<Emphasis Type="SmallCaps">d</Emphasis>-Cloprostenol enhances estrus synchronization in tropical hair sheep

To compare the effects of PGF2α (dinoprost tromethamine) and d-cloprostenol in a two-dose protocol for estrus synchronization in hair sheep during breeding season in Yucatán, México, two experiments were conducted. In experiment 1, 61 cyclic hair sheep were divided into two groups: G1 (control n?=?30), two doses of 50 μg of dinoprost tromethamine IM with 12 days between applications, and G2 (n?=?31), two doses of 50 μg of d-cloprostenol IM at the same time interval. For determination of progesterone levels, 16 ewes from each group were randomly selected. In experiment 2, 70 cyclic hair sheep were assigned at the same treatments (G1 and G2, n?=?35) and 48 h after the second application, the ewes in estrus were detected by two vasectomized rams. Sheep with detected estrus were inseminated, and 45 days after, pregnant animals were identified by ultrasonography. An exact Fisher’s test was performed for the analysis of ewes in estrus (experiments 1 and 2) and number of pregnant ewes (experiment 2); for the comparison of time between end of treatment-estrus presentation, a survival analysis was used. Duration of estrus in hours was analyzed using a generalized mixed model (GLM) ANOVA whereas plasma progesterone concentrations were analyzed by non-linear regression. There were significant differences (P?<?0.05) in the proportion of ewes in estrus upon treatments (G1, 57% vs G2, 87% and G1, 37.1% vs G2, 65.7% in experiments 1 and 2, respectively), and between the end of treatment-onset estrus interval (P?<?0.01), survival curves showed the highest number of sheep in estrus between 40 and 48 h (G1, 43.7?+?8.05 h vs G2, 42.9?+?6.7 h, experiment 1). There were no significant differences (P?>?0.05) in duration of estrus (G1, 42?+?6.1 h, vs G2, 41.1?+?11.2 h, experiment 1) and pregnancy in the ewes that presented estrus, and were inseminated (G1, 38.4% vs 52.1%, experiment 2). With regard to concentrations of progesterone, significant differences (P?<?0.01) were found between treatments, and progesterone levels before the second application of d-cloprostenol were higher. In consideration of the results, it can be concluded that in a two-dose protocol of a luteolytic agent, more ewes presented estrus in response to d-cloprostenol compared to dinoprost tromethamine with similar pregnancy rates.     

Evaluation of radiometric faecal culture and direct PCR on pooled faeces for detection of Mycobacterium avium subsp. paratuberculosis in cattle

Dilution rates for pooled faecal culture (PFC) and direct IS900 polymerase chain reaction (D-PCR) tests were evaluated on faecal samples from infected cows mixed with uninfected faeces in dilutions from 1 in 5 to 1 in 50. PFC was performed by radiometric culture, with confirmation by IS900 PCR and restriction endonuclease analysis (PCR/REA) on growth, and by mycobactin dependency testing on solid medium. Using 37 culture positive faecal samples from 12 subclinical cows, 83.8% and 94.6% of samples were confirmed positive in the PFC assay at dilutions of 1 in 50 and 1 in 30, respectively. Lower dilutions (1 in 5 to 1 in 20) provided only marginally better sensitivity, and confirmation of PFC growth by PCR/REA was significantly more sensitive than mycobactin dependency. D-PCR had significantly lower sensitivity than PFC confirmed by PCR/REA, with pools of 1 in 50, 30, 10 and 5 yielding positive results in 64.9%, 70.3%, 78.4% and 83.8% of samples, respectively. Cattle considered to be shedding 1.5 x 10(6) viable M. avium subsp. paratuberculosis (Map)/g faeces (on the basis of estimated losses in processing and growth rates in radiometric broth) were positive at dilutions up to 1 in 50 in the PFC and D-PCR. Those shedding 5 x 10(5) viable Map/g were positive in the PFC at dilutions up to 1 in 40, but required a 1 in 10 dilution or less for D-PCR. The results suggest that for cattle shedding relatively high concentrations of Map in faeces (>2 x 10(5) viable Map/g), maximal dilutions of 1 in 30 for PFC and 1 in 10 for D-PCR would be applicable.     

