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Influence of Reproductive Management Factors on Genetic Merit of Service Sires
Influence of Reproductive Management Factors on Genetic Merit of Service Sires B. G. CASSELL and R. L. NEBEL Department of Dairy Science Virginia Polytechnic Institute and State University Blacksburg 24061
ABSTRACT
Records were terminated (by sale or dry date) lactation records for cows on DHI test in Virginia for 1982 through 1984. July 1986 production evaluations, most recent type evaluations, and appropriate semen prices for date of service for AI bulls were merged with service sire identification from 384,990 DHI records. Repeat breedings and multiple lactations per cow were used. Least squares procedures revealed significant influences of season, mate's sire's PD for type and dollars, mate's milk yield deviation, registry status, and insemination number on production evaluations, PD type, and semen price of service sire. Significant effects of several of the same variables on linear type traits were observed. Season effects were possibly due to genetic trends. Genetic merit for production and type of service sire declined for daughters of sires with missing or low type and production evaluations, for mates with low or missing herdmate deviations, for grade cows, and for repeat services, especially fourth and later. Days between breedings were nonsignificant or of limited importance in predicting genetic merit of service sires. Proven bulls in AI accounted for 76.3% of all breedings, AI sample sires for 6.3%, and non-AI or unknown sires for 17.4% of breedings in these data. INTRODUCTION
Sire selection is the most important management practice affecting genetic progress in a
Received September 8, 1987. Accepted December 7, 1987.
1988 J Dairy Sci 71:1367-1377
dairy herd. Hillers et al. (8) compared artificial to natural service and concluded that each increase of 227 kg in genetic superiority of AI to natural service sires could offset the costs of 10 additional d in calving interval. Numerous factors influence the choice of sires including perceived importance of production and nonyield traits (5, 6, 10), cost of semen (1, 10), opinion of consultants (9, 13), and reproductive management factors. The last of these is the least studied and is the objective of this study. Reproductive management practices and methods of improving reproductive performance comprise a large body of published research in the United States. Among recently published efforts in this area are fertility evaluation procedures (4, 6), evaluation of owner-insemination conception results (12), timing of insemination relative to standing estrus (7), accuracy of estrous detection (11), and the importance of herd health management factors (3). These diverse topics, all related to producing a conception through AI, contribute to the profitability of the dairy farm. However, the genetic merit of the bull used is perhaps the greatest advantage offered by AI (8) and has not been studied from the perspective of service fires reported through DHI. The influence of management factors such as genetic and phenotypic merit of the cow, registry status, insemination number, or estrous interval on genetic merit of service sires likewise has not been studied. The objectives of this study were to examine the genetic merit of service sires and price of semen used to breed cows of different genetic merit and reproductive status. Included in these objectives was a determination of type of service sire (proven bull in AI, sample sire in AI, other) used on the different types of cows and reproductive situations encountered by dairy farmers in Virginia.
1367
13 68
CASSELL AND NEBEL MATERIALS AND METHODS
Two files of data were used. The record of breedings was from a file provided by the Dairy Records Processing Center in Raleigh, NC of all breedings reported through the DHI systems for Virginia from January 1, 1982 through December 31, 1984. Records were for cows with "terminated" records, i.e., records completed by a dry date or a sold date. For breedings early in 1982, early services for individual cows (those performed fall 1981) may not have been present. Likewise, later inseminations for cows bred in late 1984 may have been eliminated by the dates chosen for the study. Cow records were required to contain valid dates for birth, breeding, and either subsequent calving or date sold. The interval to first breeding was required to be at least 15 d. Service number was taken as reported through DHI but was required to be sequential for breedings within a lactation. Cows were required to be sired by and bred to Holstein sires when sires and service sires were identified. However, records were not eliminated for missing sire or service sire information. Only the first nine services on any cow were used. The second file necessary was a history file of production and type evaluations on Holstein bulls. Data were the USDA Modified Contemporary Comparison sire evaluation file as reported on the July 1986 Format 380 tape. Production evaluations were the most recent calculated through July 1986. The most recent PD type evaluation published b y the HolsteinFriesian Association of America between January 1980 and July 1986 was used. Due to a change in evaluation of linear type traits in January 1984, only linear evaluations between January 1984 and July 1986 were included. Semen prices were from a historical file of retail, direct-herd semen prices as published by major AI organizations marketing semen in Virginia. Semen prices changed every 6 mo corresponding with changes in sire evaluations. The semen price assigned to a breeding was the appropriate price for the date the breeding occurred, as shown in Table 1. Semen prices were available for between 405 and 460 active AI Holstein sires for the seven summary dates. Semen prices were known for 69% of the total breedings in the cow file, which is 90% of the services to proven bulls in
Journal of Dairy Science Vol. 71, No. 5, 1988
TABLE 1. Semen price assigned by breeding date.
Breeding date
Summary date for semen price
1-1-82 to 2-1-82 to 8-1-82 to 2-1-83 to 8-1-83 to 2-1-84 to 8-1-84 to
Summer 1981 Winter 1982 Summer 1982 Winter 1983 Summer 1983 Winter 1984 Summer 1984
1-31-82 7-31-82 1-31-83 7-31-83 1-31-84 7-31-84 12-31-84
A1. Services to proven bulls in AI were 76.3% of aJl breedings. The file of bull evaluations and semen prices was matched to the cow file for both sire and service sire identification. Breedings totaled 384,990 breedings in the final data set. These records were not complete with respect to presence of evaluations for sires and service sires for all traits. However, the final file was edited no further to avoid elimination of useful information such as management decisions, which increased the use of bulls not in AI. Effects of management and cow merit for services to proven bulls were evaluated by least squares procedures using the following model. Service sire merit = herd year i + bl(age) + b2(age 2) + seasonj + sire typeg + sire dolle + deviation m + statn + insemo + intp + residual. Service sire merit included PD for dollars, milk, fat, fat percent, type; the linear type traits udder support, rear udder, fore udder, teat placement, feet, hind legs, and stature; plus semen price. Herd year was herd year of freshening associated with a particular breeding. Age was the age at calving for a breeding. Four seasons (seasonj) were created for date bred: January to March, April to June, July to September, and October to December. Four categories of PD type for the sire of the cow bred (sire type k) were: missing type, less than - . 4 0 , - . 4 0 to 1.30, and above 1.30. The PD dollar value of the sire of the cow bred (sire dolle) was used to create four categories: missing, less than - $ 5 0 , - $ 5 0 to $80, and above $80. The break points for PD type and PD dollar values on the sire of the cow being bred were approximately one standard deviation above and below the mean of all sires with
REPRODUCTION AND SERVICE SIRE MERIT proofs for dollars and t y p e available. Three categories for milk yield deviation o f the cow being bred (deviationm) were: missing, negative, and positive deviation. The classification statn refers to t h e registry status of the cow being bred, registered, or grade. Insem o refers to the insemination n u m b e r of a breeding with f o u r categories of first, second, third, and f o u r t h or greater service. The Intp referred to interval b e t w e e n breedings and was only included in the analysis of second and subsequent services. Categories were less t h a n 18 d, 18 to 24 d, 25 to 38 d, 39 to 45 d, and greater than 45 d. Least squares constants of significant variables f r o m t h e m o d e l for prediction of service sire m e r i t were e x a m i n e d to d e t e r m i n e the t e n d e n c y o f farmers t o use b e t t e r or p o o r e r bulls for the various traits under different conditions.
