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Measures of temperament have been previously related to gain and intake in beef cattle. Intake effects may be partially mediated through social interactions in that some temperament measures may directly relate to social dominance behavior. To examine the relationships between temperament, growth, and social dominance behavior, thirty-two crossbred steers were used in a 56-d randomized complete block design experiment with a 2 × 2 factorial treatment structure. Temperament treatments (assigned on d −7) were chute exit velocity (EV; slow vs. fast) and objective chute score (OCS; low vs. high), a novel temperament measure, defined as the coefficient of variation of recorded weight values collected at five Hz for 10 s while an animal’s head was restrained in a chute. Electronic ear tags with accelerometers were used to continuously measure animal activity. Social dominance behaviors were quantified using video records of 2 h intervals directly following feeding for d 1–13. Dominance was calculated as average dominance index and David’s score. Jugular blood samples were collected to analyze antibody response to leptospirosis vaccines. There were no EV by OCS interactions (P ≥ 0.23) for average daily gain (ADG) or antibody titers. High OCS steers gained 0.26 kg/d more than low OCS steers (P < 0.01) and slow EV steers gained 0.12 kg/d more than fast EV steers (P = 0.02). Slow EV animals had an increased antibody response compared with fast EV animals (P = 0.05). Ranking in the dominance hierarchy was influenced by an EV × OCS interaction (P < 0.02), but there was not a linear relationship between dominance ranking and ADG. Low OCS steers tended to have higher daily activity counts than high OCS steers (P = 0.11), and fast EV steers had higher (P = 0.08) activity counts than slow EV steers. In conclusion, our two temperament-related measures, EV and OCS, were independently related to differences in ADG. Although dominance ranking was significantly related to the interaction of these two temperament measures, it was not linearly related to ADG. Alternatively, differences in accelerometer-based activity counts among temperament groups did correspond with trends in growth responses. [ABSTRACT FROM AUTHOR]

Ergot alkaloids in endophyte-infected grasses inhibit prolactin (PRL) secretion and may reduce milk production of cows consuming these grasses. We investigated the effects of consuming endophyte-infected fescue seed during late lactation and the dry period on mammary growth, differentiation, and milk production. Twenty-four multiparous Holstein cows were randomly assigned to 3 treatment groups. Starting at 90 ± 4 d prepartum, cows were fed endophyte-free fescue seed (control; CON), endophyte-free fescue seed plus 3×/wk subcutaneous injections of bromocriptine (0.1 mg/kg of body weight, positive control; BROMO), or endophyteinfected fescue seed (INF) as 10% of the diet on an as fed basis. Although milk yield of groups did not differ before treatment, at dry off (-60 d prepartum) INF and BROMO cows produced less milk than CON. Throughout the treatment period, basal concentrations of PRL and the prepartum increase in plasma PRL were reduced in INF and BROMO cows compared with CON cows. Three weeks after the end of treatment, circulating concentrations of PRL were equivalent across groups. In the subsequent lactation milk yield was not decreased; in fact, BROMO cows exhibited a 9% increase in milk yield relative to CON. Evaluation of mammary tissue during the dry period and the subsequent lactation, by quantitative histology and immunohistochemical analysis of proliferation markers and putative mammary stem or progenitor cell markers, indicated that feeding endophyte-infected fescue seed did not significantly affect mammary growth and development. Feeding endophyte-infected grasses during the dry period may permit effective utilization of feed resources without compromising milk production in the next lactation. [ABSTRACT FROM AUTHOR]