Estimating Transmitting Abilities of Artificial Insemination Dairy Sires1

Estimating Transmitting Abilities of Artificial Insemination Dairy Sires ~ T. P. FAIRCHILD 2, W. J. TYLER, G. R. BARR, and E. L. CORLEY ~

Department of Dairy Science, University of Wisconsin, Madison Abstract

First available D H I A production records ot7 40,501 Wisconsin Holstein eows were used to compare several methods of estimating the transmitting abilities of A.I. sires. These methods involved the use of different contemporary averages to adjust A.I. daughter records for herd-year-season effects. The different types of adjusted daughter records were compared to each other and to unadjusted records on the basis of variance components for herd effects, sire effects and herd-by-sire interaction effects. Correlation and regress]oil eoeflicieuts for the average performance of a large number of later daughters on the average performance of different ureahers of early daughters also were comouted. Variance eomponent analyses indicated that the adjustment of daughter records by use of contemporary averages substantially reduced the influence of herd variation. However, no type of daughter reeord appeared to be superior in terms of the percentage of variance due to sire effects or in terms of the degree of relationship between later and early daughters. Use of deviations ()f daughter recm'ds frmn some kind of contemporary average has been widely accepted as a fairly reliable method of proving dairy sires. However, there have been some differences of opinion c,meerning the exact form these contemporary comparisons or herdmate comparisons shouM take. The general plan followed by the progeny-testing programs of northwestern Europe is to compare the actual 1)roduction of first-lactati
(14, 16, 1S). Other variations in the use of herd-mate comparisons have concerned the restrictions ])laced on contemporary seasons of calving (3, 6, 8, 9, 20, 21), the removal of the record of the daughter in question and the records of paternal half-sisters from the herd average (2, 9, 24, 25), the adjustment of contemporary herd-mate averages for nmnber of hcrd-nmtes (24, 25), and the use of estimates of the intra-sire regression of daughter records on adjusted herd-mate averages (11, 12, 22,

25). The purpose of the ])resent study was to investigate some of the different methods of using contemporary averages to adjust daughter records for herd-year-season effeets. Data

The availabh, data included all standard DI-IIA produ(',tion reem'ds of Wisconsin Holstein cows calvi,g between July, ;1952, and October, 1961. These records were made on twice-a-day milkin~ and were from 180 to 305 days in length. Ttfis study w a s particulaNy concerned with the •st available lactatlou records of 40,501 artificially sired daughters. Of these records, 25,32,~ were considered as firstlactation records (=~ 32 months of age at calving). Howevm', only 22,484 ,)f the~,e tirst-laetatimt dau~hters had first lactation herd-mates. Experimental ~ef],re,~'s'ion

Analyses o j" re('o,rds ~r~ h e r d - m a t , "

avecage,%

The first phase ()1~ the study involved an intrasire regression analysis o1: da.ughter records on nonpaterna.1 herd-mate averages. The herdmate averages included a six-month fixed season average (6-month HM average) and a five-month rolling season average (5-month H M average). The six-month phm grouped cows according to those calving between September and February and between March and August. Other workers (7, 19) suggested the use nf these six-month periods for Wisconsin data. According to the rolling five-month plan the herd-mates were those cows calving in the same month, in the two previous months, and in the two months following the calving date of the daughter in question. When these herdmate averages w'ere used with first available daughter records, all records were corrected for age. Six-month herd-mate averages which included the actual and the mature equivalent

Received for publication May 26, 1966. Published with the approvM of the Director of the Agricultural Experiment Station. This stndy was supported in part by a grazer from the Wisconsin-Minnesota Cooperative A. I. Research Fund. -°Present address: Department of Dairy Science, "V~iversity of Maryland, College Park, Maryland. Presently Chief, Dairy Cattle Research Branch, USDA, Beltsville, Maryland. 1416