1369
RESULTS A N D DISCUSSION
Means of variables indicative o f the genetic and p h e n o t y p i c merit of t h e cow being bred are in Table 2. Cow indexes for milk w e r e available for 70% of the records and averaged 50 kg milk and I kg fat. Missing cow indexes were due to sire identification errors. Supporting d o c u m e n t s a c c o m p a n y i n g the January 1984 U S D A Modified C o n t e m p o r a r y Comparison sire and cow evaluations showed the average cow index of all registered Holstein cows passing elite status screening edits to be - 1 7 1 kg milk and - 5 kg fat. This group o f Virginia Holsteins was genetically superior to t h a t average. T h e average h e r d m a t e deviation for milk was 251 kg, again suggesting that cows in t h e study were slightly above average as producers. Differential reporting of service sire data through D H I
TABLE 2. Means, standard deviations, and percent of records with information available for Virginia Holstein cows bred between January 1, 1982 and December 31, 1984.1 % of Records with variable available
Variable
Mean
SD
Mate Cow index, milk, kg Cow index, fat, kg Mature equivalent (ME) milk, kg ME Fat, kg Herd mate average ME milk, kg Herdmate average ME fat, kg
50 1 7781 271 7530 262
263 8 1608 57 935 33
99 99 94 94
Interval between breedings, d
46
33
44
Mate's sire 2 Repeatability PD Dollars PD Milk, kg PD Fat, kg PD % Fat PD Type PD Udder support PD Rear udder PD Fore udder PD Teats PD Foot angle PD Hind legs PD Stature
90 5 50 0 --.02 .43 .71 1.27 .24 .74 .47 -.01 .37
22 65 282 10
67 67 67 67 67 41 8 8 8 8 8 8 8
.09 .86 1.42 1.40 1.29 1.03 1.19 1.60 1.52
70 70
1Records repeated for multiple lactations and repeat breedings. 2Production evaluations were calculated in July 1986. Type evaluations were the most recent published through July 1986. Journal of Dairy Science VoI. 71, No. 5, 1988
1370
CASSELL AND NEBEL
could cause this result, as would our practice of repeating records for multiple records and repeat breedings. Genetically superior cows and cows with positive deviations may have been serviced more frequently or farmers may have reported services for such cows more consistently. Logically, such cows would have more lactations than genetically inferior cows or lower producers. First services were 56.1% of all breedings, second services were 23.3%, third services 11.0%, and fourth and subsequent services accounted for 9.6% of all breedings. Characteristics of reproductive management practices are in Figures 1 and 2. Figure 1 shows distinct seasonality of breedings in Virginia as reported by farmers through DHI. The October to December period includes 32.6% of all services. January to March includes 22.3%, April to June 21%, and July to September 24.2% of all breedings. Figure 2 shows the distribution of interval between breedings for repeat breedings. The frequency of breedings showed peaks around d 21~ 42, and 63, as expected from 21-d estrous cycles. These results contributed to the establishment of service interval categories used in the statistical model explained earlier. Many cows are bred on intervals other than that expected from one normal cycle. However, the interval 18 to 24 d included 29.8% of all repeat breedings. Reimers et al. (11) published a figure of distribution of days between unsuccessful
first and second service with similar properties. They reported 93.2% o f cows in or near estrus at first service and open 21 to 24 d later were serviced again within 90 d. In our data, 91.6% of all intervals (not just first and second) were 90 d or less. The average interval between breeding of 46 d was slightly longer than the 41.1 d from the work of Coleman et al. (3), whose herds were chosen based on managers' willingness to cooperate. This result may reflect less complete reporting of breedings in the present study. Average merit of service sires for the various traits is in Table 3. Production proofs were available on service sires for 81% of the breedings; however, not all of these evaluations were known to the dairy farmer at the time of the mating. The most recent breedings in the study were from the fall of 1984; evaluations for production were from July of 1986. Some proofs on bulls used as sample sires or from natural service bulls had become available in the interim. Better bulls were used more heavily. Table 4 shows weighted averages of $60 for PD dollars, 284 kg for PD milk, and 7 for PD fat. The unweighted averages of service sires (Table 3) show $5, 34 kg, and 0 kg, respectively, for all 3134 bulls appearing as service sires. Weighted averages were slightly higher for PD type, udder support, rear udder, teats, foot angle, hind legs, and stature. For production traits, standard deviation of variables in Table 4 were less than
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Figure 1. Total breedings for 3 yr (1982 to 1984) by month of insemination. Journal of Dairy Science Vol. 71, No. 5, 1988
DAYS
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Figure 2. Distribution of number of breedings by interval in days between breedings.
REPRODUCTION AND SERVICE SIRE MERIT "
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in Table 3, again showing the impact of selection. Average production evaluations for milk, fat, and dollars were higher for sires of cows bred than for all bulls with proofs, and higher for service sires than for sires of cows bred. The opposite was true of PD% fat. Genetic trend and selection could cause such results. Table 5 contains results of analysis of services to proven bulls. Bulls with an National Association of Animal Breeders (NAAB) stud code, a nonzero repeatability, and greater than 4 yr of age at the time the cow was bred were considered to be proven bulls (Code 1) of which the farmer had knowledge of breeding value. Bulls less than 4 yr old at time of mating with NAAB stud codes were considered young sample sires (Code 2). All other services were grouped together in Code 3. Season effects in Table 5 were significant for all traits but rear udder teat placement, and foot angle. The least squares constants are all expressed as deviations from the last class in each effect. Cows bred in January to March were bred to bulls 14 kg lower for milk, 2 kg lower for fat, and $10 lower for dollars than cows bred in October to December. These results are most likely due to genetic trend in the bull population within year. Results for PD type were directional and in favor of fall matings, again suggesting genetic trend. Results for semen price showed less expensive semen was used in fall but differences between seasons were small. The three effects in the model measuring genetic and phentoypic merit of the cow being bred (sire's PD for type and dollars and cow's milk yield deviation) were significant in predicting service sire merit for most traits. However, sire's PD dollars was not significant for 5 of 13 traits. Service sires with lower PD dollars and lower semen costs were used on cows with unknown sire merit for type or dollars, low values for sires PD type or dollars, or themselves had missing or negative milk deviations. The greatest effect of measures of merit of the cow bred appeared to be on semen price. Cows with missing deviations were bred to semen costing $2.49 per unit less than cows with positive deviations. Service sire PD dollars was only $5 less and PD type only .03 less for such cows. However, missing deviations were primarily due to short lactations, which prevented determination of herdmate averages. Journal of Dairy Science Vol. 71, No. 5, 1988
1372
CASSELL AND NEBEL
Registry status had a significant and import a n t i m p a c t on service sire merit. Grades were bred to semen costing $6.48 per unit less than semen used on registered cows. Evaluations for all linear traits e x c e p t hind legs were lower for service sires used on grade cows. The lower PD dollars value of $9 and t y p e p r o o f of .12 for service sires o f grade cows seemed a small difference in genetic m e r i t for the rather substantial difference in semen price. Cows were bred to considerably b e t t e r bulls on first service t h a n on f o u r t h and later services. Semen cost was $7.31 higher, PD dollars was $19 higher, PD t y p e .10 higher, and all linear evaluations (except hind legs, which was not affected by insemination number) were higher on service sires used for first breedings. T h e decline in service sire m e r i t as insemination n u m b e r increased appeared to be linear. Emphasis on linear traits was reduced fairly drastically by third service. The prediction e q u a t i o n used was m o s t effective in predicting semen price (R 2 = .318) and least effective for hind legs (R 2 = .107). Many factors o t h e r than those considered in this m o d e l m a y influence genetic m e r i t of service sires.
