The influence of age structure and fecundity on effective population size.

Simple formulae are developed which define the effective size (Ne) of populations with overlapping generations, and their use is illustrated using data from a squirrel population. Two mating systems are considered, the random union of gametes and monogamy, in combination with age-independent fecundity. In the simplest case of age-independent (type 2) survivorship in a population of N adults, Ne = N/(2-T-1) where T is the generation time. As T increases, Ne declines asymptomatically to N/2. A generalization of this result (Ne = N/[1 + k-1-T-1], where k influences survivorship) shows that given type 1 survivorship (k greater than 1) this decline in Ne is less severe. A biased sex ratio results in Ne differing between the two mating systems; however, in both systems, a sex ratio bias resulting from survival differences has much less influence on Ne than a sex ratio bias resulting from recruitment differences. Low fecundity can increase Ne, but realistic levels of variation among breeding individuals (Poisson or greater) negate the effect. The effect on Ne of variation resulting from the presence of non-breeders is also considered.     

The influence of persistent individual differences and age at maturity on effective population size

Ratios of effective populations size, N(e), to census population size, N, are used as a measure of genetic drift in populations. Several life-history parameters have been shown to affect these ratios, including mating system and age at sexual maturation. Using a stochastic matrix model, we examine how different levels of persistent individual differences in mating success among males may affect N(e)/N, and how this relates to generation time. Individual differences of this type are shown to cause a lower N(e)/N ratio than would be expected when mating is independent among seasons. Examining the way in which age at maturity affects N(e)/N, we find that both the direction and magnitude of the effect depends on the survival rate of juveniles in the population. In particular, when maturation is delayed, lowered juvenile survival causes higher levels of genetic drift. In addition, predicted shifts in N(e)/N with changing age at maturity are shown to be dependent on which of the commonly used definitions of census population size, N, is employed. Our results demonstrate that patterns of mating success, as well as juvenile survival probabilities, have substantial effects on rates of genetic drift.     

Bovine renal lipofuscinosis: Prevalence, genetics and impact on milk production and weight at slaughter in Danish cattle

Background

Bovine renal lipofuscinosis (BRL) is an incidental finding in cattle at slaughter. Condemnation of the kidneys as unfit for human consumption was until recently considered the only implication of BRL. Recent studies have indicated a negative influence on the health of affected animals. The present study investigated the prevalence, genetics and effect of BRL on milk yield and weight at slaughter.

Methods

BRL status of slaughter cattle was recorded at four abattoirs during a 2-year-period. Data regarding breed, age, genetic descent, milk yield and weight at slaughter were extracted from the Danish Cattle Database. The prevalence of BRL was estimated stratified by breed and age-group. Furthermore, total milk yield, milk yield in last full lactation and weight at slaughter were compared for BRL-affected and non-affected Danish Holsteins and Danish Red cattle.

Results

433,759 bovines were slaughtered and 787 of these had BRL. BRL was mainly diagnosed in Danish Red, Danish Holstein and crossbreds. The age of BRL affected animals varied from 11 months to 13 years, but BRL was rarely diagnosed in cattle less than 2 years of age. The total lifelong energy corrected milk (ECM) yields were 3,136 and 4,083 kg higher for BRL affected Danish Red and Danish Holsteins, respectively. However, the median life span of affected animals was 4.9 months longer, and age-corrected total milk yield was 1,284 kg lower for BRL affected Danish Red cows. These cows produced 318 kg ECM less in their last full lactation. Weight at slaughter was not affected by BRL status. The cases occurred in patterns consistent with autosomal recessive inheritance and several family clusters of BRL were found. Analysis of segregation ratios demonstrated the expected ratio for Danish Red cattle, but not for Danish Holsteins.

Conclusion

The study confirmed that BRL is a common finding in Danish Holsteins and Danish Red cattle at slaughter. The disorder is associated with increased total milk yield due to a longer production life. However, a reduced milk yield was detected in the end of the production life in Danish Red. The study supports that BRL is inherited autosomal recessively in the Danish Red breed and Danish Holsteins, but with incomplete penetrance of the genotype in Danish Holsteins.     

