BBBCS Sire & Dam Summary 2003 - Technical Appendix

BRITISH BELGIAN BLUE NATIONAL SIRE AND DAM SUMMARY 2004

TECHNICAL APPENDIX

Model

The EBVs reported in this Summary have been produced using a multi-trait individual animal model BLUP procedure. For gestation length, calving ease, birth weight and 200-day weight, permanent environmental and maternal effects were included in the model.

The environmental effects accounted for in evaluations for each trait are shown in Table 3.

Contemporary groups are formed across sexes for birth weight and 200-day weight, since the sexes are not usually managed differently at this stage (although the biological differences between the sexes are still accounted for in the evaluations). However, for later performance records, contemporary groups are formed separately within the two sexes, since in some herds management procedures differ between the sexes.

The estimated genetic merit for 200-day weight has been divided into a direct genetic component due to the animal's own genes for growth and a maternal genetic component. This maternal genetic component results from variation in cow's genetic merit for the in utero environment they provide, their mothering ability, milking ability etc. Although both sexes carry the genes for maternal ability, they are only expressed in females during pregnancy and afterwards during the rearing of the calf.

Table 3 Fixed Effects Accounted for in Evaluation

	Gestation length	Calving ease	Birth wt	200 day wt	400 day wt	Muscling score	Muscle depth	Fat depth
Contemporary group excluding sex	*	*	*	*
Contemporary group including sex					*	*	*	*
Sex	*	*	*	*
Month of birth	*	*	*	*	*
Birth type	*	*	*	*	*	*	*	*
Foster dam				*
Embryo transplant calf	*	*	*	*
% Belgian Blue blood	*	*	*	*	*	*	*	*
Dam breed type	*	*	*	*	*	*	*	*
Age of dam-linear and quadratic covariate	*	*	*	*	*
Age at measurement - linear and quadratic covariate						*	*	*

Economic Weightings

Farm models which give estimates of economic values for carcase weight, carcase fat score, carcase conformation score, calving ease and gestation length for the UK industry have recently been developed by MLC and SAC and are based on data collected pre-BSE. Economic values for carcase weight and carcase fat score are further adjusted for anticipated correlated responses in feed intake when it is not recorded in the selection programme.

Economic values used in the index are detailed in Table 4 with their genetic standard deviations

Table 4: Breeding objective traits with economic values and genetic standard deviations as used in the index

Breeding objective trait	Economic value			Genetic standard deviation
Beef Value
Carcase weight		£1.2/kg	12.5 kg
Carcase conformation score¹		£7/unit	1.04 units
Carcase fat score¹		£-6/unit	0.73 units
Calving Value
Gestation length		£-1/day	3.2 days
Calving ease²		£7.09/s.d.	0.39 s.d.

1 Carcase conformation score and carcase fat score are expressed on a 15 unit scale. See Kempster, Cook and Grantley Smith (1986) for the relationship between the units and the EUROP carcase grading scores used commercially in the UK. 2 Calving ease is expressed on an underlying standard normal phenotypic scale, so the units for this trait are phenotypic standard deviations (s.d.) on the underlying scale.

Genetic Parameters

In order to use the recorded traits to estimate the farm model (objective) traits which are given an economic value it is necessary to use estimates of their genetic correlation between the two traits (Table 5). The genetic parameters used in the BLUP evaluations and calculation of Beef and Calving Values are shown in Table 6.

Table 5: Genetic correlations between objective and recorded traits

	Recorded trait
Objective trait	Birth weight	200 day weight	400 day weight	Muscling score	Fat depth	Muscle depth	Gestation length	Calving difficulty
Carcase weight	0.15	0.50	0.60	0.30	0.10	0.30	0.10	0.10
Carcase conformation score	0.15	0.18	0.20	0.60	0.10	0.60	0.10	0.10
Carcase fat score	0.00	0.08	0.10	0.00	0.40	0.10	0.00	0.00
Gestation length	0.55	0.10	0.05	0.20	0.00	0.20	1.00	0.21
Calving difficulty	0.58	0.29	0.10	0.20	0.00	0.20	0.21	1.00

Table 6 Genetic and phenotypic parameters used in analysis

	Gestation length	Calving ease	Birth weight (kg)	200-day maternal (kg)	200-day growth (kg)	400-day growth (kg)	Muscling score (points)	Muscle depth (mm)	Fat depth (mm)
Gestation length	0.30	-0.10	0.24		0.07	0.05	0.20	0.20	0
Calving ease	-0.21	0.12	-0.30		-0.05	-0.10	-0.20	-0.20	0
Birth weight	0.55	-0.58	0.24		0.28	0.19	0.10	0.10	0.05
200-day maternal	0	0	-0.10	0.07	-	-	-	-	-
200-day growth	0.10	-0.29	0.50	-0.15	0.34	0.79	0.40	0.31	0.16
400-day growth	0.05	-0.10	0.41	0	0.85	0.40	0.44	0.43	0.22
Muscling score	0.20	-0.20	0.39	0	0.43	0.55	0.26	0.49	0.12
Muscle depth	0.20	-0.20	0.47	0	0.75	0.55	0.65	0.26	0.16
Fat depth	0	0	0.09	0	0.22	0.12	0.12	0.18	0.29

Note:
Heritability on the diagonal
Phenotypic correlation above the diagonal
Genetic correlation below the diagonal

Accuracy

The accuracy values presented express the correlation between an animal's EBV and its true breeding value, expressed as a percentage. Exact univariate accuracies are calculated for each trait and these values are combined to give approximate multivariate accuracy estimates taking account of the combination of traits recorded on the animal concerned.

National British Belgian Blue Evaluation
BLUP
EBVs
Accuracy Values
Beef Value and Calving Value

Using the Sire & Dam Summary
Technical Appendix

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