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Selection of dairy
cattle
Proper selection is the first and the most important step to be adopted in dairying.
Records are the basis of selection and hence proper identification of animals and
record keeping are essential. Cross-bred animals with exotic inheritance of about
50 percent are preferable. This preference is based on comparison of the performance
of the animals with different percentage of exotic inheritance. Fifty percent of
the native germplasm is helpful to retain the adaptability, heat tolerance and disease
resistance traits of local animals, in cross breds. The utilisation of the Zebu
(Sahiwal) germplasm in the formation of breeds like Australian Friesian Sahiwal
(50% of Holstein and 50% Sahiwal) and its international recognition as a breed for
the tropics is an example.
Maintaining animals sustainable to the situation is the best policy. Bringing animals
from different agro-climatic conditions causes problems due to non-adjustment in
many cases. In case, purchase becomes absolutely essential it should be from similar
environmental conditions as far as possible.
Selection for breeding
Heifers
Heifers should be selected on the basis of the potential of the sire and milk production
of the dam. The heifers should have proper growth, good health and be free from
genetic abnormalities. Heifers, which have conceived within 24 months of age alone,
may be retained.
Cows
Most important economic trait to be looked into, while selecting a cow is milk production.
The present average daily milk production of the cross bred cows is around 5.5 litres.
For economic milk production a cow producing not less than 2500 kg milk in 305 days
lactation period is desirable. In general, selecting a newly calved cow yielding
ten litres per day may have 2000-2500 kg lactation yield and cow yielding 15 litres
per day initially may have a lactation yield of 3000 kg. A peak yield of at least
12 kg milk per day can be used as a criterion for this. Age at first calving should
be less than 3 years. The interval between two successive calvings should be 12
to 15 months. The cow should not have any physical deformity and should possess
dairy conformation like well developed udder, prominent milk vein, squarely placed
teats, ease in milking and good temperament. Old and unproductive cows are to be
replaced by young cows. The calves reared in the farm itself are usually used for
replacement. Normally, 20 percent of the stock has to be replaced each year. When
calves are insufficient or when the general performance of the herd is poor, cows
from outside can be purchased and added to the herd.
Bulls
Bulls contribute 50 percent of the inheritance to the next generation. Most of the
genetic improvement in a population comes through proper bull selection. It is not
very practicable to have intense selection of the females for breeding i.e., almost
all the heifers will have to be reared and used for breeding in a situation where
age at first calving and calving interval are not optimum. Hence utmost care is
to be given for bull selection. To achieve the goal of average 305 days milk yield
of 2500 kg/lactation from the present 1600 kg for crossbreds in Kerala, the bulls
used should be proven bulls or of high pedigree. The young bulls used for breeding
should be from dams with lactation milk production not less than 4500 kg and bulls
with higher sire index. If 1000 cows with this production performance are available
in the State, this bull dam selection becomes feasible. Other economic traits like
milk fat and SNF, age at first calving, calving ease, incidence of diseases etc.,
should be included in evaluation.
The farmers should be aware of the quality of bull used for breeding and all Artificial
Insemination centres/bull stations should display the details of breeding value
of the bulls used. Breeding value is generally expressed as a deviation from the
population average. It is to be borne in mind that pedigree selection is the most
important of all kinds of selection. Progeny testing is the most accurate method
and as a rule bulls for progeny testing are selected based on the pedigree. Selection
should be continuous and applied in all generations. Any slack in selection will
result not only in the stoppage of genetic improvement but also in creating negative
trends.
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