Managing a breeding bull to enhance its fertility

INTRODUCTION

It is common saying that “A bull is half of the herd.”.The cows/buffaloes are receptive to males on estrum but the mature bulls are active to any estrous cow/buffalo at any time.As such regular care of bulls is always essential to maintain them sound, both physically and reproductively.A regular calendar of operations for different managemental activities like…

Feeding, Watering, Bathing, Grooming, Brushing, Exercising, Semen Collection, Paddock cleaning, Health Check up, Vaccination, Testing for Diseases like TB, JD etc.

Housing

The house should be located north-west and south-east direction for getting sufficient sun light. The roof should be high so that it remains cool during summer.Floor space for each bull should be 3.7× 3.7 meters with 3- 3.5 meters height. The open runway should be 4.9 × 6.1 meters.

Selection     

It is better to select the bulls in their early age i.e. about a year or so. Early selection helps in their proper care, feeding and management and for their proper training. Early selection also helps bull to become adjusted with the environment in which they live. Before selection, the bull calves should undergo a very critical andrological examination.

The sires should be selected on the basis of history records, sexual health and sire index.

         Sire Index = D – b (M – A)

Where D = Daughter’s milk average

             b = Covariance of daughter’s milk average over dam’s milk average.

            M = Dam’s milk average

             A = Herd’ milk average

Feeding Ration

The growing and breeding bulls required balanced diet for their growth and production of good quality semen.Several reports have indicated that nutrition effect directly the endocrine secretion and thereby influencing the testicular function. The balanced feeding may be defined as provision of all nutrients in proper ratio and as per the requirements of the animals in particular season.

The ratio should contain enough energy, protein, vitamin and minerals. The quality of green fodder should be good and given ad libidum. Protein rich should be given regularly. There should be provision of salt bricks in the feeding manger. Two types of feeding rations are usually for breeding bulls.

   Maintenance Ration

The amount of balanced ration which is required to fulfil the maintenance need of a particular animal is called “Maintenance Ration”.

35 kg of Jowar + 2 kg Paddy straw

1 kg concentrative mixture

20 gm mineral mixture

35 gm salt

Production ration

The ration which is given in addition to maintenance ration for semen collection during service time is known as “Production Ration”.

1.    Groundnut Cake – 15 %

     Wheat bran – 42 %

     Arhar chuni – 40 %

     Mineral Mixture – 2 %

     Salt     - 1%

2.     Mustard Cake – 20%

     Wheat bran – 42%

     Mung chuni – 35%

     Mineral mixture – 2%

     Salt – 1%

3.  Coconut Cake – 30%

     Groundnut Cake – 20%

     Rice bran – 37%

     Cotton seed – 10%

     Mineral mixture – 2%

     Salt – 1%

Attendants

Both the attendants and the bulls should be familiar to each other. Regular changing of attendant should avoided. In case of all the attendant should be changed in one time. The person engaged for feeding, watering. grooming, brushing, leading and exercise should be familiar to the bulls.

     Restraining

A bull should never be left free without restraint. A Nose ring greatly help in restraining the bulls. The nose ring should be of better quality. The attendant can control a bull with the help of rope fastened to the nose ring. A hook of suitable size attached securely to a strong and long Wooden handle(about 5’-6 ‘long) is of help in separating fighting bulls. Nose strings are also used across the nasal septum to have control on bull. Nylon ropes are found better compared to rope made of cotton thread. Nylon ropes are more strong and more durable.

    Exercise

The bulls have tendency to fight which may be fatal to bulls as well as to attendant and there fore loose handling of the bulls should always be avoided. Heavy and sudden exercise should always avoided. A total of above 1 km walk on semen collection days and 2 km walk on days when the bull are not utilized for semen collection in considered optimum for their exercise. The bulls which are not sick should be given exercise daily. Exercise keeps their body tone fit and keeps them active.

“Morning exercise is better”.

