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Abstract
The effects of inbreeding were measured on hatchability and related traits, on viability and growth of squabs until weaning, in two genetically different pigeon populations. In both experiments the performance of randombred and that of inbred (F = 25%) populations descending from full-sib matings were compared. In one experiment 105 to 105 auto-sexing utility breeding pairs, in the other trial 60 to 60 racing homer pairs produced the inbred and randombred breeding populations. All pigeons were kept in the same environmentally controlled house, and were managed and fed identically. All breeding pairs were maintained in special cages, housing one breeding pair each. All production data were collected for a 12 month production period. Inbreeding reduced all traits measured, most of them significantly (P < 0.05 to P < 0.001). The mean inbreeding depression expressed as a percentage in proportion related to the performance of the outbred population for the traits studied for the auto-sexing utility and the racing homer populations respectively were: hatchability 72.5% and 65.7%, survival rate of squabs till weaning 81.0% and 93.7%, body weight of squabs till weaning: 86.6% and 98.0%. The difference between inbred and outbred populations in traits influencing hatchability for auto-sexing utility and racing homer populations respectively were: infertile eggs %: 3.57 and 3.82, early embryonic mortality %: 7.55 and 4.21, embryo mortality between the 7-14th day of incubation%: 2.42 and 3.36, late embryonic mortality %: 2.79 and 6.02. The magnitude of inbreeding depression showed similarities in both genetically different pigeon populations regarding hatchability. The racing homer population showed less inbreeding depression in survival rate of squabs, and growth of squabs till weaning age compared to the auto-sexing utility meat type population.
... A notable observation is that pigeons exhibit a distinctive reproductive pattern, where a pair of parent pigeons produces one or two eggs in a breeding cycle under natural conditions. As late adults, young pigeons rely on the full pulpy secretion provided by their parents until they are 28 days old, after which they start feeding independently [9][10][11]. This secretion, known as "pigeon milk", is produced every 4 h by the crop of the parent pigeons and is regurgitated to feed the squabs. ...
Simple Summary
Lactation is an intriguing reproductive behavior in pigeons, both male and female pigeons participate in crop milk secretion and contribute to the care of their offspring through the division of labor. The question of whether the metabolism and formation of pigeon milk in both males and females follow the same mechanism is an interesting scientific question. We integrated lactation-associated metabolomic and transcriptomic data from the crop tissues of male and female pigeons during the reproductive cycles. We identified a total of 1413 metabolites across 18 crop tissues. During the reproductive cycles, the concentrations of estrone, L-ergothioneine, and L-histidine exhibited the most dynamic changes in females, while estrone, L-anserine, 1-methylhistidine, homovanillate, oxidized glutathione, and reducing glutathione showed the most dynamic changes in males. Through screening DAMs and DEGs, our findings revealed gender-specific differences in the metabolome and gene expressions, with several metabolites and pathways showing significant variations between males and females. Our findings shed light on the distinct modulation of pigeon crop milk metabolism between males and females and provide insights into the potential functions of male and female pigeon milk in the growth, development, and immunity of young pigeons.
