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PubMed1983

Plasma levels and pharmacokinetics of norethindrone and ethinylestradiol administered in solution and as tablets to women.

Twenty-four normal adult female volunteers were dosed orally with a solution and tablet formulation containing the contraceptive combination of norethindrone (NET, 1.0 mg) and ethinylestradiol (EE2, 0.12 mg) in a crossover bioequivalence study. Blood was sampled sequentially following single oral doses and the plasma separated for analysis of NET and EE2 by specific radioimmunoassays. Comparisons of both drugs following a dose in solution and tablets were made with respect to the following parameters: (a) plasma concentrations at each sample time; (b) maximum plasma concentration (Cpmax); (c) time to maximum plasma concentration (Tmax); (d) total area under the plasma concentration vs. time curve (AUC), and (e) plasma half-life (t1/2). It was found that the tablet and solution doses were bioequivalent with respect to EE2 absorption. However, absorption of NET from solution and tablet doses exhibited significant differences with respect to plasma levels at certain time points as well as AUC (which were higher following the tablet dose), but Cpmax, Tmax and t1/2 were not significantly different. Pharmacokinetic analysis of both drugs following the tablet dose was carried out using a two-compartment open model. The absorption rate constant (ka) and peripheral to central compartment transfer rate constant (k21) were similar for NET and EE2, but statistically significant differences were observed with respect to the distribution rate constant (alpha), the central to peripheral transfer rate constant (k12), the overall elimination rate constant (ke1), and volume of distribution (V1/F). The elimination rate constant (beta) for both drugs showed a difference of borderline statistical significance.

Adolescent↗
PubMed2001

Perspectives on nutrition needs for the new millennium for South Asian regions.

South Asia is the most populated region of the world with several nutritional challenges. Though per capita food energy supply, child survival and life expectancy have improved, and even today large segments of the population are below the poverty line with high infant and maternal mortality rates. It is important to recognize the crucial role of nutrition throughout the life cycle-from conception to old age. It is very necessary now to move from food security to nutrition security and improve the quality of foods both in macro- and micronutrients in order to break the transgenerational effects of malnutrition. The key solutions to the problems should address the issue of social development, population stabilization, environmental degradation and inadequate health and nutritional services. Strategies for empowering women and actuating community participation as sustainable programmes for human development, measures to reduce underweight and stunting in children and prevention of micronutrient malnutrition across the population are required. Enhancing food and nutrition security through innovative diversified agriculture and dietary practices, prevention and control of infection, promotion of food safety and fortification of staples with appropriate attention on emerging chronic disorders are essential. Population control measures to stabilize the fertility rates, biotechnological approaches for genetically modified foods, nutrition surveillance based on assessment, analysis and action to address the logistic, technical and compliance issues with emphasis on promotion of breast feeding and complementary foods with adequate attention on the reproductive needs of adolescent girls, pregnant mothers and lactating women would eliminate low birth weight, stunting, and chronic energy deficiency in vulnerable groups. Focused studies on bioavailability of micronutrients and its enhancement, innovative horticulture interventions, fortifications, social marketing strategies would promote the intake of micronutrient and phytonutrient rich foods. In-depth epidemiological research, an insight into foetal origins of adult disease and nutrition-genes interaction and life style alterations will avert the emerging epidemic of chronic diet related disorders. An investment in preventing foetal malnutrition improves nutrition of women in reproductive age, infant and child nutrition and prevents the onset of chronic disease in adult life. Human resource development, IEC measures, technology transfer, operational and logistic research, building of databases, integrated, intersectoral, multidisciplinary plans and sound management information system and surveillance with net working and experience sharing in the region will help to overcome the common challenges and lay the foundation for a better scenario in these regions in the near future.

Adolescent↗
PubMed1983

Poly(DL-lactide-co-glycolide)/norethisterone microcapsules: an injectable biodegradable contraceptive.

