Heterosis in Fayoumi strain incrossing
Summary Many experiments have proved the superiority of hybrids resulting from incrossing of mbred lines, which have been utilized commercially in poultry production. The aim oi this experiment was to study the effect of incrossing inbred lines of Fayoumi chickens upon their combinability. The results can be summarized as follows: The fertility percentage 96.7 in comparing with 92.9 (L2j while reached in The heavier incross Lz5 X L3!.j had body weight equal to 118, II2 and io3 % in relation to the control at 4, 8 and i6 weeks of age, respectively. Heterosis in body weight became less obvious as chicks advanced in age and alleles responsible for early growth rate showed a great response to incrossbreeding. Incrossbreeding improved feed utilization of Fayoumi chicks. These results show the possibility for improving the native breed by incrossing and detecting the most efficient incrossbreds.
Factors Affecting Feed Efficiency for Egg Production in Selected Strains of Caged Layers
Abstract THE use of individual laying cages for market egg production has gained widespread popularity throughout the southern portion of the United States. Breeding is known to affect body size, rate of production, egg size, and feed conversion. Titus (1928) found that White Leghorn pullets weighing an average of 1,632 grams required 64 grams of feed per day for body maintenance, and 40 grams of feed for each egg produced. Byerly (1941) found annual feed requirement for body maintenance to be 46.8 pounds for three pound laying hens, and 81.4 pounds in the case of seven pound hens. He further determined that for each 100 standard weight eggs (12.5 pounds) the hen must consume an additional 14.2 pounds of feed. Bhuwan et al. (1949) found that with hens laying at a rate of 72 percent, approximately 71 percent of the feed consumed was used for body maintenance, 27 percent for the …
Pharmacokinetics of amikacin and chloramphenicol in the aqueous humor of rabbits
Composite data describing ocular pharmacokinetics are unreliable because of intersubject variation. To address this problem, an animal model was developed in which multiple aqueous samples from single subjects were obtained. Following direct anterior chamber or intravenous administration of amikacin or chloramphenicol, pharmacokinetic analysis of drug concentrations in the serum and anterior chamber was performed by using a nonlinear least-squares regression program. The number of anterior chamber paracenteses performed did not alter the beta elimination rates or percent penetration into the anterior chamber. The aqueous humor and peripheral-compartment terminal slopes were identical. These data indicate that complete ocular concentration-time curves can be obtained without altering antibiotic pharmacokinetics. Following direct injection into the anterior chamber, the elimination rates for both antibiotics followed a one-compartment model, whereas those following intravenous administration best fit an open, first-order, two-compartment model. Following intravenous administration, the anterior chamber elimination rate constants for both drugs were equal to that of the serum and significantly longer than that following direct injection. The elimination rates of both drugs following direct injection were similar. Systemic administration resulted in drug levels in aqueous humor that persisted longer than those following direct injection. Chloramphenicol, a lipophilic compound, gave higher mean concentrations in aqueous humor than did amikacin. Our model provides a new approach which rigorously examines ocular pharmacokinetics and provides data which suggest that for selected compounds the parenteral route of administration is preferable.