Prepartum negative energy balance (NEB) in dairy cows is caused by the increased demand of energy due to the rapid growth of fetus and decreased feed intake. However, the etiology of prepartum NEB and its association with postpartum NEB are not well understood. This study was conducted to determine the association between pre- and postpartum NEB in dairy cows. Cows were allocated into four groups based on the blood glucose (GLU) and nonesterified fatty acid (NEFA) profiles at 2-0 wk prior to calving: Group I (n=23; low GLU, high NEFA); Group II (n=30; low GLU, low NEFA); Group III (n=15; high GLU, high NEFA) and Group IV (n=24; high GLU, low NEFA). GLU showed lower levels in Groups I and II compared to Groups III and IV at 2 to 4 wk after parturition, whereas NEFA was higher in Groups I and II compared to Group IV at 0-2 and 2-4 wk after parturition. Aspartate aminotransferase (AST) in Group II was higher than that in Groups III and IV at 2-4 wk postpartum, and g-glutamyl transferase (GGT) was higher in Group I compared to Group II at 2-4 wk postpartum. In total, we found a negative correlation between GLU and AST and a positive correlation among NEFA, AST and GGT after parturition. These results suggest that NEB at 2-4 wk postpartum is closely associated with NEB at 2-0 wk prepartum, and high postpartum NEB is associated with decreased liver function.

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Subclinical ketosis in dairy cattle is associated with postpartum negative energy balance (NEB) and displaced abomasum, and it may develop into clinical ketosis. However, its incidence, causative factors and blood profiles other than ketone bodies are not well defined. We examined various blood parameters in 150 dairy cattle (52 with subclinical ketosis, 23 with clinical ketosis and 75 in good condition) in order to understand the pathophysiology of subclinical ketosis. Cows with subclinical ketosis showed lower blood glucose (GLU) and higher β-hydroxybutyric acid (BHB), non-esterified fatty acid (NEFA), triglyceride (TG), β-lipoprotein, total protein, aspartate aminotransferase (AST) and γ-Glutamyl transferase (GGT) compared to healthy cows. In contrast, they showed higher GLU, HDL-cholesterol, total cholesterol and phospholipids and lower BHB, NEFA, TG and AST compared to cows with clinical ketosis. In cows with subclinical ketosis, BHB was positively correlated with NEFA and AST, while a negative correlation was found between BHB and GLU and between GLU and AST. These data suggest that cows with subclinical ketosis have extensive mobilization of body fat and decreased liver function due to NEB compared to healthy cows, although their duration of NEB is shorter and NEB and liver dysfunction are milder than those in cows with clinical ketosis.

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Bacteriological culture of milk was performed in a farm, where an automatic milking system had been implemented three years previously, to determine the cause of increased somatic cell counts in bulk milk. Staphylococcus aureus (SA), the causative agent of contagious mastitis, was detected at a high rate; 76% of all the cows tested (19/25) and 43% of all quarters (41/96) were positive for SA. In eleven cows, infection of SA had spread to multiple quarters.
Generally, contagious mastitis caused by SA is controlled by isolation and separate milking of infected cows or discarding the milk from infected quarters. However, automatic milking systems usually require an uninterrupted operation of a single milking machine and thus do not allow such measures to be taken. In the farm tested in this study, we recommended a combination of permanent drying off, culling, lactation period treatment and simultaneous dry cow therapy after the early dry period. We found that when contagious mastitis occurs, it is difficult to control the infection in cows milked with the automated system. Therefore, to prevent the invasion and spread of SA in farms using automatic milking systems, bacterial culture tests should be conducted periodically or when there is an increase in somatic cell counts. If cows are infected, they should be culled from the herd as early as possible.

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