If for some reason or the other morning exercise is not possible, the bull may be given exercise in the afternoon hours. Too extreme weather are not suitable for exercise. Bull exerciser is a very convenient tool for giving exercise to the bull. In absence of the bull exerciser, the bulls may be given exercise in open but protected field. Buffalo Bulls are difficult to harness in bull exerciser.

Health Check up

The breeding bulls should be checked daily. Any deviation, e.g. poor food intake, depression, uneasiness, fever, diarrhea, constipation, cold, cough and bull’s behavior etc. should be noted cautiously. The whole body should be inspected thoroughly. The cause of disease should be investigated and treatment should be given promptly. Bull suffering from infectious or contagious disease should be immediately segregated from other bulls and put in segregation box. All health records of the bulls should be maintained.

     Vaccination

As the Prophylaxis is better than Cure, the periodical vaccination must be done for developing immunity against diseases. The immunization schedule shall be strictly followed to combat various diseases by producing antibodies against various bacterial antigen. The bulls should be vaccinated as per as vaccination schedule programmed for HS, BQ, Anthrax, FMD, Rinderpest. In addition there should be vaccinated against Brucellosis, Johne’s disease, T.B. and Vibriosis.

Safety Practice

Dairy bulls are recognized as the most dangerous domestic animals. The aggressive nature due to its strength and agility should be given due to considered for safety of the bull handlers. Each bull should have nose rings for restoration. Continuous gentle handling of bulls from calfhood through matured life is important. Breeding bulls should be provided with utmost comfort. Regular timely feeding and exercise. Bulls should not be aroused to become furious.

Conclusion

ü Improve Breeding

ü Maximum Utilization of Bull through A.I.

ü Control the vices of Bulls

ü Improve Sexual desire of Bulls

ü Less chance of Infertility

ü Maintain the soundness of Bull by exercise

ü Regular health check may reduce the chance of infection of disease.

ü Maintain the Nutrition given to bulls by Ration schedule.

Semen contents

A. Semen: Spermatozoa + seminal plasma

B. Sources and relative contribution to semen:

Greatest contribution: In bull: vesicular gland; In boars : prostate and bulbourethral glands

C. Chemical composition of semen:

Bull and ram semen: higher in fructose and sorbitol from vesicular gland; Boar semen: higher in Na and K from prostate gland

 1 Spermatozoa

A. Semen characteristics by species:

B. Size of spermatozoa:

Overall length: 60-70 microns in bull, boar and ram sperm; 50 microns in stallion sperm Head: 8-10 microns long; 4 microns wide; 0.5 microns thick

i.                  Normal morphology:

Structural diagram of spermatozoon

 

A. Head:

a. Nucleus: contain genetic code
b. Postnuclear cap: cover posterior portion of nucleus
c. Acrosome: cover anterior portion of nucleus and contain enzymes as hyaluronidase,corona penetrating enzyme and acrosin

B. Neck (sometimes included in "Tail") Proximal centriole: join head and tail, where head and tail separate during fertilization and in heat-damaged semen

C. Tail:

a. Mid-piece: Mitochondrial sheath: contain enzymes converting energy substrates as fructose into ATP b. Main-piece: Axial filament of 2 central fibrils, 9 pairs of inner fibrils and 9 coarse outer fibrils: its contraction by energy from ATP¡æ tail movement
c. End-piece:

ii.  Abnormal morphology

A. Reduced fertility: From 25% or more abnormal sperm

B. Classification of abnormal sperm:

Morphological abnormalities of spermatozoa identified through examination of semen for quality. 

a. Abnormal heads: asymmetrical, tapering , pyriform, giant, micro and double heads
b. Abnormal tails: enlarged, broken, bent, filiform, truncated and double mid-pieces; coiled, looped and double tails; cytoplasmic droplets (formed on neck during spermiogenesis and usually lost during maturation)

