Nature is wise: Optimum moment for the mating

Mother Nature is wise, and her wisdom, acquired after many years of never-ending work and improvement, has made that the different species develop mechanisms for attaining their end goal: perpetuate themselves, reproduce themselves efficiently.

The presence of the heat in females is one of these mechanisms.

The mating process is an "expensive" process that entails a remarkable energy cost, and Mother Nature tries to save on this minimizing the unnecessary matings that have no chances of success.

The presence of the heat, that is the only moment in which the females are receptive, has as its end goal synchronizing the ovulation with the mating.

The effective mating criterion has been modified during the last years. Before, we considered effective to attain a farrowing index of an 80% and 11 total born piglets. Now, for improving the results, it is important to "catch" all the ova produced during the ovulation, especially the first ones to arrive.

Despite her wisdom, Mother Nature did not bear in mind that, at some moment, animals would be raised in farms and ther would be weekends. Up to now, Mother Nature has been unable to overcome the problems that this can pose, so it will be our business to try.

In many articles I have discussed that one of the most important data that we must know in order to produce efficiently is the length of the gestation. This will allow us to organize the different duties in the farm in order to avoid that they coincide on a weekend.

The table above shows the mating and farrowing foreseen dates depending on the weaning day, assuming a weaning-to-breeding interval (WBI) of 4 days and a gestation length of 115 or 116 days.

The WBI can seem somewhat short, but it is the one that we are seeing with the high production modern genetic types. The red colour highlights the least favourable days for carrying out a duty, and in orange colour the days in which the availability is less than usual.

With respect to the farrowing assistance, Friday is considered as an orange day, because it is not enough with assisting it: the piglets must also be given a good start. If we want to give a good colostrum supply to the piglets we cannot start with the transfers of piglets until the day after the birth. The farrowings on Friday require more dedication during the weekend to ensure that the litters have a good start.

After seeing the Table, theoretically, the best days for weaning the piglets are Monday, Thursday and Tuesday.

As a result of a case of a lack of piglets born alive that happened in a farm where semen could not be delivered on Mondays, I started to consider which was the best day, during the week, for mating (or to wean the sows). On this occasion it was decided to wean part of the sows on Mondays.

As a result of the obtained data, we have started to wean the sows on Mondays in different production systems in which, for a time, the sows have been weaned on Mondays and Thursdays.

Figure 1. Total number of piglets born according to the mating day

When evaluating the total number of piglets born according to the mating day we can see that the best day for mating the sows is Friday.

We also see differences in the fertility according to the mating day. The best days are Tuesdays, Fridays and Saturdays.

Figure 2. Fertility %

When evaluating the number of weaned piglets according to the weaning day, there are no doubts: the best day for weaning is Monday.

Figure 3. Total number of piglets born according to the weaning day

One of the things seen when weaning on Monday is that the sows start to come into heat somewhat sooner than when they are weaned on Thursday.

In the following graph the % of sows that come into heat according to the days of their weaning is shown. Normally, 4 days after weaning 50% of the sows will have been mated. When weanings are on Monday, the percentage of sows mated 4 and 5 days after the weaning is higher than when they are weaned on Thursday.

Figure 4. % of sows that come into heat according to the day after the weaning

If the accumulated percentage of sows that come into heat after their weaning is evaluated, we can see that when weaning on Monday, five days after that 90% of the weaned sows have been mated, whilst that for attaining the same in the case of the sows weaned on Thursday we have to wait for 2 or 3 more days.

Figure 5. Accumulated % of sows that come into heat after their weaning

There is no doubt that for achieving a good coming into season it is necessary to keep an eye on the coming into heat of sows after their weaning.

Normally, the best sows, the ones that have the best ovulations, are the first ones that come into heat after their weaning: they are the ones that start to ovulate sooner.

In the particular case of the sow, the ovulation is not a precise event, but a process. The different ova do not reach the oviduct at the same time, and it is necessary that when they get there capacitated spermatozoa are present waiting to fertilize them. In order to become capacitated, the spermatozoa may need up to 24 hours from the moment of the insemination.

In order to obtain good results we must be able to fertilize all the ova. Weaning on Monday probably allows to stimulate more intensely and to be able to fertilize the first ova that reach the oviduct.

In view of this it could seem that soon, all the production systems that wean only once per week will end up doing it on Monday.

In the majority of the cases in which the weanings on Monday are tried, the system remains. The exception are those cases in which, when weaning on Monday, a good number of births start on Sunday, and this makes recommendable changing to weaning on Tuesday.