Composition and enzymatic activity in bulk milk from dairy farms with conventional or robotic milking systems.

The objective of the studies reported in this research communication was to investigate differences in composition and enzymatic activities in bulk milk samples provided from Swedish dairy farms with different management systems, i.e. automated (AMS) and conventional milking systems (CMS). A bulk milk sample was collected from each of 104 dairy farms, 51 using AMS and 53 using CMS, located in the same geographical region. Sampling took place within two consecutive days during the indoor period (October). Milk samples were analysed for contents of total fat and protein, free fatty acids (FFA), caseins and whey proteins, somatic cell count (SCC), pH, plasmin and plasminogen derived activities, and total proteolysis. Our results showed a lower protein content and higher SCC in bulk milk from AMS herds compared with milk from CMS herds. Plasmin, plasminogen and total plasmin/ plasminogen derived activities were lower in milk from AMS herds but despite this, total casein and the ß-casein fraction as % of total protein were lower in milk from AMS herds than in milk from herds using CMS. Total proteolysis was higher in milk from AMS herds, suggesting that other proteases than plasmin, e.g. cellular and bacterial proteases, contributed to the degradation of casein. This was supported by a positive correlation between SCC and total proteolysis (P < 0·01), as well as a negative correlation between total proteolysis and ß-casein fraction (P < 0·05). In conclusion, comparing the quality of bulk milk from commercial dairy herds using AMS and CMS, respectively, several differences were observed, suggesting a significant effect from management system.

Short communication: Influence of shortening the dry period of Swedish dairy cows on plasmin activity in milk.

The aim of this study was to evaluate the influence of shortening the dry period of Swedish dairy cows on plasmin activity and casein composition in milk. Swedish Holstein and Swedish Red cows, 45 in total, were assigned to a dry period of either 4 or 8wk. Milk samples were taken 10 and 5wk prepartum, and 6 and 12wk postpartum. Plasmin activity and plasminogen activity were measured with a spectrophotometric assay. Casein composition was measured by capillary zone electrophoresis. Prepartum plasminogen activity increased by 22% between 10 and 5wk prepartum, whereas no change in plasmin activity was observed during the same period. Cows with a 4-wk dry period had 61% higher plasmin activity in postpartum milk than cows with an 8-wk dry period. Cows of third or greater parity tended to have a stronger increase in plasmin activity as a result of applying a short dry period than cows of second parity. Although the αS1- and ß-casein fractions declined with increasing plasmin activity, no dry period effects were found. Based on postpartum differences in plasmin activity, it was concluded that particularly multiparous cows require more than 4wk between lactations for recovery of the mammary epithelium. Changes in casein composition as an effect of plasmin activity are not expected to have a great effect on processing quality of milk, although future work is needed to verify this.

Effect of shortening or omitting the dry period of Holstein-Friesian cows on casein composition of milk.

The aim of this study was to evaluate the effect of shortening or omitting the dry period of dairy cows on milk casein composition. For this study, we analyzed milk samples of 90 cows with a dry period of 0, 30, or 60d and either a glucogenic or a lipogenic ration in early lactation. Milk was sampled at 6 and 2wk prepartum and at 2, 6, and 12wk postpartum. Milk was analyzed for casein (CN) composition by capillary zone electrophoresis, and isoforms of κ-CN were measured by reversed phase-HPLC. Shortening the dry period from 60 to 30d reduced the αS1-CN fraction by 3.8% and increased the αS2-CN fraction by 5.5%. In milk from cows with a 0-d dry period, the glycosylated κ-CN fraction in late lactation increased from 8 to 12% between 6 and 2wk prepartum. After calving, the glycosylated κ-CN fraction in milk was higher for cows with a 0-d dry period (6.7%) compared with cows with a 60-d dry period (5.2%). The glycosylated κ-CN fraction at 2wk postpartum was negatively correlated with milk yield, suggesting that glycosylation was related to reduced productivity of mammary epithelial cells. In early lactation, the ß-CN fraction was reduced in milk of cows with a 0-d dry period. A lowered ß-CN fraction was associated with high somatic cell count and greater parity, indicating that it was the result of proteolytic activity. In conclusion, casein composition changes that result from shortening the dry period from 60 to 30d are not expected to affect processing characteristics of milk. Applying a 0-d dry period may affect processability of milk because of a higher glycosylated κ-CN fraction, and possibly because of higher proteolytic activity compared with a 60-d dry period.

Direct Cell Reprogramming of Mouse Fibroblasts into Functional Astrocytes Using Lentiviral Overexpression of the Transcription Factors NFIA, NFIB, and SOX9.

Astrocytes play an important role in maintaining brain homeostasis and their dysfunction is involved in a number of neurological disorders. An accessible source of astrocytes is essential to model neurological diseases and potential cell therapy approaches. Cell reprogramming techniques offer possibilities to reprogram terminally differentiated cells into other cell types. By overexpressing the three astrocytic transcription factors NFIA, NFIB, and SOX9, we showed that it is possible to directly transdifferentiate fibroblasts into functional astrocytes. These induced astrocytes (iAstrocytes) express glial fibrillary acidic protein (GFAP) and S100 calcium binding protein B (S100B), as well as other astrocytic markers. Moreover, electrophysiological properties indicate that iAstrocytes are functionally comparable to native brain astrocytes. Here we describe an optimized protocol to generate iAstrocytes starting from skin fibroblasts and this approach can be adapted for a wide range of somatic cell types.