This is the sixth article in a series of brief progress reports on the application Better Polled Cattle of the science of genetics to commercial agriculture. practical plan for gradual change-over from horned to polled herd offered established breeders

P. W. Gregory

California cattlemen could save ap- cass that complicates the problem geneti- in the perfection of beef characteristics proximately a million dollars annually cally. These characteristics-necessary for can make substantial contributions in the if a breed of polled Herefords could desirable beef animals-are conditioned production of a polled breed of superior be developed that would be equal to by multiple factors. It is this phase of the beef qualities. It is most essential, there- horned Herefords in conformation, effi- problem that makes the breeding pro- fore, that none of the good horned ani- ciency of feed utilization, and carcass gram difficult. The problem is to transfer mals that are registered be sacrificed. quality. the polled factor to the superior confor- Horns are a menace in the breeding mation of the horned breed. herd, in the feed lot, and in shipping. The majority of cattlemen hold the Genetic Problem Among horned animals in the feed lot, opinion that the beef qualities of the All that is necessary is for the breeder gains are less uniform. Packers know polled Herefords are inferior to those of to substitute the polled factor for the from experience that carcasses from lots the horned Herefords. horned factor in the horned herd. This of horned animals show more bruises and If it is assumed that the cattlemen are is, in reality, a complicated genetic prob- blemishes than from lots of polled or de- correct, there are at least three reasons lem, but it can be reduced to a relatively horned animals. Since the value of the for the inferiority: simple genetic problem by using the back- carcass is decreased, the packer or feeder 1. The original polled mutants did not cross mating system. It is best suited to protects his interest by paying slightly occur in individuals that had the best a problem in which the objective is to less for horned animals. conformation and beef qualities; transfer a single gene of one population The dairyman uses caustic to eliminate 2. In order to increase the number of to another population in which the char- horns, but it is more difficult for the com- polled animals in the early years there acter of primary importance is condi- mercial beef producer to dehorn with was very little selection among polled tioned by a multiple factor complex that caustic, and he resorts to other methods. animals for superior beef qualities; and breeds relatively true. The desirable Dehorning is costly. Labor is only a small 3. If the assumption that horned Here- genetic constitution of the multiple factor part of the expense. Dehorning interferes fords are superior in beef qualities is cor- complex is automatically fixed by using with normal weight increase. There is the rect, the mating system generally used the parent that possesses it as the recur- ever present danger from fly strike which, in the crossing of polled and horned rent parent in the backcrossing program. when it occurs, causes additional labor Herefords was not conducive to rapid Since pure lines do not exist in animals, output, a longer period of weight loss, improvement of the beef qualities of the problem of transferring the polled and an occasional complication that re- polled Herefords. factor to a horned herd of superior con- sults in death. The commercial cattleman The polled herds throughout the coun- formation and beef qualities can never that uses a horned breed takes a substan- try are now in various stages of develop- be reduced to such simple terms as-for tial loss from horns whether he dehorns ment. There are few polled herds that example-that of transferring a rust or or not. compare favorably in quality and con- smut resistant gene into a susceptible Although the consensus is that polled formation with the better horned breeds. commercial variety of wheat that pos- Herefords are better adapted to the range Since there is a great difference in the sesses the other desirable qualities. By or valley conditions, most commercial progress of the development of polled use of the backcross method, however, it cattlemen object to them on the ground herds, it is impossible to recommend one is possible to reduce the complexity of that they are inferior to horned Herefords breeding program that would suit the the problem sufficiently so that it can be in conformation and other beef qualities. needs of all polled breeders. approached by backcrossing. If commercial cattlemen could obtain A polled breeder that has developed It is possible for a breeder of a reg- true breeding polled bulls whose progeny his breed to a state of perfection near that istered horned herd that is better than were equal to the progeny of horned bulls of the better horned herds should not average to gradually change over to a in conformation, economy of gain, and necessarily use the same mating system polled herd that is equal to the horned quality of carcass-at a cost not greater that the owner of a relatively poor polled herd in the perfection of beef character- than that of comparable horned sires- herd should use. istics. At the same time, the breeder can there would be an immediate switch to The judicious selection of bulls coupled maintain essentially the same economic polled sires. with progeny tests and careful culling structure and amount of income from his The inheritance of the polled or horned might be all that breeders of well-devel- herd during the transition period. condition is relatively simple. Only one oped polled herds need to do. Perhaps pair of major factors-genes-is involved, it would be unwise to place too much although there may be modifying genes emphasis upon homozygosity-true-to- Breeding Program that condition the scurs-small kernel-like type-for the polled character until con- A plan of procedure is outlined in the bits of horn tissue attached to the skin of formation is well fixed in the herd. accompanying table which is a practical the horn pit of a polled animal. As the number of better polled herds way for an established breeder of horned The genetic control of the polled char- increase, breeders of registered horned cattle to proceed. acter itself is easy and offers no great cattle will be compelled to change their It should be noted that horned cows- problem. It is the efficient utilization of horned herds to polled. All registered Herd A-of superior beef qualities are to feed, conformation, and quality of car- horned herds that are average or higher be mated to polled bulls possessing su-