TRANSMJTTJN(_{ A B I L I T I E S

p r o d u c t i o n of only first-lactation h e r d - m a t e s were also used in t h a t p a r t of the analysis involving the first-lactation daughters. The herdm a t e data were a d j u s t e d f o r n m n b e r of herdnmtes by the m e t h o d first p r e s e n t e d by H e n d e r son et al. (12) : Total p r o d u c t i o n of h e r d m a t e s + breed-season a v e r a g e Numt)er of h e r d m a t e s + 1 As shown in Table 1 the i n t r a - s i r e regression estimates f o r first-lactation d a u g h t e r raeords on first-lactation a d j u s t e d h e r d - m a t e averages r a n g e d f r o n l .7S to .83, a n d tile regression coefficients f o r e i t h e r first-lactation or first available d a u g h t e r records on a l l - l a c t a t i o n - a d j u s t e d h e r d - m a t e a v e r a g e s r a n g e d f r o m .88 to .90. H i g h l y significant differences existed between the regression cocfficieats i n v o l v i n g firstlactation h e r d - m a t e averages a n d those involving all-lactation h e r d - m a t e averages. These results a r e in a g r e e m e n t with the findings of AlIaire a n d G a u n t ( 1 ) , who studied the use of firstl a c t a t i o n c o n t e m p o r a r y c o m p a r i s o n s in some detail. F o r the i n t r a - s i r e regression analyses involving the first-lactation d a u g h t e r records, the covariance between d a u g h t e r a n d h e r d - m a t e p r o d u c t i o n was s u b s t a n t i a l l y g r e a t e r w h e n the h e r d - m a t e averages r e p r e s e n t e d all-lactation herd-mates h~stead of first-lactation herd-mates. This was t r u e f o r ghe m a t u r e e q u i v a l e n t yield o f b o t h milk a n d fat. I t is difficult to ascert a i n exactly w h y this should h a v e occurred, b u t the a v e r a g e n m n b e r of first-lactation herdm a t e s p e r first:lactation d a u g h t e r record was 4.6, whereas the average n m u b e r of h e r d - m a t e s increased to 16.4 when all h e r d : m a t e records were used. Therefore, these two t y p e s of herdm a t e a v e r a g e s could have r e p r e s e n t e d some-

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OF S I R E S

w h a t different g r o u p s , a l t h o u g h one was a p a r t of the other. Selection effects, h i g h e r herliability values f o r first-laetation reeords~ a n d i n a p p r o p r i a t e age corrections are possible factors which could have c o n t r i b u t e d to the differences in the i n t r a - s i r e regression coefficients. However, in this s t u d y no a t t e m p t was made to p u r s u e this m a t t e r f u r t h e r . Varia,nce component analyses. F o r the second p a r t of' the study, d a u g h t e r records were a d j u s t e d f o r h e r d y e a r - s e a s o n effects by use c~f the following fol~nulae: I. D a u g h t e r r e c o r d - - ( 6 - m o n t h h e r d avg - - b r e e d - s e a s o n avg') I I . D a u g h t e r record ( 6 - m o n t h I t M avg' - - b r e e d - s e a s o n avg') I I I . D a u g h t e r r c e o r d - - ( a d j . 6 - m o n t h avg - - b r e e d season avg) I V . D a u g h t e r r e c o r d - - b ( a d j . 6-month I-IN a v g - - b r e e d - s e a s o n avg) V. D a u g h t e r r e e o r d ~ b (adj. 5-month t t M a v g - - b r e e d - s e a s o n avg) All records in the above f o r m u l a e were adj u s t e d to a n ~ E basis. F o r the h e r d - m a t e ( I t M ) a v e r a g e s the r e c o r d of the d a u g h t e r in question rant the records of h e r p a t e r n a l h a l f sisters were r e m o v e d f r o m the h e r d average. The a b b r e v i a t i o n , adj., r e f e r s to the a d j u s t m e n t made f o r the n m n b e r of h e r d - m a t e s a n d the b values in the above equations r e f e r to the i n t r a - s i r e regression estimates ( T a b l e 1) f o r daughter records on adjusted herd-mate averages. F i r s t - l a c t a t i o n d a u g h t e r records were adj u s t e d b y use of h e r d - m a t e a v e r a g e s based on b o t h actual a n d m a t u r e equivalent ( M E ) firstl a c t a t i o n p r o d u c t i o n , as well as b y the use of h e r d - n m t e a v e r a g e s f o r all M E lactations. Therefore, two more f o r m u l a e were involved in ad-

TABLE 1 Intra-sire regression analysis of daughter records on adjusted herd-mate averages" tterd-mate avg y (]~g) i-c (leg) A. 40,501 first available daughter records of 528 sires 6-month fixed season avg ME milk 5,697 5,629 including all lactations ME fat 208 204 5-month rolling season avg including all lactations ME fat ~' 208 204 B. 22,484 first-lactation daughter records of 517 sires 6-rr~onth fixed season avg Actual milk 4,477 4,445 inOuding first lactations Aefual f a t 163 162 ME milk 5,724 5,683 ME f a t 210 208 6-month fixed season avg ME milk 5,724 5,647 including all lactations ME f a t 210 205

b~sb .88±.01 .88--+-.01 .89±.01 .78±.01 .82-±.01 .79_+.01 .83~.01 .90±.01 .89±.01

