Anti-predator behavior in pure and hybrid red-legged partridges.

The purpose of this study was to examine the anti-predator behavior in pure red-legged partridges (Alectoris rufa) and hybrids with chukar partridges (A. rufa × (A. rufa × A. chukar)). A total of 117 birds (66 pure and 51 hybrid partridges; 74 females and 43 males) maintained in outdoor cages were used at a range of 52 to 55 wk of age. Four active fear tests were performed (novel object test, fear of humans test, emergence test, and restraint test) in order to analyze differences between pure and hybrid populations regarding the escape response type (novel object test and fear of humans test), the withdrawal distance (fear of humans test), and the reaction time (emergence test and restraint test). These variables could determine the ability of pure partridges captive to survive when released into the wild for hunting. There were no significant differences in anti-predator behavior in pure and hybrid birds, only one trend was observed in withdrawal distance (P = 0.09), being greater in pure than in hybrids partridges. There was a significant difference between sexes in the response type in the novel object test (P = 0.05); whereby the females came closer to the object than the males. The results of the present study indicate that active anti-predatory behavior was not associated with the genotype. However, since captivity could reduce the active anti-predator behavior, the results could be different if the wild birds that were tested had been sourced from their natural environment. Both sexes had similar active anti-predator behavior, although the males showing less approach behavior to a novel object that could be related to the sex-dimorphic behavior in natural social structure.

Access to pasture in an outdoor housing system affects welfare indicators and improves rooster sperm quality in two native Mediterranean breeds.

The aim of the present work was to examine the influence of access to pasture in an outdoor housing system on rooster sperm quality and response to cryopreservation and to examine the possible correlation between values for sperm quality variables and welfare indicators. Two groups of Black-barred Andaluza and Red-barred Vasca roosters were housed in an outdoor system, with one group given daily access to a grazing area containing plant species that typically grow on uncultivated Mediterranean land. Semen was collected once per week from each group, and the following sperm quality variables were assessed: sperm volume, appearance, concentration, motility, membrane integrity, acrosome integrity, and morphological abnormalities. In addition, two welfare indicators were examined: the heterophil/lymphocyte (H/L) ratio, and the duration of tonic immobility (TI). Ejaculates from the birds with access to pasture had higher percentages of sperm showing progressive motility (P = 0.019), and returned a higher motility index (P = 0.035). Unexpectedly, the H/L ratio was also higher in these birds. Virtually no differences were seen between the treatment groups with respect to sperm quality after freezing-thawing, although the semen of the Red-barred Vasca birds with access to pasture did show a higher percentage of progressive motility (P = 0.023) than the birds of the same breed with no such access. Significant correlations were detected between the H/L ratio and sperm motility (r = 0.420, P = 0.038), the sperm motility index (r = 0.526, P = 0.002), and progressive motility (r = 0.467, P = 0.003). No differences were seen between the treatment groups with respect to the duration of TI. In conclusion, access to pasture improved fresh sperm motility.

Successful chilling of red-legged partridge (Alectoris rufa) sperm for use in artificial insemination.

The fertilizing capacity of pure, fresh avian semen may disappear in just half an hour, hindering its successful use in artificial insemination (AI) projects. Longer storage requires the use of infra-physiological temperatures and of semen diluents that help preserve the spermatozoa but that do not interfere with their fertilizing capacity. This study examines the effect on sperm quality of storing red-legged partridge sperm for 3 h at 5°C with 2 different semen extenders: 1) a medium referred to as L&R-84, composed of sodium glutamate, glucose, magnesium acetate, potassium acetate, and polyvinylpyrrolidone, and 2) Lake 7.1 medium, composed of sodium glutamate, glucose, magnesium acetate, potassium citrate, and N,N-Bis(2-hydroxyethyl)taurine (BES). Extending with L&R-84 returned better curvilinear velocity (P < 0.01), straight-line velocity (P < 0.01), average path velocity (P < 0.01), linearity (P < 0.05), straightness (P < 0.05), and wobble (P < 0.05) values, while extending with the Lake 7.1 medium was associated with higher percentages (P < 0.001) of motile sperm. The fertility rate was higher (P < 0.05) when birds were inseminated with L&R-84-extended sperm than with Lake 7.1-extended sperm. The mean number of penetrations of perivitelline layer samples (taken from above the germinal disc) was also higher for the L&R-84-extended sperm (P < 0.05). These results show L&R-84 can be recommended as an extender for red-legged partridge semen to be stored for at least 3 h at 5°C.

