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Animal Sciences Commons

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2002

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Articles 1 - 30 of 671

Full-Text Articles in Animal Sciences

Breed Comparisons Of Angus, Brahman, Hereford, Pinzgauer, Sahiwal, And Tarentaise For Weight, Weight Adjusted For Condition Score, Height, And Body Condition Score, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck Dec 2002

Breed Comparisons Of Angus, Brahman, Hereford, Pinzgauer, Sahiwal, And Tarentaise For Weight, Weight Adjusted For Condition Score, Height, And Body Condition Score, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck

Department of Animal Science: Faculty Publications

Data from topcross cows (n = 468) from six breeds of sire (Angus, Brahman, Hereford, Pinzgauer, Sahiwal, Tarentaise) and two breeds of dam (Angus and Hereford) of Cycle III of the Germplasm Evaluation (GPE) program at the U.S. Meat Animal Research Center (MARC) comprising cow weight (CW, n = 9,012), height (CH, n = 9,010), and condition score (CS, n = 8,991) recorded in four seasons per year from 2 to 6 yr of age were used to estimate breed-group differences. The mixed models included cow age, season of measurement and their interactions, year of birth, pregnancy-lactation code (PL), and …


Breed Comparisons Of Angus, Charolais, Hereford, Jersey, Limousin, Simmental, And South Devon For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score Of Cows, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck Dec 2002

Breed Comparisons Of Angus, Charolais, Hereford, Jersey, Limousin, Simmental, And South Devon For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score Of Cows, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck

Department of Animal Science: Faculty Publications

Breed means and differences for weight (CW, n = 19,851), height (CH, n = 14,553), and condition scores (CS, n = 19,536) recorded in four seasons per year were evaluated for 881 cows ranging from 2 to 7 yr of age from Cycle I of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center. Cows were straightbred Herefords and Angus and top-crosses from mating of Hereford, Angus, South Devon, Jersey, Simmental, Limousin, and Charolais sires to Hereford and Angus dams. The model included cow age, season of measurement, and their interactions, with year of birth, pregnancy-lactation (PL) code, …


Comparisons Of Angus-, Braunvieh-, Chianina-, Hereford-, Gelbvieh-, Maine Anjou-, And Red Poll-Sired Cows For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck Dec 2002

Comparisons Of Angus-, Braunvieh-, Chianina-, Hereford-, Gelbvieh-, Maine Anjou-, And Red Poll-Sired Cows For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score, Jesus Arango, L. V. Cundiff, L. Dale Van Vleck

Department of Animal Science: Faculty Publications

Data from Angus, Hereford, and topcross cows (n = 641) from 2- to 8-yr-old daughters of seven breeds of sires included in Cycle II of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center, comprising cow weight (CW, n = 15,698), height (CH, n = 15,676), and condition score (CS, n = 15,667), were used to estimate breed-group differences. Data were recorded in four seasons of each year (1975 to 1982). The mixed model included cow age, season of measurement, and their interactions, year of birth, pregnancy-lactation code (PL), and breed-group as fixed effects for CW and CS. …


Estimates Of Genetic Parameters And Genetic Change For Reproduction, Weight, And Wool Characteristics Of Columbia Sheep, Kathryn J. Hanford, L. Dale Van Vleck, G. D. Snowder Dec 2002

Estimates Of Genetic Parameters And Genetic Change For Reproduction, Weight, And Wool Characteristics Of Columbia Sheep, Kathryn J. Hanford, L. Dale Van Vleck, G. D. Snowder

Department of Animal Science: Faculty Publications

Genetic parameters from both single-trait and bivariate analyses for prolificacy, weight and wool traits were estimated using REML with animal models for Columbia sheep from data collected from 1950 to 1998 at the U.S. Sheep Experiment Station (USSES), Dubois, ID. Breeding values from both single-trait and seven-trait analyses calculated using the parameters estimated from the single-trait and bivariate analyses were compared with respect to genetic trends. Number of observations were 31,401 for litter size at birth and litter size at weaning, 24,741 for birth weight, 23,903 for weaning weight, 29,572 for fleece weight and fleece grade, and 2,449 for staple …


Genetic Parameters For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score In Beef Cows, Jesus Arango, Larry V. Cundiff, L. Dale Van Vleck Dec 2002

