A study on some aspects of lifetime production in targhee and columbia sheep by Arun Kumar Basuthakur A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Animal Science Montana State University © Copyright by Arun Kumar Basuthakur (1970) Abstract: The relative lifetime lamb and wool production data for Targhee and Columbia sheep maintained by the Agricultural Experiment Station at Montana State University was analyzed for ewes born from 1950 to 1962. The productive traits concerned were analyzed by least square analysis of variance with interaction, phenotypic correlation and heritability was estimated. The total number of animals studied was 732 Targhees and 411 Columbias. In Targhees, it was observed that type of birth of the ewes sire affects the number of lambs born, whereas in Columbias the type of birth of ewe affects the trait. The interaction of type of birth was observed to be significant for number of lambs weaned in Targhees. The fleece production showed a significant effect of type of birth of ewe and her sire in Targhees but not in Columbias. Multiple births showed a positive significant correlation in Targhees with type of birth of the ewes sire whereas in Columbias type of birth of ewe was significant. Lamb and wool production showed variable significant correlations with yearling and weaning weights in both the breeds but were of low magnitude. The heritability for weaning and yearling weight were observed to be quite high in both the breeds in comparison tp other traits studied. The heritability of multiple births in Targhees was observed to be quite high compared to other breeds of sheep.  In presenting this thesis in partial fulfillment of the require­ ments for an advanced degree at Montana State University, I agree that the Library shall make it freely available for inspection. I further agree that permission for extensive copying.of this thesis for scholarly purposes.may be granted by my major professor, or, in his absence, by the Director of Libraries. It is understood that any copying.or publi­ cation of this thesis for financial gain shall not be allowed without my written permission. S ignature fijjjtn/pI Date QfcAA A STUDY ON SOME ASPECTS OF LIFETIME PRODUCTION IN TARGHEE AND COLUMBIA SHEEP ARUN KUMAR BASUTHAKUR A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Animal Science Approved: /T c/c^ ^ Head, Major Department Graduate Dean MONTANA STATE UNIVERSITY Bozeman, Montana March, 1970 iii ACKNOWLEDGEMENT The author wishes to express his most sincere appreciation- to Professor J. L. Van Horn for his valuable■suggestions and guidance through the whole graduate program in addition to my practical acquaintance with the improved sheep management and research. I am indebted to Dr. P. J. Burfening and Dr. R. L. Blackwell for their kind and keen interest with the problem of my research and their help in analyzing.and interpreting the data. I wish to express my sincere appreciation to Professor James Drummond for his kind suggestions and help. I am also thankful to Professor R. F. Eslick5 a member of my committee. I appreciate the help of Dr. E= P. Smith and his staff in programming the data and working it through the computer. Appreciation is extended to all the workers of the Red Bluff and Fort Ellis Experi­ ment Station of the University for their kind help from time to time in recording the data. Sincere appreciation is expressed to Mrs. Frankie Larson for her kind help in typing the manuscript. I am grateful and sincere appreciation is expressed to my wife, Shyamali and my son for their understanding and encouragement for my graduate work living 13,000 miles away from me in India. TABLE OF CONTENTS Page VITA ................................ ii ACKNOWLEDGEMENT ............ . . . . iii INDEX TO TABLES ............................ vi ABSTRACT •„ . ......................... vii INTRODUCTION .................................... I REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . . . . . . 3 I. Fertility and Multiple Births .............. . . . . . 3 II, Wool Production . . . . . . . . . . . . . . . . . . . . 4 III. Weaning Weight ........ . . . . . . . . . . . . . . . . 6 IV. Yearling Weight . . . . . . . . . . . . . . ........ . '9 V. Phenotypic Correlation . . . . . . . . . . . . . . . . . 9 VI. Uerxtahrlrty 1.2 EXPERIMENTAL PROCEDURE . . . . . . ........ . . . . . . . . . . 17 . 1 Management Practices . . . . . . . . . . ........ . . . . 17 Selectron . . . * . . . . . . . . . . . . . . . . . 20 Statistical Analyses . . . . . . . . ..................... 21 Phenotypic Correlation . . . . . . . . . .......... . . . 21 Heritability . . . . . . . . . . . . . . ................. 