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Age of Dam and Direct and Maternal Effects on Calf Livability1
Age of Dam and Direct and Maternal Effects on Calf Livability' M A R I O L. M A R T I N E Z , 2 A. E. F R E E M A N , and P. J. B E R G E R Department of Animal Science Iowa State University Ames 50011
ABSTRACT
The genetic relationships between calf livability (alive or dead) were investigated for first and subsequent parturitions of dams, and genetic correlations between direct and maternal effects were estimated. Data were 95,106 Holstein calvings. Heritabilities of direct effects were .4% for heifers and .6% for cows. The genetic correlation between calf livability for heifers and cows was .32. Regardless of age of dam, calf mortality was more frequent for male than female calves when calf livability was estimated as either a direct or maternal trait. Effects of gestation length on calf livability were quadratic and differed for heifers and cows. Largest rates of survival were with gestation lengths of 276 and 283 days for heifers and cows. Maternal heritabilities (estimated as four times the maternal component of variance divided by the maternal plus residual components) of .5% and .6% and dam heritabilities (estimated as four times the maternal grandsire component of variance divided by the maternal grandsire plus residual component) of .4 and .5% were small for both heifers and cows, respectively.
INTRODUCTION
Age of dams at calving affected calf mortality (2, 3, 7, 13, 14, 19). Two to four times more calf mortality for heifers than for old
Received July 28, 1982. 1Journal Paper No. J-10684 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 1053. 2 Brazilian Agricialtural Research Cooperation (EMBRAPA). CNP-Gado de Leite. 36155-Coronel Pacheco. MG. Brazil. 1983 J Dairy Sci 66:1714-1720
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cows was reported (2, 14). Weak labor of darns and malpresented calves accounted for 33 and 24% of calf mortality in births from cows (14); the same two causes were associated with 25 and 20% calf mortality in births from heifers (14). Heifers had shorter gestation than cows (1). Calves born to cows were 3.1 kg heavier and required an extra day of gestation compared with calves born from heifers (15). Heritabilities of calf mortality differed for heifers and cows (4, 13, 16, 19). These results indicate the possibility of calf livability being a different trait for heifers and cows. Based on these results, Philipsson (16) and Teixeira (19) analyzed first and later parity records separately. In general, heritability for rate of still birth has been less than 5% and also was greater when estimated as a character of the calf (direct effect) than when estimated as a character of the dam (maternal effect). Heritabilities for calf-genotype effects on calf mortality were 4.2% in heifer calvings and 1.3% in cow calvings (4). For dam genotype, Bar-Anan et al. (4) reported heritabilities 1.8% and .4% for heifers and cows. The direction and magnitude of direct and maternal effects are important for reliably predicting response to selection and were reported by Legates (12) for laboratory species: Kock (10) for beef cattle, Robinson (17) for swine, and Bradford (5) for sheep. Biometric aspects of maternal effects also have been explored by Willham (22, 23). Little work has been done on early calf mortality, although direct and maternal effects have been reported for different traits and species. Phitipsson (16), using an indirect procedure, reported a genetic correlation between direct and maternal effects of .07 for early calf mortality. Teixeira (19) ranked bulls for transmitting ability as sires (direct effect) and maternal grandsires (direct and maternal effects), assuming a genetic covariance between direct and maternal effects of zero. The rank
DAM AGE AND DIRECT AND MATERNAL EFFECTS correlation between these estimates was - . 1 1 for the 14 bulls available for this analysis. Although the two reports on calf livability may indicate a null genetic relationship between maternal and direct effects, results on other traits and species suggest a genetic antagonism between the two effects (6, 8, 11,24). Objectives of this study were: 1) to estimate the genetic relationship between livability of calves of dams in first and subsequent parturitions and 2) to estimate the genetic correlation between direct and maternal effects on calf livability. MATERIALS A N D METHODS
Data for this study were obtained from the National Association of Animal Breeders and were 95,106 records from Holstein calvings collected by individual dairy producers cooperating with artificial insemination organizations. Only records with gestation periods greater than 260 days and less than 300 days were used. These limits were chosen because they should be close to the lower and upper limits of the normal variation of gestation length (1, 14). A mixed model was used to define effects on calf livability as:
b 2 = quadratic partial regression coefficient on gestation length squared, eijkl m = random residual associated with the observation Yijklm. Components of variance and covariance were estimated by the multitrait procedure developed by Schaeffer et al. (18). A calving is the experimental unit, and this model enables quantification of the direct effect of the sire on livability of calves from heifers versus older cows. The model is used further in a maternal and direct analysis where the sire appears as the sire of the calf and subsequently as a sire of progeny which calve (maternal grandsire). Each experimental unit appears for only one trait, because the procedure assumes no error covariance among all traits, a condition which is not true if the same experimental unit is used for both traits. Computational procedures to estimate simultaneously sire and error variances and sire covariances for different traits were described by Tong et al. (21) and Thompson (20). Components of variance and covariance obtained by this method are not unique until estimates have converged in an iterative procedure. The iterative solutions at convergence are Restricted Maximum Likelihood estimates. Age-of-Dam Analysis
Yijklm -- ~ + HYSi + Bj + Sk + PI + b l (Xijklrn -- X) + b2 (Xijkl m -- ~)2
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[I]
+ eijkl m where: Yijklm = livability score; 1 = alive, 2 = dead, ~t = overall population mean, ttYS i = fixed effect of the iTM herd-yearseason; season defined as 1; Novemb e r - F e b r u a r y , and 2, March-October, Bj = random effect of the jth sire, Sk = fixed effect of male and female calves, k = 1, 2, P1 = fixed effect of the lth age of dam, 1 = 1, 2,/> 3 parities, Xijkl m = effect of gestation length of the ijklm dam, mean gestation length, b l = linear partial regression coefficient on gestation length,