Genetic Parameters For Weight, Weight Adjusted For Body Condition Score, Height, And Body Condition Score In Beef Cows, Jesus Arango, Larry V. Cundiff, L. Dale Van Vleck

Department of Animal Science: Faculty Publications

Weight (CW, n = 61,798), weight adjusted for condition score (WA), hip height (CH, n = 56,494), and condition score (CS, n = 61,434) of cows (2 through 8 yr of age) produced by crosses of 22 sire breeds with Angus and Hereford dams in the first four cycles of the Germplasm Evaluation (GPE) Program at the U.S. Meat Animal Research Center were used to estimate genetic parameters with REML. The model included sire breed, dam breed, age in years, season of measurement (1 to 4) and their interactions, and year of birth and pregnancy-lactation code (PL) as fixed effects …


Estimates Of Parameters Between Direct And Maternal Genetic Effects For Weaning Weight And Direct Genetic Effects For Carcass Traits In Crossbred Cattle, R. K. Splan, Larry V. Cundiff, M. E. Dikeman, L. Dale Van Vleck Dec 2002

Estimates Of Parameters Between Direct And Maternal Genetic Effects For Weaning Weight And Direct Genetic Effects For Carcass Traits In Crossbred Cattle, R. K. Splan, Larry V. Cundiff, M. E. Dikeman, L. Dale Van Vleck

Department of Animal Science: Faculty Publications

Estimates of heritabilities and genetic correlations were obtained for weaning weight records of 23,681 crossbred steers and heifers and carcass records from 4,094 crossbred steers using animal models. Carcass traits included hot carcass weight; retail product percentage; fat percentage; bone percentage; ribeye area; adjusted fat thickness; marbling score, Warner- Bratzler shear force and kidney, pelvic and heart fat percentage. Weaning weight was modeled with fixed effects of age of dam, sex, breed combination, and birth year, with calendar birth day as a covariate and random direct and maternal genetic and maternal permanent environmental effects. The models for carcass traits included …


Selection For Maternal Behavior In Mice—Direct And Correlated Responses, Chung-Feng Chiang, Rodger K. Johnson, Merlyn K. Nielsen Dec 2002

Selection For Maternal Behavior In Mice—Direct And Correlated Responses, Chung-Feng Chiang, Rodger K. Johnson, Merlyn K. Nielsen

Department of Animal Science: Faculty Publications

Three generations of divergent selection for a maternal care index (MCI) in mice were practiced in each of three replicates. MCI was recorded for 29–32 dams and litters in each replicate/line subclass. Pups of the top (or bottom) 6– 10 dams in each replicate, depending on number of females in the litters, were selected in high (H) and low (L) MCI lines. At birth, litters with more than 10 pups were standardized to 10 pups whereas litters with no more than 10 pups remained intact. On day 4, 8, 12, and 16 of lactation, time budgets during a 30-min session …


The Efficacy Of Three Objective Systems For Identifying Beef Cuts That Can Be Guaranteed Tender, T.L. Wheeler, D. Vote, J.M. Leheska, S.D. Shackelford, K.E. Belk, D.M. Wulf, B.L. Gwartney, M. Koohmaraie Dec 2002

The Efficacy Of Three Objective Systems For Identifying Beef Cuts That Can Be Guaranteed Tender, T.L. Wheeler, D. Vote, J.M. Leheska, S.D. Shackelford, K.E. Belk, D.M. Wulf, B.L. Gwartney, M. Koohmaraie

Animal Science Faculty Publications

The objective of this study was to determine the accuracy of three objective systems (prototype BeefCam, colorimeter, and slice shear force) for identifying guaranteed tender beef. In Phase I, 308 carcasses (105 Top Choice, 101 Low Choice, and 102 Select) from two commercial plants were tested. In Phase II, 400 carcasses (200 rolled USDA Select and 200 rolled USDA Choice) from one commercial plant were tested. The three systems were evaluated based on progressive certification of the longissimus as “tender” in 10% increments (the best 10, 20, 30%, etc., certified as “tender” by each technology; 100% certification would mean no …


Fisheries Research Report No. 142 - Identifying The Development Stages Of Preserved Eggs Of Snapper, Pagrus Auratus, From Shark Bay, Western Australia, J. Norriss, Gary Jackson Dec 2002

