Study On Factors Influencing Low Abundant Milk Proteins Expression Of Dairy Cows' Colostrum

The purpose of this study was to analyze low abundance milk proteins expression patterns and to increase the level of low abundance milk proteins of dairy cows'colostrum. Three experiments were systematically conducted to analyze the influences of lactation day, lactation number and vitamin on milk proteins expression patterns in order to provide valuable information for revealing milk secretion mechanism, designing baby formula powder, selecting raw milk for manufacturing colostral meal and for planning regimen of feeding colostrum to calves.Experiment 1: The influences of lactation day on bovine low level whey proteins expression patterns of dairy cows'colostrum was studed by using two dimension electrophoresis (2-DE) combination high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Whey proteins in 1 day, 3 day, 7 day and 21 day postpartum were separated by 2-DE and differentially expressed proteins among different sampling time were detected using ImageMaster software. Then the differentially expressed low level whey proteins were identified using LC/MS/MS. The study results showed that whey proteins expression patterns at 1 day and 3 day were found to be similar except for immunoglobulin G down-regulated. Four proteins were found to be down-regulated at 7 day after calving in comparision with that at 1 day after calving, mainly including immunoglobulin G, immunoglobulin M, lactoferrin and albumin, which are involved in immunity and molecule transport. These findings help reveal the mechanism of milk secretion and the influences of lactation day on bovine low abundance proteins of dairy cows during the early stages of lactation.Experiment 2: Two dimension electrophoresis(2-DE)combination high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) was used to study the influences of lactation number on bovine low abundance milk proteins expression patterns of dairy cows'colostrum. Milk proteins in 1 day and 21 day postpartum from dairy cows of first calving and third calving were isolated using 2-DE. Differentially expressed proteins of the same sampling times from different lactation number were detected using ImageMaster software. Then the differentially expressed low abundance milk proteins were identified using LC/MS/MS. The study results showed that milk protein expression patterns at 21 day of the two lactation number were the same. But when compared with milk protein expression patterns from the third calving at 1 day postpartum, there were four proteins found to be down-regulated at 1 day of the first calving, mainly including immunoglobulin G, immunoglobulin M, lactotransferrin and albumin, which are involved in immunity and molecule transport. These findings help reveal the effects of lactation number on bovine low abundance proteins of dairy cows during the early stages of lactation.Experiment 3: The effects of vitamin on bovine low abundance milk proteins expression patterns of dairy cows'colostrum was studed by using two dimension electrophoresis (2-DE) combination high -performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Twenty four dairy cows were randomly assigned to two groups (One as treatment, another as control). Treatment group was injected vitamin AD3E at 15 day before the expected date of delivery and the control one was injecteded with the same volume of normal saline. Milk proteins in 1 day and 21 day postpartum from the two groups were isolated using 2-DE. Differentially expressed proteins from the same sampling time of different group were detected using ImageMaster software. Then the differentially expressed low abundance milk proteins were identified using LC/MS/MS. The study results showed that milk protein expression patterns at 21 day from two groups after calving were the same. But when compared with milk protein expression patterns of the cows from the control group at 1 day postpartum, there were two proteins found to be up-regulated at 1 day from the treatment group, consisting of immunoglobulin G and albumin. These findings can provide value information for increasing bioactive matter in bovine colostrum.