Calf livability was considered a different trait for heifers as darns from cows as dams. The requirement of the two traits being measured on different groups of animals could be a problem if a dam that had her first calf in 1976 had a second calf in 1977, etc. This situation would induce environmental covariance; however, it should be small because the calvings would be in different year-seasons. Because of poor cow identification, all records in the same herd-year-seasons, from the same sire, sex, calving date, and with the same calf livability score were considered duplicated or multiple births and eliminated. This accounted for only 1.6% of the records. Also, if a dam appeared as both a heifer and a cow, her records were eliminated from the cow's data. This was done to minimize environmental covariance. Examination of the records indicated that only 2.2% of the identified heifer-dams had a second record. The sires were required to have progeny in at Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ
least five herd-year-seasons from dams of both first and later parities to insure adequate ties between herds. No restriction was imposed on the relation of herds for heifers as dams' with those for cows as dams, i.e., the five herds for cow-dams could be the same or completely different herds from the five herds for heiferdams. To define the fixed factors that influence calf livability, model [I] was used for both heifers and cows as dams. Separate effects of sex of calf and regression coefficients of gestation length were estimated for heifers and cows. Herd-year-seasons were absorbed. Characteristics of data in the age-of-dam analysis are in Table 1. Maternal and Direct Analysis
Components of variance necessary to study the relationship of maternal with direct effects of calf livability are the direct genetic variance (o~3), the maternal variance (o~a), and the direct by maternal covariance (O~M). Components of variance and covariance estimated from these data were the variance among sires (o~), the variance among maternal grandsires 2 ( O M G S ) , and the covariance between sires and maternal grandsires ( O S . M G S ) . From these components, estimates of a~3, o k , and aDM could be obtained as described by WiIlham (23): O~ = .25 O~
[1]
2 O'MGS = .0625 o~3 + .25 cr~ + .25 ODM OS.MG S =
.125 o~) + .25 ODM
[2] [31
ET AL.
The components o~3, o~t, and ODM were estimated from equations [1], [21, and [3]. The genetic correlation between the maternal trait with the direct trait was estimated from: rGD,M = ODM/(O'~) O~) "s . To estimate O S . M G S , a data set was needed with each sire represented as both a direct sire and a maternal grandsire. Data with this structure satisfied the requirements of the multipletrait evaluation if calf livability as a trait of the dam (maternal grandsire) and livability as a trait of the calf (sire) are considered separate traits. Data with identified maternal grandsires were matched with the original data to create a data file with bulls represented as both a sire and a maternal grandsire. The data, as in the age of dam analysis, were edited to exclude duplication of a single record in both data groups. Thus, it was insured that no calving by the same cow was included in the sire and maternal grandsire data sets. Sires again were required to have progeny in five herds for both traits. Analyses were separate for heifer and cow dams so that any differences of the maternal with direct relationship for dams in first versus later parities could be identified. This separation again eliminated parity from model [I]. Sex-of-calf and linear and quadratic effects of gestation length comprised fixed effects of the mixed-model equations for the two direct and maternal analyses. Characteristics of data for the maternal and direct analysis are in Table 2.
TABLE 1. Characteristics of data in the age-of-dam analysis. Parity classification
Heifers Number of sires Number of records Number of herd-year-seasons Within herd-year-season Sum of squares Residual mean squares (o~)
Journal of Dairy Science Vol. 66, No. 8, 1983
258 14,147 2,778 985.48 .088
Cows 258 67,774 8,452 2,921.80 .049
Total 258 81,921
DAM AGE AND DIRECT AND MATERNAL EFFECTS RESULTS A N D DISCUSSION Age-of-Dam
F o r t h e r e l a t i o n s h i p of calf livability in heifer d a m s w i t h calf livability in cow dams, a t o t a l o f 8 1 , 9 2 1 r e c o r d s f r o m 2 5 8 sires was used (Table 1). C o m p o n e n t s o f variance a n d covariance were i t e r a t e d u n t i l e s t i m a t e s converged. F i n a l estim a t e s o f c o m p o n e n t s of variance a n d covariance are in T a b l e 3. H e r i t a b i l i t i e s were .4 a n d .6% for heifers a n d cows. T h e s e e s t i m a t e s are lower t h a n t h o s e r e p o r t e d b y B a r - A n a n et al. (4) f o r IsraeliFriesians (4.2% in heifers, a n d 1.3% in cows). L i n d s t r o m a n d Vilva (13), h o w e v e r , f o u n d a t e n d e n c y for h e r i t a b i l i t y ( c o r r e c t e d to transf o r m t h e m e a s u r e s to c o r r e s p o n d to an a s s u m e d u n d e r l y i n g c o n t i n u o u s l y a n d n o r m a l l y dist r i b u t e d t r a i t ) of calf livability to be higher f o r cows (5.4%) as d a m s t h a n for heifers (2.7%) as dams. A n a p p r o x i m a t e s t a n d a r d e r r o r o f herita-
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b i l i t y (9) was .3% for heifers a n d less t h a n 2% f o r cows. T h e g e n e t i c c o r r e l a t i o n b e t w e e n calf livability for heifers a n d cows was .32. T h i s c o r r e l a t i o n did n o t i n d i c a t e a s t r o n g g e n e t i c r e l a t i o n s h i p b e t w e e n calf livability for heifers a n d calf livability f o r cows. A l t h o u g h heritabilities are small, s o m e genetic progress could b e m a d e t h r o u g h selection because t h e r e is some genetic v a r i a t i o n for calf livability. T h e sex e f f e c t was g r e a t e r f o r male calves f r o m heifers ( . 0 2 0 ) t h a n f r o m cows (.007). C o n s t a n t s f o r sex w i t h i n age were c o n s t r a i n e d to add to zero. T h e s e c o n s t a n t s i n d i c a t e d a m o r e p r o n o u n c e d sex e f f e c t for heifers t h a n f o r cows as dams. Regardless of effects of age o f d a m , g r e a t e r calf m o r t a l i t y o c c u r r e d f o r male t h a n f e m a l e calves. Effects of g e s t a t i o n l e n g t h b y age of d a m o n calf livability are in Figure 1. L i n e a r a n d q u a d r a t i c partial effects o f g e s t a t i o n l e n g t h o n calf livability were .0021 a n d .0003 for heifers and -.0031 a n d .0006 f o r cows. P r e d i c t e d
TABLE 2. Characteristics of data for the maternal and direct analysis. Heifers Sire Number of sires Number of progeny Number of herd-year-seasons
106 5,720 1,219
Within herd-year-season Sum of squares Residual mean squares
Cows
Maternal grandsire 106
1,692 459
372.22 .085
97.86 .087
Total
Sire
106 7,412
108 23,933 4,018
Maternal grandsire 108 4,400 1,015
989.64 .050
Total 108 28,333
162.72 .051
TABLE 3. Components of variance (Var) and covariance (Cov) for age-of-dam analysis. Variance-covariance components (X 10 s) Sire
Residual
Age-of-dam
Vara
Coy a
Vara
Heifers Cows
8.3 7.7
2.6
8,806 4,845
Cova,b 0
ax 105. bResidual component of covariance defined to be zero. Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ ET AL.