Effect of the presence of hens on roosters sperm variables.

This study examines the effect of the presence of hens on sperm variables in Black Barred Andaluza roosters (which respond well to the massage technique). Between 8 and 22 weeks of age, roosters (n = 60) were housed separate from hens in straw litter pens (4 birds/m(2)). Two groups of roosters were then formed to study the effect of hen presence on sperm variables at 36 weeks of age. The first group (n = 11 roosters) was housed with hens (n = 55; sex ratio 1:5), while the second (n = 27 roosters) was again housed separate from hens. Twenty four sperm pools were obtained over 12 weeks (12 pools from each group, each pool produced by mixing semen from 11 males) for analysis. Compared to the no-female-contact group, the roosters living with hens showed significantly (P < 0.05) reduced percentages of non-progressive motile sperm and slow sperm, and significantly increased VCL and VSL values; they also showed trends (P < 0.1) towards increased progressive motility and a higher percentage of rapid sperm. The presence of hens had no significant effect on the number of spermatozoa per ejaculate or sperm concentration. Positive correlations were recorded between VSL and VCL, and between both of these and progressive motility, and the percentage of rapid sperm. In addition, both VSL and VCL correlated negatively with non-progressive motility and the percentage of slow sperm. These results indicate that rooster sperm quality, but not quantity, improves in the presence of hens.

Association between polymorphism in the melanocortin 1 receptor gene and E locus plumage color phenotype.

The purpose of this study was to investigate the effect of the melanocortin 1 receptor (MC1R) gene on plumage color in chickens. The gene was sequenced in 77 males and 77 females from 13 Spanish breeds, carrying 6 different alleles in the E locus (E*E, E*R, E*WH, E*N, E*B, E*BC), a recessive wheaten (yellowish-white) tester line (E*Y), and a White Leghorn population (heterozygous E*E). A total of 11 significant SNP were detected. Nine of them were nonsynonymous (T212C, G274A, G376A, T398AC, G409A, A427G, C637T, A644C, and G646A, corresponding to amino acid changes Met72Thr, Glu92Lys, Val126Ile, Leu133GlnPro, Ala137Thr, Thr143Ala, Arg213Cys, His215Pro, and Val216Ile), and 2 were synonymous (C69T and C834T). With respect to the significant SNP, 7 had an allelic frequency of 0.5 or greater for some of the alleles at the E locus. These results indicated a significant correlation between MC1R polymorphism and the presence of different alleles at the E locus. All the populations carrying the E*E or E*R alleles, except the Birchen Leonesa, had the G274A polymorphism. Eleven haplotypes were made with 7 of the significant SNP. The distribution of these haplotypes in the different alleles of the E locus showed that each haplotype was predominantly associated to one allele. The number of haplotypes was greatest for the Black Menorca, Birchen Leonesa, and Blue Andaluza breeds, whereas the Quail Castellana and Red-barred Vasca breeds were monomorphic. Our results suggested that the Glu92Lys mutation may be responsible of the activation of the receptor for eumelanin production, being necessary but not sufficient to express the extended black phenotype. They also suggested that the Arg213Cys mutation may be the cause of the loss or the decrease of function of the receptor to produce eumelanin, and the Ala137Thr mutation may be a candidate to attenuate the Glu92Lys effect. The observed co-segregation of the E locus alleles and polymorphisms in MC1R confirms that the E locus is equivalent to MC1R.

Role of sperm velocity variables associated with poultry breed in 'last male precedence'.