Fisheries Research Report No. 142 - Identifying The Development Stages Of Preserved Eggs Of Snapper, Pagrus Auratus, From Shark Bay, Western Australia, J. Norriss, Gary Jackson

Fisheries Research Reports

The characteristics used to identify 19 developmental stages of preserved eggs of snapper, Pagrus auratus, collected from Shark Bay, Western Australia, during annual plankton surveys, are described and illustrated. A key is provided to enable the age of each egg stage to be estimated based on sea surface temperature and salinity observed during sampling. This report is intended as a reference for inexperienced staff, to ensure that between-year comparisons of snapper spawning biomass, estimated using the daily egg production method, are based on consistent egg staging and ageing methods.


Fisheries Research Report No. 143 - Methods Used In The Collection, Preparation And Interpretation Of Narrow-Barred Spanish Mackerel (Scomberomorus Commerson) Otoliths For A Study Of Age And Growth In Western Australia, Paul Lewis, M. C. Mackie Dec 2002

Fisheries Research Report No. 143 - Methods Used In The Collection, Preparation And Interpretation Of Narrow-Barred Spanish Mackerel (Scomberomorus Commerson) Otoliths For A Study Of Age And Growth In Western Australia, Paul Lewis, M. C. Mackie

Fisheries Research Reports

The narrow-barred Spanish mackerel (Scomberomorus commerson) is wide ranging throughout the Indo-West Pacific region where it has been the subject of various age and growth studies. Methods used in these studies have varied considerably and in some cases may have led to misleading conclusions. The purpose of this report, therefore, is to document in detail the methods used in determining the age and growth during a FRDC funded stock assessment of the species in the waters off Western Australia. These methods are considered to optimise the collection, processing, accuracy of microincrement counts, and interpretation of the annuli in both whole …


Description Of A Poorly Differentiated Carcinoma Within The Brainstem Of A White Whale (Delphinapterus Leucas) From Magnetic Resonance Images And Histological Analysis, Sam H. Ridgway, Lori Marino, T. P. Lipscomb Dec 2002

Description Of A Poorly Differentiated Carcinoma Within The Brainstem Of A White Whale (Delphinapterus Leucas) From Magnetic Resonance Images And Histological Analysis, Sam H. Ridgway, Lori Marino, T. P. Lipscomb

Veterinary Science and Medicine Collection

In this study we used magnetic resonance imaging (MRI) to investigate neuroanatomical structure in the brain of a white whale (Delphinapterus leucas) that died from a large tumor within the brainstem. This specimen was also compared with a normal white whale brain using MRI. MRI scans of the white whale specimen show how the tumor deformed surrounding brain structure. Histopathological analysis indicated a poorly differentiated carcinoma of uncertain origin. These analyses demonstrate the usefulness of supplementing histological analyses of pathology with studies of gross morphology facilitated by MRI.


Identifying The Developmental Stages Of Preserved Eggs Of Snapper, Pagrus Auratus, From Shark Bay, Western Australia, Jeffrey V. Norriss, Gary Jackson Dec 2002

Identifying The Developmental Stages Of Preserved Eggs Of Snapper, Pagrus Auratus, From Shark Bay, Western Australia, Jeffrey V. Norriss, Gary Jackson

Fisheries Research Reports

The characteristics used to identify 19 developmental stages of preserved eggs of snapper, Pagrus auratus, collected from Shark Bay, Western Australia, during annual plankton surveys, are described and illustrated. A key is provided to enable the age of each egg stage to be estimated based on sea surface temperature and salinity observed during sampling. This report is intended as a reference for inexperienced staff, to ensure that between-year comparisons of snapper spawning biomass, estimated using the daily egg production method, are based on consistent egg staging and ageing methods.