The influence of age and breed on stallion semen

This study reports on the variation in semen quality and in spermatozoal and behavioral characteristics of 168 stallions representing 9 breeds and ranging in age from 2 to 26 yr. Semen samples were collected into an artificial vagina and the number of mounts and urethral pulsations per semen sample were recorded. Semen characteristics were examined for total volume, gel-free volume, gel volume, color score, mass activity, nonmotile spermatozoa, dead spermatozoa, semen density, spermatozoa concentration, total number of spermatozoa and semen pH. Morphological characteristics of the spermatozoa included abnormal heads, abnormal mid-pieces, abaxial mid-pieces, protoplasmic droplets and abnormal tails. Sources of variation were evaluated and the overall means calculated by least-squares analyses of variance for nonorthogonal data. The significance of breed effects and between stallion variability were estimated using mixed-model procedures. All semen characteristics with the exception of color and urethral pulsations had significant variation due to age. Semen quality (gel-free volume, sperm concentration, total sperm numbers and sperm abnormalities) was poorest in stallions under 3 yr of age and over 11 yr. Significant breed variation was apparent in most characteristics except for pH, semen color, abnormal midpieces and urethral pulsations. It is recommended that both the age and breed of stallion be taken into consideration when evaluating stallion semen.     

The anterior tooth development of cattle presented for slaughter: an analysis of age,sex and breed

In a cross-sectional study, data from records of cattle slaughtered over a 1-year period at a large abattoir in South West England were analysed using an ordered category response model to investigate the inter-relationships between age, sex and breed on development of the permanent anterior (PA) teeth. Using the model, transition points at which there was a 50% probability of membership of each category of paired PA teeth were identified. Data from ∼60 000 animals were initially analysed for age and sex effect. The age transition was found to be ∼23 months moving from zero to two teeth; 30 months for two to four teeth; 37 months for four to six teeth and 42 months for six to eight teeth. Males were found to develop, on average, ∼22 days earlier than females across all stages. A reduced data set of ∼23 000 animals registered as pure-bred only was used to compare breed and type interactions and to investigate sex effects within the sub-categories. Breeds were grouped into dairy and beef-type and beef breeds split into native and continental. It was found that dairy-types moved through the transition points earlier than beef-types across all stages (interval varying between ∼8 and 12 weeks) and that collectively, native beef breeds moved through the transition points by up to 3 weeks earlier than the continental beef breeds. Interestingly, in contrast to beef animals, dairy females matured before dairy males. However, the magnitude of the difference between dairy females and males diminished at the later stages of development. Differences were found between breeds. Across the first three stages, Ayrshires and Guernseys developed between 3 and 6 weeks later than Friesian/Holsteins and Simmental, Limousin and Blonde Aquitaine 6 and 8 weeks later than Aberdeen Angus. Herefords, Charolais and South Devon developed later but by a smaller interval and Red Devon and Galloway showed the largest individual effect with transition delayed by 8 to 12 weeks.     

Location,size and age at onset of metamorphosis in the Japanese eel Anguilla japonica

This study clarifies the location, size and age at the onset of metamorphosis in Japanese eels Anguilla japonica through oceanic surveys, rearing experiments and analyses of the morphology and otoliths of leptocephali and glass eels. Twenty‐eight metamorphosing leptocephali were collected in the mesoscale eddy region to the east of Taiwan during research expeditions in 2004. Rearing experiments showed that the total length (L_T) of leptocephali decreased by an average of 12·5% during metamorphosis and 13·9% during the 2–12 h after death. Thus, the mean back‐calculated L_T at the onset of metamorphosis for 630 glass eels from Taiwan and Japan was estimated at 67·8 ± 2·7 mm (mean ± S.D.). The estimated mean ante‐mortem size of the fully grown pre‐metamorphic leptocephali collected in 2004 was 64·6 ± 3·4 mm, which was consistent with the L_T estimate for glass eels. Otolith analysis showed that the mean age at the onset of metamorphosis was 137 ± 15 days and indicated that Japanese eels may have a recruitment route through the mesoscale eddies to the east of Taiwan in addition to the direct transfer route from the North Equatorial Current to the Kuroshio Current.     