Abstract
Lactation is a unique reproductive behavior in pigeons, with the crop serving as the organ responsible for secreting pigeon milk. Both male and female pigeons can produce crop milk and rear their offspring through a division of labor. Since the time of the secretion of pigeon crop milk is different in the process of feeding the young, whether the metabolism and formation of pigeon milk use the same mechanism is a very interesting scientific question. However, the metabolic dynamics and underlying genetic mechanisms involved in the formation of pigeon crop milk remain unclear, particularly during the incubation–feeding reproductive cycle. In this study, we integrated lactation-associated metabolism and transcriptome data from the crop tissues of both male and female pigeons during the brooding and feeding stages. We mapped the changes in metabolites related to milk formation in the crop tissues during these stages. Through metabolome profiling, we identified 1413 metabolites among 18 crop tissues. During the breeding cycles, the concentrations of estrone, L-ergothioneine, and L-histidine exhibited the most dynamic changes in females. In contrast, estrone, L-anserine, 1-methylhistidine, homovanillate, oxidized glutathione, and reducing glutathione showed the most dynamic changes in males. Gender-specific differences were observed in the metabolome, with several metabolites significantly differing between males and females, many of which were correlated with cytokine binding, immunity, and cytochrome P450 activity. Using this dataset, we constructed complex regulatory networks, enabling us to identify important metabolites and key genes involved in regulating the formation of pigeon milk in male and female pigeons, respectively. Additionally, we investigated gender-associated differences in the crop metabolites of pigeons. Our study revealed differences in the modulation of pigeon crop milk metabolism between males and females and shed light on the potential functions of male and female pigeon milk in the growth, development, and immunity of young pigeons, an area that has not been previously explored. In conclusion, our results provide new insights into the metabolic regulation of pigeon crop milk formation during the brooding and breeding stages. Furthermore, our findings lay the foundation for the accurate development of artificial pigeon milk.
... Abdominal fat yield increased from d 14 to d 28, then decreased on d 35. This result might be explained by a "weaning" stress which occurred in 28-day-old pigeons (Horn and Meleg, 2000), giving rise to the decline of their abdominal fat yield. The BW on d 35 had no significant difference from d 28, and the abdominal fat yield on d 35 was lower than d 28 (P < 0.1). ...
Two experiments were conducted to fit growth curves, and determine age-related changes in carcass characteristics, organs, serum biochemical parameters, and gene expression of intestinal nutrient transporters in domestic pigeon (Columba livia). In experiment 1, body weight (BW) of 30 pigeons was respectively determined at 1, 3, 7, 14, 21, 28, and 35 days old to fit growth curves and to describe the growth of pigeons. In experiment 2, eighty-four 1-day-old squabs were grouped by weight into 7 groups. On d 1, 3, 7, 14, 21, 28, and 35, twelve birds from each group were randomly selected for slaughter and post-slaughter analysis. The results showed that BW of pigeons increased rapidly from d 1 to d 28 (a 25.7-fold increase), and then had little change until d 35. The Logistic, Gompertz, and Von Bertalanffy functions can all be well fitted with the growth curve of domestic pigeons (R2>0.90) and the Gompertz model showed the highest R2value among the models (R2=0.9997). The equation of Gompertz model was Y=507.72×e-(3.76exp(-0.17t))(Y=BW of pigeon (g); t=time (day)). In addition, breast meat yield (%) increased with age throughout the experiment, whereas the leg meat yield (%) reached to the peak on d 14. Serum total protein, albumin, globulin, and glucose concentration were increased with age, whereas serum uric acid concentration was decreased (P<0.05). Furthermore, the gene expressions of nutrient transporters (y+LAT2, LAT1, B0AT1, PepT1, and NHE2) in jejunum of pigeon were increased with age. The results of correlation analysis showed the gene expressions of B0AT1, PepT1, and NHE2 had positive correlations with BW (0.73<correlation coefficient<0.80,P<0.0001). It can be concluded that, 28-day-old should be the latest market age for meat type pigeon. And the various physiological and functional properties of organs, serum profiles, and gene expression of nutrient transporters in small intestine might cause the differences in their development patterns.
... One of the disadvantageous effects of inbreeding is the reduction of the mean phenotypic value of a trait known as inbreeding depression. Numerous authors experienced inbreeding depression in different domestic (MIGLIOR et al., 1995;WIENER et al., 1992;HORN and MELEG, 2000;CURIK et al., 2003;BRADE, 1991;FREYER et al., 2005;KOLK GEN SUNDAG et al., 2006;TRIEBLER et al., 1980;WOCAC, 2003;ZELLER and PIRCHNER, 1993) and experimental (ISSA and SEELAND, 2001) populations. Inbreeding depression is mainly apparent in traits that are closely related to fitness (FALCONER and MACKAY, 1996;PIRCHNER, 2004), but the reduction is not confined to reproductive traits. ...
