8.1
This chapter considers a case study of a traditional
genotype. The Blue Grey cow is an interesting animal
to study, since it is a crossbred between a bull which
is classed as a minority breed (Whitebred Shorthorn)
and a cow of a traditional Scottish breed (Galloway).
The resultant cow is subsequently crossed with a variety
of breeds, often continental breeds, to produce a finished beef animal for slaughter.
8.2
The pure Galloway is a true hill breed, kept in relatively
harsh environments, particularly in the hills and uplands
of southern Scotland. There are only a limited number
of breeds which could be used in these types of farming
systems. The Blue Grey cow is also able to survive in
such conditions while able to produce calves which will
satisfy the requirements of the market for quality meat.
8.3
There have been a number of experiments done over the
years looking at the performance of Blue Grey cows and
their calves. A comprehensive review of the reproductive
performance of Blue Grey cows was undertaken by Osoro
and Wright (1992). They reviewed the performance of a
total of 321 spring-calving cows which had been used
in a series of grazing experiments between 1984 and 1987
at the Hartwood Research Station of the Macaulay Land
Use Research Institute. 237 of the cows were Hereford
x Friesian while the remaining 84 cows were Blue Greys.
The study looked at the performance of spring-calving
cows (mean calving date 27th March). The mating period
which was 10 weeks long each year started 1 week after
turnout in the middle of May.
8.4 Earlier work, (Wiltbank
et al, 1964; Dunn et al, 1969; Hansen et al, 1982 and
Rutter et al, 1984) had established that a number of
factors were responsible for the length of time taken
to get cows back in calf. These included milk production,
age of the cow, suckling and genotype. Also heavily implicated
was the condition of the cow at calving which in turn
is a function of the level of nutrition in the period
up to calving.
8.5 By the end of the mating period, there
were significantly more Blue Grey cows in calf than Hereford
x Friesians, with Blue Grey cows achieving a pregnancy
rate of 90% compared to only 83% in the Hereford x Friesian
cows. Of those cows which were pregnant, the period from
the start of mating to conception was shorter for the
Blue Grey at 17 days as opposed to 27 days for the Hereford
x Friesians. At calving the body condition score of the
Blue Greys was higher (2.54 compared to 2.37). The calves,
which were all sired by Charolais bulls, were however
significantly heavier at birth when their dams were Hereford
x Friesian cows rather than Blue Greys (41.2kg compared
with 36.5kg). The calves of Hereford x Friesian cows
also grew faster at 0.95kg/day rather than 0.84kg/day
achieved by those from Blue Grey cows, presumably as
a consequence of the higher milk yield in the Hereford
x Friesian cows (Wright and Russel, 1987). As a consequence
calves from Blue Grey cows tend to be 10-15kg lighter
at weaning than those from Hereford x Friesian cows (Hodgson
et al, 1980; Wright and Russel, 1987).
8.6 As part of
the study, the age of the cow was also taken into account.
Up to the age of 7 years there was no difference in the
percentage of cows which were successfully got back into
calf. However above this age, there was a significant
decrease in the number of Hereford x Friesian cows which
became pregnant. At 10 years of age virtually 100% of
the Blue Greys became pregnant while just over 60% of
the Hereford x Friesians were able to get back in calf.
This suggests that the replacement rate of the Blue-Grey
cows would be considerably less than the Hereford x Friesian.
8.7 Other studies on the Blue Grey cow suggest that
they calve slightly lighter than Hereford x Friesian
cows, that their intake at pasture is less, but their
milk yield is lower. Wright and Russel (1987) reported
milk yields of 8.93kg/day for Hereford x Friesian cows
and 6.88kg/day for Blue Greys. This lower milk yield
is primarily a function of their partitioning less of
their energy towards milk production and more towards
body reserves. As a consequence they tend to be fatter
than more productive genotypes and lose less weight in
lactation (Hodgson et al, 1980). It is not clear if the
superior reproductive performance of the Blue Grey compared
to the Hereford x Friesian observed by Osoro and Wright
(1992) is simply a consequence of their having a higher
level of body condition. Body condition is known to have
a strong effect on reproductive performance (Wright et
al, 1992).
8.8 In an experiment looking at the post-weaning
nutrition of calves Wright and Russel (1987) found that
the Charolais-cross progeny of Hereford x Friesian cows
were heavier than those from Charolais cross Blue Grey
cows. The weight difference remained constant throughout
the experiment. This suggests that the difference was
not due to higher potential for growth, but to the higher
milk yields which have been reported for Hereford x Friesian
cows. McDougal (1978) argued that the milk yield of the
Blue Grey could be improved by more rigorous selection
of Whitebred Shorthorn bulls. This would require records
to be kept of calf performance in order to identify those
bulls which conferred improved milking ability on their
daughters.
8.9 In conclusion, the Blue Grey cow tends
to be fatter at calving and has higher reproductive performance
and a more compact calving interval. Since it tends to
be fatter at calving, it requires less expensive winter
feeding. It also loses less weight during lactation and
therefore requires less autumn feeding to return it to
condition fit for calving. It is also able to sustain
its higher reproductive rate to an older age thus leading
to a much lower replacement cost than a Hereford x Freisian
cow. The weaning weights of the calves are, however,
lower than for genotypes with higher milk yield potential.
8.10
For these reasons, the Blue Grey is well suited to extensive
production systems. Without the large fluctuations in
body condition, the Blue Grey is well adapted to systems
of lower inputs.
8.12 Since the Blue Grey
cow is a crossbred, its loss would have a serious detrimental
effect on the population of its parent breeds. The Galloway
in particular is important, being a true hill breed.
The production of females for subsequent crossing with
the Whitebred Shorthorn is a significant market for many
Galloway breeders. Significant reductions in the numbers
of Galloways would in turn have implications for the
biodiversity of hill and upland swards.
8.13 The Blue
Grey cow itself is important in that it can apparently
survive in relatively harsh conditions on terrain which
may be difficult to graze with other genotypes. The Blue
Grey is well adapted to extensive conditions and is longer
lasting and cheaper to feed than some other, larger types
of suckler cows. The Blue Grey is also easier to manage
in terms of its reproductive performance, being easier
to get back in calf after giving birth.
8.14 There is
a need however for further studies of the impact of the
Blue Grey (and indeed other breeds) on biodiversity and
in particular its impact on the composition of upland
swards. As has been stated earlier, little research has
been conducted on the impacts of different genotypes
on biodiversity.
Copyright: Scottish Executive - Licence Number C02W0004924
The full report is available at:-
www.scotland.gov.uk/library5/environment/tsab-00.asp
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