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PubMed1988

Environmental, dietary, and hormonal factors in the regulation of seasonal breeding in free-living female Indian rose-ringed parakeets (Psittacula krameri).

The roles of environmental, dietary, and hormonal factors in the timing of seasonal breeding were assessed in free-living female Indian rose-ringed parakeets, Psittacula krameri, in northwest India (22 degrees 2'N, 73 degrees E). The ovaries and oviducts began to enlarge in January, were fully developed in February, and began to regress in March. During this time there was no significant change in the concentration of plasma luteinizing hormone (LH) or estradiol. The concentration of plasma LH decreased (P less than 0.01) at the end of the breeding season. Pair bond formation occurred between September and December and was associated with an increase in levels of plasma LH but no change in plasma estradiol. Concentrations of plasma testosterone (T) and 5 alpha-dihydrotestosterone (5 alpha-DHT) did not vary significantly during the year and were similar to those in males except for higher values of 5 alpha-DHT and lower values of T during the pre- and postbreeding periods, respectively. The similar levels of plasma androgens in both sexes may be related to the equal roles that both sexes play in the defence of their nest holes. An analysis of crop sac contents showed that the birds fed chiefly on pigeon peas (Cajanus cajan) during the breeding season and on cereal grains at other times of the year. It is suggested that pigeon peas provide the extra nutrients, including calcium, required for egg production. Since pigeon peas ripen between November and March, the production of the crop may play a role in the timing of seasonal breeding. A further factor appears to be competition for nest sites. By breeding in winter, the parakeet avoids competing with other species which nest in holes.

Animals↗
PubMed1992

Year-to-year patterns of circulating levels of testosterone and corticosterone in relation to breeding density, experience, and reproductive success of the polygynous red-winged blackbird.

To determine across-year patterns in plasma testosterone (T) and corticosterone (B) levels in free-living birds, we took blood samples in the same 2-week breeding period during 4 consecutive years from territorial male red-winged blackbirds. We used our data to test predictions of the "challenge hypothesis" of T secretion and also to examine hormonal correlations with age, breeding experience, breeding density, and reproductive success. Average T and B levels across years were not significantly different. Within individuals, T levels between years were, in general, highly variable. T levels of males with territories in high-density breeding areas were significantly higher than those of males with territories in low-density areas. T levels were positively correlated with harem size and there was a trend for males with high T levels to fledge more offspring. We found no relationships between T and B levels and male age or breeding experience. Some results of the study were consistent with the predictions of the challenge hypothesis. This study constitutes one of the few examinations of across-year patterns in circulating hormone levels in wild populations.

Animals↗
PubMed1985

Lifetime breeding studies in fully fed and dietary restricted female CFY Sprague-Dawley rats. 1. Effect of age, housing conditions and diet on fecundity.

The capacity of female CFY Sprague-Dawley rats to bear multiple litters when breeding was commenced at increasing ages was assessed under the following conditions: continuous housing with male (GC), intermittent breeding of group (GI) and individually housed (I) fully fed animals, restriction of food intake (DR), refeeding of dietary restricted rats (DRA). The percentage of females pregnant, number of litters produced and total litter size were assessed. The number of litters or percent pregnant was unaffected by individual housing but there was a significantly greater decline in total litter size with increasing age of mother when compared to (GI) rats. The slope of the regression line in (I) was identical to that for (GC) females and may reflect the burden of continuous breeding or the stress of individual housing. Both litter size and overall fertility were decreased by dietary restriction but these females did retain their capacity to breed as late as 937 days in contrast to 720 days for any group of fully fed animals. There was no decline in litter size with increasing age in (DR). Returning (DR) rats to full feeding resulted in a rate of decline in litter size identical to that for (GI). All groups of (DRA) produced a maximum of three litters, commencement of breeding at 750 days resulting in production of a litter as late as 952 days.

Aging↗
PubMed1985

Effects of high ambient temperature on respiration rate, rectal temperature, fetal development and thyrold gland activity in tropical and temperate breeds of sheep.