This table contains mean values for daughter records (y) and for their adjusted herd-mate averages (x), and intra-sire regression coefficients (b) with their corresponding errors (sb). b Five-month rolling season herd-mate averages were not eoinpute4 for ME milk. J. ~)AIRY

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T . P . FAIRCHILD ET AL

j u s t m e n t of first-lactation d a u g h t e r r e c o r d s : V I . D a u g h t e r r e e o r d - - b ( a d j . 6-month first-lactation H M avg f o r actual prod u e t i o n - - b r e e d season a v g ) V I I . D a u g h t e r r e e o r d - - b ( a d j . 6-month first-lactation H M avg f o r M E prod u c t i o n - - b r e e d - s e a s o n avg) The breed-season a v e r a g e s in F o r m u l a e I - ¥ I I c o r r e s p o n d e d to the different t y p e s of cont e m p o r a r y a v e r a g e s involved in these formulae. Thus, breed-season a v e r a g e s were calculated f r o m W i s c o n s i n H o l s t e i n data f o r all of the s i x - m o n t h p e r i o d s a n d f o r all of the rolling five-month periods. F i r s t - l a c t a t i o n breed-season averages were calculated f o r use with firstlactation h e r d - n m t e averages. The sources of v a r i a t i o n influencing differences a m o n g p r o d u c t i o n records were studied b y e s t i m a t i n g c o m p o n e n t s of v a r i a n c e according to M e t h o d 1 of H e n d e r s o n (10). The l i n e a r model which described a d a u g h t e r record w a s : Yu~ = u + h~ + s: + ( h s ) , : + e , ~ where yuT0 ---- the r e c o r d m a d e in the i t~ h e r d b y the /,:~" d a u g h t e r of the jr,, sire, u - the p o p u l a t i o n mean, hj = the effect of the i TM herd, sj = the effect of the j ' " sire, ( h s ) ~ = the effect of a,, i n t e r a c t i o n between the i " h e r d a n d the j " ' sire, a n d (',::¢--a r a n d o m e r r o r effect :~ssociated with the i j k " d a u g h t e r record.

V a n V l e e k et al. (24) stated t h a t the best t y p e of record f o r r a n k i n g sires should be unbiased a n d have the snmllest variance. I n the p r e s e n t analysis the smallest v a r i a n c e was given by t h e records a d j u s t e d by use of the simple h e r d average. H o w e v e r , V a n V l e e k et al. showed algebraically t h a t m e t h o d s which use the simple h e r d a v e r a g e are biased b y a f a c t o r which depends u p o n t h e n u m b e r of herd-mates. These workers f u r t h e r stated t h a t the use of n o n p a t e r n a l h e r d - m a t e a v e r a g e s gave u n b i a s e d r a n k i n g s of sire effects a n d t h a t , a m o n g such averages, use of regressed a d j u s t e d h e r d - m a t e a v e r a g e s gave the smallest variance. Results of t h e p r e s e n t s t u d y were in a g r e e m e n t with this. A m o n g those records a d j u s t e d b y the use of h e r d - m a t e averages the smallest v a r i a n c e s resulted w h e n regressed a d j u s t e d h e r d - m a t e averages were used. The p e r c e n t a g e s o f v a r i a n c e associated with t h e estimated c o m p o n e n t s of v a r i a n c e app e a r in Tables 2 a n d 3. I n some eases the i n t e r a c t i o n c o m p o n e n t was slightly negative. W h e n this occurred the i n t e r a c t i o n c o m p o n e n t was considered as zero, a n d the p e r c e n t a g e values were calculated accordingly. The h e r d c o m p o n e n t of v a r i a n c e wt~s generally responsible f o r a b o u t 3 0 % of the total variance in u n a d j u s t e d d a u g h t e r records and, f o r all types of a d j u s t e d d a u g h t e r records, the influence (,t7 h e r d - t o - h e r d differences was substantially reduced. The p e r c e n t a g e of totnl variance r e p r e s e n t e d by the sire c o m p o n e n t was a b o u t

T A B L E _o P(.'ceut:~ge of total v:Lri:m('e :(ssoeiated with herd, sire, :~ml herd "X sire i n t e r a c t i o n ofl'e(,ts for mmd.justed and a d j u s t e d first awdl:~l,le (l:mgl~ter records"

UmMjusted daughter roeo,ds ( !OllipOlLellt

(,f v:l,'ianee Ih.rd ( H ) Si,'o (S) I1 ,-~ S Er,'or Tot:,l vnrianee ~'

