A proteomic approach was used to investigate the effects of the processing method of corn grain and soybean meal on the milk protein expression profile in lactating dairy cows. A total of 12 multiparous Holstein dairy cows were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement. The primary factors examined were corn (finely ground (FGC) v. steam-flaked (SFC)) and soybean meal (solvent-extracted (SSBM) v. heat-treated (HSBM)), which were used to formulate four diets with the same basal ingredient: 27% FGC and 9% SSBM; 27% SFC and 9% SSBM; 27% FGC and 9% HSBM; and 27% SFC and 9% HSBM. Each period lasted for 21 days. Milk samples were collected on days 18, 19 and 20 of each period. Changes in the milk proteins were assessed by two-dimensional (2D) electrophoresis and ImageMaster 2D Platinum 6.0 software. A total of 13 spots displayed variations in protein spot abundance according to the statistical analysis. These spots were identified by a matrix-assisted laser desorption/ ionization-time of flight/time of flight MS. According to the gels, the relative abundance of α s2 -casein (CN) fragments was higher in the cows fed the SFC-HSBM than that for SFC-SSBM, whereas β-CN, α-lactalbumin and zinc-alpha-2-glycoprotein fragments were down-regulated in HSBM-fed cows. The relative decrease of β-CN expression was validated by western blot and agreed with the MS data. These results suggested that the method used to process soybean meal modified the synthesis and secretion of milk proteins in lactating dairy cows' mammary glands.
ABSTRACT:The transition period is the most critical time of the cow's lactation cycle that is associated with the onset of mastitis. In this study, changes of plasma proteins in cows (n = 12) with or without subclinical mastitis after calving were determined by two-dimensional electrophoresis (2-DE), which detected 18 spots with variations in protein spots abundance. These spots were identified by liquid chromatography coupled with tandem mass spectrometry. The changes in protein profile from day 21 before calving to day 1 after calving were similar in cows with or without subclinical mastitis. Abundance of α1 acid glycoprotein (AGP) and haptoglobin was dramatically increased at parturition, while transthyretin was down-regulated at parturition, and apolipoprotein E and immunoglobulin gamma 1 were up-regulated at postpartum compared with prepartum in periparturient dairy cows. In cows infected with subclinical mastitis, AGP, haptoglobin, and serum amyloid A were dramatically increased and continued to be elevated in plasma from day 1 to day 21 after calving compared with cows free of mastitis. Changes of protein in plasma at parturition may serve as an immune system response to parturition and lactation process at the protein level and suggest that these altered proteins would not serve as a potential marker for predicting if the periparturient dairy cows are susceptible to subclinical mastitis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.