22 RESULTS AND DISCUSSIONS . . . . . . . . . . . . ............... 23 Re SU11S o . , o o o . . . . . o a o e e e o . . o . . ,* * , 23 iv VPage Least Squares Analysis......................... ............ 23 Number of Lambs Born Per E w e ..................... 23 Number of Lambs Weaned . . .................................. .24 Total Pounds of Lamb Weaned Per Ewe ....................... 24 Total Pounds of Fleece Per Ewe . . .......................... 31 Average Number of Lambs Born Per Ewe . . . * ............... 31 Average Number of Lambs Weaned Per E w e ........... 32 Average Pounds of Lamb Weaned Per Ewe ..................... 32 Average Pounds of Fleece Per Ewe . . . . . . . . . . . . . . 33 Yearling Weight of the Ewes . . . . . . . . . . . . . . . . 33 Weaning Weight of the Ewes . . . . . . . . . . . . . . . . . .34 Multiple Births . . . . . . . . . . . . . . . . . . . . . . 34 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 37 Correlation Among Traits . . . . . . . . . . . . . . . . . . 38 Heritability . . . . . . . . . . . . . . . . . . . . . . . . 42 SUMMARY . . . . . . . . . * . . o . . . . t i . . . . . . . . . . . 47 LITERATURE CITED 50 vi INDEX TO TABLES TABLE Page I„ ANNUAL WOOL PRODUCTION IN RAMBOUILLET, TARGHEE AND COLUMBIA (Hulet £t al. 1969) . . . . . . . . . . . . . . 5 IT. AVERAGE WOOL PRODUCTION IN RANGE EWES (Shelton 1968) . . 6 III. AGE OF DAM AND EFFECT..OF' TYPE OF BIRTH ON WEANING WEIGHTS IN RAMBOUILLET SHEEP ........................... 8 IV. MEAN AND STANDARD ERROR FOR YEARLING WEIGHT IN RAMBOUILLET, TARGHEE AND COLUMBIA SHEEP . . . . . . . . 9 V. SIMPLE CORRELATIONS AMONG TRAITS MEASURED IN RAMBOUILLET (Shelton at al. 1968) . . . . . . . . . . . 10 VI. ESTIMATES OF HERlTABILITY AND REPEATABILITY OF MULTIPLE BIRTH WITHIN HERDS IN DIFFERENT BREEDS (RendeI 1956) o . . . . . . . . . . . . . . . . . . . . I5 VII. LEAST SQUARE MEANS AND STANDARD ERRORS FOR SOME OF THE PRODUCTIVE TRAITS IN TARGHEE SHEEP . . . . . . . . . . 25 VIII. LEAST SQUARE MEANS AND STANDARD ERRORS FOR SOME OF THE PRODUCTIVE TRAITS IN COLUMBIA SHEEP . . . . . . . . . . 27 IX. CORRELATION COEFFipiENT OF THE PRODUCTIVE TRAITS STUDIED IN TARGHEE' AND COLUMBIA SHEEP . . . . . . . . . . 29 X. LEAST SQUARE ANALYSIS OF VARIANCE WITH INTERACTION FOR THE TARGHEE BREED . . . . . . . . . . . . . . . . . 35 XI. LEAST SQUARE ANALYSIS OF VARIANCE WITH INTERACTION FOR THE COLUMBIA BREED . . . . . . . . . . . . . . . . . 36 XII. SIMPLE CORRELATION COEFFICIENT IN TARGHEES AND COLUMBIAS FOR 14 PRODUCTIVE TRAITS . . . . . . . . . . . 40 XIII. . HERITABILITY AND STANDARD ERROR IN TARGHEE AND COLUMBIA SHEEP . . . . . . . . . . . . . . . . . . . . . 43 vii ABSTRACT The relative lifetime lamb and wool production data for Targhee and Columbia sheep maintained by the Agricultural Experiment Station at Montana State University was analyzed for ewes born from 1950 to 1962. The productive traits concerned were analyzed by least square analysis of variance with interaction, phenotypic correlation.and heritability was estimated. The total number of animals studied was 732 Targhees and 411 Columbias. In Targhees, it was observed that type of birth of the ewes sire affects the number of lambs born, whereas in Columbias the type of birth of ewe affects the trait. The interaction of type of birth was observed to be significant for number of lambs weaned in Targhees. The fleece production showed a significant effect of type of birth of ewe and her sire in Targhees but not in Columbias. Multiple births showed a positive significant correlation in Targhees with type of birth of the ewes sire whereas in Columbias type of birth of ewe was significant. Lamb and wool production showed variable significant correlations with yearling.and weaning weights in both the breeds .but were of low magnitude. The heritability for weaning.and yearling weight were observed to be quite high in both the breeds in comparison tp other traits studied. The heritability of multiple births in Targhees was observed to be quite high compared to other breeds of sheep. INTRODUCTION Sheep are perhaps one of the first ruminants domesticated by man. Sheep may be considered as man's first helpmates to supply him with wool, meat, milk and pelt. Today, there is no history, of any religion or race where somewhere there is no mention of sheep. The.history, of sheep in this country starts somewhere between 1493 to 1520, through import from Spain and Englandi During,that time, wool was more important than lambs for slaughter. As early as in 1662, the first woolen mill was established and all possible encouragement and legislation for growing.sheep was started in.1670. Modern development