Selection Of Breeding Bulls

SELECTION OF A BREEDING BULL SDDP EXTENSION MANUAL No. 5

smallholder Dairy Development Project Ministry of Agriculture August 1999 Addis Ababa, Ethiopia

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FOREWORD The SDDP extension manual No. 5 is titled as Selection of a Breeding Bull. The manual is designed and intended for use as a teaching aid for extension workers involved in dairy development not only in the project areas but else where in Ethiopia. The level of technology is largely aimed at individual Smallholder farmer and with the help of this manual another farmer's manual could be produced for use by peasant dairy farmers which will be simple and printed in local languages. We also believe that the information given in this manual will be useful to any dairy farmer. In the preparation of the manual, previously produced related manuals were reviewed and updated. The manual is produced by Smallholder Dairy Development Project (SDDP) of the Ministry of Agriculture, which is funded by Finland Government on a bilateral cooperation bases. I would like to take this opportunity to sincerely thank the Government of Finland for supporting SDDP.

Tsehay Redda SDDP Co-ordinator Ministry of Agriculture August, 1999

Acknowledgements Ato Tefera G/Meskel Dairy Goat Project Co-ordinator of Farm Africa, is gratefully acknowledged for commenting and editing of the manuscript. This manual is dedicated to the memory of Ato Zelalem Mengistu, who made the illustration for the manual. He passed away before the manual was published. Manuscript by Mr Hizkias Ketem

Table of Content

Page.

INTRODUCTION

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2. Why do we select bulls ?

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2 2.1 Individual Performance

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2 2.2 Pedigree information

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2.3 Progeny Testing

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3. Bull Fertilizer Examination

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3.1 General clinical Examination

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3.2 Special Clinical Examination

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3.3 Mating Behavior

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3.4 Semen Examination

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INTRODUCTION Bull service stations establishment in Ethiopia was first introduced in the sixties by the Addis Ababa Dairy Industry. It was taken up then by Chilalo Agricultural Project (CADU/ARDU_ Wolita Agricultural Unit (WADU). At national level the task was undertaken in the mid 1970 by the Extension and Project Implementation Department (EPID), EPID distributed a number of bulls to Service and Producer Co-operatives. After EPID, the Ministry of Agriculture (MoA) continued the programme for sometime but it did not become a widely adopted extension activity by farmers. In practice, rendering mating services through bull service stations is a realistic approach in local herd improvement and in the introduction of better performing cows in rural areas. If it is accepted by farmers it is cost effective and a more wider sector of the community can be reached more quickly. Bull service stations would be the better option than Artificial insemination service in areas where road accessibility is a restriction. Near and in larger towns where large and small scale commercial dairy farms are established and operating, these farms make available their bulls for mating of cows owned by small backyard dairy farmers, The service is being provided at a relatively high service charge. This arrangement seems to be working reasonably well in most of the places where such dairy farms are established. Under the previous socialist regime of Derg, the establishment of bull service station focused on having them at service and producers cooperatives. The bulls being the property of all but the responsibility of none, the end result was disappointing. An approach based on having bulls placed with individual farmers was attempted by the project funded by the Finland government in parts of Oromia, Amhara and Southern Region. Significantly of better service performance and upkeep of the bulls was observed under this arrangement. Bull service stations under private ownership recorded on the average 84 matings per bull per year. 1.

Why do we select bulls?

It is said many times and it still holds very true today that the Bull (Sire) is one half the herd. Every animal raised gets half of its inheritance from the sire. Rapid improvement of herd performance lies in the introduction of better blood through the sire. It is important to know about the selection of bulls and cows because it is the basis-for overall improvement of animal productivity.

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Selection in the herd

In order to make improvement in animal productivity the selection process

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should be based on reliable data, otherwise the expected improvement cannot be achieved. In livestock improvement, selection is the process of choosing some individuals in preference to others as the parents of the next generation. Selection is the basic method used both by nature and by humans to change the attributes of animals. There are different steps for selection. These are:

• • • 2.1.

