The occurrence and possible significance of some of the minor component acids of cow milk fat

Ambient 1,2-propanediol exposure accelerates the degradation of lipids and amino acids in milk via allosteric effects and affects the utilization of nutrients containing amide bond

The scandal of detecting 1, 2-propanediol (PL) in milk brought a crisis to the trust of consumers in the dairy industry, and the potential toxicity of PL has aroused the public concern about dietary exposure. A total of 200 pasteurized milk samples were collected from 15 regions, and the quantity of PL ranged between 0 and 0.31 g kg^-1. Pseudo-targeted quantitative metabolomics integrated with proteomics demonstrated that PL enhanced the reduction of κ-casein, β-casein, and 107 substances (41 amines and 66 amides) containing amide bonds. Pathway enrichment and topological analysis indicated that PL induced the metabolism of lipids, amino acids, oligosaccharide nucleotides, and alkaloids by accelerating the rate of nucleophilic reaction, and acetylcholinesterase, sarcosine oxidase, and prolyl 4-hydroxylase were determined as the vital enzymes related to the degradation of above nutrients. The results of molecular simulation calculation illustrated that the number of hydrogen bonds between acetylcholinesterase, sarcosine oxidase, and substrate increased to 2 and 3, respectively, while the position of hydrogen bonds between prolyl 4-hydroxylase and proline was shifted, indicating the change of conformation and the enhancement of hydrogen bond force were essential factors for the up-regulation of enzyme activity. This study first revealed the mechanism of deposition and transformation of PL in milk, which contributed to the knowledge of the quality control of milk and provided vital indicators to evaluate the adverse risks of PL in dairy products.

Section A. Physiology of dairy cattle: I. Reproduction and lactation

Some years ago the annual wastage of cows in dairy herds in Britain was estimated by Wright(1) to be approximately 22%, and of this about one-quarter was due to sterility. Recent figures(2) from Shropshire, Staffordshire and Warwickshire suggest that this position has not changed in the past few years. Thus in forty-eight herds containing 1925 cows there were 620 disposals in the 12 months ending September 1940. 23% of the disposals were due to sterility. The annual losses from bovine sterility in Britain have been calculated to be equivalent to £7,000,000 in milk alone. This fact is cited by Day(3) in a concise article on the control of sterility in which he discusses various factors which contribute to the problem. Some of these factors, such as contagious abortion and trichomonas infection, are pathological, but many others are functional or physiological. The present review is concerned only with the latter. Mackintosh (4), in an article on breeding and rearing to maintain the milk supply, summarizes for the practical dairy farmer many of the methods by which the incidence of functional sterility can be reduced. Both Day and Mackintosh emphasize the importance of pregnancy diagnosis, of detecting the short winter oestrus and of testing the fertility of the bull. They also mention that hormone therapy can frequently be used to great advantage for inducing oestrus. Knowledge of these factors and how best to deal with them has greatly increased during the past few years as a result of the work carried out in many research stations throughout the world.