How do you determine the best timing for mating sows? Practical methods shared
To improve the conception rate of sows and increase the number of embryos, it is not only necessary for the boar to provide high-quality sperm and for the sow to release more fertilizable eggs, but also for the boar and sow to mate at the appropriate time, so that most or all of the eggs have a chance to be fertilized. This is the key to determining the conception rate and the number of piglets born. For this reason, you should first understand the rules of estrus and ovulation in sows, and then consider comprehensively based on the time that sperm and eggs, the two types of germ cells, remain capable of fertilization in the sow's reproductive tract.
(1) The estrus pattern of sows after farrowing
After farrowing, sows usually show three estrus periods within a short time: the first occurs 2-7 days after birth, with inconspicuous signs of estrus and no normal ovulation, and is an infertile estrus; the second estrus occurs 22-32 days after birth; its signs are also inconspicuous, but if mating occurs, conception can take place and it will not affect lactation or litter performance, so it is a mating opportunity that should be used; the third is 3-7 days after weaning. According to statistics, under normal feeding and management conditions, among a large group of sows, after piglets are weaned at 35 days of age, sows that show estrus within 7 days account for 85%, making this a mating opportunity that must be seized.
(2) The ovulation pattern of sows in estrus
After a sow reaches sexual maturity, it will regularly show a sexual cycle. Within the sexual cycle, the estrus period is the peak period of the sexual cycle. During this period, the sow accepts the boar's mounting and mating, and this is also the period during which the sow continues to ovulate. Only during this time will the sow accept mating or insemination, so the period when the sow accepts the boar's mounting is an important period for mating. As for other signs of estrus, they are all auxiliary signs of estrus. When a sow in estrus accepts the boar's mounting and how long it accepts mounting are related to factors such as pig type, breed, age, and feeding and management conditions.
(3) Timely mating
Observations show that sperm survive in the sow's reproductive tract for a maximum of 42 h, but sperm remain capable of fertilization for only 25-30 h, and sperm only gain fertilization capacity after 2-4 h in the sow's reproductive tract. This is what is commonly called "sperm capacitation"; only sperm that have acquired fertilization capacity can combine with the egg.
The egg is released from the ovary and enters the ampulla of the oviduct through the infundibulum; sperm and egg can only be fertilized if they meet in this part. The time the egg passes through this part of the oviduct, which is also the time the egg remains capable of fertilization, is 8-10 h, with a maximum of about 15 h. If the egg is not fertilized in the ampulla of the oviduct, it continues to move along the oviduct toward the uterine horn, and the egg will gradually age and become enveloped by oviduct secretions, preventing sperm from entering and causing it to lose fertilization capacity.
Tests have shown that the time for sperm to reach the sow's oviduct is very short, and after capacitation, the time during which they remain capable of fertilization is much longer than the time during which the egg remains capable of fertilization. Therefore, mating or insemination must be carried out before ovulation in the sow, especially several hours before the peak ovulation stage, that is, 2-3 h before ovulation in the sow, or 12-24 h after the onset of estrus, so that sperm wait for the arrival of the egg.
Because ovulation time differs among breeds, ages, and individuals, the determination of mating time should be handled flexibly. From the perspective of breed, local pig breeds in China have a longer duration of estrus and ovulate later, so mating can be carried out on the 3rd-4th day of estrus; introduced breeds have a shorter duration of estrus and ovulate earlier, so mating can be carried out on the 2nd day of estrus; crossbred pigs can be mated on the afternoon of the 2nd day or on the 3rd day after estrus. From the perspective of age, in introduced pig breeds, the estrus period of young sows is shorter than that of older sows; in local breeds in China, the opposite is true. It can thus be seen that the mating experience of "mate early for old sows, mate late for young sows, and mate in the middle for those neither old nor young" only conforms to the estrus and ovulation patterns of pig breeds in China.
From the perspective of estrus performance, when the sow's mental state changes from restless to staring blankly (not moving when the lower back and rump are pressed by hand), the vulva changes from red and swollen to pale white with wrinkles, and the mucus changes from watery to viscous, this indicates that the suitable mating period has been reached. When the vulvar mucosa is dry and mating is refused, this indicates that the suitable mating time has passed.
At present, it is best to adopt the method of mating or inseminating twice within one estrus period, so that during ovulation the sow will always have vigorous sperm waiting for the arrival of the egg at the site of fertilization. The exact timing of the two matings or inseminations within one estrus period varies slightly depending on the pig's breed type, age, and feeding and management conditions. It is generally believed that for a sow in estrus, the first mating 8-12 h after accepting the boar's mounting, followed by a second mating 12 h later, gives relatively good conception rate and litter performance.