Today, genetic improvement in pigs has resulted in an increase in the prolificacy of litters; however, there has been no updating of the nutritional requirements of current breeding sows, mostly hyperprolific sows, throughout the cycle. Also, it should be taken into account that increasingly leaner and fast growing sows have been selected, but with a lower voluntary intake capacity. This implies the need to correct the side effects of the increase in prolificacy in the current genetic lines of our sows.

All this is forcing nutritionist veterinarians to design new strategies to feed these high-potential sows, adjusting their needs in each of the phases of the cycle, achieving an improvement in productivity (more piglets weaned per sow per year) and an increase in useful reproductive life. This implies that the nutritionist must know all the characteristics of the sow in question, as well as, the management regime, environmental conditions, type of facilities, etc. to design the most appropriate diet.

Introduction of hyperprolific sows in pig farms

The introduction of hyperprolific sows in pig farms has resulted in an increase in the size of the litter at birth (an average of 14 piglets born alive) but not so much in an increase in the number of piglets weaned per sow due to the increase in the mortality rate, as a result of lower piglet weight at birth, lower vitality and greater heterogeneity of the litter.

This implies that in sow management we are facing new challenges that must try to find solutions to improve the survival rate of newborn piglets through the use of different kinetics in the supply of nutrients with respect to the duration of gestation, different types of nutrients or different relationships between the nutrients; with the final objective of obtaining the highest possible quality and with the least possible variation in the weights of the piglet at weaning.

In intensive pig farms, a single feed is usually provided throughout the gestation period, although the idea of providing two different types of feed that differ in their amino acid content is becoming increasingly popular.

Feeding protocols in hyperprolific sows

It is recommended that the change from one food to another should be made from day 84 to day 90. Depending on the number of farrowing sessions, different feeding protocols should be used to suit the needs of the sows; in general it is recommended that the intake level be increased from 2.25 kg/day at the first farrowing session to 2.55 kg/day at the second and 2.73 kg/day at the third, reducing the total lysine content from 0.73 to 0.52 and 0.36 % respectively.

As regards energy requirements, it is estimated that the feed should contain 2,875 kcal of metabolizable energy/kg in the case of a standard gestation, but for newborn sows or in the last month of gestation it is advisable to provide a feed with 2,920 kcal of metabolizable energy/kg.

With regard to crude protein, the NRC (2012) proposes gestation levels of 1.32-0.91 % of total nitrogen during the first three months of gestation and 1.75-1.32 % for the rest of the time, depending on the number of litters.

It should be noted that some functional amino acids, such as arginine, may help improve vascularization and placental development. On the other hand, it has been demonstrated that diets with high fiber content are beneficial for pregnant sows, since they reduce constipation problems, prevent stereotypes associated with the restriction of the level of feeding during gestation, favor a greater consumption of feed during lactation under conditions of equal energy consumption during this phase and promote a greater production of colostrum; therefore, a crude fiber content of between 5.8 and 11 % and at least 17 % of neutral-detergent fiber is recommended.

Among the minerals, Ca, P, Cl and Na should be highlighted. For pregnant sows, values of 0.81-1.05 % of Ca and ��� 0.29 % of digestible P are recommended. A deficiency in these minerals leads to demineralization of the skeleton, which has a negative impact on the growth of the sows, as well as problems with the hooves and legs.

Feeding in the different gestation periods

In hyperprolific sows, during the first month of gestation, the amount of feed should be increased since the correct development of the placenta is sought, and the body condition lost during the past lactation should be recovered.

During the second and third month of gestation, the proportion of food that must be administered must be reduced because its requirements are minimal, and it is not important that it gets fat so as not to harm its milk production. And in the last month of gestation, the amount of food supplied to the pregnant sows must be increased again, since during this period each fetus must gain approximately half of its weight at birth.

When pregnant sows are brought into the nursery, they are usually given lactation feed. It is important to control the transition between gestation and lactation feed to ensure good intake during lactation and to prevent problems associated with farrowing. In practice, lactation feed is gradually reduced in the days before farrowing to avoid complications during delivery and to decrease the number of stillborn piglets.

During lactation, voluntary feed intake by sows does not cover their energy and nutrient needs. As a result, milk production relies on mobilization of body reserves, resulting in a reduction in the sow’s subcutaneous fat and body protein, which is especially important in hyperprolific sows.

To avoid this problem, it is necessary to stimulate feed consumption at the beginning of lactation which can be achieved by increasing the number of rations per day, mixing feed with water and controlling the temperature of the maternity rooms.

After weaning and until the next insemination it is common to feed the sows with gestation food. A few years ago, better results were observed in the expression of estrus, when the source of energy is starch versus fat, in iso-energy diets.

But after more studies it has been concluded that the supplements with dextrose and starch (375 g/day of each carbohydrate) are effective to stimulate the secretion of insulin, but not to stimulate the follicular development or the later development and uniformity of the fetuses and placentas in sows of high prolificacy.

Nutritional supplements in high production

Another generalized practice that is carried out in high production farms is the administration of 0.5-0.8 kg/day of a supplement rich in fish meal enriched with vitamins and minerals with the objective of carrying out a nutritional fushing between weaning and mating. It has also been seen that supplementation with carnitine and chromium has a beneficial effect on the sow’s energy status.

Finally, it is important to emphasize the importance of fatty acids in the feed; the best ratio of omega-6: omega-3 fatty acids in the diet of hyperprolific sows should be found to be close to 5:1. Using omega-3 fatty acids in gestation and lactation at levels of 0.5% seems to improve the vitality of the piglets.

Bibliography:

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• Augenstein M., Johnston L., Shurson G., Hawton D. and Pettigrew J. Formulating Farm Specific Swine Diets. University of Minnesota. 1997.
• 2013. 2捉 Ed. Eds. De Blas, C., Gasa, J., Mateos, G.G. Madrid, Espa単a.
• Santom叩 G., Pontes M. 2011. XXVII Curso de Especializaci坦n de la Fundaci坦n Espa単ola para el Desarrollo de la Nutrici坦n Animal. Madrid, Espa単a. pp. 169-225.
• 2012. National Research Council. 11捉 Ed. rev. National Academy Press, Washington DC, EEUU.