Table 6 contains results of the prediction of service sire merit for repeat breedings to Code 1 (proven bulls) only. Interval b e t w e e n breedings was included in this model. The R 2 values were higher than for Table 5 (.142 to .357). However, the influence of PD dollars and PD t y p e of the sire o f the cow being bred seemed to decline for repeat breeders. This m a y indicate that the genetic m e r i t of the cow b e c o m e s less of a m a n a g e m e n t factor in selecting a service sire as reproductive factors b e c o m e more pressing. T h e e x a m i n a t i o n of least squares constants for breeding interval showed that this factor was n o t significant for 7 of 13 traits examined, including all linear traits e x c e p t stature. The PD dollars of service sire was slightly higher for 18 to 24, 25 to 38, and 39 to 45-d intervals than for very short or very long intervals. The same was true of semen price. Results suggest that breeding interval is either u n k n o w n or considered u n i m p o r t a n t e x c e p t w h e n very short or very long intervals are involved. Table 7 contains an analysis of t y p e of bull used for all breedings and for repeat breedings. The least squares constants can be interpreted as differences (from the 0 category) in fraction
TABLE 4. Means, standard deviations, and percent of records with information available for service sires used to breed Virginia Holstein cows between January 1, 1982 and December 31, 1984.1
Variable
Mean
Repeatability PD Dollars PD Milk, kg PD Fat, kg PD % Fat PD Type PD Udder support PD Rear udder PD Fore udder PD Teats PD Foot angle PD Hind legs PD Stature Semen price, 2 $
94 60 284 7 -.03 .57 .53 .46 -.18 .16 .11 .25 .14 15.69
SD 11 58 266 9 .10 .68 1.25 1.08 1.24 1.09 1.14 1.59 .77 15.55
% of Records with variable available 81 81 81 81 81 74 49 49 49 49 49 49 49 69
1Records repeated for multiple lactations and repeat breedings. Production evaluations were calculated in July 1986. Type evaluations were the most recent published through July 1986. 2 Semen price was retail semen price appropriate for the date each cow was bred. Journal of Dairy Science Vol. 71, No. 5, 1988
T A B L E 5. Least squares constants for prediction o f service sire m e r i t when m a t i n g s were t o proven bulls. Herd year o f breeding and linear and quadratic effects o f age at calving were removed. Linear traits 2 PDI
.< o Z o
Fore udder
Teat placement
Foot angle
Hind legs
Stature
NS 4 NS NS NS
--.03 --.03 --.02 0
NS NS NS NS
NS NS NS NS
.02 --.04 -.03 0
--.04 --.05 --.05 0
.02 .00 .03
.03 .02 .04
.16 .19 .16
.08 .10 .08
Effect
Dollars
Fat
Season Jan to Mar A p r to J u n Jul t o Sep Oct t o Dec
-10 -7 -3 0
-2 -1 -1 0
-,006 -,004 -.003 0
-34 -22 -9 0
-.04 -.02 -.01 0
0
Sire's s PD type Missing <--.40 --.40 to 1.30 >1.30
-6 --6 -4 0
--1 --1 --1 0
-.004 --.008 -,004 0
-18 --14 --12 0
NS NS NS NS
--.04 -.06 -.02 0
0
0
0
--.07 --.08 -.05 O
Sire's s PD dollars Missing <-50 - 5 0 to 80 :>80
-1 -2 -1 0
--0 -0 --O 0
NS NS NS NS
NS NS NS NS
--.01 --.02 --.01 0
-.07 -.07 -.04 0
--.04 --.03 -.02 0
NS NS NS NS
NS NS NS NS
-.07 --.10 --.08 0
Mate's milk deviation Missing Negative Positive
--5 -2 0
--1 0 0
NS NS NS
--19 -9 0
--.03 -.03 0
-.12 -.09 0
-.08 -.06 0
--.05 --.05 0
--.05 --.05 0
Registry status Grade Registered
-9 0
-1 0
NS NS
--40 0
--.12 0
--.34 0
-.27 0
--.24 0
Insemination n u m b e r i 2 3 >3
19 12 7 0
3 2 1 0
78 50 27 0
.10 .07 .04
.39 .27 .15
.27 .17 .09
.10 .07 .02
Milk
Type
Udder support
Rear udder
Percent fat
.02 .03 .04
.01 .03 .03
Semen price 3
.71 .60 .16 0
,¢ ~
0
--1.80 --1.84 --1.12 0
--.99 --1.22 -.80 0
Z
0
NS NS NS NS
--.06 --,05 0
NS NS NS
--.07 --.04 0
-2.49 -1.52 0
--.24 0
--.16 0
0
--.15 0
--6.48 0
.13 .08 .02
.23 .15 .07
.34 .25 .15
7.31 4.54 2.07 0
0
.03 .08 .03
CI ,q
Z t~
Coefficient of determination
A78
-.002 -,001 .001 0
.176
.150
0
.168
0
.188
0
.202
0
.178
0
.190
0
.150
.144
.10
NS NS NS NS
.107
0
.196
t~
.318
1293,698 records for milk variables, 2 8 4 , 7 5 8 records for PD type. : 187,432 records for linear traits. 3266,388 records for semen price.
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T A B L E 6. Least squares c o n s t a n t s for prediction o f service sire m e r i t using r e p e a t breedings and services to proven bulls only. Herd-year o f b r e e d i n g and linear and q u a d r a t i c e f f e c t s o f age at calving w e r e removed.
o_ 2
oz oo oo
Linear traits 2 Teat
PD 1 Effect
Dollars
Fat
Season J a n to Mar A p t to J u n Jul to Sep O c t to Dec
-11 -7 -3 0
--2 -1 -1 0
-5 --5 --4 0
Sire's s PD t y p e Missing <-.40 - . 4 0 to 1.30 >1.30 Sire's s PD dollars Missing <--50 - 5 0 to 80 >80
NS NS NS NS
Percent fat
Rear udder
Fore udder
placement
Foot angle
Hind legs
Stature
0
NS 4 NS NS NS
--,05 -.03 --.01 0
NS NS NS NS
--.04 -.01 0 0
.04 -.05 --.03 0
--.08 -,08 --.07 0
NS NS NS NS
NS NS NS NS
NS NS NS NS
NS NS NS NS
NS NS NS NS
--.04 --.07 -.04 0
.14 .17 .15
.06 .07 .07
0
0
--1.75 -1.65 --1.05 0
NS NS NS NS
NS NS NS NS
-.09 --.11 -.07 0
--.08 -,06 -.05 0
NS NS NS NS
NS NS NS NS
--.06 -.10 -.06 0
NS NS NS NS
NS NS NS NS
--.81 -1.06 -.79 0
Milk
Type
--.01 -.01 -0 0
-35 -20 -8 0
--.04 -.01 -0 0
-1 -1 --1 0
-0 -.01 -0 0
-17 --11 -10 0
NS NS NS NS
NS NS NS NS
Udder support
.03 .05 .05
Semen price 3
.40 .44 .40 0
Mate's m i l k deviation Missing Negative Positive
-4 --2 0
-1 --0 0
NS NS NS
--17 -10 0
-.03 -.03 0
-.14 --.09 0
--.09 --.05 0
-.06 -.04 0
-.05 -.05 0
-.06 -,04 0
NS NS NS
--.08 --.05 0
--1.91 --1.21 0
Registry status Grade Registered
-8 0
-1 0
NS NS
-35 0
-.12 0
-.34 0
-.24 0
-.20 0
--,20 0
-,14 0
NS NS
-.17 0
-5.08 0
Insemination number 1 2 3 >3
"1"1' 7 0
. NS NS NS
".23 .14 0
.
. '2 1 0
. NS NS NS
.
. 46 27 0
. ".07 .04 0
.
. .24 .14 0
. '.15 .08 0
.
. ".06 .02 0
.
. '.07 .02 0
.
. '.14 .07 0
.