 2 Seminal plasma

A. Function: Serve as buffer, optimal osmotic and nutrient medium

B. pH: nearly 7.0; slightly acidic in bulls and rams; slightly alkaline in boars and stallions

C. Osmotic pressure: similar to blood and physiological saline(0.9% NaCl)

D. Energy substrates: fructose, sorbitol etc

 i. Inorganic ions

A. Major ions: Na+, Cl-, K+; minor ions : Ca++, Mg++

B. K+/Na+ ratio: High in sperm cell and low in seminal plasma

C. Function: Maintain optimal osmotic pressure for sperm survival

ii.  Buffering agents

A. Principal organic ion as buffering agent: Bicarbonate(HCO3-)

B. Source: Vesicular gland

C. Function: guard against change in pH of semen, but not sufficient

iii. Energy substrates

A. Energy substrates: Fructose, sorbitol, glycerylphosphocholine(GPC)

B. Source: Fructose and sorbitol: vesicular gland; GPC: epididymis: uniquely high in semen

C. Metabolism:

a. Fructose: used under anaerobic and aerobic conditions
b. Sorbitol and GPC:used only aerobically
c. GPC: utilized after splitted into choline and glycerylphosphate by an enzyme in female tract

 iv. Other organic compounds

A. Inositol and citric acid: considerably high, but not utilized.

B. Ergothionine: found in boar and stallion semen

 3 Energy metabolism by spermatozoa

Plasmalogen: a lipid reserved within sperm cell: used when other substrates are limiting

A. Anaerobically:Fructose _ 2 lactic acid + 2 ATP (net yield)

B. Aerobically : Fructose _ CO₂ + H2O + 38 ATP (net yield)

C. ATP + H₂O ¢¢ ADP + H₃PO₄ + 7,000 calories /mole

 4 Factors affecting rate of metabolism

A. Measurement of metabolism rate

A. Under aerobic condition: 1). O₂ consumption 2). CO₂ liberation 3) Methylene blue reduction time
B. Under anareobic condition: 1) pH reduction 2) Increase in lactic acid 3) Decrease in fructose

B. Relationship of fertile life to metabolic rate of sperm:

a. Reduced metabolic rate : extend the storage life of semen;
b. Reduced metabolic rate in epididymis: extend life of epididymal sperm
c. Sperm in fresh ejaculate of semen: fertile for a few hours under high rate of      metabolism

i. Temperature

A. High temperature: Inc. metabolic rate and dec. life span of sperm

B. At 50¡É: Irreversible loss of sperm motility

C. At body temperature: Sperm live for a few hours only: due to inc.metabolism

D. Low temperature: Extend fertile life of sperm by dec. metabolism ( when bull semen frozen at -196°C, less than 0.02% of metabolic rate at body temperature): Problems: cold shock and freeze kill

a. Cold shock: 1) Irreversible loss of sperm motility by sudden reduction of semen temperature from 15¡É to 0¡É (critical range), 2) Protecting from cold shock: Slow cooling after addition of lecithin and lipoproteins by diluting with egg yolk or milk diluter

b. Freeze kill: 1) Sperm killed during freezeing and thawing 2) Protected satisfactorily by equilibrating bull semen in a diluter containing glycerol ¡æ Desirable fertility from semen frozen for decades

ii.  pH

A. Higher metabolic rate: From pH of semen near neutrality(7.0), where most enzymes in sperm are most active.

B. Deviations toward alkalinity or acidity: Can reduce metabolic rate, but buffering capacity of diluter is rather important because pH range to be altered without permanent impairment of sperm is narrow

iii.  Osmotic presssure

A. Semen diluted with isotonic diluter maintains maximum metabolic activity

B. Hypo- or hypertonic diluter: Can reduce metabolism but detrimental to sperm

 iv. Concentration of spermatozoa

A. Inc.concentration of sperm ¡æ Inc. K+/Na+ ratio ¡æinhibit sperm metabolism

B. Moderate dilution with buffered, isotonic medium containing fructose, before cooling: Not greatly alter metabolic rate, but extend sperm life

C. Excessive dilution (over 1,000x): Depress motility and metabolic rate

 v.  Hormones

A. Androgens over physiological level: ¡é sperm metabolism

B. Fluid from female tracts: Inc. sperm metabolism; due to estrogen or other factors ¡æ ¡èsperm motility

vi.  Gases

A. CO₂

a. 5-10% partial pressure of CO2: sperm metabolism
b. Epididymal sperm: Long life by high CO2
c. CO2 gassing in diluter: Effective for sperm preservation at room temperature