to increase lamb and wool production in the United States started about 1912, when.long .wool breeds were crossed with high quality Rambouillet ewes to produce large ewes with greater production of wool and lamb. These early crosses resulted in the Columbia sheep. Under a similar demand, another high quality sheep breed was developed basically by crossing Columbia ewes with Rambouillet rams. These foundation sheep established the Targhee breed in 1926. However, the increasing population and its many fold demands of today requires more production from domestic animals to keep it pro­ gressive under the present mechanism of economy. Research in other livestock has efficiency of production. Sheep not only produce fiber with many special characteristics but also it is one of the few mammals where incidence of multiple follicular growth and twinning is frequent. -Z- Though the domestic sheep is said to have originated from two wild ancestors (Moufflon and Urial) the hundreds of completely dis­ similar breeds with its tremendous diversity of production potentiality under the present bioclimatic conditions of the world entails an enor­ mous store of genetic variability. Genetics study of sheep over the last half century revealed the presence of an impressive array of genetic phenomena. Terrill (1958) reviewed the past 50 years of sheep breeding research but still some of the results show inconclusive understand­ ing for practical emphasis under genetic law due to variablity between samples and breeds. The Columbia and Targhee sheep which form one of the major sheep populations of this country have already gone through different mechanisms of selection and are at present improved and adopted breeds. To further increase the production ability of wool and lambs 3 it is essential to further investigate and know accurately the genetic potentiality and present production ability. With the above in view, the present work was undertaken with the Columbia and Targhee sheep, stationed at the Red Bluff Sheep Research Ranch of the Montana State University, to study the phenotypic relations of different productive traits at different ages, including heritability and mechanism of inheritance of lifetime production of wool and lamb. REVIEW OF LITERATURE I. Fertility and Multiple Births There seems to be very little evidence where selection in sheep has been used to increase the number of lambs born per ewe lambing. However, studies indicate that the fertility is extremely variable between breeds and between flocks within breeds. Kennedy et al. (1950), observed that in Merino sheep multiple births were associated with age of dam. Wright et al. (1953) studying Romney and Corriedales reported an average of 0.4 more lambs per ewe for dams born as twins compared to dams botn as singles. Belie (1954) studying.eight years of production in Tsigai sheep from Belgrade also observed higher incidence of more multiple births in animals born as twins compared- to singles. He also reported in the same breed that the incidence of twinnihg increases with age And reaches a peak at four years of age. Later, Belie (1958) presented data showing that 8.1% have markedly low fertility, 2.1% have extraordinary fertility and regularly gave birth to twins or triplets and 0.1% produced two lambs more on the average than their lifetime number of lambings. In a similar study, Madsen et al. (1952) found no signifi­ cant results in number of lambs produced from crossbred range ewes sired by Columbia, Targhee and Rambouillet. In a flock of Wurttenberg ewes, Polach (1960) observed the maximum rate of twinning.at five and one-half years of age. Teodoreanu -4- et al. (1959) reported maximum number of multiple births in Palas Merino at four to eight years of age. Desai et al. (1951) also reported that ewes born twins gave birth to 0.12 more lambs than.ewes born .as singles. The frequency of triplet production was also higher in the twin born group and there was.consistently higher lifetime reproductive performance. II. Wool Production Wool production is another important trait in.sheep. Total pro­ duction however, varies from breed to breed and is affected by such things as density, fineness, staple length, lamb production age and nutrition. Nagal (1947). in a Germanland Merino.flock observed that with age the wool production slowly dropped. The average of the flock at two years.of age was:4.I kg and the average for the same flock.at eight to ten years.of age dropped to 3.5 kg. A similar observation was also reported by Sanchez (1950) that the production of Spanish Merino increases up to four years of age and then decreases with age. Wright et al. (1953) studied