'4.20 2.00 0
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REPRODUCTION AND SERVICE SIRE MERIT
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1375
of cows bred to this type of bull. Every mating was to one of the three types of bulls. The analysis in Table 7 considered each bull type as the dependent variable and each record was scored as a 1 if the cow was bred to that kind of bull and a 0 otherwise. Dairy farmers in Virginia make use of young sires in AI (6.3% of all breedings in this study) and services to bulls not in AI (17.4% of all services) in addition to the 76.3% of services to proven bulls in this study. Schermerhorn et al. (12) reported considerable use of natural service through survey data in New York. Shanks et al. (13) reported that 29% of herds responding to an Illinois survey used AI sample sires. All effects were significant except for sire's PD dollars and PD type for repeat breedings. For all breedings, seasonal effects suggested a tendency to use more proven bulls in late fall, slightly more young sires in late summer, and more unproven or u n k n o w n bulls in early summer. Results for season were significant but not large. There was a tendency for more use of proven bulls in the October to December season. The factors (sire's PD for type and dollars, cow's milk deviation) associated with genetic and phenotypic merit of the cow being bred revealed the expected tendency to use more proven bulls on genetically and phenotypically superior cows. However, constants for mate's milk deviation were larger than constants for her sire's PD, especially in predicting use of proven service sires. Many farmers may be more aware of how a cow ranks for production within the herd than they are of the relative merit of her sire when selecting a service sire. There were significantly fewer services to proven bulls among grade than registered cows. Young sires and unproven or u n k n o w n bull use was higher on grade than registered cows. Results in Table 7 further showed much larger use of proven bulls on first than on fourth or later service. Young sire use was higher on second service, a management option used by a number of herds participating in organized AI sampling programs. Services to proven bulls were higher for third than for fourth and later services. Analysis of repeat breedings in Table 7 produced lower R 2 than analysis of all services, despite the inclusion of an extra factor (breeding interval) in the model. Breeding interval was significant in prediction of rate of use of Journal of Dairy Science Vol. 71, No. 5, 1988
1376
CASSELL AND NEBEL
TABLE 7. Least squares constants for t y p e of bull used as service sire for all and repeat breedings. All breedings 1'2
Repeat breedings I
Effect
Code 1
Code 2
Code 3
Code 1
Code 2
Season Jan to Mar Apr to Jun Jul to Sep Oct to Dec
-.006 -.013 -.006 0
-.002 -.001 .003 0
.008 .014 .003 0
.003 -.009 -.007 0
-.002 -.002 .007 0
Sire's 3 PD t y p e Missing >-.40 - . 4 0 to 1.30 >1.30
-.015 --.012 -.004 0
.007 .007 .002
.008 .005 .003
-.023 --.020 --.009 0
.013 .013 .005
NS 4 NS NS NS
Sire's a PD dollars Missing <-50 - . 5 0 to 80 >80
--.024 -.019 -.012 0
.005 .012 .008
NS NS NS NS
Mate's milk deviation Missing Negative Positive
-.032 --.022 0
0
Registry status Grade Registered
-.068 0
0
0
-.042 .063 --.001 0
-.147 --.101 --.073 0
insemination number 1 2 3 >3
.190 .038 .074 0
0
0
.005 .009 .006 0
.019 .010 .006 0
.007 .006
.025 .016 0
.O23
.045
Breeding interval, d < 18 18 to 24 25 to 38 39 to 45 >45 Coefficient of d e t e r m i n a t i o n
0
-.090 0
0
.175
.358
.001 .007
.038 .019 0
.038
.
.
.051 0
.
. . .064 --.002 0
.
. --.102 -.075 0
.009 .024 .011 .020
-.006 .004 .004 .004 0
-.003 -.028 -.015 -.024 0
.301
.246
.311
0
.320
0
-.040 --.026 0
0
-.001 .011 -0 0
0
--.017 -.022 -.015 0
. . .038 .078
Code 3
1Code 1 bulls were proven bulls in A1, Code 2 were AI sample sires, and Code 3 were all ot he r bulls including unknowns. 21ncludes 293,698 services to proven bulls, 24,383 services to young sires in AI, and 66,909 services to unknown sires. 3 Sire of the cow being bred. 4 NS = Not significant (P<.01).
Journal of Dairy Science Vol. 71, No. 5, 1988
REPRODUCTION AND SERVICE SIRE MERIT the three bull types, b u t the least squares constants were small relative to insemination number. F o r proven bulls, rate of use was lower for b o t h short and long intervals than for intervals b e t w e e n 18 and 45 d. Young sire use was slightly higher for 18 to 45 d intervals than for very short or long intervals. U n p r o v e n or unk n o w n bulls were used m o r e f r e q u e n t l y for very short or very long breeding intervals than for those of 18 to 45 d. CONCLUSIONS
The DHI records of service sire use appear to be useful for the s t u d y of factors associated with choice o f service sire. Genetic merit o f service sires was n o t predicted w i t h precision by factors included in the m o d e l examined. However, results indicated that dairy farmers do consider apparent merit o f the cow being bred and her reproductive status w h e n selecting a service sire. This was m o s t apparent in the cost of semen used, with considerably m o r e investm e n t m a d e in semen used on first breeding, on registered cows, and on cows with positive deviations for milk yield. Breeding interval was a significant p r e d i c t o r o f service sire merit, but appeared to be used o n l y to identify e x t r e m e l y short or long service intervals. Merit of service sires for 18 to 24, 25 to 38, and 39 to 45 d intervals was quite u n i f o r m for p r o d u c t i o n and t y p e traits and semen costs. Genetic m e r i t of service sires for linear traits was n o t affected by breeding interval. Dairy farmers in Virginia t e n d to use y o u n g sires in AI m o r e heavily for second services to milking cows. U n p r o v e n or u n k n o w n sires were used m o r e f r e q u e n t l y for f o u r t h and later inseminations and for short or long breeding intervals. Proven bulls a c c o u n t e d for 76.3% of all services in this study. Young sample sires in AI a c c o u n t e d for 6.3% and u n p r o v e n or u n k n o w n bulls for 17.4% of all breedings. ACKNOWLEDGMENTS
The authors are grateful to J o h n Clay and Ken Butcher of the Raleigh, NC, Dairy Records
1377
Processing Center for provision of breeding records and to Cindy Cassady for c o m p u t i n g support.
REFERENCES
1 Beaudry, T. F., B. G. Cassell, M. L. McGilliard, and G. Kroll. 1986. Impact of trait maximized on sire averages from computerized sire selection. J. Dairy Sci. 69:1686. 2 Clay, J. S., R. C. McCraw, K. R. Butcher, and B. T. McDaniel. 1986. Estimating relative conception rates of service sires from DHI data. J. Dairy Sci. 69(Suppl. 1):125. (Abstr.) 3 Coleman, D. A., W. V. Thayne, and R. A. Dailey. 1985. Factors affecting reproductive performance of dairy cows. J. Dairy Sci. 68:1793. 4 Everett, R. W., and B. Bean. 1986. Semen fertility-an evaluation system for artificial insemination sires, technicians, herds, and systematic fixed effects. J. Dairy Sci. 69:1630. 5 Gonyon, D. S., F. R. Allaire, and W. R. Harvey. 1986. Quantifying dairy breeding goals. 1. A technique to elicit decisions and define equations for goals. J. Dairy Sci. 69:477. 6 Gonyon, D. S., F. R. Allaire, and W. R. Harvey. 1986. Quantifying dairy breeding goals. 2. Perceived contributions of type traits to total merit. J. Dairy Sci. 69:484. 7 Gwazdauskas, F. C., W. D. Whittier, W. E. Vinson, and R. E. Pearson. 1986. Evaluations of reproductive efficiency of dairy cattle with emphasis on timing of breeding. J. Dairy Sci. 69:290. 8 Hillers, J. K., S. C. Thonney, and C. T. Gaskins. 1982. Economic comparison of breeding dairy cows artificially versus naturally. J. Dairy Sci. 65: 861. 9 Keown, J. F. 1986. A midwestern dairy herd management survey. J. Dairy Sci. 69(Suppl. 1):148. (Abstr.) 10 McGilliard, M. L., and J. S. Clay. 1983. Breeding programs of dairymen selecting Holstein sires by computer. J. Dairy Sci. 66:654. 11 Reimers, T. J., R. D. Smith, and S. K. Newman. 1985. Management factors affecting reproductive performance of dairy cows in the northeastern United States. J. Dairy Sci. 68:963. 12 Schermerhorn, E. C., R. H. Foote, S. K. Newman, and R. D. Smith. 1986. Reproductive practices and results in dairies using owner or professional inseminators. J. Dairy Sci. 69:1673. 13 Shanks, R. D., J. K. Rooney, and M. F. Hutjens. 1983. Breeding practices on Illinois Holstein farms. J. Dairy Sci. 66:1209.
