This study evaluated the associations of temperament with body weight (BW) and body condition score (BCS) change, ovarian structures, and inflammatory response in grazing Nellore cows assigned to a fixed-time artificial insemination (FTAI) protocol. Forty multiparous cows were kept on pasture and offered free-choice access to mineral/vitamin supplementation and FTAI on d 0. Individual temperament scores (1-5) were assessed in the squeeze chute on d -30, where 1 are animals extremely calm and 5 extremely excitable. Cows with a chute score ≤ 3 were classified as "calm", and > 3 as "excitable". The BW and BCS were evaluated on d -30, 0 and 30, ovarian structures on d 0 and 14, and blood samples collected on d -30, -11, 0, 7, 14, 21 and 30. Excitable animals tended to have less (P = 0.09) BCS and lose more (P = 0.09) BCS from d -30 to 0. Temperament did not affect (P ≥ 0.12) BW and BW change. Excitable animals tended (P ≤ 0.10) to have smaller dominant follicles, corpus luteum (CL) diameters and CL volumes. Temperament did not affect (P ≥ 0.14) plasma concentrations of haptoglobin and ceruloplasmin, but excitable animals had less (P = 0.04) plasma concentrations of progesterone on d 7 and 14. Thus, excitable cows had less plasma progesterone concentrations and tended to have a greater decrease in body condition score and had smaller dominant follicles and corpus luteum size.
Several factors may influence the reproductive performance of beef cows, and one of them is temperament (Cooke et al., 2009a, 2011, 2017; Kasimanickam et al., 2014; Rueda et al., 2015). Animal temperament can be defined as a response to environmental or social stimuli (Haskell et al.,2014). Potential causes of the excitable temperament in cattle include genetics, inadequate facilities, and improper handling. According to Rueda et al. (2015), handling excitable cows in the squeeze chute increases the incidence of aggression to the handlers, insemination time, likelihood of accidents, contamination in the perineal region during artificial insemination (AI), and reduces the technician AI efficiency. In addition, excitable cows have less pregnancy percentage following fixed-time AI (FTAI; Cooke et al., 2009a, 2011, 2017; Kasimanickam et al., 2014; Rueda et al., 2015). Temperament can negatively affect reproductive performance by several mechanisms, such as decreasing dry matter intake (DMI) and nutritional status (Bruno et al., 2016), and increasing the stimulation of the hypothalamic-pituitary-adrenal axis leading to greater circulating concentrations of cortisol (Curley Jr et al., 2008) and acute phase proteins (Cooke et al., 2009a, 2012; Francisco et al., 2015). Kasimanickam et al. (2014) observed that temperament also impacts ovarian parameters, and is negatively correlated with follicles number and size of the dominant follicle. We are unaware of studies evaluating the associations of temperament with corpus luteum diameters/volumes in purebred Bos indicus cows. We hypothesized that the excitable temperament in the squeeze chute can mainly reflect in reduction of the size of the corpus luteum and in its production of progesterone. Thus, the objective of this study was to evaluate the associations of temperament with body weight (BW) and body condition score (BCS) change, ovarian structures and inflammatory response of grazing Nellore cows synchronized to FTAI