@article{lamb_tess_robison_1993, title={EVALUATION OF MATING SYSTEMS INVOLVING 5 BREEDS FOR INTEGRATED BEEF-PRODUCTION SYSTEMS .4. ACCOUNTING FOR VARIABILITY AND GENETIC TRENDS}, volume={71}, ISSN={["0021-8812"]}, DOI={10.2527/1993.713587x}, abstractNote={Computer models were used to simulate integrated cow-calf-feedlot production systems. Angus (A), Charolais (C), Hereford (H), Limousin (L), and Simmental (S) purebreds and two- and three-breed rotational crossbreds were included. Models were deterministic and based on data reported primarily from the 1970s. Variation in carcass weights were determined to predict distributions of carcass weights and values for 272- to 318-kg carcasses. Data were updated to a 1984 base by increasing birth, weaning, yearling, and mature weights to account for genetic trends within breeds. Two slaughter end points were considered: 288-kg carcass weight and low Choice grade. At low Choice grade, accounting for variation in carcass weights around the 272- to 318-kg target weight increased the estimated efficiency of A and AH crosses (input costs/carcass value), whereas at the 288-kg end point, efficiency rankings among other breed combinations were relatively unchanged. Including genetic trends resulted in increased estimated efficiencies among breed combinations with previously underweight carcasses at low Choice (A and AH), measured either as input costs/carcass weight or lean weight values. Within breeds, accounting for genetic trends and variation for weights caused breeds to be ranked differently when evaluated at low Choice.}, number={3}, journal={JOURNAL OF ANIMAL SCIENCE}, author={LAMB, MA and TESS, MW and ROBISON, OW}, year={1993}, month={Mar}, pages={587–594} }
 @article{lamb_tess_robison_1992, title={EVALUATION OF MATING SYSTEMS INVOLVING 5 BREEDS FOR INTEGRATED BEEF-PRODUCTION SYSTEMS .2. FEEDLOT SEGMENT}, volume={70}, ISSN={["1525-3163"]}, DOI={10.2527/1992.703700x}, abstractNote={Computer models were used to simulate the feedlot segment of an integrated beef production system. Five breeds, Angus (A), Charolais (C), Hereford (H), Limousin (L), and Simmental (S), in three mating systems, pure-breeding and two- and three-breed rotational crossbreeding, were evaluated for feedlot and carcass performance. Breed data were taken from the literature. Feeder calves (steers and non-replacement heifers) entered the feedlot at 205 d of age. After a 35-d adjustment period, calves were custom-fed to four slaughter end points: 440 d, 457 d, 288-kg carcass weight, or low Choice. Cattle were fed to requirements (megacalories of ME). Input costs included feed and nonfeed expenses (purchase prices, transportation, yardage, and medicinal fees). Carcass values were $2.65 and $2.54/kg of carcass weight for steer and heifers, respectively, between 272 to 318 kg. Over- or underweight carcasses were discounted $.60/kg. At the 440-d end point, Select grade steer and heifer carcasses were discounted an additional $.22 and $17/kg, respectively. Biological efficiency was measured as megacalories of ME/kg of gain, and economic efficiencies were measured as input costs per kilogram of carcass weight, input costs per kilogram of lean weight, and input costs per carcass value. Continental breed combinations (C and S) were most efficient at age- and weight-constant end points for megacalories of ME per kilogram of gain and for input costs per carcass value and most efficient at all end points for input costs per kilogram of carcass weight and input costs per kilogram of lean weight. British breed combinations (A) were most efficient at a fat-constant end point for megacalories of ME per kilogram of gain and input costs per carcass value. Therefore, choosing breed combinations for feedlots depends on slaughter end point and measures of efficiency.}, number={3}, journal={JOURNAL OF ANIMAL SCIENCE}, author={LAMB, MA and TESS, MW and ROBISON, OW}, year={1992}, month={Mar}, pages={700–713} }
 @article{lamb_tess_robison_1992, title={EVALUATION OF MATING SYSTEMS INVOLVING 5 BREEDS FOR INTEGRATED BEEF-PRODUCTION SYSTEMS .3. INTEGRATED SYSTEM}, volume={70}, ISSN={["0021-8812"]}, DOI={10.2527/1992.703714x}, abstractNote={Angus (A), Charolais (C), Hereford (H), Limousin (L), and Simmental (S) breeds were included in deterministic computer models simulating integrated cow-calf-feedlot production systems. Three mating systems were used: pure-breeding and two-and three-breed rotational crossbreeding. Breed information was taken from the literature. Herd sizes were unrestricted; however, 100 heifers were saved as replacements. Cows were removed for reproductive failure, age (greater than 10.5 yr), or death. Calves produced in the cow-calf segment were fed in a custom feedlot to four slaughter end points: 440 d, 457 d, 288-kg carcass weight, and low Choice. All animals were fed to requirements. Cull cows were slaughtered after weaning. Biological and economic efficiencies improved with crossbreeding; however, rankings of breed combinations depended on how efficiencies were measured (weight, lean, or value basis). Among purebreds, reproductive performance had a large influence on breed rankings at age and weight end points, whereas feedlot performance was important at the low Choice end point. Crossbred combinations involving British (A or H) and Continental (C or S) breeds were more efficient than other crossbred combinations at all end points. However, choosing specific breed combinations for integrated systems depends on slaughter end points, market end points (weight vs lean), and measures of efficiency (weight, lean, or value basis).}, number={3}, journal={JOURNAL OF ANIMAL SCIENCE}, author={LAMB, MA and TESS, MW and ROBISON, OW}, year={1992}, month={Mar}, pages={714–722} }