B. O₂

a. Necessary for aerobic metabolism
b. High level of O2: Toxic
C. Other gases: N2, H2, He: No effects

 vii.  Light

A. Light under oxygen: Produce harmful H₂O₂; Semen should be protected from light

B. H₂O₂ production: Prevented by addition of catalase to diluter

 viii. Antibacterial agents

A. Penicillin and dihydrostreptomycin or neomycin: Used for control of bacterial growth, with no effects on sperm metabolism

B. Antibacterial agents: ¡èsemen fertility from bulls infected with vibriosis

C. Control of bacteria in semen by antibiotics ¡æ Sparing energy substrates: Extend fertile life of sperm

Semen collection by Manual Massage Technique In Animals

Massage Method

·       The method involves the simplest technique of semen collection by massaging the seminal vesicles and ampullae of vas deferens.

·       Undoubtedly the collector should have a considerable training to adopt the skill. This method is commonly used to collect semen from cock, turkey (tom), dog, also sometimes from bulls.

BULLS:

·       It is a useful method for bulls which are lame or are unwilling to mount or are unable to copulate. The bull is securely restrained in a service crate.

Technique:

o   Hand with full arm obstetrical rubber sleeve after adequate lubrication is inserted in the rectum and faeces are evacuated.

o   The seminal vesicles are massaged pressing towards urethra for few minutes. Simultaneously an assistant is kept ready to collect semen as it drips.

o   Then the ampullae are massaged and milked one by one and are stripped off by pressing against the floor of pelvis.

o   The pelvic urethra can also be massaged.

o   After the massage of ampullae the ‘S’ curve of penis should be straightened to allow escape of semen, if retained In sigmoid flexure.

o   Prior stimulation with a cow would be of great help in collecting semen through massage technique.

o   There are chances that if massaged regularly, the bulls may become accostumed with this technique in 3-4 weeks.

There are certain restraints for efficient semen collection through massage technique:

1.     Some skill and experience is necessary to massage ampullae and the seminal vesicles per rectum.

2.     Some bulls poorly respond to this method of semen collection

3.     Semen collected through this technique is not clean as it dribbles through the prepucial hairs.

4.     The massage of ampullae sometimes stimulates urination.

DOGS:

·       Many males can be induced to ejacukate by applying pressure and massage to the penis. This is the simplest and cheapest method of semen collection in dogs.

·       Technique:

o   An estrous bitch is exposed to the dog.

o   When the dog shows sexual interests in bitch, about 3-4 cms of penis of dog is exposed by pushing the prepucial skin caudally.

o   The base of penis behind the bulbus glandis is grasped and is applied moderate pressure with fingers. 

o   Some dogs may be trained to ejaculate semen even in the absence of a teaser bitch, but in such cases the sperm concentration is usually low.

o   The semen is collected by using glass or plastic funnel attached to a warm tube into a warm vial or a barrel of syringe secured to prevent semen leakage.

o   Maintenance of proper pressure behind bulbus glandis is importamt for collection of sufficient semen.

o   Ejaculation may last for 10-15 mins. The first portion of the ejaculate contains few sperm cells. The sperm rich portion of ejaculate is whitish-grey-milky.

factors affecting libido in animals

Introduction

Reproductive performance has greater impact on economic returns than does either growth rate or product quality. In most operations, females still conceive via the natural breeding bull. Thus the reproductive capabilities of males are of paramount importance. These capabilities are largely influenced by one or more of the following factors:

a) semen quantity and quality,

b) libido and mating ability and

c) social interactions (dominance effects) in the breeding pasture.

In addition,male performance is limited by the fertility threshold of the female herd. The Breeding Soundness Examination of  males (BSE), as recommended (Society for Theriogenology, 1976), is useful in identifying  males which have physical problems, or poor semen quality. However, other problems do not become apparent until males are exposed to some form of mating ability assessment. In many cases, males receive no form of assessment prior to sale or use.

