The influence of various factors on some methods of estimating fibre and follicle population density in the skin of Merino sheep. I. Methods of delineating area of natural skin

1958 ◽  
Vol 9 (2) ◽  
pp. 237 ◽  
Author(s):  
HB Carter ◽  
HN Turner ◽  
MH Hardy
Keyword(s):  
Population Density ◽  
Body Region ◽  
Skin Area ◽  
Sampling Errors ◽  
Density Estimates ◽  
Merino Sheep ◽  
Coefficients Of Variation ◽  
Biopsy Punch ◽  
The Mean ◽  
Influence Measurement

Many factors may influence measurement of skin area for estimation of fibre or follicle population density. This paper analyses the influence of method of delineation (hairpin calliper, Hardy clipper, or Carter biopsy punch), type of sheep (wrinkled or plain), body region, and sheep individuality on the mean density estimated and on the error of estimation. With either a biopsy punch or a 1 in.2 hairpin calliper in the midside region, sampling errors of the order of 8–11 per cent. were found for density estimates in a series of field observations on Merino and Corriedale ewes, with between-sheep coefficients of variation ranging from 13 to 18 per cent.

Evaluation of controlled release devices for administration of chromium sesquioxide using fistulated grazing sheep. 2. Variation in rate of release from the device

1990 ◽  
Vol 41 (5) ◽  
pp. 977 ◽  
Author(s):  
EP Furnival ◽  
KJ Ellis ◽  
FS Pickering
Keyword(s):  
Controlled Release ◽  
Dry Matter ◽  
Statistical Correlation ◽  
Faecal Output ◽  
Merino Sheep ◽  
Coefficients Of Variation ◽  
Release Device ◽  
Flow Through ◽  
The Mean ◽  
Release Devices

Merino sheep fitted with rumen cannulae and varying in liveweight, grazed Phalaris aquatica pastures with high and low dry matter mass. One or more controlled release devices were tethered inside the rumen and attached to its cannula. The position of the plunger within the controlled release device was recorded every 2 or 3 days for periods of up to 19 days, and the mean rate of plunger movement was calculated. Faecal output and flow of rumen digesta were measured concurrently in two experiments. Rate of plunger movement was measured in 152 devices and found to be substantially constant over time, but significant differences in mean rate of plunger movement were observed between formulation type, between sheep and between pastures varying in herbage mass. Coefficients of variation between sheep ranged from � 6 to �14%, and differences between pasture means ranged from 1 to 14%. Some of this variation was associated statistically with faecal output; assuming a linear relationship, a change in dry matter output of 100 g/day was associated with a change in plunger rate of 0.05 mm/day or about 6% of the mean rate. Liquid flow through the rumen was the rumen variable which had the highest statistical correlation with the rate of plunger movement.

Estimating lizard population density: an empirical comparison between line-transect and capture–recapture methods

2013 ◽  
Vol 40 (7) ◽  
pp. 552 ◽  
Author(s):  
J. Ruiz de Infante Anton ◽  
A. Rotger ◽  
J. M. Igual ◽  
G. Tavecchia
Keyword(s):  
Population Density ◽  
Spatial Data ◽  
Natural Populations ◽  
Line Transect ◽  
Sampling Errors ◽  
Density Estimates ◽  
Mark Recapture ◽  
The Real ◽  
Podarcis Lilfordi ◽  
Capture Recapture