It is well known that when a hen mates with multiple roosters, it is the sperm of the last male that usually fertilizes most of the eggs ('last male precedence'). Sperm quality varies between males within a breed, but also between breeds, and thus, sperm competitiveness after mating may depend on the breeds of the roosters involved. The aim of the present work was to identify differences in sperm competitiveness between breeds, especially with respect to motility. A multibreed mating model was used. Blue Andaluza (BA) and Black Castellana (BC) hens left for 21 days with BA and BC roosters, respectively, were then left with Black-barred Andaluza (Bb) roosters for another 21 days (experimental groups hBA-rBC-rBb and hBC-rBA-rBb). Bb roosters (as the second breed replacing the first) fertilized the majority of eggs in both the hBC-rBA-rBb and hBA-rBC-rBb groups. The percentage of offspring sired by BA roosters (8.0%) was higher (p < 0.05) than the percentage of chicks sired by BC roosters (2.1%). The fertility of the BC hens in the hBC-rBA-rBb group was higher (p < 0.01) than that of the BA hens in the hBA-rBC-rBb group. No difference in sperm concentration was seen between the breeds. Within the rapid sperm subpopulation (sperm velocity, >50 µm/s), Bb sperm showed a higher straight-line velocity (VSL) and average path velocity (VAP) (p < 0.05) than BC sperm. The VSL and VAP values for Bb and BA sperm were similar. In conclusion, the present results show that the sperm of the BA breed, traditionally regarded as of moderate fertility, compensates for this drawback via sperm movement characteristics that afford it an advantage in competition scenarios involving males of other breeds. The VSL and VAP of the rapid sperm subpopulation may play the most important role in securing last male precedence.

Associations among fluctuating asymmetry, tonic immobility duration, and flight distance or ease of capture in chickens.

The purpose of this study was to analyze the associations among fluctuating asymmetry, duration of tonic immobility, and flight performance or ease of capture in chickens. Cocks (n = 220; 36 wk old) from 10 Spanish breeds and a White Leghorn population were used. The quantitative/qualitative relationship among fluctuating asymmetry, duration of tonic immobility, and landing accuracy (good or bad) or landing distance (long or short), and the quantitative/quantitative relationship among fluctuating asymmetry, duration of tonic immobility, and time of capture or number of attempts of capture were studied. Relative fluctuating asymmetry of toe length, wing length, and the combined relative asymmetry of toe length, leg length, wing length, and leg width was significantly greater (P < 0.05, P < 0.01, and P < 0.001, respectively) in cocks with bad landing accuracy. There was no significant difference for the duration of tonic immobility between groups of cocks with bad or good landing accuracy. Relative asymmetry of wing length and the combined relative asymmetry of the 4 traits was significantly greater (P < 0.05) in cocks with short landing distance and smaller in cocks with long landing distance. There was a significant difference for the duration of tonic immobility between groups of cocks with short or long landing distance (P < 0.001), with that of cocks with short landing distance being longer. There was no significant correlation among relative fluctuating asymmetry, duration of tonic immobility, and time of capture or attempts of capture. Associations between morphological values of toe, leg, and wing and flight performance or ease of capture were not significant. Thus, birds with less asymmetry and fear level have better flight performance than more asymmetric and fearful birds, whereas the ease of capture is not associated with fearfulness and asymmetry.

Effects of auditory and physical enrichment on 3 measurements of fear and stress (tonic immobility duration, heterophil to lymphocyte ratio, and fluctuating asymmetry) in several breeds of layer chicks.

