Bovine leptospirosis: the effects of vaccination on serological responses as determined by complement fixation and microscopic agglutination tests

Fifty-one calves were divided into six trial groups of seven to eleven animals and vaccinated with a commercial leptospiral vaccine containing serovars pomona and hardjo. Vaccinations were given at 6,7,14 or 21 months of age and animals in various groups were vaccinated on one to four occasions. Antibody responses were determined by the microscopic agglutination test (MAT) and the complement fixation test (CFT) at one to four weeks intervals until 66 weeks after the start of the trial. Fifty percent or greater agglutination in serum diluted 1:100 or more and 50% or greater fixation of complement in serum diluted 1:20 or more were considered positive titres in the MAT or CFI respectively. Positive titres were still present in some animals six weeks after vaccination at 21 months of age. In other cases MAT titres (range 1:100-1:3000) persisted for 7-23 weeks and CFI titres (range 1:20-1540) persisted for 1-14 weeks. Marked individual variation in serological findings occurred using either test. In general the number of animals producing a positive titre, and the magnitude and persistence of titres was related to the number of doses of vaccine given. It was concluded that for diagnostic purposes neither the CFT nor the MAT could reliably differentiate titres due to vaccination from those following natural infections.     

A randomized clinical trial of the effect of the time of administration of cloprostenol on detention of estrus in dairy cattle

We performed a clinical trial to study whether cows with palpable corpora lutea treated with cloprostenol by the farmer on the morning following examination (median time 0630 hours) were seen in heat and conceived more frequently than cows treated by the veterinarian immediately following the reproductive examination (median time 1210 hours).

There were no significant differences between the two groups in the proportions of cows seen in estrus or fertility at the induced estrus.

The proportions of animals that had the time of onset of estrus recorded and were seen in estrus during working hours (0800-1600 hours) were also not significantly different between the veterinary-treated and farmer-treated groups.

Under the conditions of this study, there was no reason to prefer prescribing early morning administration of cloprostenol by farmers over immediate administration of the drug by the clinician.

     

Actinobacillus suis infection of horses

Nineteen isolates of Actinobacillus suis were recovered from horses during the period October 1978-December 1980. Animals varied in age from a full term foetus to 12 years. One isolate was obtained from the nose of an apparently healthy horse, the remainder were obtained from still-born foetuses (2), foals dying within a week of birth (5), older animals with respiratory (6) or genital infections (3) or abscesses in the jaw (1). One isolate was obtained from the lung of a 2-week-old foal which had shown diarrhoea. The bacteriological characteristics of the isolates and the pathological lesions present in eight cases are described. The organism has a wide geographical distribution in New Zealand, and in the northern part of the North Island appears to be more common than A. equuli.     

Carbon allocation and morphology of cherrybark oak seedlings and sprouts under three light regimes

• ? Continued problems in regenerating oak forests has led to a need for more basic information on oak seedling biology.
• ? In the present study, carbon allocation and morphology were compared between cherrybark oak (Quercus pagoda Raf.) seedlings and sprouts at 1-Lag grown in full, 47%, and 20% sunlight.
• ? Results indicated that cherrybark oak seedling carbon allocation and morphology responded plastically to light availability. In full light, roots were sinks for ¹⁴C, while shoots were sinks for ¹⁴C under reduced light availability. Cherrybark oak sprouts exhibited similar carbon allocation patterns in response to light availability, but displayed stronger shoot sinks than seedlings when grown underreduced light availability. We also showed that young oak sprout roots are a sink for ¹⁴C-photosynthates.
• ? Results from this study point to the need for a morphological index for oak sprout development so more precise comparisons in sprout development and physiology can be made with seedlings.

     

Designing fecal pellet surveys for snowshoe hares

Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. Fecal pellet counts are often used as an index of density or habitat use of snowshoe hares, Lepus americanus, but previous surveys have used different plot types and sample sizes, leading to problems comparing results from different studies and questions about the inferential power of each study. In this paper, we use field data and simulations to examine how the precision, bias, and efficiency of four commonly used plot types vary with plot type, pellet density, and sample size. Although no one plot type was consistently superior, we recommend thin rectangles (5.08 cm × 305 cm (2 in. × 10 ft), 0.155 m²) or 1 m² circles over 0.155 m² circles or 10 cm × 10 m (1 m²) rectangles. We recommend that researchers explicitly address the power of their survey design to detect different pellet densities, because much larger sample sizes are needed at low pellet densities than at high pellet densities to obtain similar precision. Small sample sizes are also much more likely to be biased, which could lead to incorrect inferences about management of snowshoe hare populations. Both uncleared and cleared plots performed well and will have value in different research contexts.     

The relationships among palpator experience, milk progesterone concentration and estrus and fertility in cows with palpable corpora lutea treated with cloprostenol

Two hundred and fifty-one cows fresh at least 37 days with normal reproductive tracts and palpable ovarian structures which clinicians believed to be corpora lutea and which were presumed to be producing progesterone were treated with 500 micrograms of cloprostenol. The cows were stratified into three groups based on milk progesterone concentrations in whole milk samples taken at the time of examination. The low group had milk progesterone concentrations less than or equal to 1 ng/ml, the intermediate group had milk progesterone concentrations between 1 and 3 ng/ml, and the high group had milk progesterone concentrations greater than or equal to 3 ng/ml. The proportion of cows in each group inseminated within 5 days of treatment and the fertility at that breeding were compared. There were no significant differences among the groups with respect to the proportion of cows that came into estrus within 5 days. However, the conception rate of the high group (54%) was significantly greater than that of the intermediate group (26%). To study the relationship between practitioner experience and diagnostic accuracy the proportion of cows with low, intermediate and high concentrations of progesterone selected by clinicians with more than 3 years experience was compared to that for clinicians with 3 years of experience or less. Less experienced clinicians were significantly more likely to make a false positive diagnosis of functional luteal tissue in cows with palpable ovarian structures than were more experienced clinicians.