Microcapsules made from a biocompatible, biodegradable polymeric excipient, poly(DL-lactide-co-glycolide) (DL-PLGA) that contained 22 weight percent (wt %) norethisterone (NET), were prepared by a solvent-evaporation microencapsulation process. The effects of changing both the lactide-to-glycolide ratio of the DL-PLGA and the size of the microcapsules on the rate of NET release and the rate of excipient biodegradation were determined in vivo. NET release rates were determined in baboons after injecting the microcapsule formulations intramuscularly. Serum samples obtained at various times following treatment were analyzed for NET, progesterone, and estrogen by radioimmunoassay (RIA). Biodegradation kinetics were determined by injecting NET microcapsules made from radiolabeled DL-PLGA intramuscularly into the hind legs of rats. Residual radioactivity at the injection site was determined at various times after treatment by combustion analysis of the muscle tissue. Changing the ratio of the comonomers to include more glycolide (DL-lactide:glycolide-96:4, 92:8, 87:13, 74:26) increased the rate of NET release and accelerated the biodegradation of the copolymer excipient. Decreasing the size of the microcapsules increased the rate of NET release. On the basis of these studies a NET microcapsule formulation has been identified for clinical testing which releases NET for 3 months and biodegrades completely within 6 months.

Animals↗
PubMed2006

Growth and leaf physiology of monkeyflowers with different altitude ranges.

Every species is limited both geographically and ecologically to a subset of available habitats, yet for many species the causes of distribution limits are unknown. Temperature is thought to be one of the primary determinants of species distributions along latitudinal and altitudinal gradients. This study examined leaf physiology and plant performance under contrasting temperature regimes of sister species of monkeyflower, Mimulus cardinalis and Mimulus lewisii (Phrymaceae), that differ in altitude distribution to test the hypothesis that temperature is the primary determinant of differences in fitness versus altitude. Each species attained greatest aboveground biomass, net photosynthetic rate, and effective quantum yield of photosystem II when grown under temperatures characteristic of the altitudinal range center. Although both species exhibited greater stem length, stomatal conductance, and intercellular CO2 concentration in hot than in cold temperatures, these traits showed much greater reductions under cold temperature for M. cardinalis than for M. lewisii. Survival of M. lewisii was also sensitive to temperature, showing a striking decrease in hot temperatures. Within each temperature regime, the species native to that temperature displayed greatest growth and leaf physiological capacity. Populations from the altitude range center and range margin of each species were used to examine population differentiation, but central and marginal populations did not differ in most growth or leaf physiological responses to temperature. This study provides evidence that M. cardinalis and M. lewisii differ in survival, growth, and leaf physiology under temperature regimes characterizing their contrasting low and high altitude range centers, and suggests that the species' altitude range limits may arise, in part, due to metabolic limitations on growth that ultimately decrease survival and limit reproduction.

Altitude↗
PubMed1992

Epidemiological study on factors influencing fertility indices in Israeli dairy herds.

The objective of this study was to determine feeding factors connected with differences in the fertility of Israeli Kibbutz dairy herds. In an epidemiological case-control survey, data from 30, low-fertility Kibbutz dairy herds having a mean overall conception rate of 35% in multiparous cows were compared with the data from 30, high-fertility Kibbutz dairy herds having a mean overall conception rate of 48% in multiparous cows. Nutritional factors accounted for 67% of the differences between low-fertility and high-fertility herds in the overall conception rate of multiparous cows, while only 4.8% could be related to the body condition during the dry period. Among the factors which occurred more frequently in the low-fertility than in the high-fertility herds were 1) a higher average protein density and lower energy/protein ratio was fed during lactation and 2) a single feeding group was maintained for all lactating cows. 3) There were phytoestrogens in the silage or alfalfa hay, fed during lactation. 4) Faulty dry period was instituted, which was defined as the presence of at least one of the following three practices: a) the daily feed was above 3 kg of high lactation mix; b) more than 15 Mcal of net energy per day was given during the first part of the dry period; c) more than 30% of the cows were obese during the dry period. Three or more risk factors were found in one high-fertility herd and in 20 low-fertility herds. This finding emphasizes the importance of identifying and removing risk factors as a possible means for improving the reproductive performance of herds.

Journal Article↗
PubMedDate not supplied

Does inbreeding lead to decreased human fertility?

In most Western countries there is a widespread belief, fostered in part by historical prejudice and religious proscription, that inbreeding in human populations causes a reduction in fertility. Support for this belief has been claimed in HLA-based studies, with increased rates of fetal losses suggested in HLA-compatible unions. To critically assess the overall status of fertility in consanguineous unions, data on 30 populations resident in six countries were collated from a systematic review of the literature. The mean numbers of live births were then compared in four consanguinity test categories, ranging from second cousin to uncle-niece/double first cousin, and corresponding non-consanguineous reference groups. Linear regressions indicated a positive association between consanguinity and fertility at all levels of inbreeding, attaining statistical significance at first cousin level (p < 0.0001). The results were, however, subject to a number of potential limitations, in particular lack of control for important socio-demographic variables. To overcome this problem, data on first cousin marriages were abstracted from the National Family and Health Survey conducted in India during 1992-1993. Multivariate analysis showed that fertility in first cousin unions was positively influenced by a number of variables, including illiteracy, earlier age at marriage and lower contraceptive uptake, but the most important of these parameters were duration of marriage and reproductive compensation. In net terms, consanguinity was not found to be associated either with a significant positive or negative effect on fertility.