32 30 28 26 =E
o
2
~
HEIFERS
24
,,/,,'//' /J
22 20 18 16 14 12 10 8 6
/ 4~-5
4-3-2-[~0-4"
COWS 2
3
4
5A
4 DAYSOFGESTATIONLENGTHDEVIATEDFROMTHE MEAN
Figure 1. Regression of calf livability on gestation length.
values in the graph are deviated f r o m their means. Mean gestation lengths were 278.8 and 2 7 9 . 7 for heifers and cows. On the ordinate, calf livability was deviated f r o m its mean; 1.105" for heifers and 1.056 for cows. Calf m o r t a l i t y for cows increased for b o t h short and long gestation periods. A similar quadratic effect was observed in Swedish-Friesians (16). F o r cows the highest calf survival o c c u r r e d with gestation l e n g t h o f a b o u t 283 days. F o r heifers, however, the greatest calf survival rate was with gestation length of a b o u t 276 days. Calf m o r t a l i t y increased substantially for heifers with longer than average gestation periods. The increased m o r t a l i t y rate may be due to the unfavorable
ratio of size of calf to size of dam, which will increase dystocia and also calf mortality. F o r cows, however, the increase of calf size may be balanced with the increase of size of dam with o p t i m u m survival changed as in Figure .1.
Maternal and Direct Relationship
The direct by material covariance is important, because a negative covariance w o u l d result in an antagonistic situation if selection is on only one effect. Selection for the direct effect with a negative genetic correlation b e t w e e n direct and maternal effect w o u l d be e x p e c t e d initially to improve the character selected. Eventually the correlated response could be e x p e c t e d to decrease genetic progress because of the negative genetic correlation. These two counterbalancing effects w o u l d be e x p e c t e d eventually to stabilize at some p o i n t depending on the selection for each trait. Data f r o m bulls that appeared as b o t h a sire and a maternal grandsire were analyzed separately for "first and later parities. Sire and maternal grandsire c o m p o n e n t s of variance and sire-maternal grandsire c o m p o n e n t s of covariance were estimated f r o m the data outlined in Table 2. For heifers, 7,412 progeny of 106 bulls were used; cow data were 28,333 progeny of 108 bulls. Again c o m p o n e n t s of variance and covariance were iterated until estimates converged. Final c o m p o n e n t s of variance and covariance are in Table 4. These c o m p o n e n t s were partitioned into
TABLE 4. Components of variance and covariance for the maternal and direct analysis. Variance-covariance components a (X 10 5) 2
Age-of-dam
~
~hGS
aS.MGS
°~ S
°eMG S
°eS.MG S
Heifers Cows
4.6 5.9
7.8 5.9
-- 1.3 .6
8,430 4,936
8,600 5,110
0 0
ao~ = Variance among sires, a~AGS = Variance among maternal grandsires, °S. MGS = Covariance between sires and maternal grandsires, °~S = Residual component of variance for the direct effect, o eMGS 2 = Residual component of variance for the maternal effect, aeS.MGS = Residual component of covariance between direct and maternal effect, defined to be zero. Journal of Dairy Science Vol. 66, No. 8, 1983
DAM AGE AND DIRECT AND MATERNAL EFFECTS TABLE 5. Maternal components (X lO s) of variancecovariance for livability and estimates of heritability a and genetic correlation.
Direct (oh) Maternal (a~) Covariance (aDM) Direct heritability Dam heritability b Maternal heritability c Genetic correlation
HeiSts
Cows
18.4 41.0 -14.4 .2 .4 .5 - . 52
23.6 31.9 -14.2 .5 .5 .6 - . 52
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variance for families of half-sister, was given by F a l c o n e r (9) as n = 4/h 2, where n is n u m b e r of progeny per sire and h 2 is heritability of the character. Using n = 4/h 2 and the average number of progeny per sire, f r o m Tables 1 and 2, one can calculate which heritabilities could be estimated with smaller sampling variance with these numbers of progeny per sire. Based on this i n f o r m a t i o n , heritabilities for cows had smaller sampling variances than for heifers b o t h in the age-of-dam and maternal and direct analyses. Thus, the similar direct heritabilities for cows (.6 v s . . 5 % ) , f r o m the age-of-dam and maternal and direct analyses, may have been a consequence of larger n u m b e r of progeny per sire in the analysis for cows than heifers. These heritabilities were smaller than the ones reported by Bar-Anan e t al. (4) and Lindstrom and Vilva (13); however, t h e y were close to estimates by Teixeira (19) with A m e r i c a n Holsteins. G e n e t i c correlations b e t w e e n maternal and direct effects were b o t h - . 5 2 for heifers and cows. These results were different f r o m the genetic correlation of .07 r e p o r t e d by Philipsson (16), who used an indirect procedure to estimate the correlations. The genetic antagonism b e t w e e n direct and maternal effects r e p o r t e d for different traits and in different species (6, 8, 11, 24) was also observed for calf livability. Constants for sex-of-calf and partial regression coefficients of calf livability on gestation length are in Table 6. As in the age-of-dam analysis, male calves had m o r e m o r t a l i t y than
aHeritabilities expressed in percentage. bDam heritability is heritability of calf livability as a trait of the dam calculated as 4 × a M G S / ( a e2 + O~G S) where CraG S is the variance among maternal grandsires and a~ is the residual component of variance for the maternal effect. 2 2 CMaternal heritability calculated as aM/(a M + at) where a ~ is the maternal variance and ae~ is as in footnote b.