Confirmation and refinement of a QTL on BTA5 affecting milk production traits in the Fleckvieh dual purpose cattle breed

We analysed a QTL affecting milk yield (MY), milk protein yield (PY) and milk fat yield (FY) in the dual purpose cattle breed Fleckvieh on BTA5. Twenty-six microsatellite markers covering 135 cM were selected to analyse nine half-sib families containing 605 sons in a granddaughter design. We thereby assigned two new markers to the public linkage map using the CRI-MAP program. Phenotypic records were daughter yield deviations (DYD) originating from the routinely performed genetic evaluations of breeding animals. To determine the position of the QTL, three different approaches were applied: interval mapping (IM), linkage analysis by variance component analysis (LAVC), and combined linkage disequilibrium (LD) and linkage (LDL) analysis. All three methods mapped the QTL in the same marker interval ( BM2830-ETH152 ) with the greatest test-statistic value at 118, 119.33 and 119.33 cM respectively. The positive QTL allele simultaneously increases DYD in the first lactation by 272 kg milk, 7.1 kg milk protein and 7.0 kg milk fat. Although the mapping accuracy and the significance of a QTL effect increased from IM over LAVC to LDL, the confidence interval was large (13, 20 and 24 cM for FY, MY and PY respectively) for the positional cloning of the causal gene. The estimated averages of pair wise marker LD with a distance <5 cM were low (0.107) and reflect the large effective population size of the Fleckvieh subpopulation analysed. This low level of LD suggests a need for increase in marker density in following fine mapping steps.     

Reproductive disorders in dairy cattle: I. Respective influence of herds, seasons, milk yield and parity

This study was performed in two large dairy units (with 130 and 213 calving cows each) during one year. The objectives were to investigate 1) epidemiological patterns of main post-partum reproductive disorders (metritis, post-partum and post-service anestrus, repeat breeding and embryonic death) and 2) the impact of herd, calving season, milk yield and parity on these patterns. Approximately 20% of the cows in both herds were not affected by any of the disorders. Prevalence of metritis was high (32 to 44%) and appeared influenced by the herds' conditions interacting with calving months and milk yield effects. Cyclic post-partum anestrus incidence was also essentially affected by the herd effect with an added seasonal interaction. Other disorders in both herds were also primarily subjected to the seasonal effect. Individual milk yield and parity only marginally affected the epidemiological patterns. We concluded that even in similar environmental conditions, no general patterns of incidence of reproductive disorders can be drawn and that they are essentially dependent on the characteristics of each herd management.     

The effects of the brown ear-tick, Rhipicephalus appendiculatus, on milk production of Sanga cattle

Abstract. Lactating Sanga cows of the Mashona breed from Zimbabwe, receiving either a low or a high level of nutritional supplement, were exposed to two levels of infestation of adults of the brown ear-tick, Rhipicephalus appendiculatus in the highveld of Zimbabwe. The effect of the ticks on the milk yield was measured over an 11-week period during the rainy season from January to April 1986. A technique in which calves were weighed before and after suckling was used to estimate milk yield. There were significant treatment effects of ticks (P < 0.05) on milk production but no significant differences in liveweight gain between calves from tick-free and tick-infested dams. The loss in milk production was poorly related to the number of female ticks that engorged, being 9 g (SEM 4) per tick. A Friesian x Hereford (Bos taurus) reference group of cattle carried 50% more ticks than the Mashona cows, illustrating a difference in resistance between the breeds. Thirteen screw-worm (Chrysomya bezziana) strikes were recorded amongst the thirty-two Mashona cows compared with twenty-one amongst the ten Friesian × Hereford animals between January and the end of March.     