Adolescent↗
PubMed2003

Reproductive patterns and feeding habits of three nectarivorous bats (Phyllostomidae: Glossophaginae) from the Brazilian Cerrado.

The reproductive patterns and feeding habits of three sympatric nectarivorous bats, Glossophaga soricina, Anoura caudifera, and A. geoffroyi were studied in the Pousada das Araras Natural Reserve, located in Central Brazil. The bats were captured with mist nets from August 2000 to July 2001. Reproductive condition was determined by external analyses of the specimens and feeding habits from fecal samples. Glossophaga soricina was the most abundant species (65%), followed by A. geoffroyi (30%) and A. caudifera (5%). Significant differences were observed in the sex-ratio of the two more abundant species. Anoura geoffroyi showed a monoestrous pattern; its reproductive peaks occurred between the end of the dry season and the beginning of the rain season. A seasonal bimodal pattern was recorded for G. soricina, with pregnant specimens showing one peak observed in the dry season and another in the middle of the rainy season. The reproductive pattern of A. caudifera could not be satisfactorily defined because of the small sample size. However, this species apparently has a reproductive cycle similar to that of G. soricina. The patterns observed in this study seem to be related with the climate in the Brazilian savanna (Cerrado), with two well-defined seasons (dry and wet). By adjusting the parturition close to or in the rain season the three species could be favoring a greates survival rate for the offspring, since the critical lactation period would then occur in a time of maximum food availability. The three bat species showed a generalist diet, consuming fruits, pollennectar, and arthropods. Significant differences were observed in the diet of G. soricina: fruits and arthropods predominated in the dry season and pulp (fruits) in the rainy season. Males and females of this species ate the same items in similar proportions. Although A. geoffroyi has not showed a preference for a specific item, consumption of fruits and arthropods was generally greater than that of pollen.

Animals↗
PubMed2004

Phosphorus reduction through precision feeding of dairy cattle.

A study was conducted on 4 dairy farms in the Cannonsville Reservoir Basin (Delaware County, NY) to identify feeding strategies in commercial dairy herds that will reduce manure phosphorus and mass farm phosphorus balance. Lactating cow diets on all 4 farms were evaluated monthly for 28 mo using the Cornell Net Carbohydrate and Protein System. Milk production and herd reproductive performance were measured monthly. Manure phosphorus content was measured every 6 mo. Reduced phosphorus diets (precision feeding) were implemented in 2 of the herds. Mean herd phosphorus intakes in the 4 herds ranged from 107 to 165% of requirement. Dietary phosphorus intakes in the 2 herds where diets were modified were reduced from 153% of requirement to 111%, an average reduction of 25%. Predicted phosphorus intakes and manure excretions were reduced 11.8 kg/yr per cow. After dietary adjustments in the 2 herds, fecal phosphorus concentrations decreased 33%. Milk production was not adversely affected by reduced phosphorus diets. Whole farm mass phosphorus balances (amount of phosphorus remaining on the farm) on the 2 farms were reduced 49%, with the percentage of imported phosphorus remaining on the farm reduced to less than 45%. Achieving feed phosphorus reductions similar to those of this study on all of the estimated 7000 to 8000 mature dairy cattle in the Cannonsville Basin could reduce feed phosphorus imports and manure phosphorus excretions more than 64,000 kg/yr. This would slow the rate of phosphorus accumulation in agricultural soils in the Cannonsville Basin, which over time could reduce the 50,000 kg/yr average total phosphorus loading of the Cannonsville Reservoir.

Animal Feed↗
PubMed1981

A prospective multicentre trial of the ovulation method of natural family planning. II. The effectiveness phase.