the lifetime production and breeding performance of Romney and Corriedale ewes. They also observed that fleece weight and fertility changes with age. These data indicate that lambs born as singles produced more wool (0.27^-0.12! lb.) than lambs b o m as twins. Ali (1952) reported the average fleece weight -5- in Shorpshires as.9.I lbs. with a standard deviation (S.D.) of 1.3 lbs. and considers that variability of body weight is negligible to improve wool production as compared to other qualitative traits of the fleece. Hulet et al. (1969) reported wool production in Rambouillet, Targhee and Columbia sheep from two to six years of age. They have shown the average production in two groups according to the appearance of estrus during the first winter after birth. (Table I). TABLE I. ANNUAL WOOL PRODUCTION IN RAMBOUILLET, TARGHEE AND COLUMBIA (Hulet et al. 1969) Age Estrus Rambouillet (kg) Targhee (kg) Columbia (kg) 2 No 4.2-0.01 4.6-0.03 5.0-0.02 Yes' 4.2-0.08 4.5-0.05 4.9-0.07 3 No 4.4-0.01 4.8-0.02 5.3-0.03 Yes 4.4-0.09 4.7-0.05 5.3-0.09 4 No 4.4-0.02 4.8-0.03 5.3-0.03 Yes 4.3-0.06 4.6-0.08 5.1-0.13 5 No 4.3-0.03 4.8-0.03 5.2-0.05 Yes 4.3-0.09 4.7-0.09 5.0^0.22 6 No 4.4-0.10 4.7-0.13 5.1-0.18 As expected, the Columbia shows the highest production and Rambouillets the lowest among the three with Targhees intermediate. Their data does not show much variability due to age between two and -6 six years of age within each breed. In Rambouillets, Shelton (1968) reported the fleece weight from two to ten years,of age. (Table II). The fleece weights according to his work show a decrease with increas­ ing age after the age of three years. TABLE II. AVERAGE WOOL PRODUCTION IN RANGE FINE WOOL EWE'S ■ (Shelton '1968) Age No. Av. Ewe Body Weight (kg) Av. Fleece Weight (kg) 2 1330 44.0 4.36 3 .1111 46.0 4.50 4 924 51.0 4.49 5 747 53.2 ■ 4.39 6 568 53.9 4.27 7 364 53.6 4.03 8 200 53.4 3.96 9 84 51.1 3,64 III. Weaning Weight The weight at weaning is one of the most crucial.measurements in sheep production. The variability of this particular trait is influenced by the level of nutrition of the dam, age of dam, birth weight and age of lamb at weaning, type of birth and rearing, climatic conditions and breed of sheep. -7- Sidwell et al. (1949) studied the size of Navajo lambs at weaning from the lifetime production of 414 Navajo ewes in New Mexico„ The adjusted average weaning weight at approximately 139 days of age was 59.4 lbs., with a standard deviation of 9.8 lbs. Six measureable environmental factors found to have an important effect upon the wean­ ing weights.of the lambs were year of birth3 age of dam, type of birth, type of rearing, sex, and age of lamb at weaning. Weaning weights were observed to be 5.2.lbs. below average for 1939 to 1946; whereas, those in 1941 were 6.9 lbs., above average. Two-year-old ewes weaned the smallest lambs; 4-to I -year-old ewes weaned intermediate-weight lambs. Columbia rams sired the heaviest lambs at weaning followed by Corriedale crossbreds, Navajo and Romney rams,respectively. Single lambs were 11.2 lbs. heavier than twins and 2.9 lbs. heavier than twins raised as singles. Ewe-lambs averaged 4.4 lbs. less than ram .lambs. The effect of crossbreeding ,Navajo■ewes to Columbia and Romney rams and Navajo crossbred ewes to Lincoln and Cotswold rams on weaning .weight was reported by Price et al. (1951). The average weaning weight of Cotswold cross lambs was 65.1.lbs., and was significantly higher than that of the other three crosses. The average weaning weights of Columbia (64.0.lbs.) and Lincoln (63.29 lbs.) crosfe 'lambs were signifi­ cantly greater than that of the Romney cross lambs (61.38 lbs.). ' The average weaning weights of the Columbia and Romney.Sired lambs differed -8- by 2 lbs. and although the number of observations was small, the difference was significant. Similar work on the effect of age of dam.and type of birth on weaning weights of lambs in Rambouillets was reported by Shelton et al. (1968) as follows: TABLE III. AGE OF DAM AND IN RAMBOUILLET EFFECT OF TYPE OF SHEEP BIRTH ON WEANING WEIGHTS Age No. Average Weaning Weights (kg) Singles (S) Twins (T) (S-T) 2 1330 28.1 25.5 2.6 3 1111 31.8 27.7 4.1 4 924 32.0 27.3 4.7 5 747 32.0 . OO 4.2 .6 568 32.2 26.6 5.6 7 364 28.5 26.5 2.0 8 200 29.4 25.6 3.8 9 84 27.6 25.1 2.5 10 23 24.0 25.7 -1.7 In this case,, the maximum average weaning weight of lambs was for the dams from three to six years.of age. The maximum difference (5.6'kg) between singles and twins was at six years of age. Sex differ­ ence was not studied. In general, the difference in weight between the whole group of dams for singles and twins was 2 to 5 kg. -9- IV. Yearling