Date Full Report Received02/23/2015
Date Abstract Report Received02/23/2015
Funded ByNational Pork Board
This research addressed uncertainties involving the effects of the timing of transition from pen housing to stalls on replacement gilt fertility and longevity. In most US farms, replacement gilts are managed in group pens during the development and selection phases. However, once pubertal estrus is detected, females are managed as heat-no-serve in order to ensure breeding occurs at 2nd or 3rd estrus. The delay in breeding avoids problems associated with mating gilts that are too immature physiologically, in body size, and in composition. Despite the interest in loose housing systems, most North American farms maintain the breeding herd in stalls, and even if loose housing is used, stalls are still used for the first 30 days of breeding and gestation. As a result, most replacement gilts end up in a stall, but the effects of time of relocation during the cycle, on fertility, and longevity are uncertain. The shift in housing gilts in group pens to individual stalls is a stress. However, it is also known that stress for reproduction can actually have a beneficial effect in stimulating follicle development and puberty. Yet this stress may also have a detrimental effect if the timing disrupts normal reproductive processes. The timing of the movement from pens into stalls is managed based on week of pubertal estrus. Some questions for which there are limited answers include: 1) is it advantageous to have more time for acclimation into stalls prior to breeding to minimize stress and improve follicle development and reproduction?; 2) are there critical times during the estrous cycle where relocation of gilts to stalls enhances or reduces ovulation rate and egg quality?, 3) can the movement of gilts to stalls before breeding actually stimulate physiological processes that improve estrus, ovulation and fertility?, and 4) does the placement of gilts in stalls allow for more consistent feed intake and provide for similar rates of gain compared to pen housing? These important questions revolve around the reproductive processes during the estrous cycle of the gilt prior to breeding. The effect of housing and feed changes during these critical stages could impact reproduction. To study these important questions related to best management practices for replacement gilts, we propose an experiment designed to determine the effect of the timing of housing change on gilt fertility and sow longevity. In this experiment we investigate the day of gilt relocation into stalls and the duration of acclimation BEFORE breeding on measures of stress, reproduction, gilt feed intake, growth, fertility, and its impact on subsequent parity performance and sow longevity. This experiment was performed at a large modern commercial research farm in Illinois with time required to obtain parity 1 re-breed rates. Gilts (n = 563) were randomly assigned to treatment for relocation into stalls on days 4 to 7 (RELwk1); 8 to 14 (RELwk2), or 15 to 19 (RELwk3) after 1st estrus. BCS, lameness and leg inflammation, head lesions, body lesions and vulva lesions at breeding, 5, 9, 13 and 16 wk of gestation did not differ among treatments. Timing of relocation did not affect the proportion of gilts expressing a normal inter estrus interval of 18 to 24 days (82.7%) but did influence the proportion expressing shorter and longer inter-estrus intervals. Gilts in RELwk1 had a shorter inter-estrus interval (20.7 d) compared to RELwk2 and RELwk3 (22.6 d). For all gilts inseminated, there was no effect of treatment on conception (89.2%) or farrowing rate (85.2%). Measures for litter responses indicated no effect of treatment on total born (13.5), born alive (12.6), litter birth weight, weight variation or pigs born alive weighing < 0.68 kg.
The percentage of gilts re-bred within 7 d after weaning (94.4%) was also not affected by treatment. These results suggest that timing of gilt relocation prior 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 1 or 3 prior to breeding. In cases where gilt fertility may be less than optimal, producers that relocate gilts from pens to stalls before breeding should evaluate inter-estrus intervals as a response criteria. The results of this study will aid producers in defining the proper timing for relocation of gilts to stalls to enhance reproduction and allow optimal physiological conditions for adjustment to housing and to promote increased sow longevity.