The goal is to manage gilt muscular development and backfat thickness taking into account the age and weight at first mating to achieve the best prolificacy possible. Our nutritional recommendations regarding feed management are below.
1. Feeding gilts before insemination
Gilts are the basis of the sow herd. It is important that they have proper nutrition and are raised properly in a clean and well-ventilated environment so they can grow and perform to expectations. Typically, gilts make up approximately 20% of a group of farrowing females. Being a large percentage of a farrowing group, the proper development of CG36 gilts, their introduction into the herd, and their feeding program from herd introduction to first farrowing are important areas to manage to maximize their performance. This includes characteristics such as:
- excellent growth
- early puberty
- fertility
- prolificacy
- milk production
- temperament
- longevity
Up to 130 days of age or 80 kg (176 lbs.), the gilt can be fed as a typical market animal. At 130 days and older (puberty), it is preferable to use a gilt development ration for young gilts or provide vitamins, trace minerals, calcium, and phosphorus corresponding to the use of a gilt development ration for young gilts.
From 100 to 105 kg (220 to 230 lbs.), feeding should be controlled, knowing that the objectives are as follows:
| Age | 210-250 days |
| Weight | 136 to 150 kg (300 to 330 lbs.) |
| Backfat : | Between 13 – 16 mm not less than 12 mmm |
| Heat Cycles | Having had at least 2 or 3 heat cycles with proper early boar exposure beginning at 21 – 25 weeks of age. |
Gilts can be fed ad libitum if they meet the above conditions by breeding time. However, under good quarantine conditions, feed intake of 2.0 to 2.3 kg/day (4.4 to 5.1 lbs./day) is sufficient until progesterone is distributed or 3 weeks before insemination. During progesterone distribution, approximately 25 days before insemination, increase the amount of feed by 300 to 400 grams (0.7 to 0.9 lbs. per day). The increase is often necessary to ensure sufficient fat deposition at mating without excessive muscle development. At this stage, a gestation feed is usually sufficient.
Choice has completed numerous trials in commercial farms to develop these recommendations:
2. Primary studies about Backfat and Age
French farm 1500 sows study on 196 gilts (2017)
In the chart below, there is a positive effect by 0.6 in born alive for gilts, which were mated at 14mm of backfat or more vs. gilts mated at 12 mm or less. The number of gilts evaluated is the same for the three first classes. As the study was conducted in France, we didn’t look at the age because the minimum age at mating was 35 weeks (delivery at 26 weeks and mating 9 weeks later after quarantine and progestogen period).
Paraguay farm 3000 sows
We used the production data software to look at the performance according to age at mating.
It was clear that the gilts mated at 32 weeks or less had lower prolificacy than gilts mated at 33 weeks or more. That means that under 230 days of age there is a risk in a reduction of prolificacy. In the same farm, we saw that this reduction was not only on first parity but it continues in 2nd litter for the youngest gilts at first mating.
China farm 2800 sows
A global trial evaluating backfat and age for gilts at mating.
The animals with a backfat of more than 15mm and average age at approximately 33 weeks have an advantage on 0.8 piglet total born than animals mated at less than 14mm at approximately 32 weeks old.
3. Updated Studies on Backfat and Age 2021
Brazil study 112 gilts in 1700 sow farm
This is a global study evaluating age and backfat. The prolificacy is better for the animals mated at 33 weeks and older. The gilts at 32 weeks of age or less have a lower prolificacy not only because of age but because the backfat is lower by 1.5 mm to 2 mm than the other gilts.
In this second chart, we can see at the same average age at mating, the gilts have better prolificacy when the backfat is from 14 to 16 mm.
French Studies 200 sow farm
We conducted these measurements at the beginning of 2021 because of low prolificacy at first parity.
The backfat measurement was done at pregnancy check scan, It showed us that the animals were quite thin at mating. The ones, which were in better body condition performed better than the thin animals.
900 sow farm
In this 900 sow farm, the backfat of the the sows is systematically measured before farrowing, but not at mating for gilts. The results give us a good understanding about the target to achieve. All the animals are older at first mating, not less than 35 weeks, but the less productive animals have the lower backfat at farrowing.
The data in the table above, substantiates the Choice management protocols for gilts, first mating at 230+ days and a minimum of 13 mm of backfat improves productivity.
The backfat is a key point, and especially the deposit of fat before mating. A study presented in France in 2015 had this conclusion: “The backfat deposit over the period between the start of treatment altrenogest and AI is particularly favorable to improving the reproduction performance of gilts, justifying the practice of overfeeding gilts over the same period”. ( 2015.Swine Days’ Research, 47, 151-15). In other countries, it have to be combined with the gilt age at first mating.