Journal of Dairy Science Vol. 71, No. 5, 1988
ABSTRACT
Records were terminated (by sale or dry date) lactation records for cows on DHI test in Virginia for 1982 through 1984. July 1986 production evaluations, most recent type evaluations, and appropriate semen prices for date of service for AI bulls were merged with service sire identification from 384,990 DHI records. Repeat breedings and multiple lactations per cow were used. Least squares procedures revealed significant influences of season, mate's sire's PD for type and dollars, mate's milk yield deviation, registry status, and insemination number on production evaluations, PD type, and semen price of service sire. Significant effects of several of the same variables on linear type traits were observed. Season effects were possibly due to genetic trends. Genetic merit for production and type of service sire declined for daughters of sires with missing or low type and production evaluations, for mates with low or missing herdmate deviations, for grade cows, and for repeat services, especially fourth and later. Days between breedings were nonsignificant or of limited importance in predicting genetic merit of service sires. Proven bulls in AI accounted for 76.3% of all breedings, AI sample sires for 6.3%, and non-AI or unknown sires for 17.4% of breedings in these data. INTRODUCTION
Sire selection is the most important management practice affecting genetic progress in a
Received September 8, 1987. Accepted December 7, 1987.
1988 J Dairy Sci 71:1367-1377
dairy herd. Hillers et al. (8) compared artificial to natural service and concluded that each increase of 227 kg in genetic superiority of AI to natural service sires could offset the costs of 10 additional d in calving interval. Numerous factors influence the choice of sires including perceived importance of production and nonyield traits (5, 6, 10), cost of semen (1, 10), opinion of consultants (9, 13), and reproductive management factors. The last of these is the least studied and is the objective of this study. Reproductive management practices and methods of improving reproductive performance comprise a large body of published research in the United States. Among recently published efforts in this area are fertility evaluation procedures (4, 6), evaluation of owner-insemination conception results (12), timing of insemination relative to standing estrus (7), accuracy of estrous detection (11), and the importance of herd health management factors (3). These diverse topics, all related to producing a conception through AI, contribute to the profitability of the dairy farm. However, the genetic merit of the bull used is perhaps the greatest advantage offered by AI (8) and has not been studied from the perspective of service fires reported through DHI. The influence of management factors such as genetic and phenotypic merit of the cow, registry status, insemination number, or estrous interval on genetic merit of service sires likewise has not been studied. The objectives of this study were to examine the genetic merit of service sires and price of semen used to breed cows of different genetic merit and reproductive status. Included in these objectives was a determination of type of service sire (proven bull in AI, sample sire in AI, other) used on the different types of cows and reproductive situations encountered by dairy farmers in Virginia.
1367
13 68
CASSELL AND NEBEL MATERIALS AND METHODS
Two files of data were used. The record of breedings was from a file provided by the Dairy Records Processing Center in Raleigh, NC of all breedings reported through the DHI systems for Virginia from January 1, 1982 through December 31, 1984. Records were for cows with "terminated" records, i.e., records completed by a dry date or a sold date. For breedings early in 1982, early services for individual cows (those performed fall 1981) may not have been present. Likewise, later inseminations for cows bred in late 1984 may have been eliminated by the dates chosen for the study. Cow records were required to contain valid dates for birth, breeding, and either subsequent calving or date sold. The interval to first breeding was required to be at least 15 d. Service number was taken as reported through DHI but was required to be sequential for breedings within a lactation. Cows were required to be sired by and bred to Holstein sires when sires and service sires were identified. However, records were not eliminated for missing sire or service sire information. Only the first nine services on any cow were used. The second file necessary was a history file of production and type evaluations on Holstein bulls. Data were the USDA Modified Contemporary Comparison sire evaluation file as reported on the July 1986 Format 380 tape. Production evaluations were the most recent calculated through July 1986. The most recent PD type evaluation published b y the HolsteinFriesian Association of America between January 1980 and July 1986 was used. Due to a change in evaluation of linear type traits in January 1984, only linear evaluations between January 1984 and July 1986 were included. Semen prices were from a historical file of retail, direct-herd semen prices as published by major AI organizations marketing semen in Virginia. Semen prices changed every 6 mo corresponding with changes in sire evaluations. The semen price assigned to a breeding was the appropriate price for the date the breeding occurred, as shown in Table 1. Semen prices were available for between 405 and 460 active AI Holstein sires for the seven summary dates. Semen prices were known for 69% of the total breedings in the cow file, which is 90% of the services to proven bulls in
Journal of Dairy Science Vol. 71, No. 5, 1988
TABLE 1. Semen price assigned by breeding date.
Breeding date
Summary date for semen price
1-1-82 to 2-1-82 to 8-1-82 to 2-1-83 to 8-1-83 to 2-1-84 to 8-1-84 to
Summer 1981 Winter 1982 Summer 1982 Winter 1983 Summer 1983 Winter 1984 Summer 1984
1-31-82 7-31-82 1-31-83 7-31-83 1-31-84 7-31-84 12-31-84
A1. Services to proven bulls in AI were 76.3% of aJl breedings. The file of bull evaluations and semen prices was matched to the cow file for both sire and service sire identification. Breedings totaled 384,990 breedings in the final data set. These records were not complete with respect to presence of evaluations for sires and service sires for all traits. However, the final file was edited no further to avoid elimination of useful information such as management decisions, which increased the use of bulls not in AI. Effects of management and cow merit for services to proven bulls were evaluated by least squares procedures using the following model. Service sire merit = herd year i + bl(age) + b2(age 2) + seasonj + sire typeg + sire dolle + deviation m + statn + insemo + intp + residual. Service sire merit included PD for dollars, milk, fat, fat percent, type; the linear type traits udder support, rear udder, fore udder, teat placement, feet, hind legs, and stature; plus semen price. Herd year was herd year of freshening associated with a particular breeding. Age was the age at calving for a breeding. Four seasons (seasonj) were created for date bred: January to March, April to June, July to September, and October to December. Four categories of PD type for the sire of the cow bred (sire type k) were: missing type, less than - . 4 0 , - . 4 0 to 1.30, and above 1.30. The PD dollar value of the sire of the cow bred (sire dolle) was used to create four categories: missing, less than - $ 5 0 , - $ 5 0 to $80, and above $80. The break points for PD type and PD dollar values on the sire of the cow being bred were approximately one standard deviation above and below the mean of all sires with
REPRODUCTION AND SERVICE SIRE MERIT proofs for dollars and t y p e available. Three categories for milk yield deviation o f the cow being bred (deviationm) were: missing, negative, and positive deviation. The classification statn refers to t h e registry status of the cow being bred, registered, or grade. Insem o refers to the insemination n u m b e r of a breeding with f o u r categories of first, second, third, and f o u r t h or greater service. The Intp referred to interval b e t w e e n breedings and was only included in the analysis of second and subsequent services. Categories were less t h a n 18 d, 18 to 24 d, 25 to 38 d, 39 to 45 d, and greater than 45 d. Least squares constants of significant variables f r o m t h e m o d e l for prediction of service sire m e r i t were e x a m i n e d to d e t e r m i n e the t e n d e n c y o f farmers t o use b e t t e r or p o o r e r bulls for the various traits under different conditions.