Individual performance Pedigree information Progeny test

Individual performance

Individual selection is the simplest method of choosing animals on the basis of their own performance. Comparing individuals on the basis of their own performance is often called a performance test. Selection based on individual performance in comparison with herd mates should be used for traits that have high heritability such as growth rate. It is also widely used for milk production although heritability is medium or sometimes rather low. It is not realistic to expect substantial progress in traits with low heritability. The information on the performance of the individual can often be supplemented by information from its relatives, these are the parents, which are part of its pedigree, its sibs or half sibs, or its progeny. When doing so it also introduces elements of family selection. It is essential that the individual records are compared with the average of the herd during the same period. Animals that are producing above the herd average are likely to be genetically superior compared with. those that are producing below the average. The likelihood for this increases strongly if the animal repeatedly has been above the average, for example, if a cow has produced more than the herd average in several lactations.

2.2. Pedigree information The pedigree of an animal is a record of the animals which are related to him. Bulls are selected largely up on their pedigree and the milk production of their ancestors. From the production point - view, pedigree information is only valuable if it provides data on the production performance of the parents. Such performance records from the ancestors can, provide useful information about the potential genetic worth of the individual in question. This is especially so before the animal is old enough to give useful information of its own. A calf s potential for milk yield, for example, could, be based. on the milk yield of its mother until the calf grows and can be milked. However, parents never provide as much information about the breeding value of an individual as the individual itself

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2.3. Progeny testing Progeny testing and sib (sib is the relationship of one animal to another which shares a parent or both parents, full sibs share both father and mother, half-sibs share either the father or the mother, not both) testing are both special form of family selection Individuals pass their genes on to their offspring, If there are many offsprings, their average performance will give a large amount of information about the genotype of the parent, and possibly perfect information. For traits of low or moderate heritability, 4 or 5 progeny will give as much information about the breeding value of their parent as the parent animal's own performance would, For more highly heritable traits the equivalent number of progeny might be around 10. Progeny information is especially useful when individuals cannot provide information about themselves and also progeny testing has a special value for traits which are only weakly inherited. The main disadvantage of progeny testing, apart from the cost, is that the parent tends to be quite old before the records on the progeny have been collected. Progeny testing, therefore, increases the length of the generation interval which, in turn, reduces the annual rate of improvement which could otherwise be made.

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Bull fertility examination

To examine the fertility of a bull it is important to have the complete breeding history of that specific bull. The breeding history of the bull comprises : • the period the bull has been used for service if not at least the latest year it has been used. • if A.I. or natural breeding is practised the fertility results for first services and for total number of services should be provided separately for each month.

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frequency of irregular breeding intervals. A repeated number of intervals of four to five weeks indicates embryonic death which may often be caused by infections, e.g. vibriosis. Frequency of cows returning after 17 to 24 days. This shows that something is wrong with the fertilising capacity of the bull. health status of the bull. It is important to know if he has had any disease accompanied by high fever for many days. All conditions causing an increased temperature of scrotum, like skin diseases, irritating disinfectants or insect bites, may lead to testicular degeneration and lowered infertility information on the nutrition and management level, and the availability of adequate quality drinking water, because these are important factors to influence the fertility.

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3.1.

General clinical examination The appearance of the dairy bull offers far less basis for judgement as to the milking qualities he will transmit to his daughters. However, the type of the bull should not be ignored, since it is important to have cows of good conformation as much as possible. Always go for the alert, with firm feet and with no clinical defect bull.

Fig. 1: An alert bull with firm feet

3.2.

Special clinical examination

• inspection and palpation of leslicles and epididymes The inspection should disclose if there is any disease condition of the skin of the scrotum and any asymmetry or abnormal outline of the scrotal sac. The palpation of the scrotal sac should comprise size of the testicles, movability of the testicles inside the sac, consistency of the testicles, size and shape of the epididymes and the condition of the spermatic cord. The testicles should normally be of the same size or at least the difference between the two testicles should not be high. Significant difference could mean that one testicle is too small due to hypoplasia or atrophy or the other is too big due such as orchitis. The consistency of bull testicles is normally turgid and elastic and with the same resistance to pressure both at superficial and deeper palpation, After heavy degeneration, in fibrotic testis and with hypoplasia, the consistency is soft at light palpation but becomes soon quite firm at deeper palpation. Hard consistency and uneven surface at palpation combined with increases size are typical for inflammatory processes or tumors,

To facilitate the palpation of epididymis the opposite testicle should be moved upwards. If the head of epididymis is enlarged and firm it is mostly due to spermiostasis with formation of sperm granulomas, If the tail is affected the same way, there is inflammatory processes. In normal bulls the

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tail of the epididymis feels filled and spongy at palpation, A very small and firm tail indicates poor semen production of the testicle of the same side,

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Inspection and palpation of penis and prepuce.

