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Influence of feeding approaches, adaptation length, and direct-fed microbial inclusion on animal temperament and relationships with growth performance, feeding behavior, and carcass characteristics in feedlot steers
Crossbred steers (391±2.8 kg, n=113) were assigned randomly to a 2x2x2 factorial arrangement of treatments (n=14 or 15 per treatment) to determine the effects of conventional vs. natural feeding approaches (using monensin, tylosin, trenbolone acetate and estradiol vs. none), grain adaptation length (14 vs. 28 d), and direct-fed microbial supplement (DFM; with or without) containing live microorganisms and fermentation extracts. Diets consisted of corn, dried corn distillers grains with solubles, and 10% forage (hay and corn silage). Individual feed intake and feeding behavior was monitored using the Insentec roughage intake control system (Inesentec, B. V., Marknesse, the Netherlands). Weights were taken on two consecutive days at the beginning and the end of the trial and once every 28 d throughout. While weighing, temperament data was taken using chute score (1=calm to 5=struggling continuously), exit score (1=walk to 4=gallop), and exit velocity (m/s). Chute score, exit score and exit velocity were negatively correlated with HCW and marbling (P<0.05). Temperament scores did not have significant correlations with feeding behavior or growth performance. Average DMI was positively correlated with time spent at feeder, number of visits, ADG, HCW, yield grade, marbling, and back fat (P<0.05). Time spent at feeder was positively correlated with number of meals, ADG, and HCW (P<0.05). Number of visits per day was negatively correlated with G:F (P=0.008). The number of meals per day was negatively correlated with marbling (P=0.05). Average daily gain was positively correlated with G:F, HCW, and back fat (P<0.05) and negatively correlated with KPH (P=0.05). Steers that were adapted over 14 d had higher chute scores, exit scores, and exit velocities than steers on the 28 d adaptation treatment. Conventionally fed steers had increased exit velocities (P=0.005) compared to naturally fed steers. Chute scores and exit scores decreased over the 140 d trial while exit velocities increased (P<0.001). Temperament may be associated with differences in HCW and marbling. Approaches and adaptations to feeding finishing diets may have an impact on temperament of cattle in the feedlot.
Keywords: Direct-fed microorganism, finishing cattle, implants, ionophores, temperament