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A Regional Integrated Pork
Production System in Jspsn
Akira Nishids, Masayuki Jimbu,
Akira Takebe,
Tomiji Akita, Tsutomu Furukawa
*Shigeru Itoh, Kamematsu Murata,
Hiroaki Shimo,
Hiroshi Nishoji, Chikara Yoshida,
Naoto Satoh
**Takeo Abe
National Institute of Animal
Industry
Tsukuba Norindanchi, P.O.Box 5,
Ibaraki 305, Japan
*Iwate Prefectural Livestock
Experiment Station
Takizawa-mura, Iwate 020-01, Japan
**Livestock Improvement Association
of Japan
Kameido 1-28-6, koutou-ku, Tokyo
136, Japan
SUMMARY
A Landrace strain and two Large
White strains have been developed by repeated selection in closed herds
based on selection indices for desired gains at s prefectural livestock
experiment station. An efficient cross breeding system has been shown to produce
three-way crosses among these strains and a Duroc strain which has been
established at National Animal Breeding Center as terminal sire.
Sixty-eight pig farms belonging to
two agricultural cooperatives in a region, the prefectural neat processing and
distribution center and a network of supermarkets have reached an agreement for
the establishment of a regional integrated pork production system with the
three-way crosses.
Because of high quality of the pork
produced by the system, the share in the prefectural market is increasing.
DEVELOPMENT OF
A STRAIN (Landrace)
A line breeding program started at
Iwate Prefectural Livestock Experiment Station which is located in the north
part of the main island, i. e. Honsyu, in 1970 (Mikami,lS87). The main purpose
of the program was the evaluation of an closed-herd breeding scheme for the
development of highly improved strains to produce economical crossbred among
them.
We used the next procedures for the
development of a Landrace strain.
{1) We
collected animals with high performance on the traits which we were interested
in.
(2) Accurate measurements of the
traits were taken from each individual under a uniform environment.
(3) Breeding
stock was selected based on the measurements.
(4) The herd was kept closed to be
no animals and genes were introduced into the herd during the generations of
selection.
(5) The
generation interval was reduced as short as possible.
Explanations sre given to the each
procedure listed above.
(1) It is necessary to establish a
base population which has high averages and large genetic variances of the
traits concerned. Large genetic vsriances would be btought in the base
population by collecting characteristic animals differing in genetical origins.
If the genetic variation is large, sufficient genetic gains csn be expected. It
should be avoided to introduce closely related snimsls only into the base
population even if their performances sre considerably high.
(2) What we can directly messure on
animals is phenotypic value, i.e. the sum of genotypic value and environmental
effect. We have no way for measuring genotypic value of economically important
metric characters directly. Since objective nf animal breeding is improvement of
genotypic value, we have to predict it with phenotypic value. Animals which have
higher phenotypic value sr' expected to have higher genotypic vslue in average.
Therefore the environment aust be kept as uniform as possible for all the
csndidates of breeding animals and aust let the differences in genotypic values
be reflected on the differences in phenotypic values. This effort significantly
heightens the accuracy of selection.
Well adjusted measuring equipments
should be used by well trained person to centrol error in measurement.
(3) The basic idea of genetic
improvement by means of repeated selection is given in Fig.1. Suppose that there
are data of daily body weight gsin taken from 60 boars and $0 gilts and the
histogram shown in Fig.1 is obtained. In generation 1, the averages of .the
boars and the gilts are 700 and 600g, respectively, as shown in Fig.1 by the
symbol:d. The mean of these two values: (?00+000)/2=650g; is regarded as the
whole population mean at generation l. If we select the upper half of the gilts
and the high@at 8 of the boars, the aesns of the selected gilts and boars become
?00 and 900g, respectively, as shown in Fig.1 with the symbol:a. The mean of
these two values: (700+900)/2=800g; is the mean of the aelected population. The
deviation of the selected populstion mean from the whole population
mean: (BOO-650)=150g; is called as "selection differential". The selection
differential by itself can not be the predictor of the genetic gain by the
selection since our measurements are not on genotypic values but on phenotypic
values as mentioned before. Actually, from 30 to 50 percent of the selection
differential becomes realised genetic gain. The proportion of genetic gain
to selection differential is called as "heritability" and denoted as "h ". Thus,
if fhc heritability of the trait in the population is 1/8, i.e. h =0.33,
repeated selection is expected to bring us genetic gait of selection
differential multiplied by heritability: 150x(1/3}=50g; for each one generation
of' selection (Nishida and Abc,1980).