ME ndlk ME f a t 27.3 29.6 7.0 8.9 2.7 1.4 63.0 60.1 13,264 1,186 D a u g h t e r records adjust ,d by: Adj. Reg. adj. 6-month 6-month 6-month (;-month herd avg HM ~ avg" HM avg HM avg fo,' for for for ME f~/t ME f a t ME f a t ME milk (i) (ii) (iii1 (iv) I~el'd 3.9 3.7 4.1 4.3 Sh'e 8.9 9.4 9.8 7.8 0.2 5.5 4.7 5.5 H~'S Error 87.0 81.4 81.4 82.4 Total variance 1,195 1,439 1,406 10,104 " 40,501 first available daughter records, 528 sires, 2,718 herds, and elasses. ~'Variance for milk yield expressed as (kg/.o)2; variance for fat yield c HM Herd-mates. J. ]-)AIRY SCJENC~.' 52015. 49, NO. 11

Reg. adj. Reg. :ldj. 6mmnth 5-m(m~h HM avg JIM avg for for ME f a t ME fat (iv) (v) 5.2 5.0 9.9 9.9 4.1 4.2 80.8 80.9 1,399 ] ,389 24,414 herd-sh'e subexpressed as (kg)~.

TRANSMITTING ABILITIES OF SIRES

1419

TABLE 3 Percentage of total variance associated with herd, sire, and herd × sire interaction effects for unadjusted and adjusted first-lactation daughter records ~' Component of variance Herd (H) Sire (S) H x S

Error Total

variance

Unadjusted daughter records Actual Actual milk fat ME milk 28.4 30.5 29.1 8.9 10.6 9.2 0.0 0.0 0.0 62.7 58.9 61.7 8,230 1,180 13,359

ME fat 31.4 10.9 0.0 57.7 1,912

Daughter records adjusted by regressed adjusted 6-month herd-mate avg for FirstFirstFirstFirstAll All lactation lactation lactation lactation lactation lactation actual milk actual fat ME milk ME milk ME fat ME fat (VI) (¥I) (VIII (VII) (IV) (IV) Herd 5.7 5.8 5.6 5.8 6.9 8.3 Sire 9.5 11.6 10.0 12.0 10.2 12.5 H ×S 5.5 3.9 4.8 3.4 3.0 0.0 Error 79.3 78.7 79.6 78.8 79.9 79.2 Total variance 6,657 906 10,620 1,441 10,240 1,381 22,484 first-lactation daughter records, 515 sires, 2,226 herds, and 14,843 herd-sire subclasses. the same for all types of daughter records. These percentage values ranged from 7 to more than 12%. The percentage of variance due to the herd-by-sire interaction was generally small, but these interaction effects did account for as much as 5.5% of the variance in some types of adjusted daughter records. However, these percentage figures for the herd-by-sire interaction were not as large as those found by Allaire and Gaunt (1), nor were there any apparent differences due to use of first-lactation as opposed to all-lactation herd-mates. The sire components obtained when all of the daughter records were used to esthnate components of variance seemed relatively large. An attempt was, therefore, made to remove some of the nonorthogonality in the data by linfiting the data to the daughter records of those sires with at ]east 20 recorded daughters, and by further restricting the data to records from those herds in which at least 20 daughters had completed their lactations. This crude attempt to balance the data had no effect on the magnitude of the estimated sire components, and results based on these data were similar to those of the previous analysis. Relationship between early and later daughter averages. In the final phase of the study the different types of daughter records (unadjusted and adjusted) were compared by investigating the relationship between the average performance of a large number of later daughters and the average perfl)rmanee of different numbers of early daughters. In the first of these analyses the average performance of 100 later daughters was regressed on the average

performance of eumulative groups of the first 5 to 40 daughters. The 100 later daughters represented the 41st through the 140th daughter of each sire. Only 29 sires had 140 firstlactation daughters with first-lactation herdmates; therefore, a second analysis was run in which the average performance of 70 later daughters was regressed on the average performanee of the first 5, 10, 15, 20, 25, and 30 daughters. The estimated regression and correlation coefficients are shown in Tables 4 and 5. These coefficients indicate that there were no large differences among the different types of daughter records (unadjusted and adjusted) in their predictive ability. Thus, no type of daughter record appeared to be markedly superior in terms of predicting the future performance of sires. Also, there seemed to be no great advantage of using" over 20 daughters to evaluate a sire, because the correlation and regression coefficients showed little increase after the nmnber of early daughters reached about 20. The lack of increase in these regression coefficients after the number of early daughters reached 20 did not agree with estimates of the repeatability of progeny tests, as calculated from components of variance. By using daughter records adjusted for herd-year-season effects it should be possible to estimate the regression of future daughters on those tested by : Tt ~ - O " e (r- s ~. I ) A I R ¥

