Homoeothermy and growth rate in the fowl

Observations on growth rates and diurnal changes in colonic temperatures were made on seven groups of 30 to 50 White Plymouth Rock x Cornish chicks aged between 6 and 8 weeks. Ambient air temperature ranged from 22 °C to 35 °C.

Colonic temperatures in the morning (08.00 to 09.00 h) and growth rates were within the normal range. A slight hyperthermia was evident from 13.00 to 14.00 h.

Morning colonic temperatures were not correlated with the later increments in body temperatures. This suggests that the set‐point temperature for thermo‐regulatory control differs between individuals.

Growth rates were not correlated with the morning colonic temperature, except in one group; they were, however, significantly correlated with the diurnal fluctuation in colonic temperature in all groups. These results suggest that the maintenance of a constant body temperature is essential for a normal growth rate.

The variation in thermoregulatory ability accounted for 31 to 71% of the total variation in growth rate.     

Further studies of linkage and mappings of the loci of genes in group 3 on chromosome 1 of the domestic fowl

1. Evidence is presented to confirm the placing of the extended black E‐locus in linkage Group 3 on chromosome 1, E being linked with peacomb P by 43 map units. P has been shown to be linked with dark‐brown Columbian Db and sleepy‐eye se by 32 and 45 map units, respectively, se being independent of E.

2. Evidence is also presented to demonstrate independence of E and Db; hence, Db and se have their loci on the same side of P, the gene order being E‐P‐Db‐se, thus contradicting published mappings which place P between Db and se.

3. An investigation into the deductive relationships on which published mappings are based led to the conclusion that insufficient evidence existed for the inclusion of the sub‐group comprising blood group Ea‐P, naked neck Na, silky feathering h and flightless El as part of Group 3.

4. Furthermore, it appears only 4 genes in Group 3 have actually had their loci mapped; blue egg O, P, the eumelanin extension charcoal cha and the feather growth restrictor tardy t.

5. No evidence appears to have been presented to establish on which arm of chromosome 1 any of the other genes in Group 3 have their loci. A revised map of chromosome 1 and a schematic arrangement to demonstrate the relative linkage distances of the loci of the unmapped genes in Group 3 are presented and explained.     

The influence of comb type on growth rate in the domestic fowl 1

Studies were made to determine the influence of comb type genes on growth rate. Three trials compared body weights of young birds while a fourth was concerned with embryonic weight at 13 days of incubation.

One of the trials on young birds included a comparison of thyroid and adrenal weights, shank length and breast angle. The majority of birds studied were heterozygous at any particular comb type locus. The following conclusions were based on results from these studies:

No consistent effects of comb type on mean body weight, thyroid weight, adrenal weight, shank length or breast angle were found. However, there were indications that comb type may affect the variances of these characters.

No significant weight differences were found among embryos of different comb types.     

Effect of dyschondroplasia on the rate of bone growth in the fowl

A group of Leghorn and a group of broiler chicks were reared from day old. At two weeks old a metallic marker was placed unilaterally in the mid-diaphysis of the femur, tibiotarsus and tarsometatarsus of every chick. After the operation the limbs were radiographed. After a period of growth the birds were killed and the radiographs repeated. Measurements from the radiographs enabled the calculation of the rate of growth at the bone extremities. There were metaphyseal defects indicative of dyschondroplasia present in some of the broiler bone extremities, these bones were considered as a separate group. When the Leghorn and normal broilers were compared there was a significant reduction in the proportion of growth in the proximal tibiotarsus of the broilers. The dyschondroplastic bone extremities in broilers demonstrated a reduction in the proportional growth rate compared with normal extremities.     

A phenotypic effect of heterozygous recessive white in the fowl

1. The dominance of the allele C⁺ of the recessive white gene c was previously thought to represent one of the relatively uncommon examples of complete dominance in the fowl.

2. In a study with cockerel‐breeding Partridge Wyandotte Bantams, dilution effects on both phaeomelanin and eumelanin were observed in C+ heterozygotes indicating that C+ is not completely dominant over its recessive allele.     

Relationship between the rate of longitudinal bone growth and physeal thickness in the growing fowl

The thickness of the physeal cartilage (growth plate) was measured and the rate of longitudinal bone growth estimated in the femur, tibiotarsus and tarsometatarsus of different groups of domestic fowl. Birds were either a laying strain or broiler strain fed ad libitum, or a broiler strain on restricted feed. They were killed at different ages from hatching to 10 weeks and the mean thickness of the physeal cartilage and the mean estimated rate of longitudinal bone growth was calculated in the proximal bone extremities. Mean physeal thickness varied from 0.185 to 0.825 mm and longitudinal growth rates between 1.85 and 8.4 mm per week. When growth rates were plotted against physeal thickness the resulting scatter diagram suggested a positive linear relationship between the two. This study provides a range of baseline values for the assessment of proximal physeal thickness in other groups of fowl.     

