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“Select” gilts have superior lifetime productivity
Establishing effective gilt development unit (GDU) protocols was considered pivotal to the success of a long-term National Pork Board funded project designed to link gilt litter of origin traits to sow lifetime productivity (SLP). In collaboration with Holden Farms Inc., prepubertal Camborough gilts (n=6082) were delivered to a designated GDU over a 21-month period, with the goal of delivering known cyclic (“Select”) gilts to the sow breeding farm. A purpose built Boar Exposure Area (BEAR) was designed to facilitate stimulation and detection of puberty (full standing heat in the presence of a boar) by providing fenceline and direct contact (15 min daily) with at least 6 mature boars over a 28-day period, starting at approximately 170 days of age. At D14, non-pubertal gilts were mixed in new pen groups. At D23, non-cyclic gilts with no record of vulval development were eligible for treatment with PG600 to induce puberty in these “opportunity” females. Gilts without a record of puberty at D28 were deemed “Non-select”. At the end of the GDU phase 75% of the gilts were considered “Select” (4561/6082). In practice, 4980 gilts were delivered to the sow farm and retrospectively classified as: “Select” gilts expressed a pubertal estrus and either exhibited standing heat without intervention (SEL, n=3276), or exhibited estrus after PG600 treatment (SELPG, n=1137). A number of “Non-select” gilts transferred to the sow farm either did not spontaneously show estrus (NOSEL, n=417), or did not exhibit puberty immediately after PG600 treatment (NOSELPG, n=150). More SEL gilts (P ≤ 0.05) were served (SEL: 97.9, SELPG: 96.6, NOSEL: 94.3, NOSELPG: 88.9%) and farrowed to first service (SEL: 94.3, SELPG: 91.0, NOSEL: 89.2, NOSELPG: 86.0%) than the other classifications. However, once gilts were successfully bred, the percent that farrowed at parity 4 (SEL: 73.0, SELPG: 70.2, NOSEL: 70.0, NOSELPG: 70.4%), and total numbers born (SEL: 55.2, SELPG: 55.0, NOSEL: 54.2, NOSELPG: 55.7) and weaned (SEL: 42.9, SELPG: 42.4, NOSEL: 43.7, NOSELPG: 43.0) were not different (P > 0.05) among gilt classifications. Therefore, effective gilt selection, linked to successful introduction to the breeding herd, is a critical driver of SLP. These GDU/BEAR protocols will now be used to study more complex associations among gilt litter of origin, rate of selection in the GDU and SLP.
Keywords:
gilts, puberty, selection