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TABLE 4 R e g r e s s i o n a n a l y s i s of the a v e r a g e p e r f o r m a n c e of 100 l a t e r d a u g h t e r records (the 41st t h r o u g h the 140th) on a v e r a g e p e r f o r m a n c e of c u m u l a t i v e g r o u p s of the first 5 to 40 d a u g h t e r records" A.

F i r s t a v a i l a b l e d a u g h t e r records of 86 sires b U n a d j u s t e d d a u g h t e r records M E nfilk ME f a t No, of e a r l y daughters r b r b 5 10 ]5 20 25 3(I :~5 4o

.29 .40 .46 .58 .57 .58

.19 .31 .40 .52 .49 .50 .53 .5(;

A1 .63

l)aughfe~' reeordu 6-month herd avg for ME fat

6-month HM avg for ME fat

(I) 5 10 15 20 25 30 35 40

,Adj, 6-month H M a v g for ME f a t

(II)

.42 .54 .59 .67 .64 .65 .67 .69

.27 .45 .55 .61 .58 .57 .59 .62

adjuM.ed by Reg. adj. 6-mouth H M a v g for ME m i l k

Reg. adj. 6-re(ruth HM avg for ME fat

(~v)

(IIi)

Reg, ad j. 5-month H M av g f o r ME fat

(v)

(Iv)

r

b

r

b

r

b

r

b

r

b

r

b

,47 .52 .61 .65 .65 .66 .68 .69

.31 .42 .55 .60 .62 .61 .63 .65

.46 .51 ,61 .65 .~6 .67 .69 .70

.31 .42 ,55 ,61 ,63 .62 ,65 .66

.48 .53 .61 .66 .66 .67 .69 .70

.32 .44 .56 ,62 ,63 .62 .65 .66

.36 .42 .50 .60 .62 .61 .63 .64

.25 .32 .44 .55 .56 .55 .58 .60

.47 .53 .61 .66 .67 .69 .69 .7~

.32 .44 .56 .62 .63 .62 .64 .66

A6 .54 .62 .66 .67 .67 .70 .71

.31 .44 .56 .62 .64 .62 .65 .67

.'[3. P i r s t d a e t a t i o n daughters with first-lactation herd-mates (29 sires) ~ Unadjusted No. of earlF daughters

Actual r

5 10 15 20 25 30 35 40

.24 ,42 ,51 .58 .57 .58 .57 ,63

milk b

daughter

records

Actual fat, r b

,18 ,30 ,39 .39 .39 .40 .40 .47

.32 .51 .65 .68 .68 .69 .67 .72

.28 ,43 .52 .47 .48 .49 .46 .56

ME milk r b .26 .39 .49 .56 .56 .57 .58 .63

.19 .29 .38 .38 .38 .40 .4O .47

ME

fat

r

b

.35 ,50 .6l .67 .67 .69 .68 .73

.29 .42 .51 .47 .48 .48 .48 .54

D a u g h t e r records a d j u s t e d by reg. adj. 6-month I-IM avg for First-lactation actual milk

First-lactation actual f a t

(VI) 5 10 15 20 25 30 35 40

First-lactation ME milk

(VI)

Firstqaeta.~ion ME f a t

(VII)

All-lactatim~ ME milk

(VII)

r

b

r

b

r

b

r

.25 .43 .48 .57 .59 .58 .57 .62

.20 .33 .40 .~2 .42 .44 .42 .49

.36 .55 .65 .69 .71 .71 .68 .73

.29 .45 .53 .51 .51 .51 .48 .55

.26 .41 .46 ,56 .58 .58 .57 .62

.21 .32 .39 .41 ,42 .43 .42 .48

.38 .54 .63 .66 .70 .70 ,68 .73

This table eontalns estimated correlation coefficients (r) and regression coefficients ( b ) . b The s t a n d a r d errors of the regression coefficients in Seetlon A r a n g e d f r o m .06 to .08. ¢ The s t a n d a r d errors of the regression coefficients in Section J3 r a n g e d f r o m .10 to .15.