Some Definitions

·       Libido is defined as the "willingness and eagerness" of a bull to attempt to mount and

Service. Libido refers to sexual motivation, revealed through behaviors such as mate seeking, detection, courtship, and mating (also referred to as servicing or serving). Libido, or sex-drive, is a behavioral trait with a large instinctive component and as such it poses problems in its assessment and interpretation.

·       Mating ability refers to the ability and competence of the bull in fulfilling this

aspiration.

·       Serving capacity is a measure of the number of services achieved by a bull under stipulated conditions and thus includes aspects of both libido and mating ability.

Measurement of libido

 Libido is typically measured using the reaction time, defined as “the elapsed time between exposure to stimuli and first service”. As libido is evidently crucial for fertility, there appears to be a need for the development of a predictive, standardized libido test. This may, however, be unachievable due to the apparent conflicting effects of some of the test factors on libido, such as the use of multiple females and genetic/breed differences.

 However, libido is a trait which is measurable and testing procedures designed for the animal generally rely on the exploitation of several or more of the following findings:

1.     Libido has a large genetic component

2.     Animals which are polygamous tend to distribute their services among receptive females.

3.     Prestimulation of animals increases their sexual response.

4.     Competition among animals can increase their sexual response.

Factors Influencing Bull Libido

1.     Age and rearing effects. As mentioned previously, age and (or) experience of  males can influence their relative efficiency of mating, and consequently their libido scores and rankings. Thus, mating ability has a learning component.

In trials with young tropical beef bulls, libido score apparently increased with bull age between 16 and 31 mo,  a finding which differed from results with  males in Sweden, and with Hereford and Angus  males in Colorado. It was found that age affected sexual behavior traits in crossbred  males, with yearling  males showing lower libido and a higher proportion of mounts than older  males. Ologun et al. (1981) identified negative relationships in yearling beef bulls between sex drive and production traits, while in another study, underfeeding had no adverse effects on bull sexual behavior. McFarlane (1974) showed that Zebu males raised on open range showed tardy sexual responses compared with those reared more intensively.

2.     Bull to female ratio. The standard recommendation of using approximately one bull per 20 to 30 females has long been promoted. It is apparent, however, that this does not represent optimal bull usage and that it allows sub-standard males to go undetected.  males not selected for high libido have shown estrus detection rates from 90 to 98% when used at a Bull To Female Ratio (BFR) of 1:24 to 1:30, using ratios of 1:60 and 1:100, obtained rates of 64% and 51%, respectively.

In contrast, Rupp et al. (1977) obtained good reproductive efficiency with most males in single sire mating at BFRs of both 1:44 and 1:60 and concluded that a BFR of 1:25 represented inefficient bull usage. Comparison of single and multi-sire combinations revealed no effect of number of males in the pasture on estrus detection. The overall conclusion was that the reproductive capabilities of individual males were more important to reproductive success than either BFR or single vs multi-sire breeding combinations.

Overall, there seems little doubt that males are greatly under-utilized in many breeding programs. Although not practicable in many cases, single-sire mating is inherently more efficient than multi-sire mating.

3.     Social effects. Social ranking of males within groups can influence their sexual activity. Several studies employing blood-typing methods to determine paternity have shown that dominant males can sire the majority of calves in multi-sires. The effect of social interactions among males on herd fertility may be greater at lower BFRs than where there is higher breeding stress. Dominance rank was negatively correlated with sex-drive in one study with yearling males. If dominance and sex-drive are different traits, then the dominant male (or males) could impair herd fertility through failure to service females while preventing less dominant males from serving. In rams, the reproductive performance of subordinates was shown to be greatly reduced.

 In conclusion, social effects should be considered in both the breeding pasture and during libido/serving capacity tests. With multi-sire mating programs, more efficient breeding and sire utilization would occur if the bull groups were young              (preferably < 3yr), of similar age, size, genotype and social background.

