Page 164 - Agriculture_Form_Three

Agriculture for Secondary Schools

of fertilised egg or developing embryo, the organ undergoes retrogression, thus
allowing next graafian follicle maturation.

Tables 7.2 and 7.3 provide some details on the reproductive cycles, heat duration,
ovulation and gestation periods for various classes of livestock.

Table 7.2: Lengths and duration of oestrus and time of ovulation in livestock
Length of cycle Duration of oestrus
Animal species Time of ovulation (hours)
(average days) (average hours)
Cattle (cows) 20 16 - 24 10 - 14 after onset of
oestrus
Pig (sows) 21 24 - 74 18 - 60 hours after onset
of heat
Sheep (ewes) 16 30 1 before end of heat
Goat (does) 20 36 - 48 Near end of heat

Table 7.3: Age at puberty and gestation periods of farm animals

Species Age at puberty Gestation period Name of Act of giving
(month) (average days) offspring birth
Cattle 10 - 18 281 Calf Calving
Sheep 5 - 7 150 Lamb Lambing
Goat 5 - 7 151 Kid Kidding
Pig 6 - 7 114 Piglet Farrowing

Rabbit 4 - 6 30 Kitten Kindling

Note: Rabbits do not ovulate spontaneously. Ovulation in rabbits requires stimulus
of mating and thus induced in nature.

Signs of heat in farm animals
During the oestrus period, the animal is said to be ‘on heatʼ. It shows various signs

and behaviour that enable the farmer to detect the onset and the end of the period.
The following are signs of heat in farm animals.
(a) Animals become restless.
(b) Swelling and reddening of the vulva.
(c) Discharge of clear mucous from the vulva.
(d) Making noise, for example, grunting in pigs and bellowing in cows.
(e) The animal mounts others and stands still when mounted.

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