An experiment was conducted with meat ducks to determine if betaine could replace methionine in a methionine-deficient diet. In order to avoid the effects of betaine as a methyl-group donor or as an osmoprotectant or coccidiostat enhancer, sufficient amounts of methyl-donating compounds were added and clean conditions were used to reduce the coccidiosis challenge. A total of 576-day-old female meat ducks were fed one of four diets in a 2 (0 and 0.5g betaine/kg)

This study was conducted to evaluate developmental gene expression of lactoferrin and effect of supplementary iron on gene expression of lactoferrin in mice mammary gland using semi-quantitative RT-PCR analysis. In experiment 1, total twelve female ICR ( Institute of Cancer Research ) mice of four groups, each group of three mice at day 1, 9, 17 and 25 of lactation were used to determine effect of different lactating stages on mRNA expression of lactoferrin. In experiment 2, six groups mice (total twenty-four female mice at day 12 after mating) feeding purified diets (without iron or supplement iron) were assigned to two treatments (control and treatment). The feeding experimental period lasted 35 days. During feeding experiment, six mice with three animals each group were chosen at day 1, 9, 17 and 25 of lactation to determine the effect of iron on lactoferrin mRNA expression of mice at different lactating stages. The current results of experiment 1 showed that lactoferrin mRNA had strong expression at day 1 of lactation, and decreased gradually at day 9 and day 17 of lactation and then increased again markedly at day 25 of lactation. These results implicated that the expression of lactoferrin in mammary gland at different lactating stages is consistent with the changes of lactoferrin concentrations in milk. Iron significantly increased lactoferrin mRNA expression at day 1 and day 25 of lactation. Iron also increased lactoferrin gene expression at day 9 and day 17 of lactation, but statistical result was not significant. These findings raised the possibility that iron supplementation may play a role in regulation of lactoferrin levels in vivo.

抗菌肽是阳离子型活性肽，是哺乳动物防御体系的一个重要组成部分，具有分子量小，热稳定性好。无免疫原性，抗菌谱广等特点，通过改变细菌细胞膜的通透性而发挥抗菌作用，这不同于抗生素通过阻断大分子生物合成的作用机理，因而致病菌不易对其产生耐药性。本文就几种哺乳动物抗菌肽特性、抗菌机理、基因表达及其研究展望和存在问题进行了综述。

乳铁蛋白（LF）是一种天然的铁结合蛋白。乳铁蛋白肽（Lfcin）是从LF上被胃蛋白酶水解下来的25个氨基酸残基的小肽。本文综述了LF和Lfcin的结构、抗菌功能和基因表达调控的研究进展。