The Importance of Reproductive Performance in Swine.
Livestock farmers generally appreciate the time and input costs required to grow animals from birth to market weight. What is sometimes overlooked is the substantial expense involved with maintaining the mature breeding animals that are necessary to produce any stock for subsequent growing and finishing. Profitability in any commercial livestock- breeding unit is related closely to reproductive efficiency. Unfortunately, some producers and even many of their “expert” advisers pay insufficient attention to this aspect. No presently available procedure allows prediction of current or future fertility. Thus, accurate monitoring of immediate past performance is essential to identify problems quickly and to initiate solutions before consequences become too severe. Some considerations for the assessment of performance and suggestions for problem solving are presented later in this section.
Boar Selection
The boars have more impact than the females.
Select wisely and carefully.
Concentrate on performance trait(s) of economic
importance and select from source that test or
record as many boars as possible (high selection
intensity)
Make certain only healthy replacements selected.
This is especially critical if boars are purchased.
Select for physical soundness: strong feet and legs,
watch them walk, no buckling of front legs or
stiffness in hind. Boar must have good general
conformation and willingness to breed (good
libido).
Boar Management
Feed to keep fit, not fat, usually receive sow
gestating diet;
If purchased, isolate for 3-6 weeks, allow 3-4 weeks
to settle in;
Can use to breed at 6-7 months of age – occasional
service;
Ensure that first mating is successful. Use a small,
quiet sow or gilt in good estrus.
Mating in boar’s pen may be the best location
since the male is not distracted by new
surroundings.
Wait until 7-8 months of age before regular use, 2-4
times per week until one year of age.
Boar to Sow-Gilt Ratios
Natural service – 1 boar for every 20 females
AI + natural – 1 boar for every 20-30 females
All AI – 1 boar for every 40-50 females. Larger
herds require fewer boar’s
Gilt Management
Select from dams with good prolificacy and
mothering ability.
Important traits are sound feet & legs, good growth
rate & back fat, 14 or more well spaced teats with
none inverted and sexually mature by 220 days of
age.
Within herd selection makes genetic evaluation
easier and provides fewer health concerns but must
watch out for inbreeding.
Purchase from other breeder or hybrid producing
company simplifies within herd breeding program
but should make certain of genetic quality and
health status
Isolate all additions for 3-4 weeks.
Factors Influencing Puberty
Genetics
– Yorkshire and Landrace usually mature slightly
earlier than Hampshire or Duroc.
– crossbreeding advances puberty.
Nutrition
– restricted feed intake can delay puberty slightly.
recommend to allow only 0.5 kg gain per day after
market weight.
– obesity interferes with normal ovarian function.
Distress
– moving or mixing gilts – fight
– tends to cause puberty 4-7 days later
– contact with boars may advance puberty
– related to pheromones
– direct exposure most effective
– exposure should not be too early (after 155 days
of age)
– older boars more effective.
Light
– some evidence for advantage of increase light
– may decrease age at puberty
– may increase litter size
When to mate
litter size related to number of heats more than age
or weight
fewest ova at first estrus (heat) = smallest potential
litter
increase by about 1 ovum each for 2nd, 3rd heat so
potential litter size increases
normally breed in 2nd or 3rd heat so gilts farrow by
10-11 months of age.
Estrous signs
Swelling, reddening of vulva – not positive
Ears erect (especially in Yorkshire breed)
Standing reflex – response to pressure on back (see
Back Pressure Test described below). Boar
presence may be necessary, especially for gilts
Allows mounting and copulation
Characteristic grunt (or song)
Good Practices for Detecting Estrus
Use a sexually motivated boar in an adjacent pen or
introduce the boar directly into the pen containing
the females to be tested.
Boars used for estrus testing should be 9 months
of age or older.
Be certain that the boar is familiar with and
comfortable working in the testing environment.
Allow sufficient time to do a thorough job in all
pens.
Change boars regularly.
Allow no more than 15 – 20 seconds of vigorous
courtship.
Supervise the testing procedure at all times.
Keep accurate records of weaning, suspicious and
actual mating dates.
Back Pressure Test
Whenever possible, allow boar and females to have
head-to-head access through pen partition or gate.
If in or very near estrus, a female should show
definite interest in the boar almost immediately.
Rub the interested female’s flanks and scratch her
back.
Gently put firm pressure on loin region or sit on her
rump. Animals in estrus will allow this but others
will not. A positive response is when any female
stands still and allows the tester to place full
weight on her back, Gilts may only respond if a
boar is near. Most sows will show a positive
response anytime that they are in estrus.
Retest any animals showing suspicious signs in a
few hours.
Group recently weaned sows and replacement gilts
near boars.
Design all pens for easy access to facilitate entry
and exit of both people and animals during estrus
detection and mating.
A proper mating area requires ample space for all
courtship and mating activities.
Provide nonslip footing with roughened concrete and
sand or grit spread as needed.
Remove any objects or projections, such as feeders
or nipple drinkers, that might cause injury during
courtship-mating.
Try to mate animals of approximately equal sizes.
It is perhaps best to move the female into the
boar’s pen for mating since she may be easier to
get out after the mating.
Supervise all matings to insure that the boar’s penis
penetrates into the vagina, not into the anus.
A proper mating-ejaculation sequence should last at
least three minutes. If shorter, repeat the service.
Remove the female quickly after the boar
dismounts unless the copulation was interrupted
before three minutes.
Always be gentle when handling animals.
Record all events accurately and quickly.
Timing & number of services
Ovulation occurs about 36-40 hours after the
beginning of standing heat
Optimum insemination is 6-12 hours prior to
ovulation
Therefore, mate 24 hours after initiation of standing
heat and rebreed 8-16 hours later if female will still
accept the boar or is still showing a positive
(standing) response to the Back Pressure Test.
A different boar might be used at each service if
breeding only for market pigs.
Feeding Replacement Gilts
If gilts are placed on a restricted level after
selection, increase feed intake by 50% 10-14 days
before breeding. This process, called flushing,
might increase ovulation rate.
If flushed, reduce feed intake after breeding
Some believe that heavy feeding during early
gestation increases embryonic loss but most
evidence indicates that this is not true!
DR PV KUMAR
SWINE SPECIALIST