1369
RESULTS A N D DISCUSSION
Means of variables indicative o f the genetic and p h e n o t y p i c merit of t h e cow being bred are in Table 2. Cow indexes for milk w e r e available for 70% of the records and averaged 50 kg milk and I kg fat. Missing cow indexes were due to sire identification errors. Supporting d o c u m e n t s a c c o m p a n y i n g the January 1984 U S D A Modified C o n t e m p o r a r y Comparison sire and cow evaluations showed the average cow index of all registered Holstein cows passing elite status screening edits to be - 1 7 1 kg milk and - 5 kg fat. This group o f Virginia Holsteins was genetically superior to t h a t average. T h e average h e r d m a t e deviation for milk was 251 kg, again suggesting that cows in t h e study were slightly above average as producers. Differential reporting of service sire data through D H I
TABLE 2. Means, standard deviations, and percent of records with information available for Virginia Holstein cows bred between January 1, 1982 and December 31, 1984.1 % of Records with variable available
Variable
Mean
SD
Mate Cow index, milk, kg Cow index, fat, kg Mature equivalent (ME) milk, kg ME Fat, kg Herd mate average ME milk, kg Herdmate average ME fat, kg
50 1 7781 271 7530 262
263 8 1608 57 935 33
99 99 94 94
Interval between breedings, d
46
33
44
Mate's sire 2 Repeatability PD Dollars PD Milk, kg PD Fat, kg PD % Fat PD Type PD Udder support PD Rear udder PD Fore udder PD Teats PD Foot angle PD Hind legs PD Stature
90 5 50 0 --.02 .43 .71 1.27 .24 .74 .47 -.01 .37
22 65 282 10
67 67 67 67 67 41 8 8 8 8 8 8 8
.09 .86 1.42 1.40 1.29 1.03 1.19 1.60 1.52
70 70
1Records repeated for multiple lactations and repeat breedings. 2Production evaluations were calculated in July 1986. Type evaluations were the most recent published through July 1986. Journal of Dairy Science VoI. 71, No. 5, 1988
1370
CASSELL AND NEBEL
could cause this result, as would our practice of repeating records for multiple records and repeat breedings. Genetically superior cows and cows with positive deviations may have been serviced more frequently or farmers may have reported services for such cows more consistently. Logically, such cows would have more lactations than genetically inferior cows or lower producers. First services were 56.1% of all breedings, second services were 23.3%, third services 11.0%, and fourth and subsequent services accounted for 9.6% of all breedings. Characteristics of reproductive management practices are in Figures 1 and 2. Figure 1 shows distinct seasonality of breedings in Virginia as reported by farmers through DHI. The October to December period includes 32.6% of all services. January to March includes 22.3%, April to June 21%, and July to September 24.2% of all breedings. Figure 2 shows the distribution of interval between breedings for repeat breedings. The frequency of breedings showed peaks around d 21~ 42, and 63, as expected from 21-d estrous cycles. These results contributed to the establishment of service interval categories used in the statistical model explained earlier. Many cows are bred on intervals other than that expected from one normal cycle. However, the interval 18 to 24 d included 29.8% of all repeat breedings. Reimers et al. (11) published a figure of distribution of days between unsuccessful
first and second service with similar properties. They reported 93.2% o f cows in or near estrus at first service and open 21 to 24 d later were serviced again within 90 d. In our data, 91.6% of all intervals (not just first and second) were 90 d or less. The average interval between breeding of 46 d was slightly longer than the 41.1 d from the work of Coleman et al. (3), whose herds were chosen based on managers' willingness to cooperate. This result may reflect less complete reporting of breedings in the present study. Average merit of service sires for the various traits is in Table 3. Production proofs were available on service sires for 81% of the breedings; however, not all of these evaluations were known to the dairy farmer at the time of the mating. The most recent breedings in the study were from the fall of 1984; evaluations for production were from July of 1986. Some proofs on bulls used as sample sires or from natural service bulls had become available in the interim. Better bulls were used more heavily. Table 4 shows weighted averages of $60 for PD dollars, 284 kg for PD milk, and 7 for PD fat. The unweighted averages of service sires (Table 3) show $5, 34 kg, and 0 kg, respectively, for all 3134 bulls appearing as service sires. Weighted averages were slightly higher for PD type, udder support, rear udder, teats, foot angle, hind legs, and stature. For production traits, standard deviation of variables in Table 4 were less than
150GI)
4OOOO
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aoooo
Z 'tO0~O -
S
0 JAN
FEB
MAR APR
MAY JUN
JUL
AUG
SEP
OCT
NOV OEC
MONTH
Figure 1. Total breedings for 3 yr (1982 to 1984) by month of insemination. Journal of Dairy Science Vol. 71, No. 5, 1988
DAYS
IN INTERVAL
Figure 2. Distribution of number of breedings by interval in days between breedings.
REPRODUCTION AND SERVICE SIRE MERIT "
'
~
~
q~q~qqqq
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"E
e~
I
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1371
in Table 3, again showing the impact of selection. Average production evaluations for milk, fat, and dollars were higher for sires of cows bred than for all bulls with proofs, and higher for service sires than for sires of cows bred. The opposite was true of PD% fat. Genetic trend and selection could cause such results. Table 5 contains results of analysis of services to proven bulls. Bulls with an National Association of Animal Breeders (NAAB) stud code, a nonzero repeatability, and greater than 4 yr of age at the time the cow was bred were considered to be proven bulls (Code 1) of which the farmer had knowledge of breeding value. Bulls less than 4 yr old at time of mating with NAAB stud codes were considered young sample sires (Code 2). All other services were grouped together in Code 3. Season effects in Table 5 were significant for all traits but rear udder teat placement, and foot angle. The least squares constants are all expressed as deviations from the last class in each effect. Cows bred in January to March were bred to bulls 14 kg lower for milk, 2 kg lower for fat, and $10 lower for dollars than cows bred in October to December. These results are most likely due to genetic trend in the bull population within year. Results for PD type were directional and in favor of fall matings, again suggesting genetic trend. Results for semen price showed less expensive semen was used in fall but differences between seasons were small. The three effects in the model measuring genetic and phentoypic merit of the cow being bred (sire's PD for type and dollars and cow's milk yield deviation) were significant in predicting service sire merit for most traits. However, sire's PD dollars was not significant for 5 of 13 traits. Service sires with lower PD dollars and lower semen costs were used on cows with unknown sire merit for type or dollars, low values for sires PD type or dollars, or themselves had missing or negative milk deviations. The greatest effect of measures of merit of the cow bred appeared to be on semen price. Cows with missing deviations were bred to semen costing $2.49 per unit less than cows with positive deviations. Service sire PD dollars was only $5 less and PD type only .03 less for such cows. However, missing deviations were primarily due to short lactations, which prevented determination of herdmate averages. Journal of Dairy Science Vol. 71, No. 5, 1988
1372
CASSELL AND NEBEL
Registry status had a significant and import a n t i m p a c t on service sire merit. Grades were bred to semen costing $6.48 per unit less than semen used on registered cows. Evaluations for all linear traits e x c e p t hind legs were lower for service sires used on grade cows. The lower PD dollars value of $9 and t y p e p r o o f of .12 for service sires o f grade cows seemed a small difference in genetic m e r i t for the rather substantial difference in semen price. Cows were bred to considerably b e t t e r bulls on first service t h a n on f o u r t h and later services. Semen cost was $7.31 higher, PD dollars was $19 higher, PD t y p e .10 higher, and all linear evaluations (except hind legs, which was not affected by insemination number) were higher on service sires used for first breedings. T h e decline in service sire m e r i t as insemination n u m b e r increased appeared to be linear. Emphasis on linear traits was reduced fairly drastically by third service. The prediction e q u a t i o n used was m o s t effective in predicting semen price (R 2 = .318) and least effective for hind legs (R 2 = .107). Many factors o t h e r than those considered in this m o d e l m a y influence genetic m e r i t of service sires.