 @article{lamb_tess_robison_1992, title={Evaluation of mating systems involving five breeds for integrated beef production systems: I. Cow-calf segment}, volume={70}, DOI={10.2527/1992.703689x}, abstractNote={Deterministic computer models were used to simulate the cow-calf segment of an integrated production system. Angus, Charolais, Hereford, Limousin, and Simmental breeds were included in three mating systems: pure-breeding (PB) or two- (2R) or three-breed (3R) rotational crossbreeding. Breed data were taken from the literature. Herds were evaluated over the production year. Sires represented breed averages and were available from sources outside their herds, and 100 replacement heifers were saved annually. Females in 3R had the highest average energy requirements (8,144 Mcal of ME.cow-1.yr-1) and production costs ($322.31.cow-1.yr-1), and PB females had the lowest average requirements (7,748 Mcal of ME.cow-1.yr-1) and costs ($313.2.cow-1.yr-1). Purebred systems were the least biologically and economically efficient (64.9 Mcal of ME/kg of steer equivalent, $2.35/kg of steer equivalent), respectively, and 3R systems were the most efficient (56.6 Mcal of ME/kg of steer equivalent, $1.95/kg of steer equivalent). On average, 3R systems were more efficient biologically and economically than 2R systems. However, some 2R systems were as efficient as some 3R systems. Crossbred combinations containing Angus and(or) Hereford ranked more biologically and economically efficient than other breed combinations. Conversely, British purebreds ranked more biologically efficient, whereas Continental purebreds ranked more economically efficient.}, number={3}, journal={Journal of Animal Science}, author={Lamb, M. A. and Tess, M. W. and Robison, O. W.}, year={1992}, pages={689} }
 @article{lamb_robison_tess_1990, title={Genetic parameters for carcass traits in Hereford bulls}, volume={68}, number={1}, journal={Journal of Animal Science}, author={Lamb, M. A. and Robison, O. W. and Tess, M. W.}, year={1990}, pages={64} }
 @article{lamb_tess_1989, title={Evaluation of crossbreeding systems for small beef herds: 1. Single-sire systems}, volume={67}, DOI={10.2527/jas1989.67128x}, abstractNote={Stochastic computer models were developed to evaluate crossbreeding systems in small beef herds consisting of one bull, 30 cows and 10 replacements. Six systems were simulated: purebred (PB), two- and three-breed rotations using one bull per year (2R and 3R) or artificial insemination (2RAI and 3RAI) and four-breed composite (COMP). Inbreeding was avoided in all systems. Female replacements were selected from within the herd, whereas sires were purchased. Average heterosis estimates were assumed for calf survival (4.0%), conception rate (6.6%), weaning weight (5.4%, individual; 4.7%, maternal) and mature weight (2.5%). Estimates of calf and dam heterosis were used to calculate performance for calf weights weaned and sold, cull cow weights sold, total weight sold and gross calf, cow and total income. All crossbred systems were superior to the purebred system for weights sold and total income. The 2R and 3R systems utilized 82 to 85% of maximum heterosis available in 2RAI and 3RAI systems, respectively; however, no significant losses were found in weights sold or gross incomes. The COMP system ranked higher than 2R and 2RAI systems for all traits. Increasing the number of breeds (2 vs 3) did not significantly increase total weights or gross incomes. Results demonstrated that practical crossbreeding can be managed easily in small herds and that matings resulting in suboptimal heterosis levels do not cause significant losses in gross income.}, number={1}, journal={Journal of Animal Science}, author={Lamb, M. A. and Tess, M. W.}, year={1989}, pages={28} }
 @article{lamb_tess_1989, title={Evaluation of crossbreeding systems for small beef herds: II. Two-sire systems}, volume={67}, DOI={10.2527/jas1989.67140x}, abstractNote={Stochastic computer models were used to evaluate nine crossbreeding systems in beef herds consisting of two bulls, 50 cows and 15 replacements. Systems examined were: 1) purebred (PB), 2) two- and three-breed rotations using natural service (2R and 3R) or artificial insemination (2RAI and 3RAI), 3) two-breed roto-terminals not exploiting complementarity using natural service (2RT) or AI (2RTAI) and 4) two-breed roto-terminals exploiting complementarity using natural service (2RTC) or AI (2RTCAI). Average heterosis estimates were taken from literature sources. Replacement females were produced within the herd; sires were purchased. Estimates of calf and dam heterosis were used to calculate performance of calf weight weaned and sold, cow and total weights sold and gross calf, cow and total incomes. All crossbred systems were superior to PB for weights sold and income. The natural-service systems (2R, 3R, 2RT and 2RTC) utilized 90 to 98% of the heterosis available in their AI counterparts (2RAI, 3RAI, 2RTAI and 2RTCAI). No differences were found between corresponding natural-service and AI systems for weights sold and incomes. Increasing the complexity of the system did not provide important improvements in traits measured.}, number={1}, journal={Journal of Animal Science}, author={Lamb, M. A. and Tess, M. W.}, year={1989}, pages={40} }