Pedigree and field test data - collected between 1994-2005 - were analyzed in a group of 132,548 Hungarian Landrace pigs. The analysed traits were average daily gain (ADG) and lean meat percentage (LMP). In the present study inbreeding coefficients, pedigree completeness (complete generation equivalents) and inbreeding depression for ADG and LMP were estimated. Increasing the number of generations that were considered in the pedigree the estimated inbreeding coefficients did not change after the 5 th generation, but pedigree completeness was continuously increased. The estimated inbreeding depression for ADG and LMP were different applying 40 different models but the magnitude of the differences was small. The model comparison showed that the models containing litter and year-month effects had the best fit (smallest mean squared error). Increasing the inbreeding coefficient by 10 % decreased ADG by 4.01 g and practically did not affect LMP (0.003 %). It can be concluded that the estimated inbreeding depression was small and substantial depression can not be expected in the near future. However, the low level of inbreeding of the studied population can partly be explained by the short pedigrees. This suggests that Hungarian pig breeders may often import breeding animals or carry out herd replacements rather than applying continuous within group selection.
... One of the disadvantageous effects of inbreeding is the reduction of the mean phenotypic value of a trait known as inbreeding depression. Numerous authors experienced inbreeding depression in different domesticated (Miglior et al., 1995;Wiener et al., 1992;Horn and Meleg, 2000;Curik et al., 2003), wild, (Hedrick and Kalinowski, 2000), captive (non-domesticated) (Cassinello, 2005) and experimental (White, 1972) populations. Inbreeding depression is mainly apparent in traits closely related to fitness (Falconer and Mackay, 1996), but the reduction is not confined to reproductive traits. ...
Pedigree and field test data - collected between 1997-2005 - were analyzed in a group of 68062 Hungarian Landrace pigs. The analysed traits were loin depth (LD), fat depth1 (FD1) and fat depth2 (FD2). In the present study inbreeding coefficients, pedigree completeness (complete generation equivalents) and inbreeding depression for LD, FD1 and FD2 were estimated. Increasing number of generations that were considered in the pedigree the estimated inbreeding coefficients did not change after the 5th generation, but pedigree completeness was continuously increasing. The estimated inbreeding depression for LD, FD1 and FD2 were different applying 5 different models but the magnitude of the differences was small. Increasing inbreeding coefficient by 10% caused LD decrease by 0.084 mm, the FD1 by 0.062 mm and did not affect FD2. It can be concluded that the estimated inbreeding depression was low and substantial depression can not be expected in the near future. However, the low level of inbreeding of the studied population can partly be explained by the short pedigrees. This suggests that Hungarian pig breeders may often import breeding animals or carry out herd replacements rather than apply within group selection.
The goal of this study was to evaluate the influences of mannan oligosaccharides (MOSs) and/or Bifidobacterium on the growth and immunity of pigeons over a 56-day period. One hundred paired adult pigeons were randomly divided into four groups of five paired pigeons. Paired pigeons with two young squabs were housed in a man-made aviary. Parent pigeons in the control group received a basal diet (C), while the other three groups were fed with the basal diet supplemented with 20g of MOSs/kg of feed (M), 10g Bifidobacterium（1 × 10¹⁰ CFU/g）/kg of feed (B), or a combination of M and B (MB).We found higher body weights (BW) in pigeons of the B group than in the C, M, and MB groups. None of the treatments exerted significant effects involving spleen and thymus indices, whereas M birds tended to improve the bursa of Fabricius index. Pigeons fed with the M-supplemented diet exhibited improved serum immunoglobulin M (IgM) concentrations compared with those fed with C and the B- and MB-supplemented diets. In addition, M treatment increased immunoglobulin A (IgA) levels compared with MB treatment. MB treatment improved serum immunoglobulin G (IgG) concentrations compared to that by the C treatment. The concentration of secretory immunoglobulin A (sIgA) was significantly reduced in the duodenum and increased in the ileum in pigeons fed with the MB-supplemented diet. This study indicated that dietary supplementation with Bifidobacterium increased the growth performance. Dietary supplementation with MOSs or in combination with Bifidobacterium was able to improve immune function in pigeons but exerted no apparent effect on weight gain. Accordingly, in terms of economic benefits, the findings suggested that supplementation with Bifidobacterium alone may improve production performance, and that supplementation with MOSs alone may improve immune function in pigeons.
