Validation of the use of exogenous gonadotropins (PG600) to increase the efficiency of gilt development programs without affecting lifetime productivity in the breeding herd1

Abstract

The objective of this study was to validate the use of exogenous gonadotropin (PG600) treatment for stimulating estrus in noncyclic gilts and to compare lifetime productivity of gilts recorded as having natural (NAT) versus PG600-induced (PG600) first estrus in a commercial setting. Prepubertal Camborough gilts ( = 4,489) were delivered to a gilt development unit (GDU) with the goal of delivering known cyclic breeding-eligible females to the sow farm (SF). A boar exposure area (BEAR) was designed to facilitate stimulation and detection of puberty by providing fence line and direct contact (15 min daily) with mature boars over an intensive 28-d period, starting at approximately d 160 (d 0). At d 14, nonpubertal gilts were mixed in new pen groups. At d 23, noncyclic "opportunity" gilts with no record of vulval development and required to meet breeding targets, were eligible for treatment with PG600 to induce puberty. Overall, 77.6% ( = 3,475) of gilts exhibited standing estrus (NAT = 2,654; PG600 = 821) and were eligible for shipping to the SF at approximately 35 d, and 76.6% of gilts that were administered PG600 exhibited the standing reflex within 13 d of treatment. Ultimately, 72.0% of gilts entering the GDU were delivered to the SF as breeding-eligible females. Considering the gilts delivered, a greater proportion of NAT than PG600 gilts were successfully bred ( < 0.001) and had better farrowing rates to first service, and overall farrowing rates (including gilts that returned to estrus and were rebred) were greater for NAT compared to PG600 gilts ( < 0.001) . Farrowing rates at second and third parity were similar between NAT and PG600 gilts; however, at fourth parity, a greater proportion of NAT gilts farrowed. In comparison, considering only gilts served, there was no difference ( > 0.05) in the proportion of NAT and PG600 gilts farrowing a third litter, but a greater proportion of NAT than PG600 gilts farrowed their fourth litter ( < 0.001). There was no difference between NAT and PG600 gilts for litter size at parity 1 through 4 or total pigs born over 4 parities ( > 0.05). A negative correlation ( < 0.0001) was detected between age at puberty and lifetime growth rate at puberty, and growth rate classification affected age and weight at puberty. However, retention rates and total sow productivity to parity 4 were not affected by growth rate classification at puberty.

Increased age at first-mating interacting with herd size or herd productivity decreases longevity and lifetime reproductive efficiency of sows in breeding herds

“…The mean AFM and distributions in the present study are similar to published results in other countries [19][20][21]. Some large herds had early AFM of 160-190 days, but such early AFM is not recommended because gilts with early AFM may not have [10,18,19]. It is possible that these farms might have tried to meet their target number of mated sows during a certain period by mating young replacement gilts [9].…”

“…However, high productivity groups had 5.0 more herd-life piglets weaned, 5.2 more herd-life piglets born alive and 2.1 more sow life annualized piglets weaned than ordinary herds, but there were no such differences between the herd size groups (P > 0. 10).…”

“…This study clearly showed that sows with late AFM were associated with decreased longevity, prolificacy, fertility and reproductive efficiency measurements except for sow life days. However, AFM can be advanced to some degree by a puberty stimulation program for gilts [10,22], although innately fertile sows do tend to have early AFM and high lifetime performance [22]. Additionally, it is recommended that producers record and pay close attention to gilt age at first-estrus, heat-noservice events and AFM [22].…”

“…Age of gilts at first-mating (AFM), which is commonly recorded by producers, is a measurement to predict sow reproductive performance [9], although recording age at first estrus and heat-no-service events are recommended as better measures [10]. Also, herd size and PWSY are herd-level factors for sow reproductive performance [9,11].…”

Strategies for improving reproductive performance in gilts

“…As a result, this can create significant variability in a gilt's age when first estrus is achieved. Successful implementation of management practices including boar exposure, gonadotropin administration, and altering the stress levels by mixing and relocation gilts can all influence attainment of puberty (Brooks and Cole, 1970;Patterson et al, 2016;Hughes et al, 1997).…”