The effects of high ambient temperatures on rectal temperature (RT), respiration rate (RR), fetal development and serum thyroxine (T(4)) concentrations were stuaied in two experiments involving 35 ewes and 26 lambs from the following ewe groups: 1) Barbados Blackbelly (B), a tropical breed; 2) Dorset (D), a temperate breed; and 3) Blackbelly x Dorset crosses (BxD). Data were obtained on four B, five D and five BxD ewes exhibiting estrus during the summer (Exp. 1). In Exp. 2, eight B, seven D and six BxD ewes were maintained in two environmental chambers (cool, 22.2C; hot, 33.8C) from day 125 of gestation to seven days before the expected lambing date for each breed group (D and BxD, 140+/-1; B, 144+/-1 day of gestation). The B and BxD ewes were more heat-tolerant than D ewes as measured by significantly lower RT and RR in each experiment. Mean lamb birth weight, crown-rump length, number of functional uterine caruncles and caruncle weight and size did not vary significantly among breed groups or temperature chamber (Exp. 2), and there was no indication that the high temperature imposed caused fetal dwarfing in lambs removed from the uterus at a standard age of seven days before expected parturition. Serum T(4) varied markedly among breed groups (P<0.05) in each experiment with B ewes having the lowest and BxD ewes the highest concentration. In Exp. 1, follicular stage T(4) concentrations in B and BxD ewes were lower (P<0.02) than those during the luteal stage of the estrous cycle. The decrease in D ewes was not significant. High ambient temperature (Exp. 2) depressed T(4) levels in D ewes (P<0.05) and also depressed the pituitary-thyroid response to thyrotropin releasing hormone in D lambs. Such was not the case in B and BxD ewes and their lambs.

Journal Article↗
PubMed1988

B-mode ultrasound observations of bull testes during breeding soundness examinations.

The testes of 78 adult Beefmaster bulls (13 to > 31 mo old) were scanned with a 5 MHz, linear array portable ultrasound unit during routine breeding soundness examinations. Videotape recordings were used to measure mediastinum testis width and fluid width between visceral and parietal tunics (fluid width), and to count the number of fibrotic foci. Ultrasound results were compared to breeding soundness score parameters, which included total score, age classification, and percentage of primary and secondary sperm abnormalities. The overall mean mediastinum testis width and fluid width were 0.33 cm +/- 0.133 and 0.10 cm +/- 0.13, respectively; 15 testes had 1-8 fibrotic foci. There were no significant differences in mediastinum testis width and fluid width between left and right testes when compared by breeding soundness score classification or by age classification. There were no significant differences in mediastinum testis width, fluid width, breeding soundness score, or primary or secondary sperm abnormalities in bulls with fibrotic foci compared to bulls without fibrotic foci. There appears to be no significant information that routine testicular ultrasound examination adds to accepted breeding soundness evaluations performed on the same day.

Journal Article↗
PubMed1990

Time of ovulations in dairy goats induced to superovulate with porcine follicle stimulating hormone during and out of the breeding season.

Alpine dairy goats were induced to superovulate at the end of a progestagen treatment with porcine follicle stimulating hormone (pFSH) during the breeding season (n = 10 goats) and out of the breeding season (n = 10 goats). Occurrence of estrus and of the luteinizing hormone (LH) peak were checked every 4 h. Ovulations were determined every 6 h by ovarian laparoscopic examination. Among the parameters studied, the mean interval from sponge removal to the onset of estrus did not differ whatever the season of treatment, but the variability was higher for females treated out of the breeding season. Ovulations began during the laparoscopic control period for nine of ten goats during the breeding season vs seven of ten goats out of the breeding season. For these 16 females, on which the LH peak and beginning of ovulation were known, the season did not affect the intervals between the onset of estrus and the LH peak and between the LH peak and the beginning of ovulation. When ovulations are observed by laparoscopy every 6 h, for any given goat 54.9% of total ovulations (counted 7 d after estrus) occurs in less than 6 h, and 87.1% in less than 12 h. Although the interval between the LH peak and the ovulation is quite constant, the additive variabilities of the intervals between the sponge removal and the onset of estrus and between the onset of estrus and the LH peak precluded the determination of an optimal time for artificial insemination (AI) by timing sponge removal or onset of estrus.

Journal Article↗
PubMed1991

Effects of breed, age of donor and dosage of follicle stimulating hormone on the superovulatory response of beef cows.

