Abstract
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.
Highlights
After parturition almost every cow experiences a period with high energy requirement related to milk production, frequently associated to an insufficient feed intake
Significantly higher insulin growth factorI (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
Buckley et al [25] and Roche et al [26] underlined that body weight (BW) variation during postpartum period has an important role on reproductive performance; a more pronounced loss of BW was observed in the cows that did not resume ovarian activity compared to the cows with ovarian activity resumption within seven weeks postpartum, but the statistical analysis did not evidence differences
Summary
After parturition almost every cow experiences a period with high energy requirement related to milk production, frequently associated to an insufficient feed intake. This situation leads to the well known negative energy balance (NEBAL), that seems to be the most important factor affecting the reproductive efficiency after calving. The resumption of ovarian activity seems to be related to the metabolic status of the cows after calving. Several hormones and metabolic parameters have been proved to play a role in the relationship between energy balance and post partum reproductive efficiency in dairy cows. Leptin, non-esterified fatty acids (NEFA) and IGF family factors seem to be involved in the re-initiation of ovarian activity in post partum dairy cows
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