Nebraska's Sandhill Crane Populations, Past, Present And Future, Paul A. Johnsgard Dec 2002

Nebraska's Sandhill Crane Populations, Past, Present And Future, Paul A. Johnsgard

Papers in Ornithology

Although the spring concentrations of Sandhill Cranes in Nebraska's Platte Valley are now an avian phenomenon known nationwide, a general appreciation and inventory of this unique concentration of birds has only been attempted in the last few decades. I am often asked how long this largest of all crane concentrations has been occurring in the Platte Valley, and why it has developed only there. Here I will try to summarize the little-known history of this marvelous assemblage, but not dwell on the ecological reasons for it. The latter are now generally well understood to revolve around abundant spring food supplies …


Fall Field Report, August-November 2002, W. Ross Silcock Dec 2002

Fall Field Report, August-November 2002, W. Ross Silcock

Nebraska Bird Review

A few words on documentation of sightings reported is in order. I receive many reports each season of rare or hard-to-identify birds. If they fit a pattern that has developed over the years (see "Birds of Nebraska"), I tend to accept them as correct. However, if they fall outside the range of prior reports, I usually email the observer and ask for some details about the identification and circumstances of the sighting. Everyone has been very nice about this process; observers sometimes take these requests as a questioning of their ability, but I haven't run into this problem with Nebraska …


Nebraska Bird Review- Whole Issue December 2002 Volume 70 Number 4 Dec 2002

Nebraska Bird Review- Whole Issue December 2002 Volume 70 Number 4

Nebraska Bird Review

Table of Contents

Fall Field Report, August-November 2002
Compiled by W. Ross Silcock................130

Species Accounts...............134

Nou Fall Field Days......................168

Nebraska's Sandhill Crane Populations, Past, Present,
and Future by Paul A. Johnsgard.......................175

Index for Volume 70.1-4......................178


Pig Industry Biosecurity Plan - March 2003 - Protecting The Pig Industry Is Everyone's Business, Department Of Agriculture, Western Australia Dec 2002

Pig Industry Biosecurity Plan - March 2003 - Protecting The Pig Industry Is Everyone's Business, Department Of Agriculture, Western Australia

Biosecurity published reports

Farmnote 71/2002 - Farm Biosecurity

Farmnote 43/2002 - Biosecurity in the livestock industries

StockGuard has been initiated to develop a series of biosecurity plans for the animal industries in Western Australia. Through StockGuard, representatives from the animal industries have been working with the Western Australian Department of Agriculture to identify potential threats to each of the animal industries and to develop action plans detailing how these threats can be managed.

The overall purpose of StockGuard is to identify threats to the animal industries and to develop effective ways to minimise the potential impact of these threats.

If an emergency pig …


Ocean Zoning For The Gulf Of Maine: A Background Paper, Fara Courtney, Jack Wiggin Dec 2002

Ocean Zoning For The Gulf Of Maine: A Background Paper, Fara Courtney, Jack Wiggin

Urban Harbors Institute Publications

Coastal and ocean management is a constantly evolving practice. For at least two decades, coastal communities around the world have been experimenting with new ways to control a multitude of activities in their urban and rural harbors. The number and diversity of Marine Protected Areas are growing, with an increasing focus on protecting integrated biological communities, rather than individual species of concern. The United States and Canada are each developing new, comprehensive ocean polices, looking to better integrate management functions at all levels of government.

All of these initiatives – from local to national - reflect some common truths about …


Nebraska's Sandhill Crane Population, Past, Present, And Future, Paul A. Johnsgard Dec 2002

Nebraska's Sandhill Crane Population, Past, Present, And Future, Paul A. Johnsgard

Nebraska Bird Review

Although the spring concentrations of Sandhill Cranes in Nebraska's Platte Valley are now an avian phenomenon known nationwide, a general appreciation and inventory of this unique concentration of birds has only been attempted in the last few decades. I am often asked how long this largest of all crane concentrations has been occurring in the Platte Valley, and why it has developed only there. Here I will try to summarize the little-known history of this marvelous assemblage, but not dwell on the ecological reasons for it. The latter are now generally well understood to revolve around abundant spring food supplies …


Masthead From Nebraska Bird Review Dec 2002

Masthead From Nebraska Bird Review

Nebraska Bird Review

The Nebraska Bird Review (http://rip.physics.unk.edu/NOU/) is published quarterly by the Nebraska Ornithologists' Union, Inc., as its official journal, and is sent to members not in arrears of dues. Annual subscription rates (on a calendar-year basis only): $14.00 in the United States; $18.00 for all foreign countries, payable in advance. Single copies are $4.00 each, postpaid, in the United States, and $5.00 elsewhere. Send orders for back issues to Mary Prichard, NOU Librarian, University of Nebraska State Museum, Lincoln, NE 68588-0514.

Memberships in NOU (on a calendar year basis only): Active, $15.00; Sustaining, $25.00; Student, $10.00; Family Active, $20.00; Family Sustaining, …


Nou Fall Field Days Dec 2002

Nou Fall Field Days

Nebraska Bird Review

Nou Fall Field Pays

The annual NOU Fall Field Pays were held the weekend of September 6-8 at the 4-H Camp at Halsey. The count included Logan, Blain, Brown, Cherry, and Thomas Counties as well as the Nebraska National Forest. The count included 11 9 species.


Arkansas Animal Science Department Report 2002, Zelpha B. Johnson, D. Wayne Kellogg Dec 2002

Arkansas Animal Science Department Report 2002, Zelpha B. Johnson, D. Wayne Kellogg

Arkansas Agricultural Experiment Station Research Series

No abstract provided.


Immunocontraception In Japanese Quail Using Mammalian Gnrh Compared To Chicken Gnrh-I And Chicken Gnrh-Ii, Marianna Burks Dec 2002

Immunocontraception In Japanese Quail Using Mammalian Gnrh Compared To Chicken Gnrh-I And Chicken Gnrh-Ii, Marianna Burks

Open Access Master's Theses (through 2010)

Because of increasing numbers in wildlife, immunocontraceptives are being developed to decrease these animals and other birds. This study was conducted in conjunction with the United States Geological Survey Midcontinent Science Center in Fort Collins, Colorado (USGS), to determine whether mammalian GnRH (m-GnRH) can be used as a potential immunocontraceptive to decrease reproductive fertility in mature Japanese quail.

Eighty male and female Japanese quail were injected with either mGnRH, chicken GnRH-I (c-GnRH-I), chicken GnRH-II (c-GnRH-II), or vehicle (controls). Blood samples were analyzed for estrogen (E2) and testosterone (T) levels, in addition to antibody titer (Aby) development against the corresponding conjugated …


Kentucky Warbler (Vol. 78, No. 4), Kentucky Library Research Collections Nov 2002

Kentucky Warbler (Vol. 78, No. 4), Kentucky Library Research Collections

The Kentucky Warbler

No abstract provided.


Endogenous Gonadal Hormone Exposure And Bone Sarcoma Risk, Dawn M. Cooley, Benjamin C. Beranek, Deborah L. Schlittler, Nita W. Glickman, Lawrence T. Glickman, David J. Waters Nov 2002

Endogenous Gonadal Hormone Exposure And Bone Sarcoma Risk, Dawn M. Cooley, Benjamin C. Beranek, Deborah L. Schlittler, Nita W. Glickman, Lawrence T. Glickman, David J. Waters

Endocrinology Collection

Although experimental and clinical evidence suggest that endogenous sex hormones influence bone sarcoma genesis, the hypothesis has not been adequately tested in an appropriate animal model. We conducted a historical cohort study of Rottweiler dogs because they frequently undergo elective gonadectomy and spontaneously develop appendicular bone sarcomas, which mimic the biological behavior of the osteosarcomas that affect children and adolescents. Data were collected by questionnaire from owners of 683 Rottweiler dogs living in North America. To determine whether there was an association between endogenous sex hormones and risk of bone sarcoma, relative risk (RR) of incidence rates and hazard ratios …


Status Of White-Tailed And Gunison's Prairie Dogs, Craig Knowles Nov 2002

Status Of White-Tailed And Gunison's Prairie Dogs, Craig Knowles

All U.S. Government Documents (Utah Regional Depository)

The status of the white-tailed and Gunnison's prairie dogs was investigated by conducting telephone interviews with agency people knowledgeable about these species within their area of jurisdiction. Available literature on prairie dog taxonomy, and life history and ecology was also reviewed. The white-tailed and Gunnison's prairie dogs are considered distinct species with no recognized subspecies. Both species are colonial, hibernate during the winter, and occur in shrub-grassland and grassland habitats in the Intermountain West. Density of white-tailed prairie dogs within colonies (2-5 prairie dogs per acre) is typically less than densities of Gunnison’s prairie dogs within colonies (5-10 prairie dogs …


Report Of The Mackerel Independent Advisory Panel To The Executive Director, Department Of Fisheries Criteria For Access And Management Arrangements For The Proposed Interim Managed Mackerel Fishery, Department Of Fisheries Nov 2002

Report Of The Mackerel Independent Advisory Panel To The Executive Director, Department Of Fisheries Criteria For Access And Management Arrangements For The Proposed Interim Managed Mackerel Fishery, Department Of Fisheries

Fisheries Management Papers

Broadly speaking the Panel have recommended a propertional access system of access to the fishery, together with an Individual Transferable Quotas (TFQs) with mininum quota holding management arrangements.


