Page 122 - Calculating Agriculture Cover 20191124 STUDENT - A

11-12 Large Animal: Beef, Swine and Sheep CH 11]

How many Boars are needed for natural breeding? Small producers using natural breeding
will use a ratio of 1:20 for boars to sows. It is recommended that for the first month and during training,
the young boar should be allowed no more than one sow per fortnight (two weeks), gradually increasing
to two sows per week (double service) by the time he is 10 to 12 months of age
Under artificial insemination boars never see the sow they will breed. There are advantages to AI
which include: (1) No need to maintain males for breeding, hence the cost of maintenance is saved. (2) it
prevents the spread of certain diseases and sterility due to genital diseases. (3) Progeny testing can be
done at an early age. (4) Breeding life is extended for a desired sire after his death. (5) It allows the
mating of animals with great size differences without injury to either animal. (6) It is helpful to inseminate
animals that refuse to stand or accept the male at the time of oestrum. (7) It helps maintain accurate
breeding records. (8) Increases the rate of conception. (9) Well trained staff maintain the health of the
animals.

Example: If the ratio of 1:20 is used for boars to sows in breeding. Calculate the number of boars that
are required for natural breeding of a 50 sounder of sows?

Solution: # of sows ÷ # of sows/boar = # of boars required

50 ÷ 20 = # of boars required

2.5 = # of boars —> 3 boars (with this number then one boar will probably
service 17 sows.)

Piglets. Sows produce on average 10 piglets per litter and it is not uncommon for a sow to farrow
12-14 pigs with each litter. They can have 2 litters’ per year which means that a sow in the breeding herd
will produce approximately 20 piglets each year for market.

Example: During the year there were 480 piglets farrowed in a swine herd of 30 brood sows.
Determine the percent pig crop.

Solution: # birthed / dams birthing x 100% = % production per species

480 / 30 x 100% = 16 x 100% = 1600% Pig crop

Pre-weaning mortality. The pre-weaning mortality rate for piglets is about 21%. Because of pre-
weaning mortality, the swine breeder needs to calculate how many piglets need to be born to determine an
average herd production size per litter for each year. As piglets are a profit center for the business, a
management plan is required to determine a target minimum of piglets needed to reach market. Some will
foolishly state that they want as many piglets to market as they can get, which may be valid, but that type
of thinking ignores where the break even margins reside for profitability.

Example: A swine producer farrows’ and delivers approximately 480 piglets to market each year. How
many piglets need to be farrowed to have 480 piglets for market with a mortality rate of
21%?

Solution: Piglets farrowed = [# of piglets for Market ÷ (1 - Pre-wean mortality rate )]

Piglets farrowed = [480÷ (1 - 21% )]

= [480 ÷ (1 - 0.21 )]

= 480 ÷ 0.79

Piglets farrowed = 607.59  608 piglets farrowed Rounding up

Check: Piglets for Market = Piglets farrowed x (1 – Pre-wean mortality rate)

Piglets for Market = 608 farrowed x (1 – 21%)

= 608 farrowed x (1 – 0.21) change percent to decimal

Piglets for Market = 608 farrowed x 0.79

Piglets for Market = 480.32  480

INSTRUCTOR Copyrighted Material