their genetic fractions for the necessary genetic c o m p o n e n t s (Table 5). Heritability estimates of calf livability as a trait o f the dam ( d a m heritability) were similar to t h e direct (livability as trait of the calf) heritability for cows but greater for heifers. Direct heritabilities were smaller than the corresponding estimates f r o m the ageof-dam analysis. One possible reason may be the small n u m b e r of progeny available per bull in this analysis. An a p p r o x i m a t e n u m b e r of progeny per sire, which minimizes the sampling
TABLE 6. Estimates of percentage mortality for sex-of-calf and partial regression coefficients of calf livability on gestation length in the direct and maternal analysis. Heifers
Cows
Direct a
Maternal b
Direct
Maternal
1.6 --1.6
1.3 --1.3
.7 --.7
.8 --.8
-.32 .05
-.19 .04
Sex
Male Female Regression Linear Quadratic
.19 .03
.15 .07
aRefers to data set where bulls were considered as sires. bRefers to data set where bulls were considered as maternal grandsires. Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ ET AL.
females. C o n s t a n t s f o r sexes in the age-of-dam analysis and in t h e direct and m a t e r n a l analysis were similar, particularly f o r cows. No differences b e t w e e n c o n s t a n t s were o b s e r v e d w h e n t h e y were e s t i m a t e d as either d i r e c t or m a t e r n a l e f f e c t for b o t h heifers or cows. Partial regression c o e f f i c i e n t s o f calf livability on g e s t a t i o n length as a direct e f f e c t f o r b o t h heifers and cows, were similar t o t h e o n e s in t h e age-of-dam analysis. Also, t h e d i r e c t i o n o f the e f f e c t o f g e s t a t i o n length f o r b o t h heifers and c o w s did n o t change w h e n calf livability was c o n s i d e r e d as a direct or a m a t e r n a l trait. F r e q u e n c i e s o f calf m o r t a l i t y for heifers were 9.8 and 10.2% f o r sires and m a t e r n a l grandsires. C o r r e s p o n d i n g f o r cows were 5.4 and 5.5%. This suggests t h a t t h e direct g e n e t i c e f f e c t o f t h e sire and m a t e r n a l grandsire are t h e same. A l t h o u g h no divergent e f f e c t s on calf m o r t a l i t y f o r sires and m a t e r n a l grandsires were observed, genetic c o r r e l a t i o n b e t w e e n d i r e c t and m a t e r n a l e f f e c t s was negative. This indicates t h a t the genetic a n t a g o n i s m b e t w e e n direct and m a t e r n a l e f f e c t s m a y be real. S t a t e d m o r e simply, t h e e f f e c t o f the sire o n livability o f his p r o g e n y and o n livability o f calves b o r n to his p r o g e n y is d i f f e r e n t . ACKNOWLEDGMENTS
The authors acknowledge with gratitude the financial s u p p o r t o f t h e Brazilian Agricultural Research Corporation (EMBRAPA). Acknowle d g m e n t is given to s u p p o r t f r o m g r a n t n u m b e r 1-3-79 o f t h e USA-Israel Binational Agricultural R e s e a r c h D e v e l o p m e n t f u n d ( B A R D ) and t h e National A s s o c i a t i o n o f A n i m a l Breeders f o r m a j o r c o m p u t i n g expenses. REFERENCES
1 Andersen, H., and M. Plum. 1965. Gestation length and birth weight in cattle and buffaloes: A review. J. Dairy Sci. 48:1224. 2 Anderson, D. C., and R. A. Bellows. 1967. Some causes of neonatal and postnatal calf losses. J. Anita. Sci. 26:941. 3 Auran, T. 1972. Factors affecting the frequency of stillbirths in Norwegian cattle. Acta Agric. Stand. 22:178. 4 Bar-Anan, R., M. Soller, and J. C. Bowman. 1976. Genetic and environmental factors affecting the incidence of difficult calving and perinatal calf mortality in lsraeli-Friesian dairy herds. Anita. Prod. 22:299. 5 Bradford, G. E. 1972. The role of maternai effects in animal breeding. VII. Maternal effects in sheep. J. Anita. Sci. 35:1324. Journal of Dairy Science Vol. 66, No. 8, 1983
6 Brown, C. J., and V. Galvez. 1969. Maternal and other effects on birth weight of beef calves. J. Anita. Sci. 28:162. 7 Donald, H. P. 1963. Perinatal deaths among calves in a crossbred dairy herd. Anim. Prod. 5:87. 8 Everett, R. W., and W. T. Magee. 1965. Maternal ability and genetic ability of birth weight and gestation length. J. Dairy Sci. 48:957. 9 Falconer, D. S. 1960. Introduction to quantitative genetics. Ronald Press Co., New York, NY. 10 Koch, R. M. 1972. The role of maternal effects in animal breeding. VI. Maternal effects in beef cattle. J. Anita. Sci. 35:1316. 11 Koch, R. M., and R. T. Clark. 1955. Genetic and environmental relationships among economic characters in beef cattle. III. Evaluating maternal environment. J. Anita. Sci. 14:979. 12 Legates, J. E. 1972. The role of maternal effects in animal breeding. IV. Maternal effects in laboratory species. J. Anita. Sci. 35:1294. 13 Lindstrom, U. B., and V. Vilva. 1977. Frequency of stillborn calves and its association with production traits in Finnish cattle breeds. Z. Tierz. Zuechtungsbiol. 94:27. 14 Philipsson, J. 1976. Studies on calving difficulty, stillbirth and associated factors in Swedish cattle breeds. 1. General introduction and breed averages. Acta Agric. Scand. 26:151. 15 Philipsson, J. 1976. Studies on calving difficulty, stillbirth and associated factors in Swedish cattle breeds. II. Effects of nongenetic factors. Acta Agric. Scand. 26:165. 16 Philipsson, J. 1976. Studies on calving difficulty, stillbirth and associated factors in Swedish cattle breeds. III. Genetic parameters. Acta Agric. Scand. 26:211. 17 Robison, O. W. 1972. The role of maternal effects in animal breeding. V. Maternal effects in swine. J. Anim. Sci. 35:1303. 18 Schaeffer, L. R., J. W. Wilton, and R. Thompson. 