Molecular variation in pigmentation genes contributing to coat colour in native Korean Hanwoo cattle.

Pigmentation genes such as TYR (tyrosinase), TYRP1 (tyrosinase-related protein 1), DCT (previously TYRP2, or tyrosinase-related protein 2), ASIP (agouti) and MC1R (melanocortin receptor 1) play a major role in cattle coat colour. To understand the genotypic profile underlying coat colour in native Korean Hanwoo cattle and Angus black cattle, portions of the above-mentioned genes were amplified. Sequence analysis revealed variation in the TYRP1 (exon 5) and MC1R genes. Restriction enzyme analysis of these two genes could distinguish between different colours of Hanwoo cattle. Quantitative estimates of melanin and eumelanin in hair from three different-coloured Hanwoo phenotypes and Angus black showed significant differences at the breed and phenotypic levels. Finally, sequence variants in MC1R were associated with total melanin and eumelanin in breeds as well as in Hanwoo phenotypes.

Selection for eight-week body weight in two randombred chicken populations under altered water to feed ratios. 2. Feed intake, water intake, and abdominal fat levels.

Four experiments were conducted to investigate feed and water intake, feed efficiency, and abdominal fat levels of six lines of chickens developed from two randombred control populations following selection for high 8-wk BW under high (1.6%), low (.2%), and normal (.4%) dietary salt selection environments. The Athens-Canadian Randombreds (AC) and Athens Randombreds (ARB) served as base populations for development of the six lines. Progeny from these lines were evaluated in the first, fifth, sixth, and seventh generations in Experiments 1, 2, 3, and 4, respectively. In Experiment 1, abdominal fat levels were shown to be inversely related to dietary salt level. The lowest abdominal fat level was observed in birds fed the 1.6% salt diet and the highest abdominal fat level in birds fed the .2% salt diet. Birds receiving the normal (.4%) salt diet had intermediate abdominal fat levels. In Experiments 2, 3, and 4, selected lines were exposed to different dietary salt levels to measure both line and dietary salt response patterns. Significant (P < .05) differences were observed between genotypes (AC vs ARB) and between dietary salt treatments for BW, feed and water intake, and water to feed ratio. However, there was no evidence of genetic change between lines in abdominal fat level as a result of selection under different salt environments.

Divergent selection for growth in Japanese quail under split and complete nutritional environments. 7. Heterosis and combining ability among diallel crosses following twenty-seven generations of selection.

Growth patterns of quail lines divergently selected for 4-wk BW under split and complete nutrition environments were investigated utilizing a diallel mating scheme. The design, involving 16 mating combinations, allowed investigation of heterotic effects, reciprocal cross effects, and combining ability. Progeny from Generation 27 breeders were evaluated in two hatches under both selection diets. Heterosis for hatch weight was essentially zero; however, percentage heterosis from High x High crosses and Low x Low crosses ranged from 5 to 18% after 1 wk of age. Quail progeny from Low x High crosses were consistently larger than quail from reciprocal High x Low crosses under both selection diets. Reciprocal differences were greatest immediately posthatch and declined with age. However, in crosses involving males from High and Low split diet lines mated to females from High and Low complete diet lines, large reciprocal differences in BW remained at 8 wk. Mean heterosis values for BW across ages from crossing High and Low lines both within and across selection environments were negative in six of eight comparisons. Mean values ranged from +3 to -11% and indicated that greater selection responses may have been made in divergent selection for low 4-wk BW than for high BW. General combining ability of lines was greater when transmitted via females as opposed to males, and was similar under the two diets (split and complete). There was evidence that high-BW lines exhibited greater general combining ability under both dietary environments than did low-BW lines.

Epidemio-entomological survey of Japanese encephalitis in Korea.

In order to determine the seasonal prevalence and population dynamics of Culex tritaeniorhynchus in relation to the epidemics of Japanese encephalitis, and ecology of these vector mosquito in Kyungpook Province, Korea, studies were conducted during the period of 7 years from 1984 to 1990. Cx. tritaeniorhynchus first collected in June between 4th and 28th, and trapped in large numbers during the period from mid-August to early September, showed a simple sharply pointed one-peaked curve. There was a gradual decrease from mid-September, with a very small number of them collected until early October in every year. The average number of Cx. tritaeniorhynchus rapidly decreased after 1985, and the number became particularly low in 1989. The highest population density, which was observed in August during the initial three years, was found to be delayed in the following years, accompanied by a decrease in the number of mosquitoes. In the trend of nocturnal activity of Cx. tritaeniorhynchus, with oncoming darkness they become very active, gradually decreasing in activity toward mid night, but slightly increasing toward dawn. The immature stages of Cx. tritaeniorhynchus were first found in rice fields contributing to peak adult densities in mid-July. The highest average densities of Cx. tritaeniorhynchus was 14,900 per m2 on mid-August 19th. The larval Cx. tritaeniorhynchus showed high resistance levels and resistance ratios against 5 organophosphorus compounds. In the adult horizontal life table characteristics of Kyungsan colonies of Cx. tritaeniorhynchus under insectary conditions, life expectancy was 28.3 days for males and 59.8 days for females. The net reproductive rate was 7.8 and generation time was 25.6 days.

Selection for feed conversion on efficiency and growth in mice.

Selection for feed conversion substantially influenced growth and gross feed efficiency of mice. Realized heritabilities and genic correlation for increased gain on fixed feed intake (FF) and decreased feed intake on a constant gain (FG) were estimated to be .56, .73 and -.93, respectively. The genic correlations between FF and 56-day weight and between FG and 56-day weight were estimated to be .67 and -.95, respectively. The relative efficiency in changing FF or FG by selecting directly for 56-day weight was found to be .7 in either case. When efficiency was defined as the incorporation of biomass independent of maintenance, no difference was found between selection treatments. Differences in mature weight and feed intake approached significance with selected lines having higher means than controls. The absence of a correlated response in the ability to use energy for growth indicates that selection for feed to gain ratio changes maintenance requirements but not requirements for growth.