Livestock Production Science 65 2000 119–130 www.elsevier.com locate livprodsci
Genetic correlations of somatic cell count and conformation traits with herd life in dairy breeds, with an application to
national genetic evaluations for herd life in the United Kingdom
R.A. Mrode , G.J.T. Swanson, C.M. Lindberg
Animal Data Centre Ltd ., Fox Talbot House, Greenways Business Park, Bellinger Close, Chippenham, Wiltshire SN15 1BN, UK
Received 28 April 1999; received in revised form 21 October 1999; accepted 2 November 1999
Abstract
Genetic correlations r between Lifespan LS and conformation traits in the Ayrshire breed were obtained from data on
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8087 heifers which calved between 1976 and August 1990. The r were estimated from a series of multivariate analyses
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applying an animal model restricted maximum-likelihood procedure. The genetic relationship between LS and somatic cell counts SCC was studied in the Holstein Friesian HF, Ayrshire AYR and Jersey JER breeds. Estimates of r between
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LS and SCC were obtained from a bivariate analysis fitting a sire model. The four type traits with the largest r with LS
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were foot angle 0.47, udder depth 0.46, fore udder attachment 0.28 and teat length 20.28. The estimates of r
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between LS and SCC varied from 2 0.32 HF to 2 0.11 JER; higher SCC resulted in lower herd life. Genetic evaluation for LS in the United Kingdom involves a bivariate analysis utilising direct lactation information and indirect information
from conformation traits. The design matrices for the direct and indirect traits are different and either trait could be missing. A computing strategy implemented for the national evaluation of herd life that handles these problems is presented in
addition to the results from the first official evaluation. Bull predicted transmitting abilities PTAs for LS ranged from 2 0.8 to 1.4 lactations; most bull PTAs were within the range of 60.5 lactations. The predicted difference in LS is about one
lactation between daughters of extreme bulls when those with at least ten daughters were considered. A slight positive genetic trend was observed for LS in all breeds.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Lifespan; Conformation traits; Somatic cell count; Canonical transformation; Dairy cattle
1. Introduction has a major impact on net returns in dairy pro-
duction. The benefit of improved herd life on farm Herd life which reflects the cow’s productive life
includes a reduction in replacement costs and im- proved average yields from a higher proportion of
mature, higher yielding cows in the milking herd
Corresponding author. Tel.: 144-1249-467-272; fax: 144-
Rendel and Robertson, 1950.
1249-467-273. E-mail address
: enquiryanimaldata.co.uk R.A. Mrode
A problem with selection for improved herd life is
0301-6226 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 9 9 0 0 1 7 2 - 4
120 R
.A. Mrode et al. Livestock Production Science 65 2000 119 –130
that direct information is not available early in life, ment, udder depth and teat length. In other dairy
as a cow must be given time to complete lactations breeds,
apart from
Ayrshire AYR,
recording or be culled from the herd. In order to obtain early
schemes for conformation traits have not been genetic evaluations for herd life, researchers have
running for a long enough period to enable similar examined procedures for prediction of breeding
analyses to be carried out. values based not only on complete herd life in-
Dekkers 1993 indicated that herd life corrected formation but also on partial herd life information on
for production or functional herd life is a better cows which are still alive. Van Raden and Klaas-Kate
measure of involuntary culling. LS is a measure of 1993 predicted completed herd life records for
functional herd life since it is adjusted for first cows still alive in the herd and applied a lower
lactation milk yield Brotherstone et al., 1997 and weight on the projected records in the genetic
therefore reflects the ability of the cow to withstand evaluation system using an animal model. However,
involuntary culling. SCC is used as an indirect Ducrocq et al. 1988 and Ducrocq and Solkner
measure of mastitis in the UK Mrode et al., 1998. 1998 presented a non-linear approach to survival
Reduction in the rate of mastitis incidence through analysis based on the Weibull hazard function with
selection on SCC should result in a reduction in records of cows still alive in the herd treated as
involuntary culling and hence improvements in censored observations. Jairath et al. 1998 adopted a
functional herd life. Preferably both SCC and LS multivariate approach with survival in the first three
should be included in an index to improve herd life. lactations regarded as different traits. A major advan-
The construction of such an index requires knowl- tage of this multivariate approach and the non-linear
edge of the genetic relationship between both traits survival analysis is that they allow for the inclusion
and this is examined in this study. of time-dependent systematic environmental effects
As Brotherstone et al. 1997 indicated, the op- such as production and herd–year–season to be
timum use of LS and conformation traits in the associated with each lactation in the models for
genetic evaluation of herd life would require the use genetic evaluation. From the study of Vollema and
of a multivariate animal model. Initial test runs on a Groen 1998 that compared heritabilities and
subset of the national data of a million cows with evaluations from a linear model and survival analy-
records took about 84 h of computing time imple- sis, the major benefit of the survival analysis was its
menting a bivariate analysis involving LS and a ability to handle censored as well as uncensored
phenotypic index formed by combining the four type records.
traits most highly correlated with herd life Mrode In addition to partial herd life information on live
and Swanson, 1998. In conclusion, on a national cows, correlated conformation traits have been used
scale, the implementation of such a multivariate to obtain early genetic evaluations for herd life and
analysis would be impractical in terms of computing to improve its accuracy Vollema, 1998. In the
time. However, the multivariate analysis could be United Kingdom UK initial predictions of breeding
simplified by the application of a canonical trans- values for herd life were based on indirect estimation
formation, but the traits are associated with different from four conformation traits. These were not pub-
fixed effects and there is also the potential problem lished as such but incorporated in a selection index
of missing observations. Ducrocq and Besbes 1993 together with production Veerkamp et al., 1995.
proposed an algorithm that could be utilised to However, Brotherstone et al. 1997 proposed a
handle traits with different design matrices and also direct measure of herd life called Lifespan LS,
missing observations when a canonical transforma- which accounts for the number of lactations each
tion is applied. cow had completed or was expected to complete
The objectives of this paper are three-fold. Firstly based on average population probabilities. From
to estimate the genetic correlations between LS and analyses using LS and conformation data for the HF
the conformation traits in the AYR breed to de- breed, they recommended that genetic evaluation for
termine whether similar traits were associated with herd life in the UK should be based on LS and four
LS as in the Holstein breed. In practice decisions conformation traits: foot angle, fore-udder attach-
were required on whether to adopt the same index
R .A. Mrode et al. Livestock Production Science 65 2000 119 –130
121 Table 1
over all dairy breeds despite the lack of conformation
The probability of survival from lactation i to i 11 in the different
data. Secondly to estimate the association between
breeds
LS and SCC in some dairy breeds with a view to
Breed Probability of survival from lactation i to
proposing improvements to the National Index and
i 11
finally to report the application of the algorithm
1–2 2–3
3–4 4–5
.5
proposed by Ducrocq and Besbes 1993 to speed up the production of LS evaluations on a large national
Holstein Friesian 0.78
0.77 0.76
0.73 0.73
Ayrshire 0.76
0.76 0.73
0.71 0.71
data set.
Jersey 0.78
0.78 0.76
0.73 0.73
Guernsey 0.77
0.77 0.74
0.74 0.74
Shorthorn 0.76
0.75 0.73
0.72 0.72
2. Materials and method