Context In most natural populations, exhaustive counts are not possible and estimates need to be derived from partial sampling by using analytical methods that account for biological processes, sampling errors and detection probability. The methods available have contrasting pitfalls and payoffs in relation to the assumptions made but are seldom contrasted on the same population. Aims We compared density estimates derived by different sampling methods. Despite the real density being unknown, the ‘soft’ validation of density estimates might help to better understand the possible pitfalls and payoffs of each method. This was done in three closed populations and with three different habitat typologies to disentangle the effects of different capture-detection processes to those introduced by the method itself. Methods We considered the problem of estimating population density of the endemic Balearic lizard, Podarcis lilfordi, in three island populations. We compared estimates derived by distance sampling (LT) in three types of habitat with those calculated from a simultaneous 3-day capture–mark–recapture study. Capture histories of marked individuals were used to estimate density using spatially explicit capture–recapture models (SECR) and a capture–mark–recapture model without spatial data (CMR). Moreover, we empirically assessed the influence of survey duration by extending the survey in the largest island to five occasions. The real population density was unknown and absolute accuracy of each method cannot be assessed; nevertheless, relative estimates might be informative. Key results LT estimates had the greatest coefficient of variation in vegetated habitats, corresponding to possible departures from model assumptions. SECR estimates differed among islands and were from 12% to 37% lower than those derived by LT but only in the largest islands with high and dense vegetation. CMR estimates depended on the number of occasions whereas SECR did not and showed lower variance. LT and SECR estimates showed differences across islets. Conclusions Line-transect and capture–recapture methods gave comparable results but the interaction between recapture processes and habitat types should be considered when inferring density to the whole area. We found density estimates between 1500 and 2500 individuals ha–1, being a higher value than those found for lizards in continental regions. Implications Pitfalls and payoffs of each method are discussed to optimise experimental design in estimating population density.

scholarly journals Repeated Pelvic Radiographs in Infants, After Harness Treatment for Developmental Dysplasia of the Hip, Carry Very Low Radiation Risk

2021 ◽  
Author(s):  
Elizabeth Vogel ◽  
Thomas Leaver ◽  
Fiona Wall ◽  
Ben Johnson ◽  
Michael Uglow ◽  
...  
Keyword(s):  
Radiation Exposure ◽  
Radiation Risk ◽  
Low Risk ◽  
Lifetime Risk ◽  
Body Region ◽  
Pavlik Harness ◽  
Pelvic Radiographs ◽  
Risk Of Malignancy ◽  
The Mean

Abstract Objective There are no data on the effect of X-Ray irradiation to the vulnerable pelvic organs of babies during DDH follow-up. This study aims to calculate, for the first time, the radiation exposure to infants during follow-up for DDH harness treatment, and thus quantify the lifetime risk of malignancy. Methods Patients who had completed 5 years’ follow-up following successful Pavlik harness treatment were identified from the hospital DDH database. The radiation dose was extracted from the Computerised Radiology Information System database for every radiograph of every patient. The effective dose (ED) was calculated using conversion coefficients for age, sex and body region irradiated. Cumulative ED was compared to Health Protection Agency standards to calculate lifetime risk of malignancy from the radiographs. Results All radiographs of 40 infants, successfully treated in Pavlik harness for DDH, were assessed. The mean number of AP pelvis radiographs was 7.00 (range: 6–9, mode: 7). The mean cumulative ED was 0.25 mSv (Range: 0.11–0.46, SD: 0.07). This is far lower than the annual ‘safe’ limit for healthcare workers of 20 mSv and is categorised as “Very Low Risk”. Conclusion Clinicians involved in the treatment DDH can be re-assured that the cumulative radiation exposure from pelvic radiographs following Pavlik harness treatment is “Very Low Risk”. Whilst being mindful of any radiation exposure in children, this study provides a scientific answer that help addresses parental concerns.

An Assessment of Sampling Methods and Microbiological Hygiene Indicators for Process Verification in Poultry Slaughterhouses

2006 ◽  
Vol 69 (1) ◽  
pp. 145-153 ◽  
Author(s):  
M. L. HUTCHISON ◽  
L. D. WALTERS ◽  
G. C. MEAD ◽  
M. HOWELL ◽  
V. M. ALLEN
Keyword(s):  
Storage Time ◽  
Sampling Method ◽  
Indicator Bacteria ◽  
Aerobic Bacteria ◽  
Process Verification ◽  
Bacterial Indicator ◽  
Coefficients Of Variation ◽  
Microbiological Testing ◽  
The Mean ◽  
Poor Relationship