A five-country prospective study was undertaken to determine the effectiveness of the ovulation method of natural family planning. After successful completion of a teaching phase of three cycles, 725 subjects entered a 13-cycle effectiveness phase and contributed 7514 cycles of observation. The overall cumulative net probability of discontinuation for the effectiveness study after 13 cycles was 35.6%, 19.6% due to pregnancy. Pregnancy rates per 100 woman-years calculated using the modified Pearl index were as follows: conscious departure from the rules of the method, 15.4; inaccurate application of instructions, 3.5; method failure, 2.8; inadequate teaching, 0.4; and uncertain, 0.5.

Adult↗
PubMed2001

Characterizing biosecurity, health, and culling during dairy herd expansions.

Our objectives were to investigate strategies for biosecurity, expansion, and culling for expanding dairy herds in the Upper Midwest. Eighteen dairies in Iowa and Wisconsin were visited, and dairy managers and veterinarians were interviewed to characterize five biosecurity practices, herd culling practices, vaccines administered, and ensuing disease status for the herds. The majority of herds that were interviewed failed to employ comprehensive biosecurity programs for incoming cattle. Nearly 60% of herds obtained cattle from sources for which it was difficult to document genetic backgrounds and health histories, fewer than half required health testing for incoming cattle, and approximately 50% quarantined new cattle on arrival. Despite high rates of vaccination for bovine viral diarrhea, all herd owners and managers indicated that herd biosecurity was compromised as a result of expansion. Half of the interviewed herds indicated that bovine viral diarrhea and papillomatous digital dermatitis were notable disease problems. Herds that obtained cattle with unknown backgrounds and health status experienced the largest number of diseases. Before expansion, the most frequently cited reasons for culling were reproductively unsound; low milk production; mastitis, poor udder health, and high SCC; during expansion, the strategic decision to cull cows for low milk production was used less often. In addition, the stochastic simulation model, DairyORACLE, was used to evaluate economic outcomes for several expansion alternatives. Five model scenarios studied were: base scenario (herd size was maintained) and four expansion scenarios--all paired combinations of heifer quality (high, low) and voluntary culling (implemented, not implemented). Culling for low milk production yielded an additional $23.29 annually (6-yr annuity) per cow, but on the basis of purchased replacements, no voluntary culling was most profitable. Purchasing high versus low quality replacement heifers for expansions returned an additional $113.54 annually ($681.24 total net present value) per heifer purchased. Many opportunities exist to improve cattle-related factors for dairy herd expansions, including the use of comprehensive biosecurity programs, realistic planning and budgeting for cattle purchases, and cost effective purchase and culling practices.

Animal Husbandry↗
PubMed1997

Corticosterone secretion in response to capture and handling in free-living red-eared slider turtles.

The corticosterone response to capture and handling was measured in free-living red-eared slider turtles, Trachemys scripta elegans. To determine the ability of this species to exhibit this endocrine response, slider turtles were bled at the time of removal from hoop nets and again at 30 and 60 min following capture to create plasma profiles of acute corticosterone secretion from individuals. Plasma corticosterone concentration increased significantly with handling time. The greatest rise in corticosterone was within the first 30 min following capture and handling, with this rate of increase declining over the next 30 min of restraint. There was no correlation between corticosterone levels at the time of capture and the length of time it took to get the sample if the sample was taken within the first 10 min after capture. However, when these samples were included with those taken from other turtles sampled 11 to 25 min after capture, hormone levels were significantly correlated with handling time. This suggests that the critical time to obtain an initial sample that best represents the predisturbance level in slider turtles is within 10 min. There was no correlation between the turtles' energetic condition and initial corticosterone concentrations. Plasma corticosterone values at all sampling times were comparable to those observed in other reptile species. The results from this study may be used to investigate the effects of unpredictable resources on reproductive success and survival in freshwater turtles.

Animals↗
PubMed1987

Pharmacokinetics of norethisterone in humans.

The pharmacokinetics of a dose of 1mg norethisterone administered with 50 micrograms ethynyloestradiol was studied in 83 subjects. The dose was rapidly absorbed and there were wide variations in the serum NET concentrations at any particular time after dosing; the concentrations at 24 h varied from 100 to 1700 pg/ml. There was a significant negative correlation between the serum NET concentration and the time after dosing in all women. There were large inter-subject variations in the pharmacokinetic parameters, the elimination half-life and bioavailability showing 3- and 5- fold variability, respectively. Mean values for the parameters were t1/2, 7.6 h; bioavailability, 53.6 ng/ml/h; C max, 4.63 ng/ml; clearance, 22.6 l/h; and Vd 2361. There were a number of statistically significant correlations between the pharmacokinetic parameters and analysis of the correlations suggested that clearance was an important determinant of the bioavailability and of C max whereas the elimination half-life was the determinant of the NET concentration at 24 h. The pharmacokinetics of NET are compared with those of ethynyloestradiol. The wide variation in pharmacokinetics is likely to be important in determining inter-subject variations in efficacy and, particularly, side-effects of oral contraceptives especially now that low-dose formulations are widely used.