The purpose of this study was to analyze the effect of auditory enrichment (by means of classical music) or physical enrichment (by means of hanging colored string bunches and barley grains on the floor) on tonic immobility duration, heterophil to lymphocyte ratio, and fluctuating asymmetry (FA) in chicks of several layer breeds. In experiment 1, 192 chicks from 8 Spanish breeds and 1 White Leghorn population were reared in cages with or without music auditory enrichment until 8 wk of age. The effect of music auditory enrichment was significant for heterophil to lymphocyte ratio (P < 0.05). The ratios were higher in chicks reared without music than in those reared with music, suggesting that auditory enrichment from classical music reduces stress in chicks. There were significant differences in morphological trait measurements (relative asymmetry of wing length, leg width, and combined asymmetry; P < 0.05), being greater in chicks reared without music. This result suggests that FA is a good indicator for stress level in chicks, given that it follows the same trend as that found for heterophil to lymphocyte ratio. There was a significant treatment by breed interaction (P < 0.05) for tonic immobility duration, indicating no consistent effect by auditory enrichment on tonic immobility duration across breeds. In experiment 2, 180 chicks from 3 Spanish breeds were housed in pens with or without physical enrichment (colored plastic string bunches and barley grains on the floor) until 6 wk of age. The effect of physical enrichment on tonic immobility duration, heterophil to lymphocyte ratio, and FA was not significant, indicating no effect on fear and stress in layer chicks. In conclusion, auditory enrichment by means of classical music is a reliable method for reducing stress levels in several breeds of layer chicks. However, music auditory enrichment was not effective in reducing fearfulness in any of the layer breeds. Physical enrichment by means of colored plastic string bunches and floor barley grains does not appear to be an effective method for reducing stress and fear in layer chicks.

Evaluation of diversity between different Spanish chicken breeds, a tester line, and a White Leghorn population based on microsatellite markers.

The present study was conducted to evaluate the genetic variability and the genetic divergence of 13 Spanish chicken breeds, a tester line, and a White Leghorn population, using 24 microsatellite markers. A total of 150 alleles were detected across all population. The number of alleles by locus ranged from 2 to 13, with the mean value being 6.25. The mean polymorphic information content was 0.591, ranging from 0.847 to 0.172. The combined parentage exclusion probability of excluding 1 parent or 2 parents was 99 and 100%, respectively. The observed heterozygosity was lower than the expected heterozygosity for all loci, the mean values being 0.461 and 0.637. The observed and expected heterozygosity ranged from 0.003 to 0.735 and 0.181 to 0.863, respectively. Mean deficit of heterozygotes within populations (F(IS)) was 0.056 and mean fixation index of each population (F(ST)) was 0.244. The mean global deficit of heterozygotes across populations (F(IT)) was 0.286. A total of 15 private alleles in 10 microsatellites were observed, and in some populations, fixed alleles were found for 7 microsatellites. A total of 300 birds (83%) were properly assigned to the source population. The average observed heterozygosity for each population was 0.461, ranging from 0.328 (Quail Castellana) to 0.538 (Red Villafranquina), and the average expected heterozygosity was 0.488, ranging from 0.320 (Quail Castellana) to 0.550 (White-Faced Spanish). All of the Spanish breeds except the Quail Castellana were more polymorphic than the White Leghorn population. The mean value of the deviation of heterozygote number was 0.052. Nei's genetic distance showed a range from 0.109 (between White-Faced Spanish and Black Menorca) to 0.437 (between Buff Prat and White Leghorn). A phylogenetic tree constructed by the neighbor-joining method, based on Nei's genetic distance, showed a clear separation between the White Leghorn and the remaining breeds. The results indicate that the panel of microsatellite markers was useful in studying the genetic diversity of chicken breeds.

Effect of bad collocation of wing tag on feather amelanosis, heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration in white-faced black spanish hens.

The purpose of the present study was to analyze the effects of bad collocation of the wing tag on feather amelanosis, the heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration at 140 d of age in hens from the White-Faced Black Spanish breed. A total of 52 females were used. There was a significant difference (P < 0.05) for the heterophil-to-lymphocyte ratio and the tonic immobility duration between groups of females with bad or good collocation of the wing tag, with the ratio being higher and the duration being longer in the former group. Females with bad collocation of the wing tag had significant heterophilia and lymphopenia (P < 0.05). There was a significant difference (P < 0.05) in the fluctuating asymmetry of the middle and hind toe lengths, the combined asymmetry of the 4 toes, the fluctuating asymmetry of the earlobe area, and the combined asymmetry of toe and leg lengths and earlobe and wattle areas, with the asymmetry of birds with bad collocation of the wing tag being larger than that of birds with good collocation of the wing tag. Results indicate that bad collocation of the wing tag negatively affects measures of stress, such as the heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration.

