The German perspective on how to manage gilts does not differ much from any other perspectives: Gilts are “princesses.” If properly handled they guarantee herd productivity with respect to lifetime performance and longevity, said Johannes Kauffold, Faculty of Veterinary Medicine, University of Leipzig, Germany, at the 2022 Leman Swine Conference.

Low birth weight piglets, lower than 1 kg, generally perform worse than heavier litter mates, he said. Small piglets are prone to grow slower than heavier piglets and will not reach target weights at selection or breeding. For instance, a piglet born at 1 kg will weigh approximately 20 kg less than a piglet born at 1.8 kg on day 200 of life, he added.

The various measures for the selection of gilts are defined by genetic companies or are individually set by farms based on their experiences, Kauffold noted.

A body weight of 135 to 160 kg is generally recommended. Heavier weight at breeding is considered a risk factor for retention in the breeding herd and predisposes the gilt for problems with parturition, he said.

Relative fat

Backfat is also a measure to determine the gilt’s eligibility for replacement, Kauffold said. Recommendations vary considerably, ranging between 12 and 20 mm at breeding, with 12 to 14 mm being the most common. Uniformity in terms of backfat thickness within a breeding group is helpful, he added.

Problems in terms of age at puberty are almost always associated with differently “conditioned” gilts at first service. The same applies to muscle as determined by the thickness of the longissimus muscle (MT). The problem is that there are no reference values available for MT. Based on field observation, however, MT should be in a range of at least 5 to 6 cm, Kauffold explained.

While no reference values are available, data indicates that the ratio of fat to muscle —relative fat— may influence puberty attainment. The more fat the better it appears, he said. Pre-breeding feeding strategies are beneficial to this process. Lower protein and more energy may help to gain body weight due to fat versus muscle, Kauffold said.

Early puberty

Early puberty attainment is beneficial to sow lifetime performance. From a reproductive standpoint one may, non-scientifically, argue that early maturing gilts are generally more “reproductively responsive or functional” throughout their reproduction life, he noted.

Without a doubt, boar contact is the most effective tool for puberty stimulation. Direct contact is better than fence line contact. However, there are pitfalls, he said. Boars used for stimulation must be sexually active.

In North America, continuous exposure is a common procedure, but Kauffold recommended intermitted contact, which he said is supported by field observations. A rather non-scientific attempt of explanation is that boars and gilts get bored of each other after a certain amount of time, he said.

Don’t ignore health

Kauffold noted that successful gilt development also depends on good health. Diseases during rearing will have a negative effect on puberty attainment, whether through direct or indirect effects, indicated by lower daily growth due to reduced feed consumption.

Replacement gilts are expected to have a given age and weight. If age and weight are lower than expected, something may have gone wrong during rearing, and subsequently may have an effect on sow lifetime performance, Kauffold concluded.