The objective of this thesis was to study the effect of selection on inbreeding, to estimate inbreeding depression and inbreeding trend in the Ethiopian Menz sheep. Data on birth weights, weaning weights and survivals of 1439 lambs, from 537 dams and 58 sires from two lines of a research flock were analyzed. Inbreeding coefficient (F) for each animal with pedigree record was calculated using the program ASReml. Effect of selection on the level of inbreeding was estimated by comparing average inbreeding levels in the selection line and control line. Additionally, average inbreeding levels across generations in the selection line was compared to assess the effect of selection on inbreeding. The effect of inbreeding on the traits were examined by using the regression models, in which inbreeding coefficients for the individuals were fitted as covariates to models that included other environmental and genetic sources of variation and various performance traits as dependent variables. Genetic relationships between males and females were estimated in order to have insight into the inbreeding trend of the population. Only 26 animals out of 1439 were found to be inbred. The average F was low in both the selected and control lines (0.189% and 0.422%, in the selected and control lines respectively). However, average F for the inbred animals was very high, (4.2075 and 6.25% in the selected and control lines). The effects of inbreeding on performance did not differ significantly from zero for all the traits examined. Only birth weight was found to be negatively affected but not significantly. The depths of the pedigrees were somewhat low to calculate the inbreeding and its effect to satisfactory level as the inbred animals were few in number. The average genetic relationships between males and females were 0.026 and 0.024 in the selected and control lines respectively. The relationship coefficient did not show significant difference between the lines. However, the average genetic relationships among mates increased with generations.
The effect of inbreeding on racing ability of homing pigeons was analysed based on twelve competitions at different distances from 10 km to 202 km. In the experiment we compared the performance of randombred and of inbred (F = 37,5 %) homing pigeons. Number of pigeons was 53 in the control and 71 in the inbred population in the first racing, which was reduced due to disqualifications in the further racings. In most competitions, there was a significant difference, with changing direction, between the median flying speed of the inbred and control pigeons. This may be caused by the different weather conditions, and by the higher sensitivity of the inbred population to weather conditions. The overall median speed of inbred pigeons was less by 21% compared to the control, possibly due to inbreeding. Among the environmental effects wind speed, temperature and back wind were considered, and all of them were found to affect more strongly inbred pigeons than outbreds.
- notypic, genetic and environmental trends. Considered were conformation records of 706 Arab mares born in the years 1936- 1993. The mean inbreeding level of mares was 0.88%. No considerable effect of inbred rate on body conformation traits was found. The obtained partial regression coefficients were close to zero. Heritability coefficients appeared low and amounted to 0.160 (±0.078) for height at withers, 0.052 (±0.067) for chest circumference and 0.050 (±0.054) for circumference of cannon. Negligible positive genetic trend was observed for all the traits studied, whereas the environmental trends were not clear.
Inbred lines were established in 1967 (Experiment 1) and 1978 (Experiment 2). They were continued for one and two additional generations of full-sib matings in the first and second experiments, respectively. In both experiments, alternating periods of stimulatory and nonstimulatory light were used to induce egg production in two 15-week production periods.
In Experiment 1, 10 of 22 full-sib lines were lost after only one generation of full-sib mating. Of the 29 initial full-sib lines established in Experiment 2, only 6 survived two generations of full-sib inbred matings (F = .375).
