Effect of dry period length on NEFA and IGF-I plasma concentrations and postpartum ovarian activity resumption in dairy cows

The current study was carried out to examine the effects of dry period duration on NEFA and IGF-I plasma concentrations and postpartum ovarian activity resumption in dairy cows. Twenty-five pregnant Friesian cows (second and third lactation) were randomly assigned to one (standard dry period, 9 weeks, group C, n = 12) of two (short dry period, 5 weeks, group T, n = 13) treatments. Blood samples for NEFA and IGF-I analyses were collected once a week during the last 5 weeks prepartum and the first 14 weeks of lactation. Milk whey collection (twice/week) for progesterone analysis began 2 weeks after parturition and was used to detect ovarian activity resumption (at least three consecutive samples with P4 # 300 pg/mL). The data obtained were analyzed by ANOVA for repeated data (mixed) and GLM of the SAS statistical package. Short dry periods reduced milk production (26.55 vs. 27.55 kg/day; P # 0.01), without modifying milk quality. The mean interval from calving to first postpartum cycle was shorter in group T than in group C (34.5 vs. 46.9 days, P # 0.01). No differences were found in NEFA plasma concentrations between groups either before or after calving, while IGF-I circulating concentrations were higher in group T than in group C during both the dry period and the first 14 weeks of lactation (P # 0.01). In conclusion, the reduction in the dry period had a positive impact on metabolic balance and time of postpartum resumption of ovarian activity.