All-lactation ME f a t

(IV)

(IV)

b

r

b

.32 .45 .52 .50 .52 .51 .49 .55

.22 .41 .53 .57 .60 .60 .57 .61

.15 .32 .42 .43 .45 .46 .46 .50

r

b

.39 .58 .70 .71 .73 .73 .69 .74

.32 .52 .58 .5~ .56 .55 .52 ,58

TABLE 5 Regression analysis of average performance of 70 later daughter records (31st t h r o u g h 100th) on average p e r f o r m a n c e of cumulative g r o u p s of the first 5 to 30 d a u g h t e r records ~ A. F i r s t available d a u g h t e r records of 134 sires ~ U n a d j u s t e d daughter records No. of early daughters

ME milk r b

5 10 15 20 25 30

.44 .49 .54 .63 .64 .66

.26 .37 .47 .55 .57 .59

ME f a t r

b

.49 .52 .57 .64 .65 .67

.28 .41 .51 .57 .60 .61

D a u g h t e r records a d j u s t e d by 6-month herd avg f o r ME f a t

6-month H~'I avg for ME f a t

(I) 5 10 15 20 25 30

Adj. 6-month H M avg f o r ME f a t

(If)

Reg. adj. 6-month H M avg f o r ME milk

(III)

Reg. adj. 6-month t I M avg for ME f a t

(IV)

Reg. adj. 5-month H M avg f o r ME f a t

(IV)

(¥)

r

b

r

b

r

b

r

b

r

b

r

b

.48 .51 .61 .63 .65 .67

.31 .41 .54 .57 .60 .62

.47 .50 .60 .62 .64 .66

.30 .40 .54 .57 .6U .62

.48 .51 .60 .63 .65 .67

.31 .41 .54 .57 .61 .62

.47 .51 .59 .64 .66 .67

.30 .40 .52 .58 .60 .61

.49 .52 .61 .64 .65 .67

.31 .42 .55 .52 .61 .62

.49 .51 .59 .62 .65 ,67

.31 .41 .53 .57 .62 .63

]3. :Plrst lactation daughters with first-lactation herd-mates (61 sires) ¢ U n a d j u s t e d d a u g h t e r records ,No. of early daughters 5 10 15 20 25 30

A d a m milk r b .42 .51 .57 .61 .56 .59

Actual f a t r b

.32 .42 .43 .53 .49 .53

.50 .58 .65 .67 ,63 .67

ME milk

.38 .55 .62 .61 .57 .60

ME f a t

r

b

r

b

.44 .51 .57 .62 .57 .60

.32 .42 .53 .54 .49 .53

.51 .58 .65 .68 .64 .68

.37 .54 .61 ,61 .58 .60

D a u g h t e r records a d j u s t e d by reg. I t M avg f o r First-lactation actual milk

First-lactation actual f a t

(VI)

5 10 15 20 25 30

.45 .53 .58 .62 .61 .64

First-lactation ME milk

(VI)

First-lactation ME milk

(VII)

All-lactation ME f a t

(VII)

b

r

b

r

b

r

.34 .46 .57 .57 .55 .6()

.52 .61 .66 .67 .68 .71

.42 .59 .66 .63 .63 .66

.47 .53 .58 .63 .62 .65

.34 .45 .56 ,57 .56 .60

.54 .61 .66 .68 .69 .72

This table contains estimated correlation coeffclents (,r) an(l regression coefficients ( b ) . The s t a n d a r d errors of the regression coefficients in Section A r a n g e d f r o m .05 to .06. The standard errors of the regression coefficients ranged in Section B from .08 to .10.

All-lactation ME f a t

(IV) b .41 .58 .65 ,63 .64 .66

r .45 .53 .61 .65 .64 .65

(IV) b .31 .43 .55 .57 .57 .60

r .55 .64 .71 .73 ,72 ,73

b .42 .59 .67 .67 ,67 .67

1424

T.P.

FAII~CHILD

where:

.u = the number of tested daughters, cr"-~-----the variance with sires, and cr~ = the variance among sires. According to the variance component analyses (Tables 2 and 3) the sire component accounted f o r a'bout 8 to 12.5% of the total variance in adjusted daughter records. I f it is assumed that ] 0 % of the total variance in such records is due to variance among sires, then the regression of future daughters on those tested can be expressed as

I n making this n + 9" assumption it must be remembered that the e,stimates of sire effects obtained in the present study are higher than most other estimates reported in the literature. This would suggest that the estimates obtained in the present study were inflated by something other than true sire effects. I f one uses ~

to estimate expected re-

gression values, then compares these values to those in Tables 4 and 5, it ean be seen that the estimated values are or'ten within one standard deviation of the ealenlated values, as indicated hy the standard errors of these caleulah,d wdues. However, at the 30-daughter n, level, for example, the ration - gives an nq- 9 esti,m~.ted regression o? .77. A t this level the c,)effieients in Tat)lea 4 and 5, ~:aleula.ted by regressing the l)erfornmn(~e of later daughters on the performance of early daughters, are cox)sistently smaller than the estimated wdue of .77. ~t