{4) Increasing genetic uniformity
of the population under selection will be daasged by the introduction oi'
genetically unrelsted animals. If the performance of the introduced animal is
low, the populstion mean is lowered.
(5) Once the base population and
the detailed selection program are fixed, the expected genetic gain from one
generation of selection is also nearly fixed. The rate of improvement under
this condition can be accelerated only by shortening the generation
interval.
[ Base population ] Fifteen boars
and sixty gilts of Landrace acre selected from National Livestock Breeding
Station, some prefectural livestock experiment stations and private swine
breeding farms on referring to performance and progeny testing records of the
parents.
[ Selection ] Selection was
practiced for seven generations. About 50 litters were farrowed in each
generation. The first stage selection was practiced within litter basis at 25kg
of body weight. The selection criterion was the growth rate up to 25kg. One boar
and three gilts were selected to be raised as candidates for replacements from
each litter and additional two boars from each litter were castrated and
fattened to 90kg of body weight. After the first stage selection, about 50
boars, 150 gilts and 100 castrates remained from 200 boars and 200 gilts born in
50 litters. The second stage selection was undertaken individually at 90kg of
body weight. The measurements of the following four traits were obtained
(Fig.2).
(a) Average
daily gain from 30 to 90kg of body weight (D.G.;g unit).
(b) Average
backfat thickness probed ultrasonically at 10 points shown in Fig.2 (B. F.; cm).
(c) Average eye muscle area between
the 5th and 6th thoracic vertebrae of the two castrated full brothers
slaughtered at 90kg(E. M.; cm2.
(d) Average
weight proportion of ham to whole carcass of the two castrates (H. R.; %).
A selection index (I) for desired
gains was used as the selection criterion {Yamada et al,1975).
I = 0.012xD. G. - 5.184xB. F. +
0.276xE. N. + 0.400xH. R. The relative desired gains were assigned to 100g in D.
G., -0.5cm in B. F., 5cm2 in E. M. and 0.5% in H. R.. The weighting
factors in the above formula to realize the desired gains are derived as
B = P-1 G(G’ P-1G)
-1d
where b:
vector of weighting factors, P: phenotypic variance covariance matrix, G:
covariance matrix between phenotypic and genotypic value and d: vector of
desired gains.
Ten boars and sixty gilts were
selected from 50 boars and l50 gilts based on the index value. Finally, the
proportion of selection as a whole were 5% for asides and 30% for females.
The effects of selection are
summarized in Fig.3. The daily gain, the backfat thickness and the eye muscle
area were improved as planned but the ham ratio was slightly decreased.
[Correlated response ] The
correlated responses in reproductive performances and characteristics on neat
qualities were investigated through all the generations of selection.
Litter size at birth and at weaning
were held constant throughout the selection program. In the generation 6, the
average litter size in the first parturition were 9 at birth and 8 at weaning.
The mean weaning weight of a piglet linearly increased from 8.0 kg at generation
1 to 9.3 kg at generation 7. This means that the selection indirectly improved
the milk yield of sows.
The meat color, water holding
capacity ,pH, some physical and chemical characteristics of the pork were
precisely measured every generation. We did not recognize any correlated
responses in meat qualities . An average reproductive performances and meat
qualities were maintained from the beginning to the end of the selection
program.
[ Mating ] For the prevention
of serious inbreeding depression, we avoided close inbreeding. On the other
hand, a phenotypic assortative mating was adopted. The boars of higher selection
indices were mated with the gilts of higher selection indices and vice versa, in
the selected animals. The assortative mating augmented variance of the selection
index in the offspring and this augmentation enabled us to get slightly larger
selection differential under a fixed proportion of selection (Nishids et
a1.,1977).
[ Inbreeding coefficient and
coefficient of relstionship ] The mean inbreeding coefficient (F) snd the
mean coefficient of relationship (R) on the population incressed with
generation of selection (Fig.4). The R exceeded 20% and approached the
relstionship between half sibs, i.e. 25%, at the 7th generation. As a result,
the phenotypic variations of the four traits decreased. The obtained uniformity
of performance is one of the most important fruits of the selection.