CALIFORNIA AGRICULTURE, S E P T E M B ER, 1949 7 perior beef qualities and the best F,-first I-in the table-will not breed true for After they become available, bulls of generation-polled males are then mated the polled character. This is unavoidable desirable beef type that breed true for the back to the horned cows-Herd A-that but is not serious. polled condition are to be used on cows are used as the recurrent parent in sub- The breeder can sell breeding stock of Herd A. All of their progeny will be sequent generations. from the outset and his general mode polled. Polled bulls of the best conformation of operation should not be materially By using proven homozygous polled and beef qualities should be chosen to changed. bulls two or more generations, the fre- mate to the horned cows in each gen- Under this plan, replacements of the quency of the polled gene will be so high, eration. By using this procedure, the horned cows-Herd A-during the first that if random matings-with respect to genetically complicated characteristics of few generations are not to be obtained the polled gene-are used-the IIBC, gen- conformation and beef qualities can, for from Herd A. When there has been suffi- eration-only one horned calf out of 256 the most part, be fixed automatically by cient grading up by backcrossing, re- animals would be expected. backcrossing. All that is necessary to do placement females for Herd A may be This program is sound from a genetic

A Mating System Designed to Substitute the Polled for the Horned Gene in a Horned Herd in which the Beef Qualities Are Highly Developed. The Estimations Are Based upon a Breeding Herd of 100 Cows with an 80 Per Cent Calf Crop Weaned.

in the Generations One hundred horned cows IF' 20 Polled Bulls 20 Horned Bulls 20 Polled Caws 20 Horned Cows Costrate poorest in con- Castrate poorest in con- Cull poorest for buef formation. Save best two formation. Sell others as 1. Sell for commerciol beef 1. Sell for commercial beef to backcross to the horned range bulls. production. I production. 2. Sell for registered breed- 2. Sell for registered breed- ing stock.- ing stock.' 3. Use best as foundation for polled herd. I 20 Polled Bulls 20 Horned Bulls 20Select Polled as in Cows IF 1 I 'S".E"."Pii,'Pi Select as in IF 1

20 Polled Bulls 20 Horned Bulls 20 Polled Cows 20 Horned Cows Select as in IF 1 Select as in IF 1 Select as in IF 1

20 Polled Bulls 20 Horned Bulls Select as In IF 1 Use best heifers as replace- Select as in IF 1

20 Polled Bulls 20 Horned Bulls 20 Polled Cows 20 Horned Cows Select as in IF 1 Use best heifers as replace- Select as in IF 1 ments for herd A. I Less thon 20 Horned Bulls More than 20 Polled Cows Less than 20 Horned Cows Select as in IF 1 Select as in IF 1 Select as in IF 1

condition. The best of the PROPORTION OF HORNED polled bulls should be CALVES THAT WOULD OC- mated to about 15 horned CUR IF RANDOM MATINGS cows each to determine which breed true for the ARE ALLOWED

40 Polled Bulls I Costrate poorest, save best to mote to horned cows to identify bulls that breed others for breeding stock. true for polled character. Use best of these hulls on A herd. Sell remaining as herd and range bulls. 40 Polled Bulls 40 Polled Cows Select and monoge 0s in Select and monoge as in 1 out of 16 11F1 llF1 I 40 Polled Bulls 40 Polled Cows Select and monage as in llF1 r \I1 BC3J 40 Polled Bulls 40 Polled Cow Select and manage as in /W

illBC44 40 Polled Bulls I Polled I 1 out of 1,024 Random motings so far as the polled gene is concerned may be used about the 11 BC3 generation. is to select polled bulls possessing the safely used from the backcross genera- standpoint. It can be adjusted to the indi- most desirable conformation and beef tions-see IBC,. When heterozygous- vidual needs of a breeder of registered qualities. By using these procedures, a not true-to-type-polled bulls of genera- horned Herefords so that the income from greatly complicated genetic problem is tion IBCN are mated to heterozygous the purebred cattle enterprise need not be largely reduced to a monohybrid-a hy- cows, 25% of their progeny will breed reduced at any time. It is possible that brid whose parents differ in a single char- true for the polled condition. the net income may actually be increased acter-status which is the simplest type Each polled bull of the best conforma- at the outset and that the margin of of genetic problem. tion and beef quality produced from this profit may be increased as the program Since conformation and beef qualities type of mating should be mated to at least advances. are more difficult to fix into a true breed- 15 horned cows. From this test mating, P. W. Gregory is Professor of Animal Hus- ing state than polled, all polled animals it is possible to identify animals that bandry and Animal Husbandman in the Ex- in the generation prefixed by a Roman breed true for the polled condition. periment Station, Davis.

8 CALI FOR N IA AGRICULTURE, SEPTEMBER, 1949