The effects of the brown ear-tick, Rhipicephalus appendiculatus, on milk production in dairy cattle

Abstract. The effect is reported of artificially controlled levels of infestation with adults of Rhipicephalus appendiculatus on the milk yield of twenty commercial Bos taurus dairy cattle on a high plane of nutrition and eighteen crossbed B.taurus × Sanga cattle on a lower plane of nutrition in the highveld of Zimbabwe. The results showed no significant effect on milk yield of infestations averaging twenty engorging ticks per animal per day, despite severe ear damage in some animals. They indicate that milk production of dairy cattle under commercial management is not sensitive to infestation with R.appendiculatus. The results have important implications for management of ticks in Africa, but need to be interpreted within the context of the control of tick-borne diseases.     

The influence of age on laying date,clutch size,and egg size of the white-fronted tern,Sterna striata

Abstract

The age at first breeding and the influence of age on laying date, clutch size, and egg size of white-fronted terns were studied at the Kaikoura Peninsula, New Zealand, between 1971 and 1976. Of the 134 banded birds recovered breeding at Kaikoura, 63% were marked as nestlings at Kaikoura; the remainder came from colonies within 104 km. The bird is extremely capricious in its choice of nesting locality, and there are indications that it is not consistently philopatric. A small number bred as 3-year-olds, but the majority did not commence breeding until after they were 6 years old. Most pairs (73%) were of partners with an age difference of 1 year or less. Laying date and egg size varied with the age of the parent, but clutch size showed no significant change in relation to age. Mean egg volume did not vary between one-egg and two-egg clutches, but in two-egg clutches the first egg laid was significantly the larger in length, breadth, and volume. Single-egg clutches were the most common, but as the season progressed the proportion of two-egg clutches increased. There was no significant seasonal change in egg size.     

The intracellular pH of the peripheral blood lymphocytes in cattle during the development of leukemia]

The intracellular pH distribution of peripheral cattle lymphocytes has been studied in normal state and at six stages of the development of bovine leukosis by the dye microfluorimetry of single cells. It has been shown that the increase of mean intracellular pH value occurs as well some distribution parameters, such as pH range and asymmetry change during the disease process. Probable reasons responsible for the observed modification of the distribution pattern are discussed.     

The effect of age at calving on reproduction, milk production and disease incidence in the first lactation of dairy heifers

Herd health and production records of 1161 Holstein-Friesian heifers from 22 Michigan dairy herds were utilized to study the effect of age at first calving upon reproductive efficiency, milk production and the incidence of disease in the first lactation. Age at first calving was not significantly related to either milk production or reproductive efficiency. Heifers displaying dystocia were significantly older at calving than those that calved without problems. Additionally, the incidence of ketosis was associated with a significantly greater age at first calving. Heifers with diarrhea and those that aborted were significantly younger at calving than their herdmates. Incidence of 12 other common dairy diseases was not related to age at first calving. It would, therefore, appear that the dairy producers we studied could inseminate their heifers at an earlier age, and thereby increase production per day of life, without suffering serious detrimental effects in lactational milk production, reproductive efficiency or overall disease incidence.     

In vitro production of Rauscher murine leukemia virus: influence of culture age on biological properties.

Large-scale production and concentration procedures have been standardized to study the biological properties of Rauscher leukemia virus produced from the high-passaged JLS-V9-H mouse bone marrow cell line. Virus produced early (days 4 to 6) in the harvest and refeed cycle contained higher levels of ribonucleic acid-directed deoxyribonucleic acid polymerase activity and was more infectious than Rauscher leukemia virus produced later (days 7 to 10) in the growth period. The peak of virus production as detected by physical assays (virus particle count, protein, and p30 antigen) was highest at day 6, whereas the optimum biological and ribonucleic acid-directed deoxyribonucleic acid polymerase activity occurred 24 h earlier. When product characterization values of each concentrate were adjusted to a specific activity (i.e., per milligram of protein) basis, virus particle counts averaged 4 x 10(11) through days 5 to 9, and the peak infectivity occurred at day 4, whereas ribonucleic acid-directed deoxyribonucleic acid polymerase activity was highest at day 4 (endogenous) and 5 (exogenous). Sodium dodecyl sulfate-polyacrylamide gel analysis revealed only slight differences in the polypeptide pattern of Rauscher leukemia virus harvested from cultures of varying age, although Rauscher leukemia virus produced between days 3 and 5 contained more glycoprotein than either earlier or later harvests.     