Interim Management Arrangements For The Commercial Mackerel Fishery. Ministers Responses To The Final Report Of The Mackerel Independent Advisory Panel. (Fisheries Management Paper 164), Kim Chance Nov 2002

Interim Management Arrangements For The Commercial Mackerel Fishery. Ministers Responses To The Final Report Of The Mackerel Independent Advisory Panel. (Fisheries Management Paper 164), Kim Chance

Fisheries Management Papers

The Government recognises that the mackerel fishery is important to both the recreational and commercial fishing sectors. However, the purpose of these arrangements is not to allocate the mackerel resource between the sectors but within the commercial sector. Resources sharing issues are subject to investigation in the Integrated Fisheries Management Review where alternative management frameworks and principles for allocating fish stocks to ensure maximum benefit to the community are examined.


Report To The Minister For Agriculture, Forestry And Fisheries By The Integrated Fisheries Management Review Committee, Department Of Fisheries Nov 2002

Report To The Minister For Agriculture, Forestry And Fisheries By The Integrated Fisheries Management Review Committee, Department Of Fisheries

Fisheries Management Papers

The Integrated Fisheries Management Review Committee was established to develop a strategy to integrate the management and sustainable use of fish resources. The Committee’s report proposes an alternative management framework and a set of guiding principles for allocating fish stocks to ensure optimal benefits are realised for the WA community. The report does not, and was not intended to, address specific allocation issues in particular fisheries – this will be a function of the framework and processes put in place following this review.


Effects Of Urea, Isolated Soybean Protein And Blood Meal On Growing Steers Fed A Corn-Based Diet, W. F. Knaus, Donald H. Beerman, L. O. Tedeschi, M. Czajkowski, D. G. Fox, J. B. Russell Nov 2002

Effects Of Urea, Isolated Soybean Protein And Blood Meal On Growing Steers Fed A Corn-Based Diet, W. F. Knaus, Donald H. Beerman, L. O. Tedeschi, M. Czajkowski, D. G. Fox, J. B. Russell

Department of Animal Science: Faculty Publications

A short term feeding trial was conducted to assess effects of nitrogen (N) supplementation on growing cattle and the ability of the Cornell Net Carbohydrate and Protein System (CNCPS) to predict responses. Four corn-based diets were used: (1) a 30% ruminal N-deficient control diet; (2) a urea supplemented diet; (3) a urea+isolated soy protein (ISP) diet; and (4) a urea + ISP + blood meal (BM) diet. Four Holstein steers (average initial body weight of 251 kg) were randomly assigned in a 4 × 4 Latin Square treatment design. Steers were fed 95% of ad libitum intake on an hourly …


Individual, Temporal, And Seasonal Variation In Sperm Concentration In Tree Swallows, Michael P. Lombardo, Armetris N. Forman, Matthew R. Czarnowski, Patrick A. Thorpe Nov 2002

Individual, Temporal, And Seasonal Variation In Sperm Concentration In Tree Swallows, Michael P. Lombardo, Armetris N. Forman, Matthew R. Czarnowski, Patrick A. Thorpe

Peer Reviewed Publications

We determined sperm concentrations in Tree Swallows (Tachycineta bicolor) by manually expressing semen samples from males during prelaying, egg-laying, incubation, and nestling periods. Sperm concentrations varied by orders of magnitude (0-109 sperm mL-1) among males. Sperm concentrations were highest during the incubation period and lowest during the prelaying period. None of the samples collected during the prelaying, egg-laying, and incubation periods were devoid of sperm. In contrast, 45% of samples collected during the nestling period lacked sperm. Sperm concentrations (1) did not vary over the course of the morning during prelaying, egg-laying, and incubation periods …