Weight Yearling weight is another measure with which many, other charac­ teristics of future production have.been correlated. Yearling weight is thought to be of greater importance in predicting the future pro­ duction than weaning weight. Hulet et al. (1969) reported average yearling weight in Rambouillet, Targhee and Columbia sheep based on the appearance of estrus or no estrus during their first winter after birth. TABLE IV. MEAN AND STANDARD ERROR FOR YEARLING WEIGHT IN RAMBOUILLET, TARGHEE AND COLUMBIA SHEEP Rambouillet Targhee Columbia No. Lambs Mean-S.E..No..Lambs Mean-SvE. •■No. .Lambs Meah-S.Ev No estrus 2110 52.6-0.10 1663 57.7-0.26 1153 56.1-0.16 + + + Estrus 254 54.2-0.67 267 56.4-0.45 119 57.7-0.50 They reported no important interactions between estrous status and years or estrous status and type of birth and rearing for any of the weaning.or yearling traits. V. Phenotypic Correlation It is important to. know the degree of relationship among traits and the sign of the correlation. Shelton and Menzies (1968) studied the simple correlation coefficients (Table V) in a Rambouillet flock stationed at Sonora, Texas. The data collected were for the years 1930 to 1966. TABLE V. SIMPLE CORRELATIONS AMONG TRAITS MEASURED IN RAMBOUIIXET (Shelton et al. (1968) Yearling breeding weight Years in Mature breeding weight flock Number lambs b o m Number lambs raised Number dry seasons Number multiple births Average fleece weight Total wool produc- . tion Total lamb produc- .tion Lambs b o m Times bred Lambs b o m Times bred . Weaning weight .660** .418** .039 .101** .088** -.049 .126** .059 .063 .102** .130** .125** Yearling weight ■ .621** .069* ■ .131** .124** -.039 .151** .147** .105** .148** .166** .154** Mature weight .269** . 203** .159** .228** .221** .295** .349** .207** .012 -.017 Years in flock .853** .826** .409** .477** .017 .949** .821** .220**' .222** Number lambs b o m .954** -.011 .757** -.059 .793** .936** .604** .542** Number lambs raised -.016 .696** -.083** .764** .980** .565** .634** Number dry seasons .022 .209** .438** -.020 -.480** — 417** Number multiple births .021 .456** .651** .597** .498** Average fleece weight .295** -.101** -.135** -'.169** Total wool production .576** .188** . 190** Total lamb production .'532** .600** Lambs b o m Times bred .856** *(P<.05) **(P<.01) -11- There was a low but significant negative correlation between the average wool yield and the various reproductive efficiency traits in the flock. The number of multiple birth was nonsignificantIy correlated with average fleece weight. Most of the traits show a positive relationship with both weaning and yearling weight, However, of the two, yearling weight would be of more value in predict­ ing future performance due to its higher correlation. Total lamb production and multiple births were significantly positively correla­ ted with yearling and mature weight. Mature Weight and years in breeding flock show a low positive correlation with the number.of dry seasons. Years.in flock was highly correlated with total wool .and Iamb pro duc tion. Kennedy (1966) studied the phenotypic correlation between fertility ,and wool production in Merino sheep in Australia. He observed that the correlation between number of lambs born or weaned was negatively correlated with grease wool weight. He reported cor­ relations of -0.09 and -0.12 between grease wool weight,. number of lambs born and number of lambs weaned, respectively. Young, et al. (1960) while estimated phenotypic correlations between.fertility and grease or clean weight at different ages in Merino sheep in Australia and reported no consistent trend. Belie (1954) studied the effect of fertility on wool production -12- in Tsigai sheep. Wool production for ewes producing singles and twins was reported separately. His.observations show the greater the fertil­ ity in Tsigai.ewes the lower the wool production. Slen at al, (1954) obtained a correlation of 0.40 between the yearling weight and clean fleece weight. In a similar study with Corriedale sheep, Wright et al. (1953) found a significant correlation between yearling weight and grease fleece weight. Sanchez' (1950) shows positive significant correlation of 0.49 between grease fleece weight and yearling weight in Spanish Merino. Terrill and Kyle (1953) in a ^tudy of the Columbia, Targhee and Rambouillet breeds found a positive significant correlation between the yearling.and weaning weight with clean fleece weight. Spencer et al. (1928) obtained a phenotypic correlation between yearling weight and grease fleece weight of 0.1.6, in Rambouillet sheep. Basseft (1965) studied the data collected at the Montana Agricul­ tural Experiment Station, Bozeman,over the period of 1955 to 1963 and reported the following correlations between yearling weight and grease fleece weight for Rambouillet 0.49,' Targhee 0.67. and Columbia..Bi56, ,. VI. Heritability Wrigfrt et: al. (1953) studied the lifetime wool production and breeding performances of Romney and Corriedale ewes. The heritability of fleece weight was 0.52.for both breeds.