This population has been recognized
as an established strain by Judging coauaittee in 1982.
[ Management ] The piglets were
weaned at 5 weeks of age and each litter was raised in a pen up to 25 kg of body
weight. From 25kg to 90kg, the boars and the gilts were kept separately to be 5
pigs in a pen. The two castrated full brothers of the Candidates were fattened
in the same small pen. The standardized ration for performance test (TDN 70X,DCP
13X) was fed all the pigs ad libitum.
We vaccinated
pigs and gave vermifuge timely according to a health control program.
DEVELOPMENT OF STRAINS (Large White)
We have further developed two Large
White strains following the Landrace strain. The selection program started in
1980 and ended in 1988 at the same experiment station. The population sine was 8
boars and 32 gilts for each strain x generation. It was smaller than that of the
previous program on Landrace. Daily gain, backfat thickness and eye muscle area
were contained in a selection index as a selection criterion. For one of the
strains, we used an independent culling level on stress susceptibility in
addition to the selection index.
The selection was again successful.
Thus the two populations have been simultaneously recognized as highly improved
strains by the committee in 1S87.
CROSS BREEDING
SYSTEM
An efficient cross breeding system
was proposed according to the results of nicking test. The cross breeding system
was for the production of three-way crosses among the three strains developed in
the prefecture and a Duroc strain as the terminal sire. The Duroc strain was one
of the good strain made in National Livestock Breeding Station.
INTEGRATED
PORK PRODUCTION SYSTEM
In Iwate prefecture, 68 pig
producers in a region belong to two agricultural cooperatives, prefectural meat
processing and distribution center and a network of supermarkets have reached an
agreement to found a regional integrated pork production system using the
three-way crosses.
In this system, the pig producers
in a region, for instance in s town, are taking partial charge of the integrated
system as strain maintenance farms, strain multiplication farms, hybrid(F1)
sow production farms and three-way crosses production and fattening farms
(Fig. 5). This cooperation among the producers in a region reduces efflux of
fund of the region and facilitates keeping the balance of demand and supply. The
multiplication of the regional cooperating unit easily enlarges the cooperation
system. Further, since this system does not require frequent introduction of
pigs from other regions, spreading of the serious infectious diseases would be
prevented.
In the fattening farms, they feed
specially designed ration which fits the growth pattern of the three-way
crosses. They have a local slaughter house in their region which can treat 200
pig in s, day. They supplied 20,000 finished pigs in a year to the slaughter
house. The supermarkets sale the pork from the production system as a best
brand. Because of the high quality of the pork produced by the system, the share
in the prefectural market is increasing.
We are now trying to establish a
closed herd breeding scheme for the improvement of economically important
but poorly heritable traits such as litter size (Satoh et al.,l990) and
resistance to chronic disease.
REFERENCES
1. Mikami, H. 1987. Pig breeding
and development in Japan. Proceedings A Seminar on Pig Breeding and Development
in Asia, El-E13.
2. Nishida, A., Nishoji, H. and
Itoh, S. 1977. A comparison between selection differentials caused by
post-mating cull based on performance of gilt and mean performance of pair
mated. Jap. J. Swine Research 14(2):125-132. (in Japanese with English
summary)
3. Nishida, A. and Abe T. 1980.
Effects of repeated selection on population mean, heritability and distribution
of breeding value. Jpn. J. Zootech. Sci. 51:485-494.
4. Satoh, M, Nishida, A. 19SO.
Response to selection for litter size based on BLUP in golden hamsters.
Proceedings of the 4th World Congress on Genetics Applied to Livestock
Production. 13:329-332.
5.
Yamada, Y., Yokouchi, K. and Nishida, A. 1975; Selection index when genetic
gains of individual traits are of primary concern. Japan. J. Genetics.
5D(1):33-41.
Fig. 1. The basic idea of genetic improvement by repeated selection. |
Fig. 2. The three traits measured at 90kg of body weight. |
Fig. 3. The effects of selection. |
Fig. 4. The changes in mean inbreeding coefficient (F) and mean
coefficient of relationship (R). |
Fig. 5. The flow of pigs in the pork production system. L: Landrace,
W: Large White, D: Duroc |
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