire breeding values for birth weight and calving ease

Body measurements on Angus- (n = 374) and Polled Hereford-sired (n = 438) calves were used to quantify calf shape via multivariate factor analysis, and measurements on Polled Hereford-sired calves were further used to investigate relationships between calf shape and sire expected progeny differences (EPD) for birth weight and first-calf calving ease. Calf birth weight, head circumference, shoulder width, hip width, heart girth, cannon bone circumference and length, and body length were recorded at 24 h postpartum. Sire birth weight EPD was positively associated (P less than .05) with all calf measures but only with head and cannon circumference after adjustment for phenotypic birth weight and gestation length. Thus, at constant birth weight, calves from higher birth weight EPD bulls tended to have larger cannon and head circumferences. Calving ease EPD was negatively related (P less than .05) to all calf measures except shoulder width. After adjustment for birth weight, only cannon circumference was associated with calving ease EPD, and this effect was removed by additional adjustment for birth weight EPD. Thus, at constant birth weight, bulls with higher EPD for calving ease sired calves with smaller cannon circumference, but at constant birth weight EPD, body measures were not associated with calving ease EPD. Factor analysis defined underlying skeletal width and frame components of shape (independent of birth weight) for both sire breeds. Calf shape differed among sires and was in part explained by birth weight EPD. No additional variation in shape was explained by calving ease EPD. Calf shape seemed to add no information for prediction of dystocia to that provided by birth weight EPD.