< -13- Ali (1952) in his study with Shorpshire, Columbia and Hampsire sheep obtained heritability estimates.of 0.52 by the regression method and 0.32 by the correlation method for fleece weight. The analysis was composed of animals with mixed genetic materials including cross­ breds and inbreds and the above figures were calculated without controlling the variation due to body weight. Further estimates.of heritability for fleece weight in the same sample based.on.the intra-year regression of offspring on dam within breed of sire was 0.43,.which dif- ferred only slightly from the corresponding .within sire estimate of 0.51, Morley (1954) estimated heritability of grease fleece weight and yield in Merino sheep. One set of estimates was obtained by parent­ offspring regressions for the data obtained between.1943 to 1952,. and another set of half-sib analyses from data from sheep with first adult shearing.in .1953. The estimates were 0.40 and 0.39 for grease fleece weight and yield, respectively, by parent offspring, regression and 0.44 and 0.75 by the paternal half-sib method. Young . et al. (1960) studied heritability. of grease fleece weight and nine other wool characteristics in Merino sheep. Their study included three groups of sheep namely (I) half-sib selection group (2) mass selection group (3) control group. The heritabilities.of grease fleece weight by groups were: 0.499, 0.360 and 0.449, respec­ tively. The data were analyzed by dam-daughter correlation. Within -14- the major groups, the data have been classed as to mating groups which again have been sub-classed as per to type of birth of progeny and their dam. The characteristics were measured when animals were 15 to 16 months of age. Rendel (1956) analyzed the routine records of a sheep farm in Sweden from 1925 to 1942, comprising 30,989 births of pheviots, Oxford Down, Shorpshire and Swedish Landrace sheep. There were 5093 dams and 425 sires. The average number of births per ewe was 6.09, and the overall frequency of multiple births was 51.1%, the Landrace being highest with 69.1%,,and the Oxford Down next with 51.0%. Estimates of heritability of multiple births obtained by two methods were in .fairly good agreement but differed somewhat between breeds. When the results of the two methods were averaged, the heritability for multiple birth in the four sheep breeds was estimated to be 0=113. (Table VI). Robertson and Lerner's method (used by Rendel 1956) for estimate of the heritability includes the ratio between the average genotypic change and.the selection differential with the argument that even.if no artificial selection is applied there exists a natural selection for such traits as viability or incidence of multiple birth, since individuals with high viability or high fertility will get more off­ spring in the next generation'than those having.low viability x>r fertility. -15- TABLE ’VI„ ESTIMATES OF HERITABILITY AND REPEATABILITY OF MULTIPLE BIRTH WITHIN HERDS IN DIFFERENT BREEDS (Rendel 1956) Breeds Heritability Heritability— / Cheviot 0,224 0.185-0.023 Shorpshire 0.042 + 0.037-0.011 Landrace 0.088 + 0.062-0.023 Oxford Down 0.084 4* 0.080-0.020 Average 0.126 + 0.099-0.010 I/ By Robertson and Lerner's Method The heritability mentioned here of 0,113 was somewhat lower than that of Johansson and Hansson (1943) for multiple birth in sheep (0,214) calculated by dam™daughter correlation when estimated from the half-sib correlation (0,196) based on the average of two lambings, Karam,.et al, (1958) while studying.multiple birth in Texal sheep in Egypt calculated the heritability for the number of lambs born. They used both daughter-dam and half-sib correlation. The average number of lambs per lambing for each ewe was used, A heritability estimate of 0,255 was calculated by doubling the overall daughter-dam regression using 343 pairs. The available daughter-dam pairs within sire group were only 2,81 per sire. Another estimate of 0,298 was obtained by multiplying the intra-class correlation by four for the half-sib correlation. ”16- Karam (1959) reported heritability for weaning weight in Rahmani sheep as 0.18 and yearling weight as 0.19. Mac Naughton (1957) report­ ed the heritability estimates of 0.33 and 0.52 for weaning and yearling weight in