Abstract The increased DMI and poorer feed conversion of beef × dairy (BxD) crossbred cattle throughout the finishing phase suggest that their maintenance energy requirements are greater than those of native beef cattle. Our objective was to derive a performance-based maintenance energy coefficient for finishing BxD cattle and validate its accuracy using synthetic populations of feedlot cattle. Published BxD feedlot trials (steers, n = 7; heifers, n = 1; mixed pens = 2) were used to calculate a weighted adjusted final body weight (AFBW) and maintenance energy coefficient (MQ). All performance and carcass variables used in the calculations were weighted by their inverse of the standard error of the mean squared. With a weighted estimate of each contributing variable, a common AFBW and MQ were calculated, being 564 kg and 452 kg for steers and heifers, respectively, and 0.086 Mcal/W0.75 for both steers and heifers. The AFBW was used to determine equivalent BW (EqW). Retained energy (RE, Mcal/d) was determined according to: RE = 0.0557EqW × ADG1.097. The MQ (Mcal/W0.75) was determined according to: (DMI-(RE/tabular NEg))×tabular NEm/W 0.75. The synthetic datasets were multivariate normal populations created from performance close-out information from commercial feedlots in the High Plains region of the United States. Using the synthetic steer and heifer datasets, the calculated BxD MQ (0.086 Mcal/W0.75, MQBD) was compared to the native beef MQ (0.077 Mcal/W0.75, MQB), and the dairy MQ (0.084 Mcal/W0.75, MQD), in their ability to predict growth and intake. Performance-based NEm, NEg, and expected DMI were calculated and compared to the expected values based on their respective observed-to-expected ratio (OBS:EXP). The ratios were sorted into 5 groups, representing 90%, 90% to 94.9%, 95% to 105%, 105.1% to 110%, and 110% of the expected value. A Chi-square test was used to evaluate the frequency of observations within each group. The MQBD resulted in the most accurate estimates of DMI, NEm, and NEg, with the average ratios for OBS:EXP falling within 2% of the expected value, compared to 7% and 3% for MQB and MQD respectively. Expected DMI calculated using the derived MQBD resulted in 60.14% of observations falling within 5% of the actual DMI, compared with 38.95% and 57.24% (P 0.01) for MQB and MQD, respectively. Similarly, performance-based NEm using MQBD, showed 68.01% of observations were within 5% of the expected NEm, compared with 50.69% and 66.35% (P 0.01) for MQB and MQD, respectively. Results from this analysis indicate that BxD feedlot cattle have a 12% greater maintenance energy requirement than beef cattle, and 2.5% greater than dairy cattle. The application of this performance-derived MQ could allow for more accurate predictions of growth performance by BxD cattle than the current models used in feedlot cattle.
Rehder et al. (Wed,) studied this question.