WINTER BONUS MAGAZINE 2025

Growth rate, body weight, and fat Body weight at first insemination, combined with age, is often used as a key figure to determine whether to inseminate a gilt. It is also a good predictor of future reproductive performance. Body weight development is determined by average daily gain. For a gilt’s lifetime growth, growth from birth until first insemination is often used to assess gilt development. As a rule of thumb, the aim is to achieve a lifetime growth of between 600 and 650 g/day. Lower lifetime growth, of <550 g/day, can lead to underdeveloped gilts which will negatively influence reproductive performance. Too high lifetime growth of >700 g/day, can negatively influence reproductive performance and reduce sow longevity. Following the average lifetime growth, in turn, leads to a body weight at first insemination between 140 and 170 kg at an age of around 230-250 days. Please note that the optimal weight and age at first insemination depends on the breed. Always consult the manual of the breeding company for the latest updates. Body fat is an easily accessible energy source for lactating sows. Besides weight, body fat is also important for highly productive sows. At first insemination, a back fat level of 12-15 mm is advised. If you purchase gilts around first insemination or when they are already pregnant, you can use this information to check body development and support growth after gilts arrive on your farm. Feeding strategy up to first insemination Having the right feeding strategy, feed combined with the right feeding schedule optimises gilt development. Gilts of up to 25 kg can be fed like any other piglet. For both, the focus is on good body development and health. From 25–50 kg it is advisable to use a specific gilt feed. Whilst the requirements for body development of gilts are like those of a grower pig, the gilts’ requirements for vitamins and minerals are different. They require specific vitamins and minerals to support the development of their reproductive tracts as well as for their bones. From 50 kg to 120 kg a specific gilt feed is a necessity. Gilt feed should support muscle as well as fat development and a lower growth rate compared to fattening pigs. Vitamin and mineral requirements are the same as for the 25–50 kg phase. When you buy gilts around the age of first insemination, it also pays to use a specific gilt feed. During this phase, you still want to support gilt development. The gestation feed is often too low, whilst a lactation feed is too high in nutrients. The general advice is to feed gilts ad libitum up to 60 kg, after which a restricted feeding schedule should be followed. First insemination Two weeks before first insemination, gilts should be housed in (insemination) crates to get used to being confined. This helps to improve the oestrus expression. During this time, you can feed either the gilt feed or a gestation feed. Start oestrus stimulation five days before the expected date of insemination. Oestrus stimulation, boar exposure, light, and flushing, are done in the same way as it is done with sows. For gilts, it is important to • Check for oestrus twice a day. • Use a teaser boar and keep him in front of five sows for at least ten minutes. • Use a 16-hour light and 8-hour dark lighting regime. • Feed 2,5-3,0 kg gestation feed topped with 0,5 kg of Maxi-Flush or sugar (Figure 2). make sure you do not inseminate them before the second oestrus, as this negatively affects performance www.agribonus.co.za Winter 2025 BONUS 5