Relationships between milk insulin-like growth factor-I (IGF-I) concentration and body condition score with reproductive performance and milk yield in Jersey cows

Introduction - One of the most important hormones affecting reproductive and milk yield is insulin-like growth factor I (IGF-I). IGF-I is closely related to nutritional status and the post-partum ovarian activity in dairy cows. It also stimulates milk synthesis and its secretion. Body condition score (BCS) is a useful management tool routinely used to predict body fat storage and energy status in dairy cows and has a strong influence on milk production and reproductive efficiency for the upcoming lactation after calving. Many publications have been available on BCS and serum or plasma IGF-I in Holstein cows. However, the information regarding the milk of Jersey cows has been limited. Therefore, further studies have been required to reveal the effect of IGF-I and BCS on reproduction and milk yield traits of this breed. Aim - This study was conducted to investigate the relationships between milk IGF-I concentration and body condition score (BCS) with reproduction performance and milk yield of Jersey cows raised at Karakoy State Farm in Samsun. Materials and methods - The mean milk IGF-I concentration and BCS were calculated by taking the mean of the three lactation periods (70 +/- 14, 140 +/- 14, and 210 +/- 14 days) using the repeated measures analysis procedure. The enzyme-linked immunosorbent assay (ELISA) method was applied for milk IGF-I analyses. BCS was assessed using a scale of 1 to 5 points with 0.25 unit increments. Results and discussion - The effects of stage of lactation on IGF-I and BCS classes were significant (P<0.001). The effects of mean IGF-I concentration on interval calving to first service (ICFS) (0.041), calving interval (CI) (0.042), and dry period (DP) (0.030) were found statistically important. Significant correlations were also determined between mean IGF-I and ICFS (-0.184), CI (-0.183), or lactation length (LL) (-0.155), and ICFS, CI, and LL were found to be shorter in cows with higher IGF-I. Both reproduction and milk yield traits were not affected by BCS. Conclusions - The results of the study revealed that milk IGF-I concentration may be used as an indicator to detect reproduction characteristics of dairy cows.