Linkage relationships of egg albumen loci in the domestic fowl

The linkage relationships between egg albumen loci Ov, II, III and Tf are examined in segregation data from backcross matings. The suggestion of close linkage between the Ov locus and locus II is confirmed. Loci II, III and Tf show evidence of very loose linkage but the data are also compatible with the loci located on different chromosomes.     

Egg white polymorphisms and economic characters in the domestic fowl

The possible association between genes at 4 egg white loci, Ov, II, III, and Tf and 4 production characters were studied in 3 closed populations consisting of 2 flocks of White Leghorns, each of about 1000 hens, and a Light Sussex flock of 380 hens. The characters studied were: body weight at 5 different ages, egg weight at 3 different ages, age at sexual maturity and egg number at 2 ages. Only the last two characters were studied in the Light Sussex population. Three egg white loci had statistically significant effects on production traits. With body weight and egg weight, the Ov locus had an additive effect, the Ov^A allele being superior. The influence on body weight was significant only on adults, i.e., post‐sexual maturity weights. This was shown to be partly attributable to differences in age at maturity. Locus II was significantly overdominant with respect to egg number in 2 populations while the Tf locus heterozygotes were significantly inferior to the Tf^b/Tf^b homozygotes in the Light Sussex flock. In addition to these direct effects, complex interactions involving these loci were also present on egg number. The additive genetic variance controlled by these loci was also determined. The proportion of the variance attributable to these loci (as a fraction of the additive genetic variance of the trait) was not large enough for any single trait to be of practical importance in selection.     

A search for an association between maternal egg white protein polymorphisms and embryonic mortality in the domestic fowl

The possible association between the maternal genotype at two egg white loci and viability of their embryos was examined in two closed flocks of White Leghorn hens. One of the populations was polymorphic at the ovalbumin locus and locus II and the other at locus II only. Two generations of the first population comprising 536 hens and 9092 fertile eggs and one generation of the second comprising 83 hens and 1159 eggs were used in the study. Significant effects were observed with mortality at different stages of incubation but the results were not consistent for the two strains or for the 2 years studied.     

A study of changes in fasting metabolic rate with duration of egg production in the domestic fowl

The fasting metabolic rate (FMR) of six Warren SSL hens was determined at point of lay, peak production and post‐peak production (70 per cent). The results showed that the averages of the FMRs for the six hens during the first two periods were similar (3.12 and 3.06 kcal/h kg^?), but that the post‐peak production average showed a marked increase in FMR to 3.75 kcal/h kg^? indicating that the FMR of the laying fowl may not always be constant, and that an increase can occur after peak production.     

Patterns of cell proliferation and growth rate in limb bones of the domestic fowl (Gallus domesticus)

The growth rates of each extremity of the tibiotarsus (TibT) and tarsometatarsus (TMT) bones and of a phalangeal bone were measured in Rhode Island red chicks. Histological sections of the growth plates at each of these sites were made for measurements of the thickness of the flattened dividing cell layer and counts of the number of cells between its boundaries. The diameter of the mature chondrocytes in the metaphysis was also measured. The extent of the dividing cell population within the flattened cell layer and the proportion of cells in division were measured from autoradiographs prepared after labelling dividing cells in vitro or in vivo (three birds in each group) with tritiated thymidine. From the results the rate of cell production in the plane of growth at each growth plate was estimated. It varied from about six cells per day at each end of the phalanx to just over 50 cells per day at the proximal end of the TibT and TMT. The duration of the cycle time was estimated to be 13 to 21 hours at the proximal TibT and TMT and distal TibT but considerably longer at the distal TMT and at both ends of the phalanx. Variation in growth rate between extremities of the bones examined was associated largely with variation in the dividing cell populations and the thickness of the flattened cell layer, but it appears that there were also significant differences in cell cycle times between sites. The in vitro and in vivo labelling techniques gave comparable results.     