4.     Genotype differences. Anecdotal evidence for breed differences in bull sex-drive has long been reported. For example, differences between beef and dairy breeds in semen collection ease are noted. Zebu males have a reputation for "sexual sluggishness" and a tendency to mount females in full estrus only. When comparing libido scores of six breed groups in Queensland, those males with a Brahman component in their breeding had consistently lower scores than either British or Africander derived breed types. With subsequent trials, Bos indicus genotypes generally did not perform successfully in serving capacity type tests employing restrained females. More success was obtained with the use of unrestrained estrus-induced females and single bull tests. It was obvious that the testing procedure was more unsettling to a number of these males than with the Bos taurus  males. Even in the breeding pasture, difficulties were encountered in observing mating behavior because of apparent wariness by the bull(s) towards the observer. Despite this, the best performing Bos indicus  males were equal to the best of the other genotypes. Interestingly, when different trials employing either Bos taurus or Bos indicus  males mated with synchronized females were compared, the Bos indicus  males achieved similar fertility although they displayed less sexual activity.

Other factors include:

1.     Systemic diseases

Any diseases causing depression, anorexia, fever, loss of weight and pain etc. would affect the sexual desire of the bull e.g. tumors, severe parasitism traumatic gastritis, etc. the extent of loss of sexual desire depends on the severity of the case.

2.     Injuries and diseases of the reproductive organs

Injuries affecting the joints, muscles, nerves and tendons particularly affecting the rear quarter may affect the libido. Also the tumors or other affection of the penis, prepuce, the scrotum etc. may affect it.

3.     Endocrine factors

Deficiency of the circulating androgens may cause reduction of sexual desire without other clinical symptoms.

Pitfalls in Libido/Serving Capacity Testing

In general, successful testing of  males for libido and mating ability requires careful planning and lots of patience. Some of the pitfalls which may be encountered are described as follows:

1.     Testing of  males that are excessively apprehensive or agitated.

Apart from taking precautions to handle cattle quietly and to avoid distractions, there is no easy solution to this problem, which can lead to depressed scores.

2.     Testing of  males immediately following their subjection to other procedures such as electroejaculation, vaccination and parasite control measures.

3.     Testing under adverse weather conditions, such as in extreme heat, cold, or inclement weather.

4.     Testing of  males in groups in which one or more  males are markedly dominant, such as with mixed-age groups of  males.

The exposure of only two  males to test at a time, and subsequent retesting with a different bull, helps to minimize this problem. It should be noted, however, that a dominant bull can exert an inhibitory effect from a distance (eg. from an adjacent pen).

5.     Use of inadequate stimuli.

Restrained females should be incapable of excessive movement or some  males may be deterred. The service crates used should not impede mounting and service. If unrestrained females are used, they should be in full estrus.

6.     Spreading of venereal diseases.

Every precaution should be taken to ensure that diseases such as vibriosis and trichomoniasis are not transmitted by such procedures.

7.     Injury or undue stress to restrained females.

Humane considerations mandate that females be closely monitored for signs of stress and be replaced if these become evident. Mild sedation of females and prior lubrication of their genital regions are also recommended.

Alternative Assessment Procedures

The indirect determination of bull libido as reflected by blood concentrations of hormones has some attraction as it could reduce or eliminate the time, labor and aesthetic concerns which occur with libido/serving capacity testing. This would also allow assessment of males which did not respond well to yard or pen testing. Earlier attempts at linking luteinizing hormone (LH) or testosterone (T) levels with bull sex-drive were, however, disappointing. Difficulties were posed by the episodic nature of hormone release and the inhibiting effects of handling or restraint of the animal. By inducing LH or T release with parenteral administration of gonadotropin releasing hormone (GnRH), a number of these difficulties have been avoided. A significant  relationship between induced T levels and bull fertility, while Perry et al. (1988) obtained positive relationships with induced LH levels. Work is proceeding with such indirect tests to define  dosages, sampling times and the effects of bull age, genotype, season and nutrition. Although criticism has been levelled at such procedures for not allowing concurrent assessment of mating ability, the additional use of the BSE and judicious pasture observation should minimize these concerns.

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