Levels of insulin-like growth factor in bovine, goat, and sheep milk in different lactation periods: The etiological factor of cancer in humans

Abstract

Background and Aim: Despite the positive aspects of consuming dairy products, there are also some reservations. Recently, a large number of publications have demonstrated convincing evidence of a relationship between the intake of dairy products and the development of cancer in humans. This study aimed to determine the level of insulin-like growth factor [IGF], which can cause cancer in consumers, in the milk of farm animals (cows, goats, and sheep) obtained at different stages of lactation. Materials and Methods: Enzyme-linked immunosorbent assay and statistical method were used for data processing. The IGF level in milk was determined using an enzyme-linked immunosorbent assay. Milk was collected from cows of Holstein and Ukrainian Black-and-White dairy breed, goats of Alpine and Saanen breed, and sheep of Tsigai and East Friesian breed. Milk samples in cows were collected at the beginning, on the peak, and at the end of lactation. Results: The obtained results showed that the highest IGF level was detected in milk obtained at the beginning of lactation, but its level depended on the animal species. More specifically, the highest level of the hormone was typical for goat's milk and for cow's milk of Holstein breed. Slightly lower values were revealed in the milk of cows of Black-and-White Ukrainian breed and sheep. During lactation, the absolute content of IGF in the milk of all studied animal species decreased. It should be noted that the most pronounced decrease in the IGF level in milk during lactation was noted in sheep (25-40 times), and minor changes were observed in goats (12-14 times). The results also showed that there were individual variations in the IGF level in milk in farm animals. Conclusion: The highest IGF level was noted in goat's milk, and the lowest level was observed in sheep's milk. Cow's milk, in this regard, had an intermediate IGF level. The level of this particular hormone depends on the period of lactation and the individual characteristics of the animal. It is advisable to include IGF as one of the assessment factors of dairy products' safety because this hormone can cause cancer in consumers of milk and dairy products.