Data were obtained on 1039 recoveries of embryos from beef cows of four breeds at two locations, in clinic and on farm. General linear models procedures were utilized to determine the effects of breed, location, age of donor, dosage of follicle stimulating hormone (FSH) and the interaction of age and FSH on the following dependent variables: 1) the mean number of ova (unfertilized oocytes and embryos) recovered; 2) the mean number and percentage of embryos (fertilized; live and dead) recovered; and 3) the mean number and percentage of transferable embryos recovered. The interaction of age of donor and dosage of FSH with breed and location prevented the pooling of data over breed and location. The mean number of ova recovered was affected by age of the donor (Charolais-in clinic), or the interaction between age of donor and dosage of FSH (Polled Hereford-in clinic and -on farm and Simmental -on farm). The mean number of embryos was affected by age of donor (Polled Hereford-in clinic), dosage of FSH (Simmental-in clinic) or their interaction (Angus-on farm). The mean number of transferable embryos was affected by age of donor (Polled Hereford-in clinic and -on farm, Simmental-in clinic and Angus-on farm). General linear models procedures were utilized to determine the effects of the embryo (stage of development and quality) and the recipient (synchrony with the donor) on the rate of pregnancy. Rate of pregnancy varied with embryo quality score and synchrony of the recipient and the embryo. In conclusion, the superovulatory response was found to be highly breed-specific, and most of the variability in embryos produced was attributed to the number of ova recovered. However, the number of ova, embryos and transferable embryos recovered was further influenced by age of the donor, dosage of FSH or their interaction.

Journal Article↗
PubMed1995

Reduced breeding success of Cormorants (Phalacrocorax carbo sinensis) in relation to persistent organochlorine pollution of aquatic habitats in The Netherlands.

Cormorants (Phalacrocorax carbo sinensis) breeding in the heavily contaminated sedimentation area of the rivers Rhine and Meuse have a severely reduced breeding success as compared to several other Dutch colonies. A detailed analysis of reproductive performance in combination with chemical analysis of eggs and food from colonies in differently contaminated aquatic habitats is presented. The differences in breeding success between colonies are caused mainly in the egg-stage of breeding. Eggshell thinning and increased embryonic mortality cause the differences in hatching success. The observed effects seem to be related to chlorinated hydrocarbons. Significant correlations are found for concentrations of DDE with eggshell thinning and for concentrations of PCBs with hatching and breeding success. The correlations between concentrations of chlorinated hydrocarbons in eggs and biological effects measured in the field are established both on colony and individual clutch level.

Journal Article↗
PubMed1988

Association of sperm, vaginal cytology, and reproductive organ weight data with results of continuous breeding reproduction studies in Swiss (CD-1) mice.

In continuous breeding reproduction studies in which an adverse effect on fertility was detected over an 18-week treatment period, a crossover mating trial was then conducted to determine the affected sex. Results of 25 crossover breeding studies conducted using Swiss (CD-1) mice were compared with results of sperm morphology and vaginal cytology examinations (SMVCEs) conducted at the conclusion of the mating trial. SMVCE endpoints include sperm concentration, motility, and morphology, vaginal cytology, and male reproductive organ weights. In most SMVCE studies multiple endpoints were adversely affected. For male reproductive toxicants, sperm motility was decreased in 89% of the studies, and absolute right epididymis and right testis weights were affected less frequently (80% each). Among studies with no detectable reduction in male breeding performance, 87% exhibited no detectable decrease in epididymis weight. Eighty-two percent had no change in cauda epididymis weight and 80% had no significant change in sperm concentration. An increase in female cycle length was associated (100%) with an effect on breeding due to female dysfunction. Overall accuracy, defined as correct identification of toxicants and nontoxicants, was highest for epididymis weight (84%), followed by cauda epididymis weight and sperm motility (79% each), and sperm concentration (76%). Female cycle length was so variable that the overall accuracy of the parameter in 13 studies was 69%. With the variety of chemicals used in this analysis, the association of abnormal sperm morphology with reproductive outcome was 71%. Control data (mean, 95% confidence interval around the mean, median, and statistical sensitivity) for each male endpoint (parent, and offspring at 10 weeks of age following a single breeding) were summarized from each of the two laboratories that conducted the studies. For several endpoints, statistical power was dependent on the laboratory conducting the studies. In general, the statistical sensitivity was relatively high for reproductive organ weights, although it was less for smaller organs such as the prostate. On the basis of both the biological and statistical analyses, it is recommended that multiple SMVCE endpoints, including sperm measures, be included in screens for reproductive toxicants.

Animals↗
PubMed2005

Nonspecific immune response of peripheral blood neutrophils in two horse breeds (Anglo-Arabian and Spanish-Arabian): response to exercise.

The aim of the present paper was: (1) to find out if there were any differences in the nonspecific immunological pattern of peripheral blood neutrophil between two breeds of horses (AA and SA); (2) to evaluate the effects of an exercise in the aerobic-anaerobic threshold. This has been observed in a group of 11 untrained horses (6 SA and 5 AA) of 2.5 years old. No statistically significant differences were found in the different stages of immune response between the rest and immediately after physical exercise to two breeds. However, the chemotaxis was significant higher at rest in the AA than SA breed. A positive correlation was found at rest between the phagocytic and oxidative metabolism activity for AA breed and a negative correlation too between the adherence and chemotaxis with phagocytic capacity, immediately after exercise test, for the same breed.