Effects of housing system and cold stress on heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration of chickens.

The purpose of this study was to analyze the effect of housing system and cold stress on the heterophil-to-lymphocyte ratio, the fluctuating asymmetry, and the tonic immobility duration of chickens. In experiment 1, hens (n=120; 36 wk old) from 5 Spanish breeds and a White Leghorn population, which had been housed in pens with or without access to an outdoor area from 20 wk of age, were used. The effect of housing system on heterophil-to-lymphocyte ratio varied from breed to breed, differences between housing systems being significant (P<0.05) in 2 breeds. In these breeds (Red-Barred Vasca and Birchen Leonesa), heterophil-to-lymphocyte ratio was significantly greater in hens housed in deep litter. Housing effect was significant for the relative asymmetry of leg length (P<0.01), wattle length (P<0.05), and the combined relative asymmetry (P<0.05), the relative asymmetry of hens housed in deep litter being larger. There was no significant difference for the duration of tonic immobility between hens housed in deep litter or free range. Thus, hens with access to an outdoor area were less stressed than hens without access to an outdoor area, although the fearfulness was similar in both groups of birds. In experiment 2, cocks (n=120; 36 wk old) from 4 Spanish breeds, a synthetic breed, and the White Leghorn population, which had been housed in cages with or without a cold stress (0 to 10 degrees C) from 24 wk of age, were used. Cold x breed interaction was significant for heterophil-to-lymphocyte ratio (P<0.05), differences between cold-stressed and control birds being significant in 2 breeds. In these breeds (Red-Barred Vasca and Buff Prat), heterophil-to-lymphocyte ratio was significantly greater in cold-stressed birds. Cold stress effect was significant for the relative asymmetry of toe length (P<0.001) and the combined relative asymmetry (P<0.05), the relative asymmetry of birds with cold stress being larger than that of control birds. Thus, cold stress seriously negatively affects the welfare of cocks.

Effect of lighting stress on fluctuating asymmetry, heterophil-to-lymphocyte ratio, and tonic immobility duration in eleven breeds of chickens.

The purpose of the present study was to analyze the effect of a lighting stress on the fluctuating asymmetry (FA), the heterophil-to-lymphocyte ratio, and the tonic immobility duration of chickens. The experiment (440 birds) measured the FA of several traits (outer, middle, inner, and hind toe lengths and leg, wing, second primary feather, and spur lengths), the heterophil-to-lymphocyte ratio, and the tonic immobility duration in 36-wk-old hens and cocks of 8 Spanish breeds of chickens (Black-Barred Andaluza, Black-Red Andaluza, Black Castellana, Buff Prat, Red-Barred Vasca, Red Villafranquina, Birchen Leonesa, and Blue Leonesa), a synthetic breed (Quail Castellana), a White Leghorn population, and the e(y) tester line, which had been housed in continuous light (24L:0D) or in a light-dark regimen (14L:10D) for 16 wk. There was a significant difference between lighting treatments in both females and males on the combined FA of the 4 toes (P < 0.01) and the combined FA of toe, leg, wing, feather, and spur (in males) lengths (P < 0.05), the FA of birds housed under continuous light being greater than that of control birds. There was a significant difference (P < 0.001) for the heterophil-to-lymphocyte ratio and the tonic immobility duration between lighting treatments, the ratio being higher and the duration being longer in the group of birds housed under continuous light. Thus, birds exposed to continuous light were more stressed and fearful than control hens. Results were consistent across the breeds and indicate that a continuous light regimen seriously negatively affects the welfare of birds.

Influence of perches and footpad dermatitis on tonic immobility and heterophil to lymphocyte ratio of chickens.