Table 6 contains results of the prediction of service sire merit for repeat breedings to Code 1 (proven bulls) only. Interval b e t w e e n breedings was included in this model. The R 2 values were higher than for Table 5 (.142 to .357). However, the influence of PD dollars and PD t y p e of the sire o f the cow being bred seemed to decline for repeat breeders. This m a y indicate that the genetic m e r i t of the cow b e c o m e s less of a m a n a g e m e n t factor in selecting a service sire as reproductive factors b e c o m e more pressing. T h e e x a m i n a t i o n of least squares constants for breeding interval showed that this factor was n o t significant for 7 of 13 traits examined, including all linear traits e x c e p t stature. The PD dollars of service sire was slightly higher for 18 to 24, 25 to 38, and 39 to 45-d intervals than for very short or very long intervals. The same was true of semen price. Results suggest that breeding interval is either u n k n o w n or considered u n i m p o r t a n t e x c e p t w h e n very short or very long intervals are involved. Table 7 contains an analysis of t y p e of bull used for all breedings and for repeat breedings. The least squares constants can be interpreted as differences (from the 0 category) in fraction
TABLE 4. Means, standard deviations, and percent of records with information available for service sires used to breed Virginia Holstein cows between January 1, 1982 and December 31, 1984.1
Variable
Mean
Repeatability PD Dollars PD Milk, kg PD Fat, kg PD % Fat PD Type PD Udder support PD Rear udder PD Fore udder PD Teats PD Foot angle PD Hind legs PD Stature Semen price, 2 $
94 60 284 7 -.03 .57 .53 .46 -.18 .16 .11 .25 .14 15.69
SD 11 58 266 9 .10 .68 1.25 1.08 1.24 1.09 1.14 1.59 .77 15.55
% of Records with variable available 81 81 81 81 81 74 49 49 49 49 49 49 49 69
1Records repeated for multiple lactations and repeat breedings. Production evaluations were calculated in July 1986. Type evaluations were the most recent published through July 1986. 2 Semen price was retail semen price appropriate for the date each cow was bred. Journal of Dairy Science Vol. 71, No. 5, 1988
T A B L E 5. Least squares constants for prediction o f service sire m e r i t when m a t i n g s were t o proven bulls. Herd year o f breeding and linear and quadratic effects o f age at calving were removed. Linear traits 2 PDI
.< o Z o
Fore udder
Teat placement
Foot angle
Hind legs
Stature
NS 4 NS NS NS
--.03 --.03 --.02 0
NS NS NS NS
NS NS NS NS
.02 --.04 -.03 0
--.04 --.05 --.05 0
.02 .00 .03
.03 .02 .04
.16 .19 .16
.08 .10 .08
Effect
Dollars
Fat
Season Jan to Mar A p r to J u n Jul t o Sep Oct t o Dec
-10 -7 -3 0
-2 -1 -1 0
-,006 -,004 -.003 0
-34 -22 -9 0
-.04 -.02 -.01 0
0
Sire's s PD type Missing <--.40 --.40 to 1.30 >1.30
-6 --6 -4 0
--1 --1 --1 0
-.004 --.008 -,004 0
-18 --14 --12 0
NS NS NS NS
--.04 -.06 -.02 0
0
0
0
--.07 --.08 -.05 O
Sire's s PD dollars Missing <-50 - 5 0 to 80 :>80
-1 -2 -1 0
--0 -0 --O 0
NS NS NS NS
NS NS NS NS
--.01 --.02 --.01 0
-.07 -.07 -.04 0
--.04 --.03 -.02 0
NS NS NS NS
NS NS NS NS
-.07 --.10 --.08 0
Mate's milk deviation Missing Negative Positive
--5 -2 0
--1 0 0
NS NS NS
--19 -9 0
--.03 -.03 0
-.12 -.09 0
-.08 -.06 0
--.05 --.05 0
--.05 --.05 0
Registry status Grade Registered
-9 0
-1 0
NS NS
--40 0
--.12 0
--.34 0
-.27 0
--.24 0
Insemination n u m b e r i 2 3 >3
19 12 7 0
3 2 1 0
78 50 27 0
.10 .07 .04
.39 .27 .15
.27 .17 .09
.10 .07 .02
Milk
Type
Udder support
Rear udder
Percent fat
.02 .03 .04
.01 .03 .03
Semen price 3
.71 .60 .16 0
,¢ ~
0
--1.80 --1.84 --1.12 0
--.99 --1.22 -.80 0
Z
0
NS NS NS NS
--.06 --,05 0
NS NS NS
--.07 --.04 0
-2.49 -1.52 0
--.24 0
--.16 0
0
--.15 0
--6.48 0
.13 .08 .02
.23 .15 .07
.34 .25 .15
7.31 4.54 2.07 0
0
.03 .08 .03
CI ,q
Z t~
Coefficient of determination
A78
-.002 -,001 .001 0
.176
.150
0
.168
0
.188
0
.202
0
.178
0
.190
0
.150
.144
.10
NS NS NS NS
.107
0
.196
t~
.318
1293,698 records for milk variables, 2 8 4 , 7 5 8 records for PD type. : 187,432 records for linear traits. 3266,388 records for semen price.
0o
0o
4 NS = Not significant (P<.01). SSire o f the cow being bred,
,q
.q 4~
e~
o
tt~
<
T A B L E 6. Least squares c o n s t a n t s for prediction o f service sire m e r i t using r e p e a t breedings and services to proven bulls only. Herd-year o f b r e e d i n g and linear and q u a d r a t i c e f f e c t s o f age at calving w e r e removed.
o_ 2
oz oo oo
Linear traits 2 Teat
PD 1 Effect
Dollars
Fat
Season J a n to Mar A p t to J u n Jul to Sep O c t to Dec
-11 -7 -3 0
--2 -1 -1 0
-5 --5 --4 0
Sire's s PD t y p e Missing <-.40 - . 4 0 to 1.30 >1.30 Sire's s PD dollars Missing <--50 - 5 0 to 80 >80
NS NS NS NS
Percent fat
Rear udder
Fore udder
placement
Foot angle
Hind legs
Stature
0
NS 4 NS NS NS
--,05 -.03 --.01 0
NS NS NS NS
--.04 -.01 0 0
.04 -.05 --.03 0
--.08 -,08 --.07 0
NS NS NS NS
NS NS NS NS
NS NS NS NS
NS NS NS NS
NS NS NS NS
--.04 --.07 -.04 0
.14 .17 .15
.06 .07 .07
0
0
--1.75 -1.65 --1.05 0
NS NS NS NS
NS NS NS NS
-.09 --.11 -.07 0
--.08 -,06 -.05 0
NS NS NS NS
NS NS NS NS
--.06 -.10 -.06 0
NS NS NS NS
NS NS NS NS
--.81 -1.06 -.79 0
Milk
Type
--.01 -.01 -0 0
-35 -20 -8 0
--.04 -.01 -0 0
-1 -1 --1 0
-0 -.01 -0 0
-17 --11 -10 0
NS NS NS NS
NS NS NS NS
Udder support
.03 .05 .05
Semen price 3
.40 .44 .40 0
Mate's m i l k deviation Missing Negative Positive
-4 --2 0
-1 --0 0
NS NS NS
--17 -10 0
-.03 -.03 0
-.14 --.09 0
--.09 --.05 0
-.06 -.04 0
-.05 -.05 0
-.06 -,04 0
NS NS NS
--.08 --.05 0
--1.91 --1.21 0
Registry status Grade Registered
-8 0
-1 0
NS NS
-35 0
-.12 0
-.34 0
-.24 0
-.20 0
--,20 0
-,14 0
NS NS
-.17 0
-5.08 0
Insemination number 1 2 3 >3
"1"1' 7 0
. NS NS NS
".23 .14 0
.
. '2 1 0
. NS NS NS
.
. 46 27 0
. ".07 .04 0
.
. .24 .14 0
. '.15 .08 0
.
. ".06 .02 0
.
. '.07 .02 0
.
. '.14 .07 0
.