Animals↗
PubMed2006

Breeding and maintenance of an Mecp2-deficient mouse model of Rett syndrome.

In this report, we present a retrospective assessment of our experiences in maintaining a colony of Mecp2-deficient mice, and present conditions that we have found to foster breeding success of this mutant mouse strain. Data from our colony of mutant Mecp2 mice show that the Mecp2-null allele is under-represented in the weaned litter population, that litters born to heterozygous Mecp2-null females are consistently smaller in number than wild-type, and that fewer litters from heterozygous Mecp2-null females survive to weaning age than wild-type. Our results also reveal that overall litter viability is significantly higher in heterozygous Mecp2-null females that frequently breed, and that the addition of sunflower seeds to the cages of expecting dams improves the overall breeding success of these mice. Taken together, these data highlight the breeding tendencies for this mutant mouse strain, and from these data, we suggest strategies to maximise their breeding efficiency.

Alleles↗
PubMed2005

Prevalence of antibodies to Neospora caninum in local and imported cattle breeds in the Kars province of Turkey.

This study investigates the seroprevalence of Neospora caninum in cattle in the province of Kars in north-eastern Turkey. A total of 301 serum samples, 228 from local breeds of cows with a history of recent abortion and the remaining 73 collected at random from Simmental cows imported from Germany or their offspring, were tested for anti-Neospora antibodies by ELISA. All the serum samples from local breeds were negative for N. caninum antibodies, apart from one which tested inconclusive. In contrast six of the samples (8.2% with 95%CI: 2-14.5%) from Simmental cows tested positive. There was a significant difference (P<0.001) in the seroprevalence of N. caninum between local and Simmental breeds, even if the inconclusive test was considered positive, and the odds ratio of its occurrence in the Simmental breed was 20.3. In conclusion, it is unlikely that N. caninum contributes to abortion in local cattle breeds and our results also suggest that N. caninum was introduced to the region by the importation of Simmental cattle and that the vertical transmission of the parasite in cattle is important in the region.

Animals↗
PubMed2006

Plasma steroid hormones in two Arctic-breeding shorebirds: monogamy versus polygyny.

Steroid hormones are predicted to vary with mating systems, degree of paternal care and aggression, as proposed in the "challenge hypothesis." We measured plasma concentrations of testosterone (T) and 5alpha-dihydrotestosterone (DHT) in two high Arctic breeding and closely related shorebird species, the polygynous pectoral sandpiper (Calidris melanotos) and the monogamous semipalmated sandpiper (Calidris pusilla) to examine whether the hormonal findings corroborate the predictions of the challenge hypothesis. In both species, males showed significantly higher levels of DHT and T than females, but in pectoral sandpipers median T levels were 34 times greater in males than in females, whereas in semipalmated sandpiper there was only a 4.9-fold difference. T and DHT concentrations correlated in semipalmated sandpipers and in male, but not in female, pectoral sandpipers. In semipalmated sandpipers, androgen levels were highest in the beginning of the breeding season and then declined, whereas male pectoral sandpipers showed extremely high androgen levels which were sustained throughout the breeding season. In both species, androgen levels were independent of body condition. Several incubating male semipalmated sandpipers had high circulating T levels, suggesting that low T is not required to exhibit paternal care. Our results are consistent with the challenge hypothesis in that androgen concentrations were higher throughout the breeding season in the polygynous compared to the monogamous species. Our study also supports previous studies suggesting that the short breeding season in the high Arctic and the importance of male care to nest success may be factors leading to behavioral T insensitivity.

Animals↗
PubMed2004

Markers of bone metabolism in dog breeds of different size.

Serum and urinary markers of bone turnover may be of value in animals as noninvasive tools for determining the response of the skeleton to disease and injury. Although normal values for bone markers have been reported for the Beagle, concerns remain that breed to breed differences will complicate the interpretation of bone marker data in dogs. To explore this, we examined serum bone markers in two breeds of vastly different size, Pomeranians and Irish Wolfhounds. Our hypothesis was that serum concentrations of bone markers are similar in toy and giant dog breeds and fall within the same range as those reported for Beagles. Bone alkaline phosphatase (BALP) and carboxy-terminal telopeptide of type I collagen (ICTP), respectively markers of bone formation and bone resorption, were measured in age matched Pomeranians (n=14) and Irish Wolfhounds (n=14). No statistically significant differences between the mean BALP and mean ICTP serum concentrations from Pomeranians and Irish Wolfhounds were found. All BALP and ICTP concentrations were within the reference range reported for Beagles. The results of this study suggest that serum BALP and ICTP concentrations in giant and toy breeds are the same as in Beagles and that these assays may be used for dogs of all sizes.