In vitro production of Rauscher murine leukemia virus: influence of culture age on biological properties.

Large-scale production and concentration procedures have been standardized to study the biological properties of Rauscher leukemia virus produced from the high-passaged JLS-V9-H mouse bone marrow cell line. Virus produced early (days 4 to 6) in the harvest and refeed cycle contained higher levels of ribonucleic acid-directed deoxyribonucleic acid polymerase activity and was more infectious than Rauscher leukemia virus produced later (days 7 to 10) in the growth period. The peak of virus production as detected by physical assays (virus particle count, protein, and p30 antigen) was highest at day 6, whereas the optimum biological and ribonucleic acid-directed deoxyribonucleic acid polymerase activity occurred 24 h earlier. When product characterization values of each concentrate were adjusted to a specific activity (i.e., per milligram of protein) basis, virus particle counts averaged 4 x 10(11) through days 5 to 9, and the peak infectivity occurred at day 4, whereas ribonucleic acid-directed deoxyribonucleic acid polymerase activity was highest at day 4 (endogenous) and 5 (exogenous). Sodium dodecyl sulfate-polyacrylamide gel analysis revealed only slight differences in the polypeptide pattern of Rauscher leukemia virus harvested from cultures of varying age, although Rauscher leukemia virus produced between days 3 and 5 contained more glycoprotein than either earlier or later harvests.     

The influence of age and size on temporal mate signalling behaviour

I investigated how male size, condition and age influence both time spent calling and how signals are apportioned throughout the night (i.e. temporal calling pattern) in the Texas field cricket, Gryllus integer. I quantified male calling time and temporal calling pattern using an electronic apparatus that continuously monitored male calling/noncalling behaviour throughout the night. Male condition, measured using the residuals from an allometric regression of male mass on overall body size, did not explain any variation in either time spent calling or temporal calling pattern. However, some intrapopulation variation in time spent calling and temporal calling pattern was explained by differences in male size and age. Large males called more often than small males. Young and very old adult males called significantly less often than middle-age males. As males aged they initiated calling earlier in the evening, probably increasing their susceptibility to parasitism by the tachinid parasitoid Ormia ochracea. Overall, age and size differences explained 10-40% of signalling variation in male G. integer. Copyright 2000 The Association for the Study of Animal Behaviour.     

The influence of age and denture wear on the size of edentulous structures

Objectives : This study was designed to evaluate the influence of age and denture use on the size of arches and residual ridges in edentulous patients. Design : At two nursing homes, maxillary and mandibular stone casts of 302 fully edentulous patients were utilized to measure the size of the arches and residual ridges, according to age and use of complete dentures. Age cohorts were divided into three groups; 60–69, 70–79, and 80–89 years old. Two hundred and forty‐nine denture wearers used complete dentures for at least 2 years before examinations. Fifty‐three non‐denture users had never worn removable prostheses. Chi‐square analysis (p<0.05) was used to establish the possible relations between the linear values and the size indexes of the ridges and arches and the two examined parameters: age and denture wear. Results : Young old patients possessed edentulous structures that were not significantly larger than elderly old patients in both the maxilla and the mandible. Non‐denture users had significantly bigger arches and ridges in both edentulous jaws than denture users. Conclusions : Young old, non‐denture users tended to have bigger residual edentulous tissues compared to elderly old patients who used complete dentures.