In this study, we analyzed DNA sequence of mitochondrial DNA (mtDNA) control regions on the 130 native domestic pigs and eight wild boars in the mainland South and South-east Asian countries including Bhutan, Cambodia, Laos, Myanmar, and Vietnam. Forty-four haplotypes were found in the 138 individuals, 41 were in the domestic and four were in wild boars. Only one haplotype was shared by domestic and wild population in Bhutan. In other cases, mtDNA of wild boars did not show close affinity to that of the domestic pigs in the same location, indicating that the native domestic pigs in these countries did not originate in the present habitat. Phylogenetic analyzes of mtDNA haplotypes recapitulated several major clusters identified in other studies, but 11 haplotypes were grouped in a new cluster we named MTSEA. In most cases, more than one lineage group were present in a sampling station, indicating that the present indigenous domestic pigs may have multiple origins. The MTSEA haplotypes were present in relatively high frequencies in domestic pigs in the mountainous area of mainland South-east Asia (Cambodia and Laos), with a few found in Myanmar and Bhutan. The distributions of MTSEA haplotypes are in great conformity with the distribution of present-day Mon-Khmer language and indicated the existence of yet another independent domestication. The D2 haplotypes that distribute high frequency (almost 100%) throughout the Chinese breeds were dominant in Bhutan, Myanmar, and Vietnam. These results suggest an existence of human-mediated dispersal of domestic pigs from north to the south during the historical expansion of Sino-Tibetan and Tai peoples. The D3 haplotypes previously reported in north India were found in sympatric domestic and wild pigs in Bhutan. The D3 haplotype is an important proof of independent domestication event and/or great gene flow between wild and domestic pigs in the foot of Himalaya.

A single amino acid substitution between Asn and Ser at position 631 in the chicken Mx protein has been reported to determine resistant and sensitive antiviral activity. In this study, we investigate whether various kinds of chicken breeds and jungle fowls carry the resistant or sensitive Mx allelic gene by using the mismatched PCR-restriction fragment length polymorphism (RFLP) technique. In total, 271 samples from 36 strains of 17 chicken breeds and from 3 kinds of jungle fowls were examined. The rates of the resistant Mx gene and sensitive gene were 59.2% and 40.8%, respectively. Only a Red jungle fowl captured in Laos carried the resistant Mx gene, and the other three Red jungle fowls from Indonesia and Gray and Green jungle fowls all had the sensitive Mx gene. These results were confirmed by the determination of amino acid sequences in the GTPase effector domain of jungle fowls.

1. After W-methylhistidine (W-MH) distribution among the various organs or the tissues was determined in male broiler chickens of 15 d of age, the rates of degradation of myofibrillar proteins in male layer and broiler chickens at different stages of growth were determined by means of W-MH.2. About 75 and 8% of the total W-MH in the tissues occurred respectively in skeletal muscle and stomach, and most of the remainder in the intestine and the skin.3. The rates of degradation of myofibrillar proteins in the male layer and broiler chickens of 21,42 and 63 d of age were calculated to be 6.1, 4.5 and 2.4% /d (layer) and 5.0, 2.8 and 0.9%/d (broiler) respectively. These calculations involve the assumption that 80% of the total excreted W-MH was derived from skeletal muscle.4. The results strongly indicate that the rapid growth of the broiler chicken is facilitated by the reduced rate of protein degradation.Growth in animals takes place either by an increase in the rate of tissue protein synthesis or by a reductiori in the rate of protein degradation. Therefore, the processes of protein synthesis and protein degradation play equally important roles in the control of protein deposition in animals. The rate of degradation of myofibrillar proteins has been calculated from urinary excretion of Nr-methylhistidine (Nr-MH) in small animals (Young et al. In the present investigation, W-MH distribution among various organs and tissues was determined in broiler chickens, and the rates of degradation of myofibrillar proteins of skeletal muscle in broiler and layer chickens at different stages of growth were estimated.The present results strongly suggest that rapid growth of broiler chickens originates in the slower rate of body protein degradation. M A T E R I A L S A N D METHODSExpt. 1. Distribution of Nr-MH among organs and tissues. Five commercial male broiler chickens of 15 d of age and weighing 173-205 g were used. The animals were killed by decapitation and the viscera removed quickly and weighed. After removal of the viscera, the skin was removed and weighed. The carcass was weighed and the skeletal muscle excised with a knife and weighed; however, as the skeletal muscle could not be excised completely the bones were boiled for 3 h to remove muscle. The bones were then crushed and a part used for NT-MH determination. Samples of the organs and tissues were retained for analysis of Nr-MH and stored at -20".The Nr-MH content in the samples was analysed by a modification of the method of Nishizawa et al. (1978). The samples were weighed into Ehrlenmyer flasks and hydrolysed with 6 M-hydrochloric acid in an autoclave (1 15' ) for 20 h. The samples were completely hydrolysed by autoclaving for 20 h. Almost 100% recovery was demonstrated by treating 6 N U T 54