For closer examination penis can be prolapsed with the help of a tranquilliser: When necessary the prepuce can be manually examined after introduction of one or two fingers through the preputial opening, Your fingers should be washed and clean!

3.3. Mating behaviour The mating behaviour of the bull is of great importance for the semen quality. The sexual behaviour leading to copulation is depending on series of reflexes caused by specific stimuli, called behavioural chain. It is important to evaluate the different phases of the mating behaviour separately to get a complete picture of the serving capacity of the bull. A simple score for each one of the different steps will help in the evaluation, When collecting semen for evaluation of the breeding soundness of a bull, it is important not too allow the bull to mount the teaser until_ he has got full erection. Especially young bulls will often try to mount without erection and if they are allowed to serve and ejaculate at this stage the semen is always of poor quality.

3.4. Semen examination For a complete examination of fertility and evaluation of the sperm producing capacity of a bull, three ejaculates should be collected. The field examination of semen should be done after collection of each ejaculate.

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volume and macroscopic appearance

The volume of the bull ejaculate varies from 2 to 10 ml. Usually the second ejaculate is larger than the first one. There is also an increase of volume with age of the bull up to 4-5 years. The density of the ejaculate which reflects the sperm concentration varies between bulls and ejaculates, Usually the first ejaculate shows the highest sperm concentration if the bull is well prepared before collection and thereafter there is a slight drop with each consecutive ejaculate. More exact methods for estimation of sperm concentration are counting of a sample diluted 1: 100 or 1: 200 in a hemocytometer or measuring the light transmission. However, under field condition the following description gives an approximate idea of the

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concentration: Creamy-grainy Milky opaque Opalescent Watery

> 1,000,000/mm3 1,000,000-500,000 500,000-200,000 < 200,000

The colour of bull semen is normally white or yellowish white. A reddish colour indicates a mixture of blood at the time of collection. An old haemorrhage in the testicles or along the duct system can give a brown colour to the ejaculate. • mass activity and motility of sperm In concentrated semen there is a microscopic wave pattern ranging rom very slow to very rapid motion depending on the quality of ;emen. The mass activity is evaluated in a drop of semen without cover slip under low magnification (about 50 x). The activity can be graded in the following ways No mass activity Slow wave motion Rapid wave motion with formation of eddies at the end of wave Eddies (swirling wave of motion) Good semen should have a mass activity of at least

=0 =+

= ++ _ +++ ++.

Motility means the percentage of sperm moving straight forward over the field in the microscope. It is evaluated in a small drop of semen under cover slip at a magnification of about 200 x. Only sperm moving in a straight forward direction should be included in the motility count, while sperm moving in circles, in backward direction or showing pendulating movement should be excluded. Good semen should have at least 60 % motility at the time of collection. Both mass activity and mortality should be examined at body temperature.

• pH. OH can be measured in different ways. Under field c6ondition it might be easiest to use indicator paper strips giving the range 6.0-6'.5. Another method is to mix 0.5 ml. of semen with 3 drops of 0.2% bromthymolblue solution in 95 % alcohol. The colour is yellow at PH 6.0 and changes to green at 6.8, turns bluish green at 7.2 and is blue when pH is 7.6 or above. Normal bull semen has a pH of 6.0-7.0 pH above 7 can be seen in semen with very low concentration or when there is an inflammatory process in the genital tract, usually in the seminal vesicles. • morphological examination of sperm Examination of sperm morphology is a very valuable aid in predicting the fertility of a bull. However, it needs a lot of experience to evaluate sperm morphology and it should preferably be done in a specialised laboratory.

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References

Grald Wiener, 1994, Animal Breeding. Centre for Tropical Veterinary Medicine University of Edinburgh Settergren, L.A.M.O.S. Bull Fertility Examination. Un published 12

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