Animal Science: Practical Book PDF Download [Grade-12]

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Development of breeding plan of cattle

Objectives

 To conserve indigenous genetic resource

 To increase the milk production with high fat percentage

 To improve the body configuration

 To increase the feed efficiency

 To decrease the generation interval and age of first calving

 To increase lactation length

 To reduce calving interval.

Theory

Nepal has great diversity in cattle population.There are various breed of cattle.

However, the indigenous breeds are in danger of extinction due to injudicioususe

of crossbreeding program and superiority of cross bred cattle compared tolocal

breeds. This has drawn the attention towards keeping cross bred animals. So, it is a

prime necessity to preserve the genetic resource. But, the productivity of local cattle

are less compared to exotic breeds, so it has become a necessity to employ

appropriate breeding strategy for upgrading local breeds with exotic breeds suitable

for local production environment.

Breeding system

The breeding system will involve two steps:

 Line breeding of indigenous breeds at their particular production environment

in order to conserve the native germ plasm

 Cross breeding of selected females of local breed with suitable other exotic

or local breeds as per necessity of the production environment

For bringing exotic breed into the native gene pool the 3 tier breeding scheme will

be used.

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1. Nucleus

Breeding unit in the exporting country ( for 100%jersey semen)

2. Multiplier:

Breeding unit in the country at various eco-zones

3. Producer:

 Producing (commercial ) unit in the country at particular ecozones

 An example of genetic improvement program and its effect:

 Let's consider grading up of local cattle breed say,

 Terai and exotic cattle breed jersey for improving milk production

 The milk production traits are medium to high in heritability in cattle

indicating additive and nonadditive genetic effect in both. Progress can be

made by selection and breeding.

 The cross breeding will be carried to maintain 87.5% blood level of jersey.

 Three successive generations crossing of female with 100% pure jersey male

will be carried out at multiplier herd established at different districts of Terai

region as per requirement.

 Same procedure will be disseminated to commercial level.

Conclusion

Practical Book : Grade 12 3

Unit: Two

Male reproductive system of sheep and goat

The male reproductive system consists of testicles, which produce sperm and sex

hormones, a duct system for sperm transport, accessory sex glands, and the penis,

or male organ of copulation, which deposits semen in the female.

Fig 2.1 Male reproductive system of sheep and goat

Male reproductive system

1. Testes: The testes are paired organs which descend from the abdominal

cavity during fetal development to lie in the scrotum. They produce the male

gametes (spermatozoa) and secrete the male sex hormone, testosterone.

Testosterone is essential for the development of male characteristics,

maintaining normal sexual behavior and sperm production.

2. Scrotum: The scrotum is a muscular sac containing the testes. It supports and

protects the testes and also plays a major role in temperature regulation. It

maintains the temperature 3 to 5 C below body temperature for optimal

function.

2. Vas deferens: The vas deferens is the duct that rises from the tail of the

epididymis into the abdomen, where it joins the urethra at the neck of the

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bladder. It is often referred to as the ‘spermatic cord.’ Removal of a section

of the vas deferens in each testis is known as a vasectomy, preventing passage

of sperm from the epididymis.

4. Accessory sex glands: The accessory sex glands include the bulbo-urethral,

prostate, and seminal vesicle glands and the ampulla. Accessory glands

secrete additional fluids, which when combined with the sperm and other

secretions from the epididymis, form the semen. Some of the secretions

contain nutrients like fructose while others produce alkali secretion to raise

the pH of the ejaculate. These secretions are added quickly and forcibly

during the mating to propel sperm into the urethra.

5. Penis: This is the final part of the male reproductive tract and its function is

to deposit semen into the vaginal tract of the female. At the end of the penis

is a narrow tube called the urethral process (or ‘worm') that sprays the semen

in and around the cervix of the ewe/doe. The preputial sheath protects the

penis, except during mating.

Practical Book : Grade 12 5

Unit: Three

Male reproductive system of pig

Source:ThePigSite

Fig 3.1: male reproductive system of pig

The male reproductive system (Fig. 5-32) consists of two testicles, each of which

is held almost vertically with the tail of the epididymis at the top. The epididymis

is the area within which all the mature sperm is stored and held until ejaculation.

From each testicle a tube, the urethra, carries the sperm into the abdomen via the

inguinal canal. (If this hole is enlarged an inguinal rupture will be seen). From there

it enters the neck of the bladder and continues in the groin down the penis to the

exterior as the urethra. Thus from the neck of the bladder to the tip of the penis the

urethra can carry either sperm or urine. There are three glands called the seminal

vesicles, the prostrate and the bulbo urethral glands. The seminal vesicles produce

the bulk of the ejaculate (300ml) and fructose to nourish the sperm. The prostrate

gland provides other nutrients and the bulbo urethral gland and produce the jelly

that you often see at the end of mating

During service the sperm in the epididymis are pulsated down the urethra to be

joined by the seminal fluids. This is a continuous process during the period of

mating. You can see it if you stand behind the boar and you should check it when

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you supervise services.

The penis, which is long and rigid has a sigmoid or S - shape in its top half and an

anti clockwise spiral at the end. It is 300-500mm long.

The preputial sack is filled with very smelly fluids including pheromones and it also

has a very high bacterial content. The bacteria are potential pathogens and emptying

the sac by squeezing at service increases the risk of infection entering the womb,

particularly towards the end of the heat period.

Sperm is produced and matured under the influence of luteinising hormones (LH)

and follicle stimulating hormones (FSH) and the whole process is controlled by the

pituitary gland which is at the base of the brain.

Treatment for poor sperm quality is disappointing, however prostaglandins injected

weekly are claimed to have some effect on libido. The evidence is not convincing.

Practical Book : Grade 12 7

Unit: Four

Male reproductive system of poultry

Fig 4.1: male reproductive system of poultry

Source Food and Agriculture Organization of the United Nations

The reproductive system of the gander consists of three distinct parts:

The testicles

There are two bean-shaped testicles inside the body cavity which produce both

spermatozoa and male hormones. They are highly vascularized and change in size

and position according to whether the gander is sexually active or not. The age of

sexual maturity for ganders is directly related to their lighting programme.

However, spermatozoa production does not usually begin until the ganders are at

least 30 weeks of age. From the testicles the spermatozoa move to the epididymis.

The vas deferens

These (there are two) follow the urethras and transport the spermatozoa from the

testicles and the epididymis to the copulatory organ. Their apparent length is 15 cm,

but they have numerous bends and twists and in fact measure more than 30 cm. The

vas deferenes are the location of spermatozoa maturation and storage. They

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terminate at the seminal vesicles located in the cloaca wall.

The copulative organ

Contrary to the rooster, Gallus gallus, the copulatory organ of the gander is very

well developed. It is invaginated, spiral-like and is about 15 cm in length. A

spermatic furrow runs along the entire length of the organ and transports the semen

after ejaculation.