Fractional rates (% X day-1) of synthesis and degradation were determined by measuring the output of N tau-methylhistidine (MeHis) in the excreta at 4 and 8 weeks of age in the chicken. At 4 weeks of age, the fractional rate of synthesis of the meat-type stock was twice that of the egg-type stock (White Leghorn), but the fractional rates of synthesis at 8 weeks of age were similar (4.1-5.1% X day-1) among stocks. The fractional rate of degradation (1.3-1.5% X day-1) of the meat-type stock at 8 weeks of age was less than half the rate of the egg-type stock (2.9% X day-1). The fractional rates of synthesis and degradation at 4 weeks of age in the Satsuma native fowl were relatively high compared with those in the other stocks. In particular, the rate of degradation (8.6% X day-1) at 4 weeks of age was approximately twice that of other stocks. These results show that fractional rates of synthesis and degradation of muscle protein in the chicken differ among genetically diverse groups. The effect of changes in rates of synthesis and degradation on the change in fractional growth rate also differed. From regression coefficients (bks . FGR and bKd . FGR) of these rates in skeletal muscle protein on the fractional growth rate, it was recognized that the change in growth rate accompanies the changes in both synthesis and degradation in White Leghorn and commercial broilers but only the change in synthesis in White Plymouth Rock (dw) and Satsuma native fowl.

Introduction In much animal production, commercial animals are crossbreds from closed lines or breeds under long‐term directional selection. Therefore it is desirable to be able to predict heterosis gains over the generations as it is done for genetic progress under within‐line selection. However, heterosis is the phenotypic expression of a complex phenomenon which may involve several types of genetic effects like dominance and epistasis. In animal breeding, basic quantitative genetics theory indicates that heterosis should be proportional to (squared) differences in gene frequency between populations (e.g. F alconer and M acK ay 1996), and it has been found approximately correct, so it is commonly used for planning crosses. Under that type of heterosis, however, selection towards the same objective in two populations should bring gene frequencies closer, and therefore it should eventually decrease heterosis. On the other hand, reciprocal recurrent selection designed to increase genetic distance between lines should eventually achieve maximum heterosis (O llivier 1982). Some experiments reviewed by brun (1982) have already compared genetic progress under within‐line and reciprocal recurrent selection, but they did not focus on comparing the trend of heterosis with generations between the two selection methods. Also, heterosis was monitored periodically in some selection experiments on poultry, and results were reviewed by F airfull (1990). They were somewhat contradictory, but they generally failed to relate genetic progress to loss of heterosis under within‐line selection. Moreover, in commercial production, as purebreds and crossbreds are not contemporaries and are generally maintained under very different management systems, estimations of heterosis and of the evolution of crossbred advantage over the generations may be difficult to obtain. Using the Japanese quail as an experimental animal, the present work was initiated specifically to follow the changes in heterosis brought about by selection for a single heterotic trait, early egg production (M invielleet al. 1995). For that purpose, two selection methods expected to have opposite effects on heterosis, directional within‐line (or individual) selection and reciprocal recurrent selection, were applied for 13 generations in four quail lines started from two different origins, and trends of heterosis in the selected character and in weight and egg traits were evaluated.