Biological Availability↗
PubMed2002

Population genetic structure of Pyrenophora teres Drechs. the causal agent of net blotch in Sardinian landraces of barley (Hordeum vulgare L.).

Monoconidial cultures of Pyrenophora teres, the causal agent of barley net blotch, were isolated from leaves collected from six populations of the barley landrace "S'orgiu sardu" growing in five agro-ecological areas of Sardinia, Italy, and genotyped using AFLPs. The 150 isolates were from lesions of either the "net form" (P. teres f. sp. teres) or the "spot form" (P. teres f. sp. maculata) of the disease. Of 121 AFLP markers, 42%, were polymorphic. Cluster analysis resolved the isolates into two strongly divergent groups (F(ST) = 0.79), corresponding to the net (45% of the isolates) and the spot (55% of the isolates) forms (designated the NFR and SFR groups, respectively). The absence of intermediate genotypes and the low number of shared markers between the two groups indicated that hybridization between the two formae is rare or absent under the field condition of Sardinia. Five of the barley populations hosted both forms but in different proportions. The SFR populations were similar in overall polymorphism to the NFR populations. However, compared to the SFR form, the NFR occurred in all fields sampled and showed a higher population divergence (F(ST) = 0.43 versus F(ST) = 0.09 with all isolates; F(ST) = 0.37 versus F(ST) = 0.06 with clone corrected samples) probably due to a lower migration rate. AFLP fingerprints resolved 117 distinct genotypes among the 150 isolates sampled (78%), 87% in SFR and 68% in NFR isolates. Although the absolute numbers may be a function of the number of AFLP markers assayed, the relative difference suggests that clonality is more prevalent among the NFR isolates (with 11 of 46 haplotypes observed more than once), compared with SFR isolates (7 of 71 haplotypes). Both digenic and multilocus linkage disequilibrium analyses suggested that sexual reproduction occurs at significant levels within the NFR and SFR populations, and that the relative contribution of sexual and asexual reproduction varies among different environments.

Fungi↗
PubMed2001

Swimming speeds and buoyancy compensation of migrating adult chum salmon Oncorhynchus keta revealed by speed/depth/acceleration data logger.

Although the homing migration of Pacific salmon is well documented, the swimming behaviour of the returning salmon has been poorly described, principally as a result of the difficulties encountered in monitoring salmon behaviour in the sea. The present study describes the use of a recently developed electronic data logger to obtain simultaneous recordings of the swimming speed, depth, fin-beating activity and body angle of free-ranging chum salmon Oncorhynchus keta during their homing migration in coastal waters. Chum salmon migrated horizontally at speeds of 1.5-3.0 km h(-1). The gross horizontal distance salmon moved during total recording periods were 1.24- to 19.0-fold greater than the net distance from the release site to the retrieval points. It is suggested that homing salmon did not drift passively but swam actively to the spawning grounds. Salmon preferred the surface water, but also made frequent vertical migrations. The travelled depth of each salmon ranged from 0.36 to 0.64 km per hour. Salmon descended at faster rates and steeper angles than they ascended. Both tailbeat frequency and tail thrust were higher during the ascent than the descent phase. These results suggest that chum salmon spent more energy during the ascent than the descent phase. Profiles of descent rate assumed an arched shape with respect to a change in hydrostatic pressure, while ascent rate increased with decreasing depth. High tailbeat frequencies were found during the course of ascent, which suggests that the salmon did not regulate the volume of air in the swim bladder during short-term vertical migrations.

Animal Migration↗
PubMed2005

Global energy gradients and size in colonial organisms: worker mass and worker number in ant colonies.