Studies to determine the appropriateness of the use of populations of indicator bacteria on poultry carcasses for process verification were undertaken in commercial slaughterhouses. Samples were collected from neck skin by excision or from whole carcass rinses and were examined for a range of presumptive process hygiene indicator bacteria. Coefficients of variation were calculated for each bacterial indicator and were significantly lower in excised samples, indicating more reproducible bacterial recovery by this sampling method. Total viable counts of aerobic bacteria, Enterobacteriaceae, and Pseudomonas in samples collected by excision had the lowest coefficients of variation when compared with other indicators and were therefore used for further study. The uncertainties associated with the quantification of each bacterial indicator were calculated and were lowest overall for total viable counts of aerobic bacteria. In general, uncertainty was higher for lower bacterial numbers. Results of microbiological testing on pooled excised neck skin samples were not significantly different from the mean of individually analyzed samples. Bacterial numbers increased by 1 log unit when cultures were stored under chilled conditions typical of those used for transporting samples to external laboratories, but the increases were not significant for Pseudomonas and aerobic bacteria when storage time was less than 17 h. Weak relationships were identified between bacterial indicator numbers and duration of processing, although cleanliness of the processing environment diminished visibly during this time. In the plants visited for this study, there was a poor relationship between presumptive bacterial indicator numbers and process hygiene. Consequently, bacterial analyses for process verification purposes may be of limited value.

Biomass estimates derived from sector subsampling of 360° spherical images

2021 ◽  
Author(s):  
Xiao Dai ◽  
Mark J Ducey ◽  
Haozhou Wang ◽  
Ting-Ru Yang ◽  
Yung-Han Hsu ◽  
...  
Keyword(s):  
Basal Area ◽  
Sampling Errors ◽  
Eastern Canada ◽  
Individual Tree ◽  
Inventory Costs ◽  
Standard Error Estimation ◽  
The Mean ◽  
Biomass Ratio ◽  
Spherical Images ◽  
Additional Level

Abstract Efficient subsampling designs reduce forest inventory costs by focusing sampling efforts on more variable forest attributes. Sector subsampling is an efficient and accurate alternative to big basal area factor (big BAF) sampling to estimate the mean basal area to biomass ratio. In this study, we apply sector subsampling of spherical images to estimate aboveground biomass and compare our image-based estimates with field data collected from three early spacing trials on western Newfoundland Island in eastern Canada. The results show that sector subsampling of spherical images produced increased sampling errors of 0.3–3.4 per cent with only about 60 trees measured across 30 spherical images compared with about 4000 trees measured in the field. Photo-derived basal area was underestimated because of occluded trees; however, we implemented an additional level of subsampling, collecting field-based basal area counts, to correct for bias due to occluded trees. We applied Bruce’s formula for standard error estimation to our three-level hierarchical subsampling scheme and showed that Bruce’s formula is generalizable to any dimension of hierarchical subsampling. Spherical images are easily and quickly captured in the field using a consumer-grade 360° camera and sector subsampling, including all individual tree measurements, were obtained using a custom-developed python software package. The system is an efficient and accurate photo-based alternative to field-based big BAF subsampling.

scholarly journals Population density of helminths in ducks: effects of host’s age, sex, breed and season

1970 ◽  
Vol 6 (1) ◽  
pp. 45-51 ◽  
Author(s):  
T Farjana ◽  
KR Islam ◽  
MMH Mondal
Keyword(s):  
Population Density ◽  
Key Words ◽  
Parasitic Infection ◽  
Winter Season ◽  
Helminth Parasites ◽  
Domestic Ducks ◽  
The Mean

 A study was conducted to investigate the population density of helminth parasites in domestic ducks (Anas boschas domesticus) in relation to host's age, sex, breed and seasons of the year from March 2002 to May 2003. A total of 300 ducks were collected from different villages of Netrokona and Mymensingh districts of Bangladesh and autopsied to collect the parasites and counted to determine the population density of parasites. Off 300 ducks examined, 290 (96.66%) were infected with 17 species of helminth parasites in which 11 species were trematodes, 4 were cestodes and 2 nematodes. Among the parasites, density of cestodes was the highest (33.15±5.26), followed by trematodes (5.98±1.32); and nematodes (2.95±0.68). Mean density of parasites increased with the increase of age (young: 21.23±1.09, adult: 26.18±2.14 and old: 27.87±2.98) while the mean density of most of the helminth parasites was higher in female ducks (31.35±4.72) than in males (27.52±3.32). Indigenous ducks (33.72±3.61) were infected with the highest load of helminths than Khaki Campbell breed (29.61±4.32) of ducks. Mean density of most trematodes (5.42±0.80) were highest in winter season whereas mean density of all cestodes (48.43±4.85) and nematodes (4.13±1.76) were highest in summer.  The present study suggests that age, sex, breed of ducks and seasons of the year influence the parasitic infection to a greater extend. Key words: Population density, helminths, duck, Bangladesh DOI = 10.3329/bjvm.v6i1.1338 Bangl. J. Vet. Med. (2008). 6 (1): 45-51

