Factors affecting plasma prolactin concentrations throughout gestation in high producing dairy cows

Area of Science:

• Veterinary Medicine
• Reproductive Physiology
• Dairy Science

Background:

• Plasma prolactin concentrations are crucial indicators of reproductive status in dairy cows.
• Factors such as photoperiod, season, and infection can influence hormonal profiles during gestation.
• Neospora caninum is a significant cause of abortion in cattle, impacting herd productivity.

Purpose of the Study:

• To investigate the relationships between plasma prolactin and various factors during dairy cow gestation.
• To assess the impact of photoperiod, season, milk production, Neospora caninum seropositivity, twin pregnancy, PAG-1, progesterone, and cortisol on prolactin levels.
• To explore differences in prolactin concentrations between aborting and non-aborting cows, particularly in relation to Neospora caninum infection.

Main Methods:

• Plasma prolactin, PAG-1, progesterone, and cortisol levels were measured throughout gestation in lactating dairy cows.
• Pregnancy was monitored using ultrasonography and rectal palpation.
• Statistical analysis (GLM repeated measures) was employed to identify associations between prolactin and other factors.

Main Results:

• High prolactin concentrations were associated with high cortisol, high PAG-1, Neospora caninum seropositivity, positive photoperiod, twin pregnancy, and low progesterone.
• An interaction was observed where high-producing cows with high cortisol had the highest prolactin levels.
• Significantly lower prolactin levels were found in aborting Neospora-seropositive cows compared to non-aborting ones on Day 210 of gestation.

Conclusions:

• Positive photoperiod and Neospora caninum infection increase plasma prolactin concentrations during gestation.
• Reduced prolactin in aborting cows suggests a potential protective effect against Neospora caninum infection.
• Prolactin may play a role in mitigating the effects of Neospora caninum in pregnant dairy cows.