Alkaline Phosphatase↗
PubMed2003

The effects of variation in climatic temperature (1980-2001) on breeding activity and tadpole stage duration in the common toad, Bufo bufo.

The effects of variation in climatic temperature on breeding behaviour and tadpole growth were investigated using data collected during a 22-year study of a single population of common toads, Bufo bufo, in southern England. Although the start of the breeding season each year, taken as the day when adult toads first arrived at their breeding pond in large numbers, showed no trend over time (1980-2001) it was highly correlated with climatic temperature. Thus, toads started breeding approximately 50 days earlier in the year following very mild winters (1993: February 2nd) compared with very cold ones (1986: March 23rd). Regression analysis of the relationship between the mean temperature of the 40 days immediately preceding the main arrival of toads at the breeding pond revealed that for every 1 degrees increase (or decrease) the toads arrived 12 days earlier (or later). Although the duration of the tadpole stage was longer when spawning was early, toadlets still emerged from the pond earlier than when spawning was late. The increased length of the tadpole stage, in years when spawning was early, was due to an increase in the proportion of cold days when the minimum ground temperature was at or below 0 degrees C. Thus, the tadpole stage was approximately 6 days longer (or shorter) for every 5% increase (or decrease) in the proportion of cold days the tadpoles were exposed to.

Animals↗
PubMed1997

Ovarian response to hCG injections during the prepubertal period in three breeds of sheep with different ovulation rates and litter sizes.

A positive correlation was reported between ovulation (OR) rate in response to hCG in prepubertal ewe lambs and adult ewes. The finding suggested that the response to hCG may be used to select prepubertal ewe lambs for prolificacy. We studied plasma FSH concentrations and ovarian response to hCG injection during the prepubertal period in breeds with high (Chios), medium (Florina) and low (Karagouniki) OR and litter sizes (LS). The results showed that Chios ewe lambs presented a higher profile of plasma FSH during the 3rd to 7th wk of age when compared to the breeds with medium (Florina) and low (Karagouniki) OR and LS. The ovarian response to hCG showed that the Chios ewe lambs responded earlier, by exhibiting ovulation at 6 wks and more effectively, by demonstrating a higher OR than the other two breeds. There was no correlation among plasma FSH concentrations during prepubertal age (3rd to 7th wk), ovulation rate after hCG injection, or litter size at first and second lambing for all breeds. Therefore we concluded that the plasma FSH concentrations and/or the ovarian response to hCG injection during the prepubertal period is not a suitable criterion for early selection for litter size in the adult ewe of these breeds.

Journal Article↗
PubMed1997

Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle.

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n = 35) or two (n = 10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n = 18, P < 0.05) and 3 waves in the heifers (64.7%, n = 16, P < 0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P < 0.05), and the ovulatory wave was shorter than the preceding waves (P < 0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P < 0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smaller than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle.

Journal Article↗
PubMed2000

Changes in exploration from courtship to the breeding state in red-rumped parrots (Psephotus haematonotus).

Animals explore their environment to gather information about feeding areas, resting places, or suitable territories for reproduction. During the annual cycle seasonal variation in exploration occurs at least in some species. In this study, exploratory behaviour of red-rumped parrots (Psephotus haematonotus) was investigated during part of the reproductive period including courtship and incubation. On 2 test days 14 pairs in either the courtship or the breeding state were confronted with three unknown objects in their familiar aviary for 6 h on each of 2 days. Test days were separated by a 2-day pause. Exploration by the males did not change from courtship to breeding, whereas in females latency to first contact increased, and duration of exploration and the number of objects touched decreased from courtship to breeding state. Considering the pair as a unit, the total duration of exploration was shorter in breeding pairs than in pairs during courtship. Changes in exploration from the first to the second day of object exposure occurred in both sexes. Males explored longer on the second day, females contacted the objects significantly later on the second day but showed no significant changes in duration of exploration. The changes in exploration might be due to changed cost/benefit considerations during courtship and breeding.

Journal Article↗