PUBERTY vs SEXUAL MATURITY in Gilts
PUBERTY is NOT the same as SEXUAL MATURITY.
Gilts can show heat (onset of puberty) but not ovulate.
FOR MATING GILTS, SEXUAL MATURITY SHOULD INCLUDE:
(1) Standing (for back pressure test ) for TWO days during one heat
(2) Ovulation of 14+ eggs
(3) A Uterine size to accommodate a target number of piglets
(4) Evidence of normal heat intervals (so more than 1 but 3rd is optimum for maximum litter size..
(5) at least 16mm backfat to milk from.
(6) at least 120 kg
PHYSIOLOGY OF PUBERTY:
The start of puberty is 40% heritable (VERY HIGH).
Typically range for the start of puberty is between 190 and 230 days.
This is influenced by:
Environmental conditions the herd is kept in
Genetics
PUBERTY INDUCTION PROCEDURES:
This is done for groups of gilts growing up in a typical grower-finisher environment under ad lib feeding.
(1) Typically this is started with exposure to boar at 24 weeks (160 - 180 days) of age
(DO NOT ALLOW THEM TO GET MATED) - so can be marketed if they fail the selection process
(2) Move gilts to a new pen near the boar
(3) A bigger pen that allows more space per pig
(4) Exposure to a mature boar
(5) Relocation help bringing them on heat
(6) Mixing them into new group helps too (groups of 4 or more is best)
Gilts selection criteria:
(1) Select replacement gilts from sows that reached puberty earlier
(2) Fastest growing gilts - (slow growers is more likely to have delayed puberty)
(3) Responding to induction increases with age
- you are therefore identifying younger animals to select
BOAR TO BE USED FOR EXPOSURE:
Older than 9 months
High Libido - active champing and salivating for pheromone production
Vocal and calm temperament
EXPOSURE:
Expose DAILY rather than intermittent - do not skip a day or weekends!
Minimum of 10 minutes per gilt per day (little extra benefit beyond 30 minutes)
CONTINUOUS housing of gilts WITH boars or even next to boars reduces the efficacy of exposure..
DIRECT PHYSICAL CONTACT is the best
WHY WAIT TILL GILTS WEIGH 120kg BEFORE MATING THEM?
120kg is 60% of mature breed weight - SO THEY STILL NEED TO GROW over 80kg
There is a negative correlation between a high feeding rate during early pregnancy and appetite in lactation.
So if you try and put the weight onto gilts AFTER mating her appetite in lactation will be low and she will lose a LOT of weight and won't get on heat 4 days after weaning again