The purpose of the present study was to analyze the effect of perches and footpad dermatitis on stress and fear levels of chickens. In experiment 1 heterophil to lymphocyte ratio and tonic immobility duration were measured in 36-wk-old hens (36 birds) from 2 Spanish breeds of chickens (Black Menorca and Quail Castellana) housed in pens with or without perches from 20 wk of age. There was a significant difference in the heterophil to lymphocyte ratio between perch treatments (P < 0.05), the ratio of hens with perches being lower than that of hens without perches. Hens with perches had significant lymphophilia (P < 0.05). There was no significant difference for the duration of tonic immobility between hens with or without perches. Thus, hens with perches were less stressed than hens without perches, as indicated by the heterophil to lymphocyte ratio. Heterophil to lymphocyte ratio and heterophil number for Black Menorcas were significantly smaller (P < 0.001) than for Quail Castellanas, whereas lymphocyte number was greater in Black Menorcas. The Black Menorca hens had significantly (P < 0.01) shorter tonic immobility duration. In experiment 2 heterophil to lymphocyte ratio and tonic immobility duration were measured in 52-wk-old cocks (36 birds) of each of two different Spanish breeds of chickens (Black Barred Andaluza and Red Barred Vasca) housed in cages from 36 wk of age and showing or not showing footpad dermatitis. There was no significant effect of footpad dermatitis on the heterophil to lymphocyte ratio, its numerator, or its denominator, whereas there was significant effect on tonic immobility duration (P < 0.05) with tonic immobility of cocks with footpad dermatitis being longer than that of cocks without footpads. Thus, cocks with footpad dermatitis were more fearful than cocks without footpad dermatitis, as indicated by the tonic immobility duration. Heterophil to lymphocyte ratio and heterophil number were significantly smaller (P < 0.05) for Black Barred Andaluzas than for the Red Barred Vascas.

Estimation of heritability for fluctuating asymmetry in chickens by restricted maximum likelihood. Effects of age and sex.

The purposes of the present study were to estimate the heritability of the fluctuating asymmetry in chickens, using the restricted maximum likelihood procedure, and to evaluate the effects of age and sex on the fluctuating asymmetry. Leg, wing, and feather lengths and ear-lobe and wattle areas were measured. In experiment 1, 1,073 birds were used from 2 generations with complete pedigree of the Quail Castellana breed to estimate the heritability for the fluctuating asymmetry at 36 wk of age. The estimated heritability of absolute fluctuating asymmetry was not significantly different from zero for all 5 traits, and similar estimates were obtained for relative fluctuating asymmetry, directional asymmetry, transformed absolute and relative fluctuating asymmetry, and 3 alternative indexes of fluctuating asymmetry. The heritability of the combined absolute or relative fluctuating asymmetry was still very low, indicating that fluctuating asymmetry was determined solely by environmental sources of variation and that fluctuating asymmetry estimates should not be confounded by appreciable additive genetic contributions. The genetic correlation between sides was not significantly different from one, indicating that differences between sides were purely environmental in origin. Different traits rarely showed much correlation in their level of fluctuating asymmetry, indicating that the level of fluctuating asymmetry in all traits did not reflect equally the quality of animals. In experiment 2, fluctuating asymmetry differences among ages and sexes were investigated at 8, 12, 16, 20, 24, 28, 32, 36, and 40 wk in 360 birds from the same breed. Significant variation with age was observed in leg length, wing length, feather length (females), and wattle area (females), which was mainly related to onset of sexual maturity and adult stage. Females showed significantly greater fluctuating asymmetry for ear-lobe area than males. There were significant differences in fluctuating asymmetry for wing length, feather length, and wattle area near the onset of sexual maturity, with males having significantly greater fluctuating asymmetry than females for wing length and the opposite being true for feather length and wattle area.

Effect of photoperiod on heterophil to lymphocyte ratio and tonic immobility duration of chickens.

