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PubMed2006

No associations between PrP genotypes and reproduction traits in INRA 401 sheep.

In this study, the potential association of PrP genotypes with ewe reproductive traits and lamb growth traits was investigated. Data were included on ewes and lambs of the INRA 401 breed from the Bourges-La Sapinière INRA experimental farm. This breed was chosen because of good breeding (prolificacy and maternal abilities) and carcass qualities, and the large number of available animals with performance records and PrP genotypes. Ewes were categorized into 3 PrP genotype classes: ARR homozygous, ARR heterozygous, and animals without any ARR haplotype. Two analyses differing in the traits considered were carried out. Firstly, the potential association of the PrP genotype of ewes with their reproduction traits (fertility, litter size, and ovulation rate) was studied. The data included 801, 779, and 587 genotyped ewes for fertility, litter size, and ovulation rate, respectively. Secondly, the association of the PrP genotype of the ewes with growth traits of their lambs (birth weight, ADG between 10 and 30 d of age) was investigated. The data included 3,749 and 3,512 lambs for birth weight and ADG, respectively. The different traits were analyzed using an animal model, where the PrP genotype effect was included as a fixed effect. The reproductive traits were modeled under a probit or a threshold approach. The results of this study indicate no evidence of an association between PrP genotypes and reproductive and growth traits. It is unlikely that selection for scrapie resistance will have an effect on the reproductive or performance traits studied in the INRA 401 breed.

Animals↗
PubMed1984

Influence of protein intake, energy intake and stage of gestation on growth, reproductive performance, nitrogen balance and carcass composition in gestating gilts.

Thirty-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P less than .01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P less than .05 and linear effect, P less than .01, respectively). Nitrogen retention (P less than .01), efficiency of N retention (P less than .05) and dry matter digestibility (P less than .01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P less than .01), liver weight (linear effect P less than .01) SM weight (quadratic effect, P less than .05) and SM percentage M (linear effect P less than .10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P less than .10, P less than .05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.

Animals↗
PubMed1984

Effects of concurrent lactation and postpartum mating on reproductive performance in mice selected for large litter size.

Reproductive and maternal performance of a line of mice selected for large first parity litter size (L+) and a control line (K) were compared under two mating systems: (1) postpartum mating (PP), in which females undergo concurrent gestation and lactation, and (2) postweaning mating (PW), in which females wean their litter before being remated. Females were evaluated in their first two parities. Litters in each line were standardized at birth to 4, 8, 12 or 16 pups in parity 1, and to 10 pups in parity 2. Concurrent gestation had no adverse effect on postnatal maternal performance in parity 1 of either line. In parity 2, both L+ and K declined in reproductive and postnatal maternal performance in PP compared with PW. The pattern of delayed implantation as number of pups nursed increased was similar in both lines under the PP regimen. Several interactions indicated that reproductive performance of L+ was more adversely affected than in K under postpartum mating. Pup mortality was greater in L+ than K under PP but not under PW. In the PP regimen, L+ dams nursing 12 and 16 pups had a lower mating success rate and dams nursing 16 pups had a smaller litter size and higher pup mortality than did K dams. Thus, when L+ dams nurse their natural litter, frequently exceeding 16 pups, their reproductive advantage over K dams observed in PW would be eliminated in PP. If the differences in the first two litters reflect subsequent parities, lifetime reproductive performance in the PP environment would be reduced in the high fecundity line. High fecundity appears to depend upon the environment of selection.

Animals↗
PubMed1997

The European study of assisted reproduction families: a comparison of family functioning and child development between Eastern and Western Europe.

Developments in reproductive technology over the past 20 years have given infertile couples new opportunities to have children. Although assisted reproduction does not appear to lead to negative consequences with respect to parent-child relationships or the socioemotional development of the child, the outcome for children and their parents may well differ according to the social and cultural environment. The aim of the present study was to compare family functioning and the social and emotional development of children in families created as a result of assisted reproductive techniques in Western Europe with assisted reproduction families in an Eastern European country (Bulgaria) where there is a history of specific pronatalist interventions. The findings indicate greater difficulties in parental adjustment and child behavior in assisted conception families in Eastern Europe. In addition, Eastern European parents were more uncertain than Western European parents about whether they would tell the child, and Eastern European parents were much more secretive with respect to telling others. Thus the outcomes of assisted reproduction for family functioning and child development appear to be independent, to some extent at least, on the social context in which these techniques are carried out.

Adaptation, Psychological↗
PubMed1996

Occupational hazards for the male reproductive system.

