Puberty In Farm Animals

                         Puberty

Derived from the Latin word “pubscere” means covered with hairs.

Puberty is the stage when an animal is able to release viable gametes (ova in female and

spermatozoa in the male) and shows complete sexual behavior sequences.

 In a female, puberty is the age when the first estrus accompanied by ovulation occurs

and females can support pregnancy without any deleterious effects. The ability of females

to ovulate, conceive, and carry the pregnancy.

 In a male, puberty is the age when first time ejaculated with a threshold number of

spermatozoa enough for successful fertilization and manifest sexual behavior.

 It occurs when an animal has reached a critical somatic development (Bodyweight)

for each species or breed.

 At puberty, an animal attains about 60% of its mature body weight.

 Initiation of puberty is a function of animal age and body weight.

 During the pre-pubertal period, the growth of genital organs is similar to that of other

organs; but at the puberty growth rate of genital organs is increased.

Age at Puberty in different species

In few species, males reached puberty earlier than female-like canine, equine and feline.

Cow = 12-18 months in exotic breeds, 18-24 in Local breeds

Buffalo = 24-30 months

Mare = 18-24 months

Camel = 30-36 months

Sheep/Goat = 6-10 months

Bitch = 6-8 (Small breeds); 8-12 months (Large breeds).

Sow = 6-10 months

Cat = 6-8 months

Gonadal Changes during Development

 Undifferentiated gonads have a Sex Cord, which is formed by Germ cells (Oogonia)

and Somatic cells.

 In the testis, these sex cords develop into Seminiferous Tubules of the testis.

 In the ovary, germ cells divide by mitosis to form the Primary Oocytes. Each

oocyte is wrapped by a single layer of somatic cells to form a Primordial Follicle.

 Oogonia and oocytes are formed during the first half of fetal life.

 In a 110-day old cow fetus, there are around 27, 00, 000 oocytes.

 Oocytes pool formed during fetal life is the only source of oocytes available during

entire sexual life of a female.

 As the fetus develops, Primordial follicles decrease by atresia.

 These follicles grow but never ovulate before Puberty.

 At birth, there are around 100,000 Primordial Follicles.

 At puberty, the number of Primordial Follicles decreases to 50,000.

Endocrine Changes

 Secretion of GnRH, FSH, and LH starts early in fetal life.

 In cow and ewe, it starts when the fetus is 1-2 months of age (Shortly after sexual

differentiation).

 It decreases 2 months before birth in cow, and near birth in sheep.

 This low level persists for some time after birth (Period of Infancy); 3 months in the calf,

1 month in lamb.

 Then, as puberty approaches, secretion of both FSH and LH starts increasing.

 This is due to an increase in the frequency and magnitude of pulses (episodes), due to

an increase in sensitivity of the Anterior Pituitary gland to GnRH.

 Secretion of estradiol also starts in early fetal life; 60 days in the calf and 30-50 days in

lamb.

Factors Affecting the Onset of Puberty

Genetic Make up

 Earlier in exotic breeds as compared to (Local).

 Earlier in Dairy breeds as compare to Beef breeds.

 Inbreeding increases the age of puberty.

 Crossbreeding decreases the age of puberty.

Management

Nutrition Concentration of feed and feeding practices, whether balanced or not.

Rearing System Whether close or open. Sexual connection between male and female

Hormonal Fundamental role of Kisspeptin (product of the kiss-1 gene) and its receptors

GRP54 as a regulator of puberty onset. Other hormones include Leptin, Insulin, Insulin-like

growth factor-1 (IGF-1), thyroid hormones, and Neuropeptides (Neuropeptide Y, Galanin like

peptide, orexin, and gheriline).

Environmental Photoperiod, season, and temperature.