One of the most important pillars of industrial pig production in any given age has been the replacement of breeding sows. In recent years, this has possibly become even more important, as the economic efficiency of pig production is greatly influenced by the quantity and quality of prefatteners that can be produced as a result of breeding herd performance.
Some pig farmers produce breeding gilts on their own farms, in a manner that can be considered traditional. In this case, 10–15% of the sow population is used for the production of replacement gilts. Of the total number of offspring born, 55–65% of the female offspring are used for breeding. During their rearing the gilt population is selected at least twice (but rather three times): their health status is examined and particular attention is paid to traits such as the number of teats or the leg structure. The young gilts are often reared together with the fattening stock, and their group rearing starts when they have reached a body weight of 80–100 kg. From that time on, their feeding is different from that of the fattening pigs: they receive a dedicated breeding gilt diet or a pregnant sow diet until their insemination.
One of the biggest drawbacks of this briefly presented method is that the remaining gilts (i.e. those that have not been bred) are reared as fatteners, and individuals of the male sex and the females unfit for breeding will have inferior growth as compared to the end-product progeny. As a result, their fattening period will be longer and the ‘all-in/all-out’ principle will be more difficult to realise in the fattening units. A further problem is that the lean meat yield, a parameter valuable for the slaughterhouses, will also be substantially lower. This means that the fattening of these animals is much less profitable than that of the terminal progeny.
However, it is an advantage that the health risk is markedly lower, as grandparent stocks serving the genetic progress are brought to the farm much less frequently and in substantially lower numbers, and thus there is no need for a constant quarantine procedure.
Genetic progress offers vast opportunities also today, and it is vitally important to exploit the advantages offered. The different breeding organisations are working hard to make this possible. They are working with high numbers of animals and highly intensive selection, thus only the animals showing the best performance during the performance tests are retained. Among other things this is why more and more pig farmers abandon the practice of producing breeding animals on their own and start purchasing gilts in order to achieve the best possible production results.
It is a fact that breeding stock replacement with purchased animals poses a continuous risk of infection, as a new gilt stock is introduced to the farm 3–4 times a year. Among other things this is why it is important to keep purchasing gilts from the same donor farm of high health status as far as possible. Another thing that serves the protection of the farm’s own herd is that the incoming gilts must be first kept in quarantine. The newly introduced gilts must be prepared for the farm conditions, and primarily for the health situation prevailing on the farm, there and in that period. It is extremely important to avoid contact between the newly introduced animals and the herd that was already present on the farm! The quarantine period gives time for recognising any potential disease problem and setting up the vaccination protocol. Here also, similar attention should be paid to disinfection, labour organisation and the proper housing of animals as in the commercial herd! As the gilt stock arriving at the quarantine facility consists of gilts of multiple ages, oestrus detection must be started already in the quarantine unit.
From the quarantine unit, the gilts are transferred to a sow barn of group system. Their further rearing is usually performed in small group system. Whenever this is possible, the animals should stay in the same group in which they were in the quarantine unit. They should preferably kept at a low stocking density: the recommended space allotment is 0.7–1 m2 (minimum 0.55 m2) per gilt for gilts of 50–110 kg body weight and 1.5–2 m2 (minimum 1 m2) per gilt for gilts of >110 kg body weight. As the development of robust leg structure is also a very important consideration, the barns should have solid floor in at least 60–80% of their floor space. Particular attention should be paid to lighting! Gilts require an illumination of at least 100 lux light intensity for 16 hours a day.
Irrespective of whether breeding stock replacement is done with purchased gilts or with gilts produced locally on the farm, one of the most important aspects of their rearing is their nutrition. In order to ensure that the fattening herd can achieve the highest possible body weight gain, already the maternal lines are selected for this trait. However, appropriate robustness and longevity can only be achieved by restricted feeding.
In recent years, we have participated, and are still participating in the rearing of gilts of several different genetic lines (Topigs, Choice, Hypor, etc.). In order to achieve the best possible results, the breeding organisations specify accurate expectations and parameters for gilt rearing, with regard to the feeding phases and the analytical composition of the diets fed. On the basis of these recommendations we can determine the diets of specific composition that have to be fed to gilts in the different phases of rearing. These recommendations generally propose two- or three-phase feeding from 30 kg body weight until the time of the first breeding. They specify in detail the accurate composition of the diets to be fed in a given period, from the crude protein levels through the vitamin concentrations up to the levels of microelements. Also, there are specific recommendations on the daily amounts of diet fed during the different feeding phases, which amounts are illustrated by feeding curves. However, these recommendations are not ‘set in stone’ and require adjustment on the basis of the local farm experience in many cases.
Owing to the activity of the Bonafarm Group and the genetic line selected by it, we have gained the most abundant experience with the rearing of DanBred gilts in recent years. In 2020, the pig production division of Bonafarm produced 22 thousand gilts partly for its own use but mostly for the farms of its ‘external’ partners.
The biggest challenge is posed by the already mentioned restricted feeding. Last year’s data based on the results achieved by 500 thousand to 600 thousand fattening pigs show a daily body weight gain of 990 grams. Naturally, the good fattening ability of the maternal line is also needed for achieving such results, which means that the gilts are also capable of achieving very high daily body weight gain (as opposed to the recommendation, which is only 800 grams!). A further difficulty stems from the fact that a certain proportion of the farms use ‘ad libitum’ feeding, whereas in other units the phased feeding of gilts is also possible. Accordingly, we are preparing diets of different composition depending on the feeding technology (Table 1).
Overweight due to excessive feed intake can be prevented by increasing the fibre content of the ration. The slowly absorbing fibre sources (beet pulp, bran) induce saturation in the digestive tract, and their volume increases as a result of absorbing water. A full digestive tract calms down the herd, reducing the degree of aggression to a minimum. Thus, by accurately adjusting the fibre content of the diet we can regulate the feed intake of the herd.
The first breeding of gilts takes place after the second or third observed oestrus. Table 2 presents the recommendations of some breeding organisations on the basic parameters to be taken into consideration when determining the time of first breeding:
Development of the F1 population of the farm requires thorough planning as well as good technology and management. Pig production can be profitable only if the sows can produce and rear as many large litters and as many viable piglets as possible. To achieve this, observance of the recommendations of breeding organisations, good farm management and a feeding program maximally meeting the requirements of gilts are equally required.
Senior Swine Consultant
Bonafarm-Bábolna Feed Ltd.