The etiology of male infertilities is largely undetermined, and our knowledge of exogenous factors affecting the male reproductive system is still limited. In particular, the role of specific environmental and occupational factors is incompletely elucidated. Various occupational (physical and chemical) agents have been shown to affect male reproductive functions in animals, but large differences in reproductive function and/or xenobiotic handling between species limit extrapolation to humans. When available, human data are often conflicting and, except in a few instances, usually refer to broad and heterogenous occupational categories or to groups of agents (e.g., solvents). It is often difficult to elucidate the role of a single agent because occupational exposure conditions are often complex and various confounding factors related to lifestyle (smoking, alcohol, and diet) or socioeconomic state may also affect sperm quality, fertility, or pregnancy outcomes. The objective of this work is to summarize the main epidemiological and, where relevant, experimental findings pertaining to agents (physical and chemical) encountered in the occupational environment that might affect the male reproductive system (sperm count, motility and morphology, libido, and fertility) and/or related pregnancy outcomes (spontaneous abortion, stillbirth, low birth weight, and birth defects and childhood malignancy in offspring). Some methodological issues related to research on the reproductive effects of toxicants are also discussed briefly.

Anesthetics↗
PubMed2004

Reflections upon the trends of education and research in small animal reproduction in Europe.

An open questionnaire-based survey was performed among 86 institutions of veterinary education in 32 European countries: 15 within the European Union (EU) and 17 outside the EU, in Central and Eastern Europe and the European Free Trade Association (EFTA). The survey aimed to provide a view of the general status of education and research in small animal reproduction (SAR) in Europe. It further aimed to disclose whether ongoing trends in organization (e.g., from the classical animal reproduction discipline orientation [DO] toward a species-oriented [SO] organization) among veterinary colleges responsible for undergraduate education and research in SAR have affected the provision of clinical services, continuing professional development (CPD), specialization, post-graduate education, and research. Response rates reached 80% among EU institutions and 48.4% in other countries (overall response rate = 68.6%). A clear, significant majority of institutions (> 60%) were DO, with a well-defined comparative subject in the veterinary curriculum. No differences were reported for either orientation in their ability to provide undergraduate education or clinical services in SAR. However, more DO institutions reported active research in SAR than their SO counterparts. Similar (and stronger) differences were seen for post-graduate education, CPD, and participation in specialization programs (national or European). Finally, more DO than SO institutions provided assisted reproductive technologies (ARTs), such as AI with frozen semen, to customers. The analysis of the data emanating from the respondents' perceptions, supports the advantages of the more classical, DO-based approach. The results highlight the need for caution when institutions abandon the comparative benefits of the classical DO animal reproduction subject for a SO approach, which tends to prioritize clinical specialized service rather than research and research education. In the author's opinion, in the absence of the data generated by comparative research and used in research education and the development of new technologies in SAR, there is a risk that sound science-based academic preparation for undergraduates and candidates for post-graduate research education is constrained. To counteract these negative trends, SAR must be recognized as a very important branch of the department of animal reproduction. Access to resources, personnel for teaching and research, and curriculum space should be made available in order to provide the basis for relevant post-graduate training, specialization, and research.

Animals↗
PubMed2004

Relationships of efficiency to reproductive disorders in Danish milk production: a stochastic frontier analysis.

Relationships of various reproductive disorders and milk production performance of Danish dairy farms were investigated. A stochastic frontier production function was estimated using data collected in 1998 from 514 Danish dairy farms. Measures of farm-level milk production efficiency relative to this production frontier were obtained, and relationships between milk production efficiency and the incidence risk of reproductive disorders were examined. There were moderate positive relationships between milk production efficiency and retained placenta, induction of estrus, uterine infections, ovarian cysts, and induction of birth. Inclusion of reproductive management variables showed that these moderate relationships disappeared, but directions of coefficients for almost all those variables remained the same. Dystocia showed a weak negative correlation with milk production efficiency. Farms that were mainly managed by young farmers had the highest average efficiency scores. The estimated milk losses due to inefficiency averaged 1142, 488, and 256 kg of energy-corrected milk per cow, respectively, for low-, medium-, and high-efficiency herds. It is concluded that the availability of younger cows, which enabled farmers to replace cows with reproductive disorders, contributed to high cow productivity in efficient farms. Thus, a high replacement rate more than compensates for the possible negative effect of reproductive disorders. The use of frontier production and efficiency/inefficiency functions to analyze herd data may enable dairy advisors to identify inefficient herds and to simulate the effect of alternative management procedures on the individual herd's efficiency.

Animals↗
PubMed2005

A spreadsheet-based model demonstrating the nonuniform economic effects of varying reproductive performance in Ohio dairy herds.

