A field study on glucose, non-esterified fatty acids, beta-hydroxybutyrate and thyroid hormones in dairy cows during the breeding period in Fars province, Iran

It was hypothesized that under apparently good management practices in dairy farms, some cows may not be metabolically perfect during the breeding period and this may affect their performance. This study was conducted to assess probable metabolic drawbacks in mid-lactation dairy cows affecting their performance. Thirty-seven clinically healthy Holstein cows were assessed for plasma concentrations of glucose, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), thyroxin (T4), and tri-iodothyronine (T3) on days 60, 90 and 120 of lactation. The relationships of the measured analytes with some performance indices were also studied. Continuous declines in plasma glucose (within reference values; P