Effect of a high-concentrate diet on milk components and mammary health in Holstein dairy cows.

In order to evaluate the milk yield, milk quality, and health of dairy cows fed a high-concentrate (HC) diet, eight lactating Holstein dairy cattle were randomly assigned to HC or low-concentrate (LC) diet groups and fed for 50 days, and the auto-control studying before and after treatment with the two diets was used. During the experiment, plasma and milk samples were collected and measured. With regard to milk component, HC feeding led to higher milk production (P < 0.05), but significantly lower milk protein percentage (P < 0.05), milk protein yield (P < 0.05), and milk fat percentage (P < 0.05) throughout the five periods than LC feeding. Milk somatic cell count and N-acetyl-D-glucosaminidase activity (P < 0.01) were higher than those observed under LC feeding. mRNA expression levels of interleukin-8 (IL-8), C-C motif chemokine ligand (CCL5), and lactalbumin alpha (α-LA) were investigated by qPCR and found to be significantly lower (P < 0.01) in cattle fed the HC diet. The amino acid content was analyzed by high performance liquid chromatography (HPLC), and the content of Asp (P < 0.01), Gln (P < 0.01), Ala (P < 0.05), Leu (P < 0.05), Lys (P < 0.05), and Ile (P < 0.01) was significantly lower in the HC group, whereas the content of Arg (P < 0.05) and Phe (P < 0.01) was significantly higher. These results suggest that the HC diet might have an important influence on mammary health. The amino acid content was lower, suggesting that depletion of amino acids, resulting in depleted milk protein, affects milk quality.

Antisense expression of Gossypium hirsutum UDP-glucuronate decarboxylase in Arabidopsis leads to changes in cell wall components.

UDP-glucuronate decarboxylase (UDP-xylose synthase; UXS, EC 4.1.1.35) is an essential enzyme of the non-cellulosic polysaccharide biosynthetic pathway. In the present study, using transient expression of fluorescently labeled Gossypium hirsutum UXS (GhUXS3) protein in onion epidermal cells, we observed that this protein was distributed in the cytoplasm. The GhUXS3 cDNA of cotton was expressed in an antisense orientation in Arabidopsis thaliana by Agrobacterium tumefaciens-mediated transformation. Homozygous plants showing down-regulation of UXS were analyzed with northern blots. Compared to the untransformed control, transgenic plant showed shorter roots, earlier blossom formation, and delayed senescence. Biochemical analysis indicated that levels of rhamnose, mannose, galactose, glucose, xylose, and cellulose were reduced in some of the down-regulated antisense plants. These results suggest that GhUXS3 regulates the conversion of non-cellulosic polysaccharides and modulates their composition in plant cell walls. We also discuss a possible cellular function for GhUXS in determining the quality of cotton fibers.