A spreadsheet-based model was developed to estimate the economic effect of varying reproductive performance in dairy herds. Scenarios were created to model an average cow with respect to production, herd lifetime, and reproductive events. Average milk yield per day of life as well as lifetime calf and replacement heifer production were examined. Additional inputs representing milk, feed, semen, calf, and salvage prices were used to calculate net cash flow for each day of herd life for the average cow in a scenario. Economic comparison of different scenarios was accomplished using an equivalent annual cash flow (annuity) methodology.Herd performance measures and prices representative of Ohio dairy herds were used to establish a baseline average cow that had a 160-d calving-to-conception interval [days open (DO)]. Alternative scenarios that differed from baseline in DO, annual culling rate, and feed and milk prices were created to characterize the effects of changes. Under scenario inputs representative of typical Ohio dairy herds, the model indicated that a lower annual culling rate (25%) was preferable to higher annual culling rates (34 or 45%). The model estimated maximum average milk yield per day of life to occur at 110 DO. At 34% annual culling rate, calves and replacement heifers produced per lifetime declined as DO increased; beyond 150 DO, the modeled cow produced less than 1 replacement heifer per lifetime. The model also estimated a loss of $1.37 per cow per year for a 1-d increase in DO beyond 160 d. At 20% higher feed and milk prices, the model estimated a loss of $1.52 per cow per year; at 20% lower feed and milk prices, the model estimated a loss of $1.23 per cow per year. Furthermore, the model suggested that the loss associated with a 1-d increase in DO changed as DO changed. Using baseline inputs, the model calculated losses for a 1-d increase of $0.44 per cow per year at 130 DO and $1.71 per cow per year at 190 DO. The nonuniform nature of the cost of additional DO is important to veterinarians and producers. The implication is that inefficient reproduction becomes marginally more costly to producers as performance declines and warrants increased attention. Conversely, marginal benefits of improved reproduction decrease as performance improves. Herds with strong reproductive performance have less opportunity to capture economic benefits of improvement.

Animals↗
PubMed1991

How behavioral stress disrupts the endocrine control of reproduction in domestic animals.

Behavioral stress can prevent animals from achieving normal reproductive success. Stressors associated with intensive livestock management may be responsible for reduced reproductive efficiency. However, before appropriate management decisions can be made to alleviate the effects of behavioral stress on reproduction, it is necessary to identify the mechanisms by which stress disrupts normal reproduction. The neuroendocrine regulation of follicular development and ovulation requires a complex and delicate interplay between the pituitary gonadotropins and the feedback actions of the major follicular steroid, estradiol. Because of this complexity, the regulation of the follicular stage of the estrous cycle and ovulation is especially vulnerable to the effects of stress. Although the pathophysiological mechanisms by which stress disrupts reproduction are not fully understood, the stress-induced secretion of adrenal glucocorticoids seems to be of special significance because these steroids can effect both the synthesis and secretion of gonadotropins. Of additional importance may be the role of corticotropin-releasing hormone and adrenocorticotropin on the regulation of the hypothalamic-pituitary-gonadal axis.

Animals↗
PubMed1992

Structure of breeding programs to capitalize on reproductive technology for genetic improvement.

Potential rates of genetic progress are limited by biological constraints, which along with genetic parameters determine the structure of breeding programs to be employed for maximum genetic improvement. The objective here is to determine whether current progeny-testing programs in dairy cattle, which have been dictated and constrained by low female reproductive rates, need to be changed to capitalize on new reproductive technologies and how these changes should be implemented. Many differences between breeding programs diminish when selection on animal model genetic evaluations across all age and population groups is adopted as a strategy. Progeny-testing schemes then evolve toward dispersed open nucleus breeding schemes when multiple ovulation and embryo transfer is used on bull-dams. Nucleus breeding schemes have been advocated to capitalize on embryo transfer technology. In nucleus breeding schemes utilizing high reproductive rates, inbreeding, rather than reproductive rate, poses a limit to genetic progress, and strategies that maximize response to selection while limiting inbreeding need to be employed. One strategy is mating each dam to several sires rather than only one sire. In vitro embryo production techniques can be used to facilitate such mating strategies. Large-scale in vitro embryo production programs, in which large numbers of embryos per female are tested in the commercial population, offer the greatest potential for genetic gain with low rates of inbreeding. Cloning has an impact mainly on methods for dissemination of genetic improvement. Breeding herds, genetically inferior to marketed clones, are needed for continuous genetic gain. Reproductive technologies offer the potential for genetic improvement. Whether new breeding programs require changes in population structure, e.g., by creation of nucleus breeding herds, depends mainly on logistics and on quantity and quality of field information.