Corriedale sheep. Bosman (1958) reported heritability estimates for two groups of Merinos as 0.09. and 0.47 for grease fleece weight, 0.23 and 0.44 for clean fleece weight, 0.48 and 0.22 for wool production. Vesely et al. (1961) reported heritability of Rambouillet sheep from Canada for weaning weight 0.28*0.09, yearling weight 0.37*0.11,. and clean.fleece weight 0.48^-0.08. The heritability was calculated by intra-sire regression of daughter on dam adjusting the data for year, age of dam, type of birth and rearing and age of lamb or yearling ewe. The data were collected for over a 12 year period. Vachal (1962) reported heritability of grease fleece weight as 0.37 in Stravropol Merino sheep. His sample consisted of 536 dam- daughter pairs sired by 69 rams of about two years of age. While in another group with Mutton Merino blood, he obtained heritability of 0.299 calculated on 241 dam-daughter pairs. EXPERIMENTAL PROCEDURE The data under study were those records which were regularly recorded as part of the normal routine research activity of the Animal and Range Science Department, Montana Agricultural Experiment Station, Bozeman, Montana= These data include the female lambs of Targhee and Columbia breeding born from 1950 to 1962 and their subsequent produc­ tion in the band. In general, the ewes were bred from two years to eight years of age. The total production of wool was considered from their first year but for lamb production, it was from the second year when they were expected to produce the first lamb crop. The age of culling was the period the animal lived in the band from its year of birth and the production was calculated accordingly. The elimination of ewes from the band was due to death or as otherwise discussed under selec­ tion. The number of ewes available for study are tabulated in Tables VII and VIII. Management Practices - All the animals were managed as a typical band of range ewes on the unfenced area of the Station.and on National Forest allotments. The animals were collected and brought to the headquarters of the Station only during breeding, lambing.and data collecting time. In general, the breeding.season for the period was mid-November to early December and consequently the lambing time was April and May. . -18- The ewes were mated in small flocks of 40 to 60 with their respective breed of rams under a pen-mating system. During the breeding season, mixed hay and alfalfa hay were supplied in addition to the continuous flowing water. At the end of the breeding season, the ewes were herded together on the range until the start of the expected lambing season. Hay was fed whenever snow was too deep for grazing or if there was not sufficient feed. During the lambing season, the herd was brought to the•shed and the ewes were managed under shed lambing conditions. Just after parturition, the dam and the lamb were taken to a 4' x 4' pen or "jug" and kept for 24 hours or more depending upon the condition of the lamb and mothering ability of the dam. Then both the . dam and the lamb were collected in a small pen where five to ten such animals can be kept at a time and maintained for five to six days prior to putting them in a larger group. The time for the passage of the dams and lambs from. the jug to the corral depended on the number of jugs available and speed of parturition during the season. The same number paint brand was branded on the lamb and mother. The lamb numbers were checked from a breeding sheet previously prepared and accordingly the lamb was eartagged, weighed and a docking ring applied while in the jug. The lamb number and birth weight was entered in the lambing book according to breed and band including dam number and sire number. The number of the lamb, birth weight and day of birth -19- was also entered on the respective ewe card. Ewes and lambs were then grazed during May and June on the Station and by July taken in a single flock to the forest allotment for summer grazing. At the end of August, when the age of the lambs was approximately 18 weeks, the animals were collected and a weaning weight determined at the summer pasture. The animals were weighed on a platform balance and males and females were separated. The animals, after being col­ lected in the drafting yard, were led through the squeeze into a chute provided with cutting gates. The ewes, and lambs were thus separated before weighing. The weights were entered on a work sheet. The female lambs joined their mother again whereas the male lambs were weaned and transferred to a separate pasture for grazing. All weaning weights thus recorded was also entered on their respective dam cards. During September, the flock was