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Performance, feed efficiency, and carcass composition of growing beef dairy steers.

J. Johnson




Performance, feed efficiency, and carcass composition of growing beef dairy steers.
J. Johnson*, G. Toro, C. Lundgren, A. Arnett, N. Deeb. STgenetics Navasota, TX.

The era of sexed semen and genomics along with changing packer demands has created a perfect opportunity for dairymen to add value to terminal dairy calves by utilizing beef sires on low genomic dairy females. Between 2017 and 2018, domestic sales of dairy semen dropped by more than 1.3M straws while an astonishing 1.5M additional straws of beef semen were sold. Given the impact beef � dairy calves will have on the industry, the objective of this study was to evaluate the performance, feed efficiency, and carcass composition of beef � dairy steers. Performance, DMI, and final ultrasound measurements of back fat depth, LM area, and intramuscular fat were collected on 18 AN � HO and 32 AN � F1 JE-HO steers during a 70-d period at our research farm in Texas. RFI was calculated from linear regression of DMI on mean BW0.75 and ADG. Effects of dam breed and RFI class were evaluated using a mixed model which included the random effect of pen and fixed effects of dam breed, RFI class, and dam breed � RFI class. ADG and DMI ranged from 1.12 to 1.94 kg/d and 7.98 to 12.3 kg/d, averaging 1.55 and 9.83 kg/d, respectively. Steers born to HO dams had higher (P < 0.05) initial and final BW, ADG, and DMI than calves of F1 JE-HO dams, but no differences were observed across dam breeds for feed efficiency or carcass composition traits. As expected, low-RFI steers consumed 11% less feed (9.50 vs. 10.68 kg/d; P < 0.05) and had 14% higher (P < 0.05) G:F than their high-RFI counterparts with no differences (P > 0.05) observed in BW or ADG. Ultrasound measurements did not differ (P > 0.05) across RFI classes and no significant dam breed by RFI class interactions were observed. Results from this study provide information regarding the expected performance of beef � dairy calves and demonstrates opportunity to identify elite beef sires based on performance and feed efficiency. The practice of using beef sires on dairy females will not diminish in the near future, however, selection of high-quality sires will become vital for long-term profitability. The data presented is part of an ongoing project to evaluate the performance, feed efficiency, and carcass traits of beef � dairy progeny.

Keywords: beef, dairy, residual feed intake (RFI).