The regression, . . . . . . . . . . , is based on the Jl -}- 0-'20 cr'~

assumption that any environmenta,1 correlation am()ng lmt(,rnaI ha.i?-sisters is removed by adjustin g the records for herd year-season effeets. l lowever, the I)resenee ,)1' environm(mtal eorrelations among paternal half-sibs not removed by use of contemporary comparisons will cause the repeatability o? a prog'eny test to increase only slightly as the number of tested daughters increases. This is one possible explanation f o r the discrepancy between the calculated regressions and those estimated from variance eomlmnents. I t should also be noted that the sires involved in the regression analyses were only a p a r t of those upon which the variance component estimates were based, and this sampling differvnce could be another reason for the difference between the calculated and the estimated regression values. The supposition that residual correlations exist in deviation reeords, g. I)AIICY SCIENOE VOL. 49, NO. 11

ET

AL

i.e., adjusted daughter records, is supported by Bereskin and Lush (6). Based on results o£ their investigation of this possibility, they coneluded that residual eorrelations in deviation records are likely to be of considerable importance, even when the distribution of daughter records is similar to that prevailing under ideal A.I. eonditions. More recently, however, ¥ a n V l e e k (23) has presented evidence to show that environmental correlations among paternal half-sibs are of negligible importance in A.I. sire evaluatiom Conclusions The p r i m a r y purpose fo using contemporary herd-mate eomparisons in evaluating progeny records is to remove herd effects and the present study indicated that the use of sueh eomparismls was sueeessful in this regard. However, the regression analyses <)t' late}' on early daughter averages indicated that there were no large differences among the different types of re,~o)'ds (unadjusted and adjusted) in terms of their ability to predict the future perf<)rmanees ot' sires' daughters. Ii' the dat.i had not been restricted to Wiseonsin records, and had ineluded sires with dau~'hters from different geographical cegions, use of herd-mate averages to adjust daughter re<,m'ds mi~'ht have al>peared more adwmtagenus. Some worke)'s (14, 1.5, 17) haw' de%nded the use of o,,ly film lactation herd ,Hates ?or making eotltemDoral'y <'ol/lparisotts, }?l'('ailse the early ev-dm, tiolJ . f sires inw)lw,s only the firstlactation revorn daughters had no first-bl<4ation herdnlates and, as stated previously, for those first]aetati
TRANSMITTING

ABILITIES

a bias. No selection bias was evident in the p r e s e n t study. I n Table 1 it can be seen that, based on M E p r o d u c t i o n , mean values f o r firstlactation h e r d - m a t e s v e r a g e s were actually h i g h e r than c o r r e s p o n d i n g values f o r alllactation h e r d - m a t e averages. I t would a p p e a r t h a t f u r t h e r research is necessary to determine the value o f using only first-lactation h e r d - m a t e s with first-lactation d a u g h t e r r e c o r d s ; to determine the i m p o r t a n c e of environmental correlations in deviation reco r d s ; and simi)ly to i m p r o v e out" methods of sire evaluation. Use of regressed a d j u s t e d h e r d - m a t e averages is certainly our best method o f adjusting' d a u g h t e r records f o r h e r d - y e a r season effects and, althoug'h the [)resent analyses were unable to p r e d i c t a substantial t/dvant~lge f o r any p a r t i c u l a r t y p e of d a u g h t e r record, it would seem desirable t~ use w h a t e v e r t:ype of record, i.e., w h a t e v e r t y p e of sire p r o o f , is theoretically most correct. W i t h centralized p r o c e s s i n g of d a i r y records and with use o f high-speed eomlmters, complex m e t h o d s o f assessing p r o g e n y tests p r e s e n t no problem. Therefore, it is imt)erative that we e o n s t a n t l y reevaluate our pr(,eedures and strive to i m p r o v e them. References