Animals↗
PubMed1993

Interactions of high milk yield and reproductive performance in dairy cows.

Correlations between reproductive traits and measures of milk yield indicate that higher yield is associated phenotypically and genetically with reduced reproductive performance in lactating cows. Numerous recent studies have reported that reproductive performance is compromised, primarily through delayed ovarian activity and reduced conception rates, by the demands of high milk yield. However, daily managerial decisions to obtain efficient reproductive performance have considerable impact. Management can offset depression in fertility, because high yielding herds often achieve the fewest days open. Selection for milk yield has increased blood concentrations of somatotropin and prolactin, stimulators of lactation, and decreased insulin, a hormone that is antagonistic to lactation and may be important for normal follicular development. These changes in hormone concentrations promote higher milk yield but may be potentially detrimental to other physiological functions, such as reproduction, if the management is not adequate to meet the metabolic demands of lactation. Timing and magnitude of negative energy balance apparently interact to determine the extent to which negative energy balance alters hypothalamic secretion of GnRH and its effect on gonadotropin secretion and, therefore, ovarian secretion of progesterone, which affects expression of estrus and support of the uterus during early pregnancy.

Animals↗
PubMed1997

Estimation of economic values of indices for reproductive performance in dairy herds using computer simulation.

Relationships between measures for reproductive performance and net revenue were studied using data that had been generated by a stochastic model in a computer simulation program for Ontario dairy herds. These measures included projected calving interval, involuntary culling rate, and adjusted calving interval. Adjusted calving interval was calculated by dividing the projected calving interval for pregnant cows by the fraction of the cows that were not culled for reproductive failure. The regression of adjusted calving interval on net revenue had an R2 of 0.72, which was higher than the R2 of 0.59 obtained by the regression of projected calving interval on net revenue. Hence, the estimation of financial losses from suboptimal reproductive performance was more accurate when adjusted calving interval was used as a measure of this performance than when projected calving interval was used. This difference is because projected calving interval did not consider cows that were culled for reproductive reasons, but those cows contributed to a reduction in profit because of suboptimal reproductive performance. The highest R2 (0.78) was obtained with a model that included projected calving interval and involuntary culling rate. However, use of that model might not be practical because herd operators differ in their ability to distinguish between involuntary and voluntary culling. The mean reduction in net revenue from a 1-d increase in adjusted calving interval was estimated at $4.7 (Canadian) per cow. This economic value was not significantly affected by level of adjusted calving interval, carcass price, feed costs, cost of a replacement heifer, or milk price.

Animals↗
PubMed1998

A veterinary perspective of on-farm evaluation of nutrition and reproduction.

Reproductive herd health programs of the 1960s and 1970s focused primarily on the control of infectious and noninfectious diseases of the reproductive tract, estrus detection, breeding technique, semen quality and handling, and endocrine imbalances. Despite veterinary intervention, conception rates dropped from 55% before this period to 45% after this period, but milk production increased greatly. Because studies have shown that the additional nutritional needs for high producing cows may be a factor limiting reproduction, bovine practitioners have become more involved with dairy nutrition. New emphasis has been placed on the concept of total production medicine with the anticipation that improved nutrition would improve reproduction. Because of a better understanding of the dynamics of energy in the dairy cow and its effect on reproduction, fertility examinations now include nutrition monitoring and body condition scoring. Several relationships between nutrition and fertility have been identified: high producing thin cows that drop 0.75 to 1.0 in body condition score resulting in anestrus; fat dry cows that develop fatty livers and associated postpartum disease; heifers that have good milk production but prolonged anestrus; dry cows with ration imbalances during the transition period that develop milk fever, retained placenta, displaced abomasum, metritis, or endometritis; lactating cows with disease in midlactation, especially feet and leg problems, resulting in lowered fertility; and healthy, lactating cows with poor conception that have high concentrations of urea N in blood or milk.

Animal Nutritional Physiological Phenomena↗
PubMed1999

A comparative study of reproductive performance in organic and conventional dairy husbandry.

