Interactions between nutrition, blood metabolic profile and milk composition in dairy goats

The aim of this study was to investigate changes in the concentrations of blood and milk constituents of dairy goats under the effects of stable diet and grazing during lactation from April to June. The experiment was carried out on 10 dairy goats fed a ration composed of concentrate mixture, sugar beet silage and grass hay during winter season (stable diet), and pasture season. Jugular blood and milk samples were taken from all goats during lactation months of April through June at one-month intervals. The blood concentration of total protein (TPP), urea, glucose, triacylglycerols, total ketones, serum non-esterified fattty acids (NEFA), Na, K, Ca, inorganic phosphorus (Pi), Cu, Zn, aspartic amino transferase (AST), gamma-glutamyl transferase (GGT), creatine kinase (CK), lactate dehydrogenase (LDH), pH and haemoglobin (Hb) were determined. The measurements of milk contents of fat, protein, casein, urea, lactose, citric acid, total ketones, pH and titratable acidity were performed, too. The results showed variations in serum NEFA, plasma triacylglycerols, Pi , plasma CK and plasma urea during the first months of lactation. In addition to milk levels of total ketones, citric acid, fat and urea were changed, Highest correlation coefficients were found between plasma and milk urea (r = 0.88; p < 0.001). However, there were correlations between milk fat, plasma urea, blood haemoglobin, plasma glucose, plasma triacylglycerols, blood total ketones and plasma Mg. Citric acid in milk was positively correlated with plasma glucose (r = 0.46; p < 0.01) and negatively with plasma total protein (r = - 0.31; p < 0.05). In conclusion, high concentration of serum NEFA, blood total ketones and plasma urea in addition to the decline in the milk concentrations of citric acid and protein, along with increase in milk concentrations of ketone bodies and urea during the first lactation months were observed and may be associated with corresponding energy deficit and induce considerable metabolic changes in dairy goats.