羊草生长率的研究和生长率假说的验证

生长率假说（GRH）是研究生物生长率与化学计量特征之间关系的理论。为了验证生长率假说，以北方草原重要建群种羊草（Leymus chinensis）为材料，将取自内蒙古和吉林省4个地点的羊草在相同的光照、水肥条件下盆栽土培，用称重法测定了羊草的生长率，用PCR的方法分析了羊草核糖体DNA基因间隔区（IGS）长度，研究了羊草生长率与羊草磷含量、氮磷比、IGS长度及取样地土壤中氮、磷含量之间的关系。结果表明，羊草生长率与羊草全磷含量存在正相关关系，与羊草氮磷比存在负相关关系，生长率较高的羊草具有较长的IGS，符合生长率假说的预测。不同来源的羊草种植在相同环境下，来自氮、磷含量较高土壤的羊草具有较高的生长率，这可能是羊草对特定地域生境条件长期适应的结果。高的生长率和长的IGS可能是植物对较高氮、磷含量环境的适应。     

猪显性白毛调控基因KIT不同基因型对仔猪初生重影响的研究

为了研究白毛调控基因KIT不同基因型对仔猪初生重的影响,试验采用限制性内切酶片段长度多态性分析(RFLP)的方法,分析基因KIT不同基因型(III、ii、i)对仔猪初生重的影响。结果表明:携带隐性基因i的猪初生重比携带显性基因I的猪重,且差异显著(P<0.05);不同基因型间断奶重差异不显著(P>0.05)。     

双肌臀大白猪生长速度遗传力估计及表征性状比较

利用mtdfreml软件包估计双肌臀大白猪达100kg体重日龄和平均日增重这两个表征生长速度性状的遗传力。具体步骤是先用sas软件包对固定效应进行不同水平间差异显著性检验。尔后确定固定效应的水平数。最后用mtdfreml进行遗传参数估计，得出双肌臀大白猪达100kg体重日龄和平均日增重两个性状的遗传力估值。这对于双肌臀大白猪的育种实践将起到一不定的促进作用。同时通过这两个性状遗传力估值的比较，验证了平均日增重较达100kg体重日龄在猪的育种实践中能更好的代表生长速度，更快的提高育种进展这一观点。     

Genetic correlations between test station and on-farm performance for growth rate and backfat in pigs

Record of performance data taken on Yorkshire pigs on-farm in 123 breeder herds and at a central test station were used to estimate genetic correlations between measures of backfat depth and days to 90 kg on boars at the test station and boars and gilts on-farm. The data involved records on 3,513 station-tested boars, 13,760 farm-tested boars and 28,203 farm-tested gilts from 838, 2,098 and 2,339 sires, respectively. For backfat depth, estimates of genetic correlations were .85 for test station and on-farm boars and 1.04 for test station boars and on-farm gilts. Estimates of genetic correlations between test station and on-farm measures of days to 90 kg were .80 for boars and .74 for boars and gilts. Based on these results, selection of boars on the basis of test station performance for backfat and growth rate would be expected to result in genetic improvement on-farm in both sexes under North American testing and management conditions.     

双肌臀大白猪生长速度遗传力估计及选择性状比较

作者利用mtdfreml软件包估计双肌臀大白猪达100kg体重日龄和平均日增重这2个代表生长速度性状的遗传力。具体步骤是先用sas软件包对固定效应进行不同水平间差异显著性检验，而后确定固定效应的水平数，最后用mtdfreml进行遗传参数估计，得出双肌臀大白猪达100kg体重日龄和平均日增重2个性状的遗传力估值。结果，双肌臀大白猪达100kg体重日龄和平均日增重2个性状的遗传力估值分别为0．06和0．29。并提出了这2个性状在实际育种中的注意事项。这对于双肌臀大白猪的育种实践将起到一定的促进作用。     

Changes in the collodiaphyseal angle with growth in the fowl (Gallus domesticus)

The angle formed between the femoral neck and shaft is referred to as the collodiaphyseal angle. In man, the angle decreases during growth and is frequently different in the right and left limbs. This study examines the collodiaphyseal angle in another biped, the growing fowl. Three groups (A, B and C) of growing fowls were examined. The weight difference between birds would alter the forces applied to the growing proximal femur and at the end of the experimental period the birds in group B weighted three times those in group A. Nevertheless, in all three groups the collodiaphyseal angle decreased from 120 degrees to 108 degrees over the growth period. Where there was a difference in collodiaphyseal angle between right and left limbs the angle was more frequently greater in the right. Bodyweight apparently had little effect on the development of collodiaphyseal angle in the fowl, possibly due to the trocharteric/antitrocharteric articulation reducing the stresses applied to the femoral neck.