(1) Allaire, F. ]3., and Gmmt, S. N. 1965. l~irst-Laetatlon Contempo,.ary Comparisons as Indicators of Environmental Influences on Daughter Records Used for Sire Evaluation. J. Dairy Sol., 48:454. (2) Burr, G. [~. 1958. A Comparison of Four Methods Used in Evaluating the Transmitring Ability of Holstein-Friesian Bulls. M.S. thesis, University of Toronto. (3) ;Bcrcskin, B., and Freeman, A. E. !965. Genetic " r o d Enviromnental Factors iu Dairy Sire Evaluation. I. Effects of Herds, Mouths, and Year-Seasons on Variance Among Lactation Records; Repeatability aud Hteritability. J. Dairy Sci., 48:347. (4) ]lereskin, ]3., and Freeman, A. E. 1965. Genetic and Environmental Factors in Dairy Sire Ewduation. II. Uses and Limitations of Deviatio,~ Records and the Role of Dams. J. Dairy Ski., 48:352. (5) Bereskin, ]3., and Hazel, L. N. 1962. The Role of Herd Averages in Dairy Sire Evaluation. J. Animal Sei., 21:969. (6) ]3ereskin, ]3., and Lush, J. L. 1965. Genetic and Environmental Factors in Dairy Sire Evaluation. III. Influence of Environmental and Other Extraneous Correlations Among the :[)aughters. J. Dairy Be]., 48: 356. (7) Corley, E. L., Dm.kwall, J. W., and Heizer, E. E. ].963. Production Performance of Artificially aad Nonartificially Sired Herdmates in Wisconsin. J. Dsiry Sei., 45:50.

O]~" S I R E S

1425

(8) Gaunt, S. N. 1958. Relative Merits of Five Ways of Adjusting for the Herd Influence on Artificially Sired (AI) Daughters' Records. J. Dairy Sei., 41:745. (9) Gaunt, S. N., ]lartlett, M. A. Goodwill, and Comstock, W. L. 1964. Comparison of Five Methods of Adjusting for Environmental Differences in the Evaluation of Dairy Sires. J. Dairy Sei., 47:1243. (10) Henderson, C. R. 1953. Estimation of Varilance and Covariance Components. Biometrics, 9:226. (11) Henderson, C. R., and Carter, H. W. 1957. Improvement of Progeny Tests by Adjusting for Herd, Year, and Season of Calving. J. ])airy Ski., 40:638. (12} Henderson, C. R., Carter, H. W., and Godfrey, J. T. 1954. Use of Contemporary Herd Averages iu Appraising P~'ogeny Tests of Dairy Bulls. J. Animal Ski., 13: 959. (13) Johansson, L 1960. Progeny Testing Methods in Europe. J. Dairy Sei., 43:706. (1.4) Johansson, I. 1961. Genetic Aspects of Dairy Cattle ]lreeding. University of Illinois Press, Urbana. (15) McArthur, A. T. G. 1954. The Assessment of Progeny Tests of Dairy ]lulls Made Under Farm Conditions. Proc. ]lrit. Soe. Animal Prod., p. 75. (16") Miller, IL II. 1962. A New Method for Compariug Sires. JcIoard's Dairyman, 107 (t5) : 816. Augus~ 10. (17) Robertson, A., Stewart, A., and Ashton, E. l). 1956. The Progeny Assessment of l)Mry Sires for Milk: The Use of Contemporary Comparisons. Proe. ]lrit. Soc. Animal Prod., p. 4~3. (18) Searle, S. R. 1964. Review of Sire-Proving Methods in New Zealand, Great Britain, and New York State. J. Dairy Sei., 47:402. (19) Sendelbach, A. G. 1960. Repeatability of Sire Provings. Ph.D. thesis, University of Wisconsin, Madison. (2(I) Tucker, W. L., and Legates, J. E. ]962. Effective Use of Herd-Mates in Dairy Sire Ewtluation. J. Animal Sci., 21:976. (21) Tucker, W. L., and Legates, J. E. 1965. Seasonal l)ivision of Herd-Mates in Sire Evaluation. J. Dairy Ski., 48:234. (22) VanVleck, L. D. 1963. ]%gression of l~ecords on tIerd-mate Averages. J. Dairy Sei., 46 : 846. (23) ¥anVleck, L. 1). 1966. Environmental Correlations in Sire Evaluations. J. Dairy Sci., 49:56. (04) VanVlekk, L. D., Heidhues, T., and tIenderson, C. R. 1961. Analysis of Deviations of Dairy Records from Different Contemporary Averages. J. Dairy Sci., 44:269. (25) VanVleek, L. D., 0'Bleness, G. V., and Henderson, C. l~. 1961. Comparison of Procedures Used for Evaluating Sires Used i~L Artificial Insemination. J. Dairy Sci., 44:708. J. DAIRY SCIENCE VOL. 49. NO. 11