1978. Simultaneous estimation of variance and covariance components from multitrait mixed model equations. Biometrics 34:199. 19 Teixeira, N. M. 1978. Genetic differences in dystocia, calf condition and calf livahility in Holsteins. Ph.D. Diss., Univ. Microfilm No. 79-7286, Iowa State Univ., Ames. 20 Thompson, J. R. 1980. Dystocia in dairy cattle. Age of dam, maternal considerations, and relationships with economic traits. Ph.D. Diss., Univ. Microfilm No. 81-06064, Iowa State Univ., Ames. 21 Tong, A.K.W., B. W. Kennedy, and J. E. Moxley. 1979. Heritabilities and genetic correlations for the first three lactations from records subject to culling. J. Dairy Sci. 62:1784. 22 Willham, R. L. 1963. The covariance between relatives for characters composed of components contributed by related individuals. Biometrics 19:18. 23 Willham, R. L. 1972. The role of maternal effects in animal breeding. III. Biometrical aspects of maternal effects in animals. J. Anita. Sci. 35: 1288. 24 Young, C. W., and J. E. Legates. 1965. Genetic, phenotypic, and maternal interrelationships of growth in mice. Genetics 52:563.
ABSTRACT
The genetic relationships between calf livability (alive or dead) were investigated for first and subsequent parturitions of dams, and genetic correlations between direct and maternal effects were estimated. Data were 95,106 Holstein calvings. Heritabilities of direct effects were .4% for heifers and .6% for cows. The genetic correlation between calf livability for heifers and cows was .32. Regardless of age of dam, calf mortality was more frequent for male than female calves when calf livability was estimated as either a direct or maternal trait. Effects of gestation length on calf livability were quadratic and differed for heifers and cows. Largest rates of survival were with gestation lengths of 276 and 283 days for heifers and cows. Maternal heritabilities (estimated as four times the maternal component of variance divided by the maternal plus residual components) of .5% and .6% and dam heritabilities (estimated as four times the maternal grandsire component of variance divided by the maternal grandsire plus residual component) of .4 and .5% were small for both heifers and cows, respectively.
INTRODUCTION
Age of dams at calving affected calf mortality (2, 3, 7, 13, 14, 19). Two to four times more calf mortality for heifers than for old
Received July 28, 1982. 1Journal Paper No. J-10684 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 1053. 2 Brazilian Agricialtural Research Cooperation (EMBRAPA). CNP-Gado de Leite. 36155-Coronel Pacheco. MG. Brazil. 1983 J Dairy Sci 66:1714-1720
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cows was reported (2, 14). Weak labor of darns and malpresented calves accounted for 33 and 24% of calf mortality in births from cows (14); the same two causes were associated with 25 and 20% calf mortality in births from heifers (14). Heifers had shorter gestation than cows (1). Calves born to cows were 3.1 kg heavier and required an extra day of gestation compared with calves born from heifers (15). Heritabilities of calf mortality differed for heifers and cows (4, 13, 16, 19). These results indicate the possibility of calf livability being a different trait for heifers and cows. Based on these results, Philipsson (16) and Teixeira (19) analyzed first and later parity records separately. In general, heritability for rate of still birth has been less than 5% and also was greater when estimated as a character of the calf (direct effect) than when estimated as a character of the dam (maternal effect). Heritabilities for calf-genotype effects on calf mortality were 4.2% in heifer calvings and 1.3% in cow calvings (4). For dam genotype, Bar-Anan et al. (4) reported heritabilities 1.8% and .4% for heifers and cows. The direction and magnitude of direct and maternal effects are important for reliably predicting response to selection and were reported by Legates (12) for laboratory species: Kock (10) for beef cattle, Robinson (17) for swine, and Bradford (5) for sheep. Biometric aspects of maternal effects also have been explored by Willham (22, 23). Little work has been done on early calf mortality, although direct and maternal effects have been reported for different traits and species. Phitipsson (16), using an indirect procedure, reported a genetic correlation between direct and maternal effects of .07 for early calf mortality. Teixeira (19) ranked bulls for transmitting ability as sires (direct effect) and maternal grandsires (direct and maternal effects), assuming a genetic covariance between direct and maternal effects of zero. The rank
DAM AGE AND DIRECT AND MATERNAL EFFECTS correlation between these estimates was - . 1 1 for the 14 bulls available for this analysis. Although the two reports on calf livability may indicate a null genetic relationship between maternal and direct effects, results on other traits and species suggest a genetic antagonism between the two effects (6, 8, 11,24). Objectives of this study were: 1) to estimate the genetic relationship between livability of calves of dams in first and subsequent parturitions and 2) to estimate the genetic correlation between direct and maternal effects on calf livability. MATERIALS A N D METHODS
Data for this study were obtained from the National Association of Animal Breeders and were 95,106 records from Holstein calvings collected by individual dairy producers cooperating with artificial insemination organizations. Only records with gestation periods greater than 260 days and less than 300 days were used. These limits were chosen because they should be close to the lower and upper limits of the normal variation of gestation length (1, 14). A mixed model was used to define effects on calf livability as:
b 2 = quadratic partial regression coefficient on gestation length squared, eijkl m = random residual associated with the observation Yijklm. Components of variance and covariance were estimated by the multitrait procedure developed by Schaeffer et al. (18). A calving is the experimental unit, and this model enables quantification of the direct effect of the sire on livability of calves from heifers versus older cows. The model is used further in a maternal and direct analysis where the sire appears as the sire of the calf and subsequently as a sire of progeny which calve (maternal grandsire). Each experimental unit appears for only one trait, because the procedure assumes no error covariance among all traits, a condition which is not true if the same experimental unit is used for both traits. Computational procedures to estimate simultaneously sire and error variances and sire covariances for different traits were described by Tong et al. (21) and Thompson (20). Components of variance and covariance obtained by this method are not unique until estimates have converged in an iterative procedure. The iterative solutions at convergence are Restricted Maximum Likelihood estimates. Age-of-Dam Analysis
Yijklm -- ~ + HYSi + Bj + Sk + PI + b l (Xijklrn -- X) + b2 (Xijkl m -- ~)2
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[I]
+ eijkl m where: Yijklm = livability score; 1 = alive, 2 = dead, ~t = overall population mean, ttYS i = fixed effect of the iTM herd-yearseason; season defined as 1; Novemb e r - F e b r u a r y , and 2, March-October, Bj = random effect of the jth sire, Sk = fixed effect of male and female calves, k = 1, 2, P1 = fixed effect of the lth age of dam, 1 = 1, 2,/> 3 parities, Xijkl m = effect of gestation length of the ijklm dam, mean gestation length, b l = linear partial regression coefficient on gestation length,
Calf livability was considered a different trait for heifers as darns from cows as dams. The requirement of the two traits being measured on different groups of animals could be a problem if a dam that had her first calf in 1976 had a second calf in 1977, etc. This situation would induce environmental covariance; however, it should be small because the calvings would be in different year-seasons. Because of poor cow identification, all records in the same herd-year-seasons, from the same sire, sex, calving date, and with the same calf livability score were considered duplicated or multiple births and eliminated. This accounted for only 1.6% of the records. Also, if a dam appeared as both a heifer and a cow, her records were eliminated from the cow's data. This was done to minimize environmental covariance. Examination of the records indicated that only 2.2% of the identified heifer-dams had a second record. The sires were required to have progeny in at Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ
least five herd-year-seasons from dams of both first and later parities to insure adequate ties between herds. No restriction was imposed on the relation of herds for heifers as dams' with those for cows as dams, i.e., the five herds for cow-dams could be the same or completely different herds from the five herds for heiferdams. To define the fixed factors that influence calf livability, model [I] was used for both heifers and cows as dams. Separate effects of sex of calf and regression coefficients of gestation length were estimated for heifers and cows. Herd-year-seasons were absorbed. Characteristics of data in the age-of-dam analysis are in Table 1. Maternal and Direct Analysis
Components of variance necessary to study the relationship of maternal with direct effects of calf livability are the direct genetic variance (o~3), the maternal variance (o~a), and the direct by maternal covariance (O~M). Components of variance and covariance estimated from these data were the variance among sires (o~), the variance among maternal grandsires 2 ( O M G S ) , and the covariance between sires and maternal grandsires ( O S . M G S ) . From these components, estimates of a~3, o k , and aDM could be obtained as described by WiIlham (23): O~ = .25 O~
[1]
2 O'MGS = .0625 o~3 + .25 cr~ + .25 ODM OS.MG S =
.125 o~) + .25 ODM
[2] [31
ET AL.
The components o~3, o~t, and ODM were estimated from equations [1], [21, and [3]. The genetic correlation between the maternal trait with the direct trait was estimated from: rGD,M = ODM/(O'~) O~) "s . To estimate O S . M G S , a data set was needed with each sire represented as both a direct sire and a maternal grandsire. Data with this structure satisfied the requirements of the multipletrait evaluation if calf livability as a trait of the dam (maternal grandsire) and livability as a trait of the calf (sire) are considered separate traits. Data with identified maternal grandsires were matched with the original data to create a data file with bulls represented as both a sire and a maternal grandsire. The data, as in the age of dam analysis, were edited to exclude duplication of a single record in both data groups. Thus, it was insured that no calving by the same cow was included in the sire and maternal grandsire data sets. Sires again were required to have progeny in five herds for both traits. Analyses were separate for heifer and cow dams so that any differences of the maternal with direct relationship for dams in first versus later parities could be identified. This separation again eliminated parity from model [I]. Sex-of-calf and linear and quadratic effects of gestation length comprised fixed effects of the mixed-model equations for the two direct and maternal analyses. Characteristics of data for the maternal and direct analysis are in Table 2.