Sampling and repeatability of radiometric faecal culture in bovine Johne's disease

The repeatability of detection of Mycobacterium avium subsp. paratuberculosis (Map) within and between samplings from 16 paratuberculous dairy cows (13 subclinical; 3 clinical) was investigated by radiometric culture of quadrants of faecal dung pats collected on four to seven occasions over a 10-16-day period. Results were compared to serological status and to pathological and bacteriological findings in multiple tissues obtained at slaughter from 15 of the animals 2-6 weeks after the faecal samplings. From faecal samples taken on 77 occasions over the 2-week period, 296/308 (96%) quadrants were culture positive, with samples from all cattle showing evidence of faecal shedding of Map. Histological lesions typical of paratuberculosis were present in 14 of the 15 cows examined at slaughter, varying in severity from mild (two animals) to moderate (4) and advanced (8), and all predilection tissue sites yielded Map. The negative faecal samples were derived from a single animal that was culture positive in two quadrants on each of the first two (of four) sampling occasions (i.e. culture positive in only 4 of 16 collected quadrants). This animal was found to be histologically negative at slaughter, and culture positive from three of five predilection tissue sites. Faecal samples from cows with subclinical and clinical paratuberculosis, with lesion severity ranging from mild to severe at multiple predilection sites, produced faeces with relatively consistent concentrations of Map within samples. There was significant variation in concentrations of Map between samples in individual animals over a period of 2 weeks, but this did not affect the dichotomous positive-negative culture status for 15 of the 16 cattle. A faecal sample collected non-randomly per rectum thus provides a representative specimen for detection of Map by radiometric culture on a single sampling occasion.     

Unraveling the morphological patterns of a subantarctic eelpout: a geometric morphometric approach

Phenotypic variation in organisms depends on the genotype and the environmental constraints of the habitat that they exploit. Therefore, for marine species inhabiting contrasting aquatic conditions, it is expected to find covariation between the shape and its spatial distribution. We studied the morphology of the head and cephalic sensory canals of the eelpout Austrolycus depressiceps (4.5–22.5 cm TL) across its latitudinal distribution in South Pacific (45°S–55°S). Geometric morphometric analyses show that the shape varied from individuals with larger snout and an extended suborbital canal to individuals with shorter snouts and frontally compressed suborbital canal. There was size variation across the sampled populations, but that size does not have a clear latitudinal gradient. Only 8% of the shape variation relates to this size variation (allometry), represented by a decrease in the relative size of the eye, and a depression of the posterior margin of the head. There were spatial differences in the shape of the head, but these differences were probably caused by allometric effects. Additionally, 2 of the canals of the cephalic lateralis pores and the head shape showed modularity in its development. This study shows that the morphology of marine fish with a shallow distribution varies across distances of hundreds of kilometers (i.e., phenotypic modulation).     

Historical influences dominate the composition of regenerating plant communities in abandoned citrus groves in north-central Florida

The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history. There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables, and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies may ultimately be less important than land use history in understanding current plant community composition in regenerating agricultural areas.     

Jackknife method for estimating the variance of the age composition using two-phase sampling with an application to commercial catches of swordfish (Xiphias gladius)

An estimate of the age composition of a commercial swordfish catch and its variance was obtained using the replicate full jackknife estimator for two-phase sampling where the sampling units in the first phase are clusters (vessel-trips) and the units of the second phase are individual fishes. The jackknife variance estimator was compared with an analytical estimator of variance commonly used in fisheries studies which ignores the clustering, and assumes simple random sampling of individual fish. The application of these naïve estimators to the Chilean South Pacific swordfish fishery results in an underestimation of the variance. This is a consequence of using an inappropriate primary sampling unit of analysis in the first-phase sample where the vessel-trip unit is replaced by an individual fish unit, thus ignoring the intra-cluster correlation in age samples. The jackknife estimator of variance is an alternative useful for complex two-phase sampling designs.     

Richard Lang

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Richard Lang