标题：Bovine colostrum as substrate for the preparation of growth factor-enriched protein extracts: Identifying the optimal collection period during lactation
摘要：A growing number of growth factor-enriched bioactive protein extracts derived from
colostrum are proposed for the treatment of inflammatory and cutaneous diseases. However, growth
factor concentrations peak in the first secretions after parturition and vary widely among cows. The
aim of this study was to identify the optimal collection period for colostrum used to prepare growth
factor-enriched protein extracts and to characterize the relationship between growth factor and
protein contents in colostrum and in milk collected during early lactation. Lacteal secretions from
five Holstein cows from the first milking ($<$ 12 h) to the 21st day after parturition were analysed for total protein and growth factor (TGF-$\beta$2, TGF-$\beta$1 and IGF-I) contents. Although concentrations varied widely between cows, statistically significant decreases were obtained for all components during the early stages of lactation. The concentrations of each growth factor during lactation were highly correlated ($R$$^{2}$ > 0.93) and were also correlated with the total protein content ($R$$^{2}$ > 0.90). The greatest decreases in the concentrations of the three growth factors (78–84%) were observed within 24–48 h after parturition, while values stabilized in mature milk. However, relative to protein, these decreases appeared much smaller (37–45%). Overall, these results suggest that the first 48 h after parturition would be optimal for harvesting colostrum for the production of growth factor-enriched protein extracts.