Egg weight, sexual maturity, and body weight were depressed significantly (P<.01) in birds 37.5% inbred. The two traits most severely affected were egg production and hatchability, which were reduced substantially after only one generation of full-sib mating.
The results indicate that establishment and maintenance of highly inbred lines of partridge will require selection of matings from families having superior reproductive traits as well as alternating cycles of inbreeding such as by full-sib mating with crosses of unrelated inbred lines.
The deleterious effect of inbreeding on fertility and hatchability was studied in a population of Leghorns developed primarily for immunogenetics studies. The 1983 population averaged 42% inbreeding and traced back to only two sires and five dams of the 1965 base population. Up to 1975 (Period 1), the population was maintained as a single-unit closed flock, during which time inbreeding increased an average of 1.44% per year. After 1975 (Period 2), the population was split into five sublines. Inbreeding then increased at the average rate of 2.7% per year. The regression of fertility on inbreeding was -.31 +/- .04 in Period 1 and -.17 +/- .06 in Period 2. Corresponding values for hatchability of fertile eggs were +.08 +/- .05 in Period 1 and -.24 +/- .07 in Period 2. The regression of hatchability of total eggs set was -.15 +/- .04 in Period 1 and -.35 +/- .10 in Period 2. The evidence implies that both fertility and hatchability have a heritable basis. As expected, the deleterious effects of inbreeding on reproduction was more severe in Period 2, with sublining.
Five consecutive generations of full-sib matings in Japanese quail reduced the initial 17 inbred lines to six. In general, fertility, hatchability and egg production were affected to a greater extent by inbreeding than were body weights and egg weights.
Ten inbred lines of Ring-necked pheasants were established in 1978 and mated for four generations using a system of repeated backcrossing of daughters to a common sire. In the event the old sire died, the surviving daughters were mated to a surviving brother or half-brother of the same generation.
Only 4 of 10 original inbred lines survived four generations of backcrossing; two involved matings with the original sire and two with brothers or half-brothers of Generations 1 and 3, respectively.
Egg production, hatchability, and viability were the three traits most affected by inbreeding depression. For 4 generations of inbreeding, the coefficients of regression for all inbred lines on a 10% increase in inbreeding were −5.89, −.42, −1.73, and −3.04 for egg production, egg weight, fertility, and hatchability, respectively.
Inbreeding had less severe effects on reproductive traits in two of the four surviving lines. There is evidence that intense early selection among lines for high performance after one generation of inbreeding F = .250 will enhance the success of establishing highly viable inbred lines of pheasants.
Phenotypic and genetic correlations of quantitative traits were estimated in an auto sexing meat-type pigeon population. The pigeons were kept in pairs in a specially designed three tier cage system, in a windowless environmentaly controlled house at a constant 12 hour light period thro-ughout the year. For the estimation of correlations related to bodyweight at different ages, data of 220 sire-son and dam-daughter pairs were used. In the estimation of correlations related to production traits the data of 321 dam-daughter pairs were analysed. The phenotypic (rP) and genetic (rG) correlations between the traits studied were: 28 days body weight - adult body weight in males rP: 0.88, rG: 0.57, in females rP: 0.77, rG: 0.62, number of eggs produced per year - body weight at 28 days of age rP: -0.04, rG: -0.54, hatchability - number of eggs produced per year rP: 0.11, rG: 0.02, hatchability - number of squabs hatched per year rP: 0.78, rG: 0.17, hatchability - total weight of squabs produced per year rP: 0.74, rG: 0.17.
1. An equation relating batch size to between‐treatment differences has been adapted for hatchability studies and its implications for research considered.2. Very large egg batches are required to detect small improvements in the hatchability of good hatching strains.3. Small‐scale laboratory studies on hatchability are best confined to strains and species of low hatchability in which larger between‐treatment differences may be expected.4. The results of hatchability studies should always be subjected to tests of statistical significance.5. There is a strong case for studying continuous variates in the laboratory before proceeding to large‐scale hatchability studies.