'4.20 2.00 0
¢3 Oq t~ > Z Z Oq
zzz~
zz~
..~ Z ~ ~V ee~
A
"2
el
e,i
0J
8
e~
8
o
~
REPRODUCTION AND SERVICE SIRE MERIT
.-o~
1375
of cows bred to this type of bull. Every mating was to one of the three types of bulls. The analysis in Table 7 considered each bull type as the dependent variable and each record was scored as a 1 if the cow was bred to that kind of bull and a 0 otherwise. Dairy farmers in Virginia make use of young sires in AI (6.3% of all breedings in this study) and services to bulls not in AI (17.4% of all services) in addition to the 76.3% of services to proven bulls in this study. Schermerhorn et al. (12) reported considerable use of natural service through survey data in New York. Shanks et al. (13) reported that 29% of herds responding to an Illinois survey used AI sample sires. All effects were significant except for sire's PD dollars and PD type for repeat breedings. For all breedings, seasonal effects suggested a tendency to use more proven bulls in late fall, slightly more young sires in late summer, and more unproven or u n k n o w n bulls in early summer. Results for season were significant but not large. There was a tendency for more use of proven bulls in the October to December season. The factors (sire's PD for type and dollars, cow's milk deviation) associated with genetic and phenotypic merit of the cow being bred revealed the expected tendency to use more proven bulls on genetically and phenotypically superior cows. However, constants for mate's milk deviation were larger than constants for her sire's PD, especially in predicting use of proven service sires. Many farmers may be more aware of how a cow ranks for production within the herd than they are of the relative merit of her sire when selecting a service sire. There were significantly fewer services to proven bulls among grade than registered cows. Young sires and unproven or u n k n o w n bull use was higher on grade than registered cows. Results in Table 7 further showed much larger use of proven bulls on first than on fourth or later service. Young sire use was higher on second service, a management option used by a number of herds participating in organized AI sampling programs. Services to proven bulls were higher for third than for fourth and later services. Analysis of repeat breedings in Table 7 produced lower R 2 than analysis of all services, despite the inclusion of an extra factor (breeding interval) in the model. Breeding interval was significant in prediction of rate of use of Journal of Dairy Science Vol. 71, No. 5, 1988
1376
CASSELL AND NEBEL
TABLE 7. Least squares constants for t y p e of bull used as service sire for all and repeat breedings. All breedings 1'2
Repeat breedings I
Effect
Code 1
Code 2
Code 3
Code 1
Code 2
Season Jan to Mar Apr to Jun Jul to Sep Oct to Dec
-.006 -.013 -.006 0
-.002 -.001 .003 0
.008 .014 .003 0
.003 -.009 -.007 0
-.002 -.002 .007 0
Sire's 3 PD t y p e Missing >-.40 - . 4 0 to 1.30 >1.30
-.015 --.012 -.004 0
.007 .007 .002
.008 .005 .003
-.023 --.020 --.009 0
.013 .013 .005
NS 4 NS NS NS
Sire's a PD dollars Missing <-50 - . 5 0 to 80 >80
--.024 -.019 -.012 0
.005 .012 .008
NS NS NS NS
Mate's milk deviation Missing Negative Positive
-.032 --.022 0
0
Registry status Grade Registered
-.068 0
0
0
-.042 .063 --.001 0
-.147 --.101 --.073 0
insemination number 1 2 3 >3
.190 .038 .074 0
0
0
.005 .009 .006 0
.019 .010 .006 0
.007 .006
.025 .016 0
.O23
.045
Breeding interval, d < 18 18 to 24 25 to 38 39 to 45 >45 Coefficient of d e t e r m i n a t i o n
0
-.090 0
0
.175
.358
.001 .007
.038 .019 0
.038
.
.
.051 0
.
. . .064 --.002 0
.
. --.102 -.075 0
.009 .024 .011 .020
-.006 .004 .004 .004 0
-.003 -.028 -.015 -.024 0
.301
.246
.311
0
.320
0
-.040 --.026 0
0
-.001 .011 -0 0
0
--.017 -.022 -.015 0
. . .038 .078
Code 3
1Code 1 bulls were proven bulls in A1, Code 2 were AI sample sires, and Code 3 were all ot he r bulls including unknowns. 21ncludes 293,698 services to proven bulls, 24,383 services to young sires in AI, and 66,909 services to unknown sires. 3 Sire of the cow being bred. 4 NS = Not significant (P<.01).
Journal of Dairy Science Vol. 71, No. 5, 1988
REPRODUCTION AND SERVICE SIRE MERIT the three bull types, b u t the least squares constants were small relative to insemination number. F o r proven bulls, rate of use was lower for b o t h short and long intervals than for intervals b e t w e e n 18 and 45 d. Young sire use was slightly higher for 18 to 45 d intervals than for very short or long intervals. U n p r o v e n or unk n o w n bulls were used m o r e f r e q u e n t l y for very short or very long breeding intervals than for those of 18 to 45 d. CONCLUSIONS
The DHI records of service sire use appear to be useful for the s t u d y of factors associated with choice o f service sire. Genetic merit o f service sires was n o t predicted w i t h precision by factors included in the m o d e l examined. However, results indicated that dairy farmers do consider apparent merit o f the cow being bred and her reproductive status w h e n selecting a service sire. This was m o s t apparent in the cost of semen used, with considerably m o r e investm e n t m a d e in semen used on first breeding, on registered cows, and on cows with positive deviations for milk yield. Breeding interval was a significant p r e d i c t o r o f service sire merit, but appeared to be used o n l y to identify e x t r e m e l y short or long service intervals. Merit of service sires for 18 to 24, 25 to 38, and 39 to 45 d intervals was quite u n i f o r m for p r o d u c t i o n and t y p e traits and semen costs. Genetic m e r i t of service sires for linear traits was n o t affected by breeding interval. Dairy farmers in Virginia t e n d to use y o u n g sires in AI m o r e heavily for second services to milking cows. U n p r o v e n or u n k n o w n sires were used m o r e f r e q u e n t l y for f o u r t h and later inseminations and for short or long breeding intervals. Proven bulls a c c o u n t e d for 76.3% of all services in this study. Young sample sires in AI a c c o u n t e d for 6.3% and u n p r o v e n or u n k n o w n bulls for 17.4% of all breedings. ACKNOWLEDGMENTS
The authors are grateful to J o h n Clay and Ken Butcher of the Raleigh, NC, Dairy Records
1377
Processing Center for provision of breeding records and to Cindy Cassady for c o m p u t i n g support.
REFERENCES
1 Beaudry, T. F., B. G. Cassell, M. L. McGilliard, and G. Kroll. 1986. Impact of trait maximized on sire averages from computerized sire selection. J. Dairy Sci. 69:1686. 2 Clay, J. S., R. C. McCraw, K. R. Butcher, and B. T. McDaniel. 1986. Estimating relative conception rates of service sires from DHI data. J. Dairy Sci. 69(Suppl. 1):125. (Abstr.) 3 Coleman, D. A., W. V. Thayne, and R. A. Dailey. 1985. Factors affecting reproductive performance of dairy cows. J. Dairy Sci. 68:1793. 4 Everett, R. W., and B. Bean. 1986. Semen fertility-an evaluation system for artificial insemination sires, technicians, herds, and systematic fixed effects. J. Dairy Sci. 69:1630. 5 Gonyon, D. S., F. R. Allaire, and W. R. Harvey. 1986. Quantifying dairy breeding goals. 1. A technique to elicit decisions and define equations for goals. J. Dairy Sci. 69:477. 6 Gonyon, D. S., F. R. Allaire, and W. R. Harvey. 1986. Quantifying dairy breeding goals. 2. Perceived contributions of type traits to total merit. J. Dairy Sci. 69:484. 7 Gwazdauskas, F. C., W. D. Whittier, W. E. Vinson, and R. E. Pearson. 1986. Evaluations of reproductive efficiency of dairy cattle with emphasis on timing of breeding. J. Dairy Sci. 69:290. 8 Hillers, J. K., S. C. Thonney, and C. T. Gaskins. 1982. Economic comparison of breeding dairy cows artificially versus naturally. J. Dairy Sci. 65: 861. 9 Keown, J. F. 1986. A midwestern dairy herd management survey. J. Dairy Sci. 69(Suppl. 1):148. (Abstr.) 10 McGilliard, M. L., and J. S. Clay. 1983. Breeding programs of dairymen selecting Holstein sires by computer. J. Dairy Sci. 66:654. 11 Reimers, T. J., R. D. Smith, and S. K. Newman. 1985. Management factors affecting reproductive performance of dairy cows in the northeastern United States. J. Dairy Sci. 68:963. 12 Schermerhorn, E. C., R. H. Foote, S. K. Newman, and R. D. Smith. 1986. Reproductive practices and results in dairies using owner or professional inseminators. J. Dairy Sci. 69:1673. 13 Shanks, R. D., J. K. Rooney, and M. F. Hutjens. 1983. Breeding practices on Illinois Holstein farms. J. Dairy Sci. 66:1209.
Journal of Dairy Science Vol. 71, No. 5, 1988