TABLE 1. Characteristics of data in the age-of-dam analysis. Parity classification
Heifers Number of sires Number of records Number of herd-year-seasons Within herd-year-season Sum of squares Residual mean squares (o~)
Journal of Dairy Science Vol. 66, No. 8, 1983
258 14,147 2,778 985.48 .088
Cows 258 67,774 8,452 2,921.80 .049
Total 258 81,921
DAM AGE AND DIRECT AND MATERNAL EFFECTS RESULTS A N D DISCUSSION Age-of-Dam
F o r t h e r e l a t i o n s h i p of calf livability in heifer d a m s w i t h calf livability in cow dams, a t o t a l o f 8 1 , 9 2 1 r e c o r d s f r o m 2 5 8 sires was used (Table 1). C o m p o n e n t s o f variance a n d covariance were i t e r a t e d u n t i l e s t i m a t e s converged. F i n a l estim a t e s o f c o m p o n e n t s of variance a n d covariance are in T a b l e 3. H e r i t a b i l i t i e s were .4 a n d .6% for heifers a n d cows. T h e s e e s t i m a t e s are lower t h a n t h o s e r e p o r t e d b y B a r - A n a n et al. (4) f o r IsraeliFriesians (4.2% in heifers, a n d 1.3% in cows). L i n d s t r o m a n d Vilva (13), h o w e v e r , f o u n d a t e n d e n c y for h e r i t a b i l i t y ( c o r r e c t e d to transf o r m t h e m e a s u r e s to c o r r e s p o n d to an a s s u m e d u n d e r l y i n g c o n t i n u o u s l y a n d n o r m a l l y dist r i b u t e d t r a i t ) of calf livability to be higher f o r cows (5.4%) as d a m s t h a n for heifers (2.7%) as dams. A n a p p r o x i m a t e s t a n d a r d e r r o r o f herita-
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b i l i t y (9) was .3% for heifers a n d less t h a n 2% f o r cows. T h e g e n e t i c c o r r e l a t i o n b e t w e e n calf livability for heifers a n d cows was .32. T h i s c o r r e l a t i o n did n o t i n d i c a t e a s t r o n g g e n e t i c r e l a t i o n s h i p b e t w e e n calf livability for heifers a n d calf livability f o r cows. A l t h o u g h heritabilities are small, s o m e genetic progress could b e m a d e t h r o u g h selection because t h e r e is some genetic v a r i a t i o n for calf livability. T h e sex e f f e c t was g r e a t e r f o r male calves f r o m heifers ( . 0 2 0 ) t h a n f r o m cows (.007). C o n s t a n t s f o r sex w i t h i n age were c o n s t r a i n e d to add to zero. T h e s e c o n s t a n t s i n d i c a t e d a m o r e p r o n o u n c e d sex e f f e c t for heifers t h a n f o r cows as dams. Regardless of effects of age o f d a m , g r e a t e r calf m o r t a l i t y o c c u r r e d f o r male t h a n f e m a l e calves. Effects of g e s t a t i o n l e n g t h b y age of d a m o n calf livability are in Figure 1. L i n e a r a n d q u a d r a t i c partial effects o f g e s t a t i o n l e n g t h o n calf livability were .0021 a n d .0003 for heifers and -.0031 a n d .0006 f o r cows. P r e d i c t e d
TABLE 2. Characteristics of data for the maternal and direct analysis. Heifers Sire Number of sires Number of progeny Number of herd-year-seasons
106 5,720 1,219
Within herd-year-season Sum of squares Residual mean squares
Cows
Maternal grandsire 106
1,692 459
372.22 .085
97.86 .087
Total
Sire
106 7,412
108 23,933 4,018
Maternal grandsire 108 4,400 1,015
989.64 .050
Total 108 28,333
162.72 .051
TABLE 3. Components of variance (Var) and covariance (Cov) for age-of-dam analysis. Variance-covariance components (X 10 s) Sire
Residual
Age-of-dam
Vara
Coy a
Vara
Heifers Cows
8.3 7.7
2.6
8,806 4,845
Cova,b 0
ax 105. bResidual component of covariance defined to be zero. Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ ET AL.
32 30 28 26 =E
o
2
~
HEIFERS
24
,,/,,'//' /J
22 20 18 16 14 12 10 8 6
/ 4~-5
4-3-2-[~0-4"
COWS 2
3
4
5A
4 DAYSOFGESTATIONLENGTHDEVIATEDFROMTHE MEAN
Figure 1. Regression of calf livability on gestation length.
values in the graph are deviated f r o m their means. Mean gestation lengths were 278.8 and 2 7 9 . 7 for heifers and cows. On the ordinate, calf livability was deviated f r o m its mean; 1.105" for heifers and 1.056 for cows. Calf m o r t a l i t y for cows increased for b o t h short and long gestation periods. A similar quadratic effect was observed in Swedish-Friesians (16). F o r cows the highest calf survival o c c u r r e d with gestation l e n g t h o f a b o u t 283 days. F o r heifers, however, the greatest calf survival rate was with gestation length of a b o u t 276 days. Calf m o r t a l i t y increased substantially for heifers with longer than average gestation periods. The increased m o r t a l i t y rate may be due to the unfavorable
ratio of size of calf to size of dam, which will increase dystocia and also calf mortality. F o r cows, however, the increase of calf size may be balanced with the increase of size of dam with o p t i m u m survival changed as in Figure .1.
Maternal and Direct Relationship
The direct by material covariance is important, because a negative covariance w o u l d result in an antagonistic situation if selection is on only one effect. Selection for the direct effect with a negative genetic correlation b e t w e e n direct and maternal effect w o u l d be e x p e c t e d initially to improve the character selected. Eventually the correlated response could be e x p e c t e d to decrease genetic progress because of the negative genetic correlation. These two counterbalancing effects w o u l d be e x p e c t e d eventually to stabilize at some p o i n t depending on the selection for each trait. Data f r o m bulls that appeared as b o t h a sire and a maternal grandsire were analyzed separately for "first and later parities. Sire and maternal grandsire c o m p o n e n t s of variance and sire-maternal grandsire c o m p o n e n t s of covariance were estimated f r o m the data outlined in Table 2. For heifers, 7,412 progeny of 106 bulls were used; cow data were 28,333 progeny of 108 bulls. Again c o m p o n e n t s of variance and covariance were iterated until estimates converged. Final c o m p o n e n t s of variance and covariance are in Table 4. These c o m p o n e n t s were partitioned into
TABLE 4. Components of variance and covariance for the maternal and direct analysis. Variance-covariance components a (X 10 5) 2
Age-of-dam
~
~hGS
aS.MGS
°~ S
°eMG S
°eS.MG S
Heifers Cows
4.6 5.9
7.8 5.9
-- 1.3 .6
8,430 4,936
8,600 5,110
0 0
ao~ = Variance among sires, a~AGS = Variance among maternal grandsires, °S. MGS = Covariance between sires and maternal grandsires, °~S = Residual component of variance for the direct effect, o eMGS 2 = Residual component of variance for the maternal effect, aeS.MGS = Residual component of covariance between direct and maternal effect, defined to be zero. Journal of Dairy Science Vol. 66, No. 8, 1983
DAM AGE AND DIRECT AND MATERNAL EFFECTS TABLE 5. Maternal components (X lO s) of variancecovariance for livability and estimates of heritability a and genetic correlation.
