Alterations in milk metabolome and coagulation ability during the lactation of dairy cows.

Milk composition has been known to change during lactation. To help understand the changes in metabolic profile throughout the whole lactation, liquid chromatography mass-spectrometry was used to analyze 306 milk samples from 82 primi- and multiparous dairy cows. Changes in metabolic profile common to all cows throughout lactation were ascertained based on principal component and general linear model analysis. Sets of specific markers; for instance, 225, 397, and 641-642 m/z (positive mode), and 186, 241, and 601-604 (negative mode), with at least a 1.5-fold higher intensity during the first 60 d compared with the last 60 d of lactation were observed. The metabolome was affected by parity and milking time. Markers, identified as peptides differentiating parity, were observed. A significant increase for citrate was observed in evening milk. Milk coagulation traits were strongly animal specific. The curd firmness values were influenced by milking time. Sets of markers were associated with curd firmness in positive (197 m/z) and negative (612, 737, 835, 836, 902, 1000, 1038, and 1079 m/z) ion mode.

Comparison of the metabolic profiles of noncoagulating and coagulating bovine milk.

We hypothesize that, through milk composition and different milk metabolites, it is possible to characterize the technological properties (e.g., coagulation) of milk. In this research, liquid chromatography mass spectrometry was used to obtain profiles of low molecular weight organic compounds in 143 milk samples. The metabolic profiles of milk from cows were correlated with their coagulation properties. Using multivariate data analysis methods, we demonstrated that the metabolic profiles of the milk were correlated with coagulation ability. Several marker ions responsible for differential coagulation were found. Although not all affected metabolites could be identified, the most significant differences were found for carnitine and oligosaccharides. Exploitation of these results may increase the use of biomarkers to assess the coagulation ability of milk. This study represents the first large-scale metabolomic profiling of noncoagulating and coagulating bovine milk samples in Estonia.

Effects of sodium fertilizers and supplements on milk production and mammary gland health.

A series of experiments was conducted to investigate the effects of sodium fertilizers and supplements on the milk production and mammary health of dairy cows. In Expt 1, where sodium fertilizer was applied to productive pastures consisting mainly of the natrophile perennial rye-grass, the herbage sodium content and the milk yield of cows was increased and milk somatic cell count (SCC) reduced. In Expt 2, which used pastures containing less productive, natrophobic grasses and broad-leaved plants in Estonia, sodium fertilizer did not increase herbage sodium content and did not affect milk production or composition. In Expt 3 the sodium content of the diet of individually tethered cows was increased from 1 to either 6 or 11 g/kg dry matter (DM) by adding salt to their restricted feed allowance, and the cows' milk yield was increased by the high level of sodium supplement and milk SCC were reduced by both levels of sodium supplement. The calcium and magnesium status of cows was improved by the sodium supplement. In Expt 4 a low level of supplementary salt was included in the ration of tethered cows to increase the sodium content of the diet from 2 to 3.6 g/kg DM. No effects on milk yield or SCC were found, but the sodium supplement reduced Staphylococcus aureus contamination of the milk, but not the proportion of milk samples infected with Escherichia coli. It was concluded that the optimum dietary sodium concentration for maximum milk yield was greater than the published requirements, and that substantial increases in sodium intake above current requirements also reduced milk SCC.