LRF and TRF test during long-term danazol treatment: increase of the LH and FSH responses but decrease of the prolactin and TSH responses

1983 ◽  
Vol 104 (1) ◽  
pp. 1-5 ◽  
Author(s):  
J. Leppäluoto ◽  
L. Rönnberg ◽  
P. Ylöstalo
Keyword(s):  
Clinical Symptoms ◽  
Follicular Phase ◽  
Blood Samples ◽  
Hormone Levels ◽  
Coefficients Of Variation ◽  
The Mean ◽  
Thyroid Hormone Levels ◽  
Low Serum

Abstract. Seven patients suffering from severe endometriosis were treated with danazol 200 mg × 3 daily for 6 months. Clinical symptoms were alleviated and menses disappeared in response to the treatment. After cessation of the treatment the menstrual bleedings returned in 1–3 months. Blood samples for determination of gonadotrophins, prolactin (Prl), oestradiol (E2), progesterone, thyroid hormones and thyrotrophin in radioimmunoassays were taken and a combined TRF and LRF test carried out in the follicular phase before treatment, at the 6th month of treatment and after reappearance of the first menses. There were no statistically significant changes in the basal levels of serum FSH, LH or TSH during the danazol treatment. Neither was there any change in episodic secretions of FSH, LH or Prl, as determined by the mean coefficients of variation of the hormone levels in seven consecutive samples taken at 20 min intervals. On the other hand, serum E2, Prl and thyroid hormone levels were significantly decreased in the 6th month of treatment. In the TRF-LRF test the responses of serum FSH and LH were significantly higher and those of serum Prl and TSH significantly lower during danazol treatment than before. Prl responses remained lowered after the treatment. It appears that low serum oestrogen levels, induced by the danazol treatment, sensitize the pituitary gonadotrophs to exogenous LRF, but make the sensitivity of thyrotrophs and lactotrophs lower to exogenous TRF. These results thus indicate that danazol does not make the pituitary gonadotrophs insensitive to LRF, but danazol may rather inhibit the secretion of hypothalamic LRF.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

Density and activity patterns of ocelot populations in Yasuní National Park, Ecuador

Mammalia ◽  
2016 ◽  
Vol 80 (4) ◽  
Author(s):  
Julia Salvador ◽  
Santiago Espinosa
Keyword(s):  
Population Density ◽  
Habitat Loss ◽  
National Park ◽  
Conservation Status ◽  
Activity Patterns ◽  
Camera Trap ◽  
Oil Extraction ◽  
Density Estimates ◽  
Yasuni National Park ◽  
Ecuadorian Amazon

AbstractOcelots were historically hunted for their skins but habitat loss is now their most serious threat, causing rapid declines in populations throughout their range. Ocelot abundance has been estimated for various locations across the Neotropics, but we still lack this information from some countries, including Ecuador. Knowing whether ocelot abundance is increasing or decreasing is important to assess the conservation status of this species and the conditions of its habitats in the Ecuadorian Amazon and in the region. To determine whether ocelot abundance and its behavior are affected by human-related activities, camera-trap surveys were carried out in two localities of Yasuní National Park (YNP), one that has experienced hunting, oil extraction, and roads (Maxus Road) and one that is largely unaffected by these activities (Lorocachi). During the survey, 35 and 36 individual ocelots were photographed in Maxus Road and Lorocachi, respectively. Population density estimates were similar for both localities, ranging from 0.31 (SE±6) to 0.85 (SE±17) ocelots/km

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