Direct (oh) Maternal (a~) Covariance (aDM) Direct heritability Dam heritability b Maternal heritability c Genetic correlation
HeiSts
Cows
18.4 41.0 -14.4 .2 .4 .5 - . 52
23.6 31.9 -14.2 .5 .5 .6 - . 52
17!9
variance for families of half-sister, was given by F a l c o n e r (9) as n = 4/h 2, where n is n u m b e r of progeny per sire and h 2 is heritability of the character. Using n = 4/h 2 and the average number of progeny per sire, f r o m Tables 1 and 2, one can calculate which heritabilities could be estimated with smaller sampling variance with these numbers of progeny per sire. Based on this i n f o r m a t i o n , heritabilities for cows had smaller sampling variances than for heifers b o t h in the age-of-dam and maternal and direct analyses. Thus, the similar direct heritabilities for cows (.6 v s . . 5 % ) , f r o m the age-of-dam and maternal and direct analyses, may have been a consequence of larger n u m b e r of progeny per sire in the analysis for cows than heifers. These heritabilities were smaller than the ones reported by Bar-Anan e t al. (4) and Lindstrom and Vilva (13); however, t h e y were close to estimates by Teixeira (19) with A m e r i c a n Holsteins. G e n e t i c correlations b e t w e e n maternal and direct effects were b o t h - . 5 2 for heifers and cows. These results were different f r o m the genetic correlation of .07 r e p o r t e d by Philipsson (16), who used an indirect procedure to estimate the correlations. The genetic antagonism b e t w e e n direct and maternal effects r e p o r t e d for different traits and in different species (6, 8, 11, 24) was also observed for calf livability. Constants for sex-of-calf and partial regression coefficients of calf livability on gestation length are in Table 6. As in the age-of-dam analysis, male calves had m o r e m o r t a l i t y than
aHeritabilities expressed in percentage. bDam heritability is heritability of calf livability as a trait of the dam calculated as 4 × a M G S / ( a e2 + O~G S) where CraG S is the variance among maternal grandsires and a~ is the residual component of variance for the maternal effect. 2 2 CMaternal heritability calculated as aM/(a M + at) where a ~ is the maternal variance and ae~ is as in footnote b.
their genetic fractions for the necessary genetic c o m p o n e n t s (Table 5). Heritability estimates of calf livability as a trait o f the dam ( d a m heritability) were similar to t h e direct (livability as trait of the calf) heritability for cows but greater for heifers. Direct heritabilities were smaller than the corresponding estimates f r o m the ageof-dam analysis. One possible reason may be the small n u m b e r of progeny available per bull in this analysis. An a p p r o x i m a t e n u m b e r of progeny per sire, which minimizes the sampling
TABLE 6. Estimates of percentage mortality for sex-of-calf and partial regression coefficients of calf livability on gestation length in the direct and maternal analysis. Heifers
Cows
Direct a
Maternal b
Direct
Maternal
1.6 --1.6
1.3 --1.3
.7 --.7
.8 --.8
-.32 .05
-.19 .04
Sex
Male Female Regression Linear Quadratic
.19 .03
.15 .07
aRefers to data set where bulls were considered as sires. bRefers to data set where bulls were considered as maternal grandsires. Journal of Dairy Science Vol. 66, No. 8, 1983
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MARTINEZ ET AL.
females. C o n s t a n t s f o r sexes in the age-of-dam analysis and in t h e direct and m a t e r n a l analysis were similar, particularly f o r cows. No differences b e t w e e n c o n s t a n t s were o b s e r v e d w h e n t h e y were e s t i m a t e d as either d i r e c t or m a t e r n a l e f f e c t for b o t h heifers or cows. Partial regression c o e f f i c i e n t s o f calf livability on g e s t a t i o n length as a direct e f f e c t f o r b o t h heifers and cows, were similar t o t h e o n e s in t h e age-of-dam analysis. Also, t h e d i r e c t i o n o f the e f f e c t o f g e s t a t i o n length f o r b o t h heifers and c o w s did n o t change w h e n calf livability was c o n s i d e r e d as a direct or a m a t e r n a l trait. F r e q u e n c i e s o f calf m o r t a l i t y for heifers were 9.8 and 10.2% f o r sires and m a t e r n a l grandsires. C o r r e s p o n d i n g f o r cows were 5.4 and 5.5%. This suggests t h a t t h e direct g e n e t i c e f f e c t o f t h e sire and m a t e r n a l grandsire are t h e same. A l t h o u g h no divergent e f f e c t s on calf m o r t a l i t y f o r sires and m a t e r n a l grandsires were observed, genetic c o r r e l a t i o n b e t w e e n d i r e c t and m a t e r n a l e f f e c t s was negative. This indicates t h a t the genetic a n t a g o n i s m b e t w e e n direct and m a t e r n a l e f f e c t s m a y be real. S t a t e d m o r e simply, t h e e f f e c t o f the sire o n livability o f his p r o g e n y and o n livability o f calves b o r n to his p r o g e n y is d i f f e r e n t . ACKNOWLEDGMENTS
The authors acknowledge with gratitude the financial s u p p o r t o f t h e Brazilian Agricultural Research Corporation (EMBRAPA). Acknowle d g m e n t is given to s u p p o r t f r o m g r a n t n u m b e r 1-3-79 o f t h e USA-Israel Binational Agricultural R e s e a r c h D e v e l o p m e n t f u n d ( B A R D ) and t h e National A s s o c i a t i o n o f A n i m a l Breeders f o r m a j o r c o m p u t i n g expenses. REFERENCES
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