In the purpose to provide further information in respect of the relationship between metabolism and post
partum (PP) ovarian activity resumption in dairy cows, the aim of the present study was to characterize
the energy balance (EB) and leptin, NEFA and IGF-I plasma levels in Swedish Red and White (SRW) cows
with and without ovarian activity re-initiation within 7 weeks PP. The study was conducted on 12
primiparous SRW cows fed the same diet as total mixed ration for ad libitum intake. The EB was calculated
weekly from parturition until seven weeks PP. Blood samples were collected weekly from one week
before until 7 weeks after calving for leptin, NEFA and IGF-I analysis. For progesterone (P4) analysis, blood
samples were collected two times per week from parturition until the end of the study. P4 profile was
used in addition to the clinical examination to detect cows with and without ovarian activity resumption.
The clinical and ultrasonographic examination, coupled with P4 profile analysis showed the resumption of
ovarian activity within 7 weeks after calving in 8 (group A) and no ovarian resumption in 4 cows (group
B). No significant differences were detected in the whole period of observation in the amount of milk
production between the two groups, while the mean milk protein content was significantly lower in group
B at the third week PP. The calculated EB was negative in both groups in the first three weeks after calving,
but more marked in group B. NEFA and Leptin plasma levels did not show significant differences between
the two groups. In conclusion, the results of the present study showed that, when low milk producing
primiparous cows are concerned, no significant differences in BW loss, milk yield, EB and leptin and NEFA
plasma levels between the cows with and without resumption of ovarian activity within 7 weeks post
partum were seen. However, significantly higher IGF-I levels in the first two weeks after calving were found
in cows with post partum ovarian activity resumption, highlighting the important role of IGF-I as sensitive
signal between metabolism and reproduction.
