Growth rates of main and reciprocal crosses of Isa Brown and local chickens

The absolute and relative instantaneous growth rates of F1 hybrid chickens were determined at 2- 10 and 12-20 week periods of growth. The hybrids were hatched from eggs laid by 69 Isa Brown and local chicken parents. A total of 123, 49 and 116 chicks of Isa Brown x frizzle feathered (IBxF), Isa Brown x naked neck (IBxNa) and Isa Brown x normal feathered IBxN) main crosses and 137, 42 and 64 chicks of frizzle feathered x Isa Brown (FxIB), naked neck x Isa Brown (Na x IB) and normal feathered x Isa Brown (NxIB) reciprocal crosses, respectively were produced at day-old. The greatest absolute growth rates of 49.44g/week at 2-10 weeks and 71.11 g/week at 12-20 weeks were obtained from IBxN and FxIB genotypes, respectively. Instantaneously, IBxNa had the greatest rate of 0.28 g/time at 2-10 weeks, while IB x F and Na x IB each at 12-20 weeks were found to grow at the greatest rate of 0.091 g/time, respectively. It was concluded that normal and naked neck genes could be utilised in main crosses to develop fast growing broiler chicks while frizzle and naked neck genes could be used in reciprocal crosses to improve good laying pullets without precocious maturity.

Food restriction prior to release reduces precocious maturity and improves migration tendency of Atlantic salmon (Salmo salar) smolts

Since food availability is known to affect both the precocious maturation and start of feeding migration in wild juvenile salmonids, we examined if a reduction in otherwise plentiful feeding in hatcheries could improve migration tendency and the subsequent survival of released Atlantic salmon (Salmo salar) smolts. A reduction in diet lipid content and feed ration (FR) the previous spring and in FR in the winter prior to release proved efficient; spring-diet treatment halved the proportion of mature males in the autumn prior to release, and a reduction in FR in the winter prior to release decreased latency before leaving the stocking site. In addition, a reduction in FR in winter affected the onset of migration, improved migration speed, and defined the direction of migration downstream in controlled experiments. However, diet manipulations neither affected the swimming endurance nor improved the generally poor tag recapture rates. We conclude that reduced FR at specific times could be used to reduce both precocious male maturity and improve the migration tendency of released salmon.

Britten and the String Quartet

THAT BENJAMIN BRITTEN already possessed in his early twenties a most astonishing technical assurance has never been in doubt; nor that he commanded a range of feeling and a stylistic integrity which proclaimed a uniquely precocious maturity. So much was evident from early published scores like the Sinfonietta, Phantasy for oboe quartet, Variations on a theme of Frank Bridge, and Our Hunting Fathers. The route by which he had reached this early maturity, however, was not generally known until comparatively recently, and the book which was for decades to remain the most reliable and perceptive guide to his music—the symposium of 1952 edited by Donald Mitchell and Hans Keller—said little about the pre-opus 1 works, or about influences.

Reproduction Versus Somatic Growth: Hormonal Control in Octopus Vulgaris

Octopus vulgaris can be forced into precocious maturity by removal of the subpedunculate lobe from the brain, an operation that releases the optic glands from inhibition, and allows them to secrete a gonadotropin. 14C-leucine was injected into the bloodstream of immature animals and its subsequent incorporation into muscle protein followed by taking successive samples from the arms. The optic glands were then activated, and a further injection of 3H-leucine given and followed by means of further arm samples. Optic gland secretion suppresses protein synthesis in the muscles. This is associated with an increase in the total amino acid pool in the muscles and with a considerable increase in the concentration of free amino acids circulating in the blood. If an ovary is present these events are associated with a rapid growth of the ovary and its ducts, and a loss of weight elsewhere. In ovariectomized animals the ducts grow, but there is no yolk to absorb the large pool of free amino acids, and the animals gain weight by osmotic uptake of water into the muscles. The developing ovary may produce a hormone that increases the release of amino acids from muscle, since the concentration circulating in the blood of intact animals remains at least as high as in ovariectomized octopuses, despite the demands of the developing ovary. These matters are discussed in relation to other evidence for a gonadial hormone and in relation to the ‘self-destruct’ effect of the optic gland secretion in determining the post-reproductive death of octopuses.