Body mass shapes processes from cell metabolism to community dynamics. Little is known, however, about how the average body mass of individuals varies among ecological communities. Ants alter colony mass by independently changing worker mass and/or worker number. In a survey of 49 ecosystems from tundra to tropical rainforest, average worker mass and worker number were uncorrelated (r(s) = 0.2, P > 0.14) and varied 100-fold. Data supported the hypothesis that higher mean monthly temperatures, T, reduce worker mass by increasing metabolic costs during worker development. In contrast, worker number was unimodal over a 1,000-fold gradient of net primary productivity (NPP, g of carbon per m2 per yr), a measure of organic carbon available to consumers. At the lowest levels of NPP colonies appeared to be carbon-limited; above 60 g of carbon per m2 per yr average worker number decreased to a global low. This decline in worker number with increasing NPP supports the hypothesis that abundant carbon ameliorates the Achilles heel of small taxa in competition with large taxa: their relatively high metabolic demands. Higher predation rates in resource-rich environments may also play a role in limiting worker number. In all, about half the global variation in worker mass and number was accounted for by gradients of NPP and T. Changes in global temperature and rainfall may thus mold gradients of ectotherm size, with consequences for the structure and function of the ecosystems.

Animals↗
PubMed2004

Interactive effects of ultraviolet-B radiation and temperature on cotton physiology, growth, development and hyperspectral reflectance.

Current conditions of 2-11 kJ m(-2) day(-1) of UV-B radiation and temperatures of >30 degrees C during flowering in cotton cultivated regions are projected to increase in the future. A controlled environment study was conducted in sunlit growth chambers to determine the effects of UV-B radiation and temperature on physiology, growth, development and leaf hyperspectral reflectance of cotton. Plants were grown in the growth chambers at three day/night temperatures (24/16 degrees C, 30/22 degrees C and 36/28 degrees C) and three levels of UV-B radiation (0, 7 and 14 kJ m(-2) day(-1)) at each temperature from emergence to 79 days under optimum nutrient and water conditions. Increases in main stem node number and the node of first fruiting branch and decrease in duration to first flower bud (square) and flower were recorded with increase in temperature. Main effects of temperature and UV-B radiation were significant for net photosynthetic rates, stomatal conductance, total chlorophyll and carotenoid concentrations of uppermost, fully expanded leaves during squaring and flowering. A significant interaction between temperature and UV-B radiation was detected for total biomass and its components. The UV-B radiation of 7 kJ m(-2) day(-1) reduced boll yield by 68% and 97% at 30/22 degrees C and 36/28 degrees C, respectively, compared with yield at 0 kJ m(-2) day(-1) and 30/22 degrees C. No bolls were produced in the three temperature treatments under 14 kJ m(-2) day(-1) UV-B radiation. The first-order interactions between temperature, UV-B radiation and leaf age were significant for leaf reflectance. This study suggests a growth- and process-related temperature dependence of sensitivity to UV-B radiation.

Carbon Dioxide↗
PubMed1984

A two-year experience with Norplant implants in Assiut, Egypt.

This report describes the two-year experience of 250 acceptors of NORPLANT implants and 100 TCu-380-Ag IUD acceptors in Assiut, Egypt. The two-year net continuation rate was 67.9 per 100 for implant users and 52.3 per 100 for IUD users. The most important cause for NORPLANT removal was the disruption of menstrual rhythm. However, by the end of the second year, three-quarters of NORPLANT users had monthly menstrual periods and about 60 percent described the amount of blood loss as average, 15 percent as decreased, 15 percent as increased and 10 percent as variable. About 88 percent of the NORPLANT acceptors rated their experience with the contraceptive as good or excellent.

Adult↗
PubMed2000

Effects of inbreeding on production and survival in Jerseys.

Responses of registered Jersey cows to various levels of inbreeding were examined with pedigree data supplied by the American Jersey Cattle Association and test-day production data from 1970 through 1998 obtained from the Animal Breeding Center at Cornell University. Rate of increase in level of inbreeding is accelerating with time, making it more difficult for producers to make matings that avoid the potentially deleterious effects of inbreeding. Production losses caused by inbreeding were significant and curvilinear for all traits studied except somatic cell linear score, with the greatest losses at higher levels of inbreeding. Inbreeding was found to have the greatest effect on production at early ages and early in lactation. Early onset of the deleterious effects of inbreeding resulted in larger net present value losses than if effects of inbreeding occurred later in the life of an animal. Losses were probably enhanced because of the need to freshen animals as early as possible to maximize net present value returns. Survival decreased as level of inbreeding increased and was likely to have a greater negative impact on the financial health of the dairy enterprise than production losses.

Age Factors↗