The experimental objectives of the current study were to analyze the effects of photoperiod on heterophil to lymphocyte ratio and tonic immobility duration of laying hens. There were two different trials. The first trial measured heterophil to lymphocyte ratio in 36-wk-old hens of three Spanish breeds of chickens (Castellana, Prat, and Vasca) exposed to lighting programs of 23L:1D, 14L:10D, or 18.5L:5.5D. There were no significant differences among lighting regimes. Results were consistent across the breeds. The second trial measured duration of tonic immobility in 36-wk-old hens of a synthetic breed (originated from a cross between the Castellana and Prat breeds) exposed to lighting programs of 23L:1D or 14L:10D. There was a significant difference between the two lighting regimens (P < 0.05). Hens housed under lighting of 23L:1D showed longer tonic immobility than did hens housed under lighting of 14L:10D. There was no evidence of an increased stress response as judged by heterophil to lymphocyte ratio, but there was evidence of an increased fear response as judged by tonic immobility duration. The results of the present study suggest that a near continuous light pattern can have negative consequences in reducing welfare in egg-laying hens.

Estimation of heritability for heterophil:lymphocyte ratio in chickens by restricted maximum likelihood. Effects of age, sex, and crossing.

The objectives of the current study were to estimate the heritability of the heterophil to lymphocyte ratio and to evaluate the effects of age, sex, and crossing on that ratio. There were three different experiments. In Experiment 1, we used a total of 711 birds from two generations with complete pedigree of a Spanish breed of chickens (Quail Castellana) to estimate the heritability for the leukocyte ratio at 36 wk of age by restricted maximum likelihood. The estimated heritability (0.59 +/- 0.09) indicated that leukocyte ratio should easily respond to selection. Heritabilities for heterophil and lymphocyte numbers were also high (0.56 +/- 0.07 and 0.65 +/- 0.07). In Experiment 2, leukocyte ratio differences among ages and sexes were investigated at 8, 12, 16, 20, 24, 28, 32, and 36 wk, in 576 birds from the same breed. Males showed significantly greater heterophil to lymphocyte ratios than females at the onset of sexual maturity and as adults. Significant variations with age for leukocyte ratio were observed in both sexes, which were mainly related to onset of sexual maturity, from which the leukocyte ratio increased more or less continuously. In females, the effect of age was also significant on heterophil and lymphocyte numbers. Finally, in Experiment 3, crossing effects were evaluated in 96 birds from a cross between the Quail Castellana and a White Leghorn population at 8 wk of age. The negative heterosis percentages found in the F1 and F2 generations were significant (-26% and -36%, respectively).

Influence of mating ratio and group size on indicators of fearfulness and stress of hens and cocks.

The effects of the male to female mating ratio on the heterophil to lymphocyte ratio and duration of tonic immobility (indicators of stress and fearfulness, respectively) were analyzed in two different experiments with different group sizes. In Experiment 1, four different mating ratios (1:11, 1:5, 1:3, and 1:1) and 10 different Spanish breeds of chickens were used; each breeding pen had 12 birds. In Experiment 2, two different mating ratios (1:11 and 1:1) and four breeds were analyzed; 60 birds were used. There were significant differences among mating ratios (P < 0.001) for the heterophil to lymphocyte ratio in females of both group sizes. Hens housed with a mating ratio of 1:1 had higher heterophil to lymphocyte ratios than did hens housed with a 1:11 mating ratio in the group with 12 birds (0.53 vs. 0.35) or that with 60 birds (0.76 vs. 0.37). Hens in a mating ratio of 1:1 had significant heterophilia and lymphopenia (P < 0.001). The 1:5 and 1:3 male to female mating ratios did not differ significantly from the 1:11 mating ratio. The effect of the group size was significant when the mating ratio was 1:1 but not when it was 1:11. There was no significant difference among mating ratios in terms of tonic immobility for hens. Cocks housed with a mating ratio of 1:1 and a group size of 60 birds showed shorter duration of tonic immobility (P < 0.05) than did cocks housed with a 1:11 mating ratio (203 vs. 296 s). The results suggest that very high mating ratios should not be used in conservation populations because it increases physiological and psychological stress responses.

Association between plumage condition and fear and stress levels in five breeds of chickens.