trailed from the summer range to the Station. The same type of drafting yard as mentioned above was used. The animals were weighed individually, branded and the weight recorded on work sheets. The shearing program at the Station occurs during the month of June or in later years in April. Each animal was machine shorn and the fleece was rolled down from the shearing cabin. The fleece was individ­ ually collected, weighed on a hanging-pan spring balance at the spot -20- and rolled in a cheese cloth or plastic bag including an identification tag bearing the number of the animal. The number and weight of the fleece was also recorded on a work sheet. A number of fleeces were then packed together and transported to the Wool Laboratory of the University for further analysis. The fleece weight, in addition to other wool quality standards, were then entered on the ewe production record card. Though the above was the general management practice as a whole, some of the animals from both the breeds have gone through different kinds of nutrition, flushing and other management experiments, No. separate management was done for the treated or untreated groups. Selection No particular type of selection was practiced during the early years of this study. Only ewes with some visible defects were eliminated from the flock. Ewes with continuous reproductive failure were also culled. However, no record of any particular type of selec­ tion in practice for the early years were available. During the later parts of the study, some regular and systematic type of selection was practiced. A ewe that did not produce" a lamb for two consecutive years was taken out of the band. Face cover, weaning and yearling weights, type of birth and general wool production and grade was used in selection for the latter years of the study. -21 - Selection was more intence for the Targhees than the Columbias for some years at the beginning as the Targhee flock was large and Columbia numbers were quite small. During that period to increase the number of Columbia sheep,, no ewe excepting an extreme case of continuous reproductive failure or visible defects was eliminated from the flock. For rams, also no particular type of selection method is available in the record for the early years. They were selected by visual appraisal giving some importance to verility and body weight. During later years however, consideration of characteristics as mentioned above was used for selecting stud rams including rate of growth. Statistical Analyses To avoid entanglement effect of age at culling, years of birth, type of birth of ewe and of her sire and interaction of type of birth in this case, from the disproportionate subclass frequencies, the least squares method of analysis was undertaken. The method as dis­ cussed and suggested by Harvey (1960) was followed. Phenotypic Correlation The estimate used for the correlation is the ratio of the covari­ ance to the geometric mean of the two variances. The conventional formula according to Fisher (1967) and Mather (1946) as used by other workers in the field has been used to calculate the correlation between two metric characters. -22- Heritability Heritability estimates were calculated from the intra-class corre­ lation.of paternal half-sibs, which were computed within year subclasses using a nested analysis of variance. 2 The sire variance (6g) contains one-fourth of the additive genetic variance while three-fourths of the additive genetic variance is 2 included in the error variance (6e) in addition to other sources of variation. o 2 The general formula used is h^ = 4bg s e i 2 “i = Heritability of trait 2 hg = Between sire component of variance = Within sire component RESULTS AND DISCUSSION Least - Squares Analysis Results Lifetime production records of lamb and wool from 732 Targhee and 411 Columbia ewes including their weaning.and yearling weight were analyzed by the least squares method. No adjustments for any data were made. The analysis of variance was undertaken for each trait to analyze the effect of age at culling, year of birth, type of birth of the ewe, type of birth of the ewe's sire and the interaction between type of birth of the ewe and her sire on the ewe's lifetime. The data for each breed were tabulated and analyzed separately. (Tables X and XI). Number of Lambs Born Per Ewe The effect of year of birth and type of birth of the ewe are significant (P«c.05) in the Columbia. But neither the type of birth of her sire nor the pooled interaction between the type of birth of the ewe and her sire shows any significant effect on.the number of lambs produced. In the Targhees, the year of birth is significant (P-