Managing gilts prior to breeding is important for ensuring fertility. High gilt replacement rates and reduced sow longevity continue to cause problems for breeding herds. Much of the research suggests that ensuring proper age, weight and maturity at breeding is critical for herd longevity and lifetime production. One of the common steps in gilt entry into modern production systems is the change in gilt housing from group pens to individual stalls for breeding. There is no available data to suggest whether there is an effect for the timing of relocation prior to breeding.

More time prior to breeding would allow additional days for gilt acclimation to the stall and could affect feed intake, estrus expression and fertility. The timing of relocation may have no effect, reduce or even improve fertility. If there is no effect, relocation may safely occur at intervals prior to breeding, allowing flexibility in animal movement and flow. If there are declines or improvements in fertility, then relocation could be scheduled around sensitive periods.

An Illinois-based team of researchers designed a study to test the effects of the timing of mature gilt relocation from pens to individual stalls prior to breeding on measures of fertility and well-being. The study was performed in replicates on a 6,000-sow commercial research farm. Gilts (a total of 563) were randomly assigned to treatment for relocation into stalls on days four to seven which will be referred to as relocation week one (RELwk1); days eight to 14, known as relocation week two (RELwk2), or days15 to 19 as relocation week three (RELwk3) after the first detected estrus.

Data collected included inter-estrus interval, number of services, farrowing, total born, and wean-to-service interval. Individual piglet birth weight was also obtained on sub-sets of litters (a total of 42 per treatment). Measures of well-being included body weight, backfat, body condition score and lameness from week one until week 16.

Gilt body weight at breeding (318.12 lb./144.6 kg), at week five (348.48 lb./158.4 kg), and average daily gain from first estrus to week five (511.0 g) were not affected (P > 0.10) by treatment. Body condition score, lameness and lesions at breeding during weeks five, nine, 13 and 16 of gestation also did not differ (P > 0.10) among treatments.

The timing of relocation did not affect (P > 0.10) the proportion of gilts expressing a normal inter-estrus interval of 18 to 24 days (82.7%) but did influence (P < 0.05) the proportion expressing shorter (P < 0.001) and longer (P < 0.001) inter-estrus intervals.

Gilts in RELwk1 had a shorter (P < 0.001) inter-estrus interval (20.7 days) compared to RELwk2 and RELwk3 (22.6 days). Gilts from RELwk1 had more short intervals (9.8%) while gilts in RELwk3 expressed more delayed cycles (19.4%). Short intervals were associated with reduced total-born pigs, while delayed cycles were associated with reduced farrowing rate (P < 0.05).

However, there was no effect of timing of relocation on farrowing rate (85.2%) or litter traits among treatment groups. Measures for litter traits indicated no effect of treatment (P > 0.10) on total born pigs (13.5), pigs born alive (12.6), litter birth weight, within-litter birth weight variation or on the number of pigs born alive that weighed less than 1.5 lb./0.68 kg. The percentage of gilts re-bred within seven days after weaning (94.4%) was also not affected by treatment (P > 0.10).

These results suggest that timing of gilt relocation prior to breeding had no effect on measures of well-being and had no effect on the percentage of gilts with normal estrous cycles and their subsequent fertility. However, a proportion of the gilts exhibited shorter and longer inter-estrus intervals in response to relocation in weeks one or three prior to breeding. In cases where gilt fertility may be less than optimal, producers who relocate gilts from pens to stalls before breeding should evaluate inter-estrus intervals as response criteria.

Researchers: J. Shen, Dept. of Animal Sciences, University of Illinois, Urbana, L. L. Greiner, Innovative Swine Solutions, LLC, Carthage, IL, J. F. Connor, Carthage Veterinary Service, Ltd., Carthage, IL. and R. V. Knox, University of Illinois. 

Contact Rob Knox at (217)244-5177 or email [email protected].