A comparative cohort study of reproductive performance in organic and conventional dairy husbandry was conducted using longitudinal data from the Norwegian National Board of Animal Production Recording from January 1, 1994 to December 31, 1996. The present study is the first study comparing reproductive efficiency in organic and conventional husbandry in which characteristics such as herd size, breeding season, milk yield, parity, breed, use of artificial insemination (AI), and geographical distribution were taken into account. The organically managed cohort comprised 998 lactation periods, and the conventionally managed cohort comprised 3016 lactation periods. Both groups were similar in herd size and geographical distribution. The following reproduction variables were studied: days open, calving interval, calving to first AI interval, calving to last AI interval, and AI per cow. No consistent difference in reproductive performance was found between the cohorts before adjustments were made for milk yield, breeding season, service, and parity. After inclusion of these independent variables in the repeated measures, mixed-model analyses, reproductive efficiency of organically managed dairy cows was impaired compared with those under conventional management. In organic dairy farming, breeding efficiency was difficult to maintain in cows bred during winter. Organic husbandry proved more efficient than did conventional husbandry in converting roughage into milk. Furthermore, the average multiparity percentage was higher in organically managed cows.

Animals↗
PubMed1991

Comparison of Henderson's Method I and restricted maximum likelihood estimation of genetic parameters of reproductive traits.

Genetic parameters of simulated reproductive traits were estimated with Henderson's Method I or restricted maximum likelihood (REML). Each of the 25 samples consisted of 2,667 birds from 50 sires. When reproductive traits were measured on all birds, the means of both sets of estimates were equal to the true value; however, precision was higher with REML. When they were only measured on the 60 (20%) heaviest birds, Henderson's Method I was severely biased by selection (up to 40% for estimates of heritability of reproductive traits and up to 45% for estimates of genetic correlation between reproductive traits and body weight). This bias, as well as the variance of estimates, increased with selection rate and absolute value of genetic correlation between body weight and reproductive traits (or another criterion of selection). Conversely, REML was not biased by selection. It should therefore be preferred when sequential selection occurs.

Analysis of Variance↗
PubMed1990

Changes in mallard (Anas platyrhynchos) serum chemistry due to age, sex, and reproductive condition.

Selected serum constituents were analyzed from 50 adult mallards (Anas platyrhynchos) of both sexes during several stages of reproduction: pre-egg laying, egg laying, incubating, molting, and postreproductive. Similar assays were conducted on sera from ducklings aged 5 to 58 days. Values for total protein (TPR), albumin (ALB), glucose (GLU), gamma-glutamyl transferase (GGT), calcium (CA), phosphorus (PHOS) and magnesium (MG) differed by sex. When all data were combined and analyzed for sex-related differences within each reproductive condition separately, all assays except lactate dehydrogenase (LD-L), cholinesterase (CHE), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CRN) and direct bilirubin (BIDI) differed between sexes during one or more reproductive periods. Each assay showed differences among the various reproductive conditions regardless of gender. The pattern of change differed between sexes. All assays except ALB, GLU, CA and MG showed age-related changes. Lipemia in the sample interfered with all chemistries except TPR, LD-L and CA. Results indicate that when using clinical chemistry as a diagnostic tool in the mallard, age and reproductive condition should be determined in order to compare the data to appropriate control values.

Age Factors↗
PubMed1993

Concepts and measures of reproductive morbidity.

This paper presents a conceptual and methodological framework developed by an interdisciplinary group of researchers to diagnose reproductive morbidity at the community level. The paper also presents a determinants structure that delineates the health and social factors hypothesized to influence reproductive morbidity. The high prevalence of reproductive-morbidity conditions revealed by implementation of the study framework in two villages of Giza in Egypt is reported. Based on this research experience and the process of presenting its results to the larger professional community, the paper discusses policy implications of the study in terms of reproductive-health services, education and training programs and research efforts for measurement of reproductive ill-health at a community setting.

Adolescent↗
PubMed1999

Reproduction in water buffalo: comparative aspects and implications for management.

The domestic buffalo occupies an important niche in many ecologically disadvantaged agricultural systems, providing milk, meat and draught power. Although buffalo can adapt to harsh environments and live on low quality forage, their reproductive efficiency is often compromised by such conditions. Climatic stress depresses ovarian cyclicity, oestrous expression and conception rates. Poor nutrition, usually related to seasonal fluctuations in availability and quality of feed, delays puberty and increases the duration of postpartum anoestrus. Management factors such as the system of grazing (free, tethered or none) and sucking by calves (restricted or ad libitum) also modulate reproductive functions. Finally, the skills and capabilities of farmers as well as the quality of support services such as artificial insemination and disease control also influence fertility. The relative importance of these factors vary greatly depending on ecological conditions and production systems. Improvement of reproductive efficiency therefore requires the identification of specific limiting factors under a given situation and the development and field testing of strategies for improvements and interventions that are sustainable with available local resources. The application of modern reproductive technologies in buffaloes requires an appreciation of their biology and reproductive physiology as well as the potentials and limitations under each specific production system.

Animal Husbandry↗