Duration of tonic immobility and heterophil to lymphocyte ratio (indices of fear and stress, respectively) were compared in hens having very poor or perfect plumage at 72 wk of age. Five Spanish breeds of chickens (Castellana, Andaluza, Vasca, Villafranquina, and Leonesa) were used. There were significant differences among groups in terms of tonic immobility duration and heterophil to lymphocyte ratio (P < 0.05). Very poorly feathered hens showed shorter tonic immobility (243.03+/-26.81 s) and higher leukocyte ratio (0.42+/-0.02) than did hens with a perfect plumage (322.32+/-26.81 s and 0.35+/-0.02, respectively). Differences were consistent across the breeds. Thus, hens with very poor plumage were less fearful and more stressed than hens with a perfect plumage. The results suggest that very poor plumage is associated with indicators of fearfulness and stress.

The effect of dynamic compression on the response of articular cartilage to insulin-like growth factor-I.

Articular cartilage is routinely subjected to mechanical forces and to cell-regulatory molecules. Previous studies have shown that mechanical stimuli can influence articular chondrocyte metabolic activity, and biochemical studies have shown that growth factors and cytokines control many of the same cell functions. Little is known, however, of the relationships or interplay, if any, between these two key components of the articular environment. This study investigated the comparative and interactive effects of low amplitude, sinusoidal, dynamic compression and insulin-like growth factor-I (IGF-I), a polypeptide in synovial fluid that is anabolic for cartilage. In bovine patellofemoral cartilage explants, IGF-I increased protein and proteoglycan synthesis 90% and 120%, respectively while dynamic compression increased protein and proteoglycan synthesis 40% and 90%, respectively. Stimulation by IGF-I was significantly greater than by dynamic compression for both protein and proteoglycan synthesis. When applied together, the two stimuli enhanced protein and proteoglycan synthesis by 180% and 290%, respectively, a degree greater than that achieved by either stimulus alone. IGF-I augmented protein synthesis with a time constant of 12.2 h. Dynamic compression increased protein synthesis with a time constant of 2.9 h, a rate significantly faster than that of IGF-I, suggesting that these signals act via distinct cell activation pathways. When used together, dynamic compression and IGF-I acted with a time constant of 5.6 h. Thus, dynamic compression accelerated the biosynthetic response to IGF-I and increased transport of IGF-I into the articular cartilage matrix, suggesting that, in addition to independently stimulating articular chondrocytes, cyclic compression may improve the access of soluble growth factors to these relatively isolated cells.

Mechanical and physicochemical regulation of the action of insulin-like growth factor-I on articular cartilage.

The development and maintenance of healthy joints is a complex process involving many physical and biological stimuli. This study investigates the interaction between insulin-like growth factor-I (IGF-I) and static mechanical compression in the regulation of articular cartilage metabolism. Bovine cartilage explants were treated with concentrations of IGF-I from 0 to 300 ng/ml in the presence or absence of 0-50% static compression, and the transient and steady-state incorporation of [(3)H]proline and [(35)S]sulfate into matrix components were measured. In parallel studies, cartilage explants were treated with 0-300 ng/ml IGF-I at media pH ranging from 6.4 to 7.2 and the steady-state incorporation of [(3)H]proline and [(35)S]sulfate was measured. The effect of 50% static compression on IGF-I transport was determined by measuring the uptake of (125)I-labeled IGF-I into cartilage explants. Static compression decreased both [(3)H]proline and [(35)S]sulfate incorporation in a dose-dependent manner in the presence or absence of IGF-I. IGF-I increased [(3)H]proline and [(35)S]sulfate incorporation in a dose-dependent manner in the presence or absence of compression, but the anabolic effect of the growth factor was lessened when the tissue was compressed by 50%. The response of cartilage explants to IGF-I was similarly lessened in unstrained tissue cultured in media at pH 6.4, a condition which results in a similar intratissue pH to that when cartilage is compressed by 50%. The characteristic time constant (tau) for IGF-I stimulation of cartilage explants was approximately 24 h, while tau for inhibition of biosynthesis by static compression was approximately 2 h. Samples which were both compressed and treated with IGF-I demonstrated an initial decrease in biosynthetic activity at 2 h, followed by an increase at 24 h. Static compression did not alter tau for (125)I-labeled IGF-I transport into cartilage but decreased the concentration of (125)I-labeled IGF-I in the tissue at equilibrium.