48 J
.A. Archer, L. Bergh Livestock Production Science 65 2000 47 –55
the appropriate test duration may differ for cattle of Vryburg, Cedara and Glen from 1977 to 1997.
different biological types. Studies in Australia have Numbers of records available for Afrikaner, Angus,
shown marked differences in feeding patterns be- Bonsmara, Hereford and Simmental at each test
tween Bos taurus and Bos indicus cattle in the same station are given in Table 1.
feedlot environment Robinson et al. 1997, sug- The Phase C performance tests are conducted by
gesting that differences between breeds in time sending bulls to central performance test stations
required to obtain a reliable estimate of feed intake where feed intake and growth data are collected for a
may exist. The purpose of the present study was to period of 112 days 140 days prior to 1991,
investigate the test duration required to obtain an following a 28 day pre-test adjustment period 35
accurate measure of feed intake, growth rate and days prior to 1991. Up to 12 8 prior to 1991
feed efficiency in cattle representing different bio- intakes of animals were tested per station per year.
logical types. Entry criteria are imposed on bulls in an effort to
minimise differences in age and weight of bulls entering the test. The diet of the bulls during the test
2. Materials and methods period consisted of a pelleted ration containing 13.0
MJ ME kg dry matter and 13 protein. The ration 2.1. Data
was composed of maize 400 kg tonne, cottonseed 75 kg tonne, wheat pollard 120 kg tonne, lucerne
Data from the centralised performance test for 50 kg tonne, maize rests straw 206 kg tonne,
young bulls Phase C1 of the South African Nation- molasses 90 kg tonne, hominy chop 34 kg tonne,
al Beef Cattle Performance Testing Scheme were urea 5.5 kg tonne, salt 5.0 kg tonne, limestone
used in this study. Five breeds with comparatively ground 14.2 kg tonne, monocalcium phosphate
large numbers of records available were chosen to 3.2 kg tonne and a vitamin–mineral premix which
represent four major biological types used in beef included the rumen modifier Rumensin 2.1 kg
production. The breeds used were Angus and tonne. Cattle were placed in pens with electronic
Hereford representing British breeds, Simmental gates which allowed individual access to particular
representing European-type breeds, Afrikaner [an feeders, and feed intake was recorded weekly during
indigenous breed of Sanga Bos taurus africanus the test period, with the exception of the test station
origin] and Bonsmara a stabilised composite com- at Irene where feed intake was recorded fortnightly,
prised of 5 8ths Afrikaner and 3 8ths Hereford and but was divided by two to provide weekly records.
Shorthorn. The data was collected at six governmen- During the test, animals were weighed every week
t-owned central test-stations ARC-owned since after a 12-h overnight fast during which animals
1995 at Irene, Omatjene in Namibia, Queenstown, were not given access to food or water.
Table 1 Distribution of bulls by test centre, and number of bulls with missing sire information
Test centre Afrikaner
Angus Bonsmara
Hereford Simmental
Irene 384
118 2188
70 986
Omatjene 38
6 41
Queenstown 587
768 385
260 Vryburg
55 96
2319 432
1299 Cedara
48 162
293 203
576 Glen
207 87
1214 36
240 Total no. bulls tested
732 1050
6788 1215
3402 No. bulls missing sire information
3 563
90 73
J .A. Archer, L. Bergh Livestock Production Science 65 2000 47 –55
49
2.2. Analyses to the residual errors from the model. Relatively
small numbers of animals in each test meant that it Test durations ranging from 1 to 16 weeks were
was not possible to fit separate regression slopes for considered, with all tests beginning at the test start
each test, but results from Australian data [J.A. date, following a 28-day pre-test adjustment period.
Archer, P.F. Arthur, R.M. Herd and E.C. Richardson, The length of test was progressively increased in
unpublished data] suggest that where conditions are weekly increments by including an extra week of
relatively uniform across different tests, common feed intake and weight data in the data set analysed.
regression coefficients across tests with a fixed effect Growth of each individual was modelled by linear
to adjust for test effects are adequate. regression of weight against time on test, using the
Variance components for each trait and test dura- regression procedure of SAS 1989, and the regres-
tion were calculated from univariate analyses using sion coefficient estimates were used to calculate
ASREML
Gilmour et al., 1998. The model fitted average daily gain ADG during the test, and the
included age and weight at start of test as covariates, mid-weight mean of start and end weights. The
test unique test centre, year and test number combi- linear model fitted to weight data from each separate
nation as a fixed effect, and sire fitted as a random animal included an intercept, a linear term for
effect. A number of records had missing sire in- number of days on test and the residual error term.
formation see Table 1 for numbers missing in each Information on daily feed intake DFI and growth
breed. These records were retained in the data, as was used to calculate two indices of efficiency.
they provided information about the test group Firstly feed conversion ratio FCR was calculated as
effect, but did not contribute to the sire variance total feed intake divided by total gain. The second
component. Dam information was not used in the index of efficiency used was residual feed intake
analyses as there was a limited number of dams with RFI. Residual feed intake was calculated by model-
more than one progeny in the data, and the objective ling daily feed intake within each breed using the
was not to estimate genetic parameters. general linear model procedure of SAS 1989, with
terms fitted in the model including a class variable for each test defined as a unique combination of test
3. Results
