Systems of Crossbreeding – Experiences in Research & Do’s and Don’ts R. Mark Enns Colorado State University

Overview Crossbreeding systems Research experience and recommendations

Factors to consider when selecting a system Amount of hybrid vigor –Two types Individual –For weaning weight – 5% –For weaning rate – 0% Maternal –For weaning weight – 6% –For weaning rate – 8% –Total Weaning wt per cow exposed – 18% Kress and MacNeil, 1999

Factors to consider when selecting a system Amount of hybrid vigor –Two types Individual Maternal Breed complementarity Consistency of product Replacement generation – males and females Simplicity of the system –Dr. Gosey calls “management ease” test Accuracy of evaluation –In the future? Assumption: Have appropriately selected the breeds to go into the system Bourdon, 2000

The Key Find a system that is beneficial for the specific production situation and whose downside is relatively minor.

Examples

3 breed spatial rotation A higher proportion Breed B A higher proportion Breed C X Breed A X A higher proportion Breed A Breed B X Replacement

Attributes Hybrid vigorIncreased hybrid vigor Breed Complementaritypotential Consistencyinversely related to complementarity

Attributes Replacementsyes Genetic evaluationlikely Simplicitylow

3-Breed Rotation in Time Most females a higher proportion Breeds B and C X Breed A Most females a higher proportion Breeds C and A X Breed B Most females a higher proportion Breeds A and B X Breed C Most females a higher proportion Breeds B and C X Breed A Time Replacement and remaining older females

Attributes of Rotations in Time Hybrid Vigor--somewhat reduced Breed complementarity, consistency of performance, replacement considerations, and accuracy of genetic prediction Simplicity – greatly increased

Rotations in time designed for small producers Weakness:Consistency of decisions over time

Terminal Sire Systems Maternal-breed females are mated to paternal-breed sires Goal: to efficiently produce progeny that are especially marketable

Static Terminal System Purchased F 1 AxB maternal females Breed C terminal X F 1 C x (A x B) market offspring

Key Consider the factors that are most important to the producer –Give the program the greatest probability of success

Comparison of systems Crossbreeding SystemHVCompConstEaseACC Spatial Rotation+ - Varies + Rotation in Time+ - varies+++ Terminal system (purchase replacement ♀) Composite system (already formed) Assumption: All of the above produce their own replacement females except the terminal system Bourdon, 2000

Numerous other systems Only limited by the breeder’s creativity

Rotation/Terminal Systems X A higher proportion Breed B A higher proportion Breed A X Breed B Replacement Excess (often older) females Male offspring sold Male offspring sold F 1 C x (A/B) market offspring

Composite/Terminal System Younger maternal composite females X Maternal composite Older maternal composite females X Terminal Breed F1 market offspring Male offspring sold

More systems than can be outlined in a hour

Research – Do’s and Don’ts

Heterosis will not overcome poor breed choice –Advantage of Zebu cross dams in Florida for pregnancy rate was 5.8% units over that in Nebraska (1.8% units) Olson et al., 1991 –Holstein Hereford cross had a 23% advantage over HA for calf weaned/cow-exposed, and Brahman cross a 13% advantage (Setshwaelo et al., 1990) Cross must be appropriate for its production environment –Drs. Kress and Franke will discuss next week.

Continous use of the same breed will result in loss of heterosis –Dr. Gosey 3 generations of using Angus bulls on F1 cows resulted in a loss of 87% of hybrid vigor

Crossbreeding works Increases in lifetime production due to maternal heterosis have been estimated at up to 1.44 calves when calving first as 2 year olds (Cundiff et al., 1992) defined as cumulative 200 day weight Nunez et al., (1991) crossbred cows had lower probabilities of being culled than straightbreds (Angus, Hereford, Shorthorns) Davis et al. (1994) reported F1 cows averaged 1.2 year longer lifespan than straightbred cows –Net profit per cow exposed increased ~$75

Do not be tempted to retain replacement females from terminal sire mating systems in restrictive environments Energy consumed to produce calf weight varies between breeds –Jenkins et al. (1991) In most environments –At low to moderate resource availability the British breeds tend to be most efficient at converting intake into calf weight –At higher levels of availability (intake) the continental breed tend be the most efficient Jenkins et al. (1994)

Develop a plan and stick to it, otherwise … Using Dr. Gosey’s example –15/16 Angus Realized that have lost heterosis, so go back to Hereford bulls –Use bulls for 3 years and 15% female replacement rate, 1 year after last crop born 38% of females are now F1 62% of females are still Angus

38% are now F1 and 62% are still Angus –So switch to a 3 rd breed for 3 years A year after the last crop is born –24 % are HxA –38% are Angus –39% are new cross Point: –Without a plan and some determination to maintain focus can get quite the collection of different breeds Influences marketability

Choose not only breeds but appropriate animals within breeds Colorado State University experience –Generalization: Black baldy cows are adapted to the eastern Colorado shortgrass prairies –Can we identify another genotype that might be adapted to that environment but bring more performance in the feedlot and on the rail?

Approach Given: Hereford x Angus cross works well –Choose a breed from which we could find animals with similar milk production levels –Continental breed

Approach Given Hereford Angus cross works well –Choose a breed from which we could find animals with similar milk production levels –Continental breed Limousin –HxA and LxA females

EPD Guidelines BWYWMilk Hereford≤ to 708 to 15 Percentiles20%55% to 30%80% to 45% On NALF Scale≤ to to 14.6

2003 CalvesNo.WWCalf Age Adj WW Hereford x Angus Lim-Flex

2003 CalvesNo.WWCalf Age Adj WW Hereford x Angus Lim-Flex CalvesNo.WWCalf AgeAdj WW Hereford x Angus LimFlex

No.Weight Frame Score Hereford x Angus Lim-Flex Difference19-.5 Yearling performance –Weight and Frame Score

WeightFS Pelvic Area Hereford x Angus Lim-Flex Difference19-.5 Yearling performance

% Bred 1 st 21days Total % Bred% Open Hereford x Angus Lim-Flex Difference Breeding performance –60 Day breeding season

After 1 st calf, all rebred except 1 Although preliminary, we believe we may have another adapted F1 cross appropriate to the eastern Colorado environment

Breed Averages LimFlex CW – 793 REA – YG – 3.27(2.6) YG4 – 0% CAB – 40% $/cwt - $ Last 83 days Avg Daily Intake – 30.0 ADG – 3.06 $/hd – $ Angus CW – 762 REA – YG – 3.45(3.4) YG4 – 40% CAB – 20% $/cwt - $ Avg Daily Intake – 31.7 ADG – 3.79 $/hd – $

Do’s and Don’ts Choose a system that has a high probability of success –simplicity Make appropriate breed choice Make appropriate choice from within breed Stick to the plan to avoid “mongrelization” Commercial producers should crossbreed

R. Mark Enns Dept. of Animal Sciences Colorado State University Fort Collins, CO Phone: