Periparturient plasma prolactin concentrations and maternal behavior in beef cattle

Maternal ability of a cow contributes to calf health and survival, particularly in extensive beef production systems. Improving maternal behavior could mitigate calf wastage, and therefore, characterizing physiological drivers of superior maternal behavior, and its objective assessment thereof are of interest. Whilst the hormonal milieu around calving is complex, past studies have demonstrated that periparturient blood prolactin concentrations are a key component. It is yet to be established whether plasma prolactin concentrations can be used to predict maternal behavior postcalving in beef cattle. Use of radio telemetry and activity meters have afforded novel opportunities for objective behavioral quantification in extensive systems, and therefore the primary objective was to evaluate the relationship between periparturient prolactin concentrations (PPC) and maternal behavior of cows assessed both subjectively via maternal behavior scores (MBS), and objectively via measuring cow-calf contact using proximity loggers. Measures of maternal behavior and PPC were also compared against transfer of passive immunity (TPI) and calf performance measures such as weaning weights (WW) and average daily gain (ADG). It was predicted that periparturient plasma prolactin concentrations are correlated to cow-calf contact in the postpartum period and calf health parameters. Thirty-one multiparous Angus cows (age 9 - 11 years) were selected after a single-sire controlled mating period. A month prior to the expected calving dates, cows were fitted with ultra-high frequency proximity logger collars provided by SIRTRACK® (now LOTEK, Havelock North, NZ) and had blood collected for assessment of PPC. On the day of calving, calves were fitted with proximity logger collars and MBS was recorded based on the cow’s response to calf handling. Throughout the calving period, cows were yarded, and blood was continually collected every second or third day. A commercial bovine prolactin ELISA kit (AssayGenie) was used to measure PPC. Area Under the Curve (AUC) analysis was performed to quantify PPC, which was then used to assess correlation with MBS and cow-calf proximity logger contact data. The loggers recorded between 702 - 1,893 contacts (mean 1,394, SD 294, ± SEM 54) and between 47,884 - 350,360 seconds of total contact time (mean 178,694, SD 97,366, ± SEM 17,777), Cow-calf contact over 12 days was negatively correlated with PPC (r = -0.45; p = 0.012). Precalving PPC was also weakly negatively correlated with MBS (r = -0.31; p = 0.043). Neither cow-calf contact nor MBS were correlated (p > 0.05) with calf performance (WW, ADG) or health (Calf Vigour Scores, serum total protein 24 - 72 hours postcalving). Average weaning weights of calves grouped according to their dams’ assigned MBS at birth tended to be greater for higher MBS, although not significant (p > 0.05). Overall, results indicated that PPC could influence cow-calf interactions and MBS. However, further research is warranted to validate these results, and to evaluate the efficacy of using cow-calf contact data as an objective measure of maternal behavior. Keywords: Maternal behavior, beef cattle, calving, prolactin, proximity logger, calf health