Date Full Report Received07/19/2018
Date Abstract Report Received07/19/2018
InvestigationInstitution: University of Alberta
Primary Investigator: Dr. George Foxcroft PhD BSc
Co-Investigators: W. L. Flowers, Robert V. Knox
Funded ByNational Pork Board
- Objectives: The specific objectives of the Preliminary (Phase 1) Trial of Project #14-149 included:• Describing a repeatable sow birth weight phenotype as the basis for studying the impact of gilt “litter of origin” on sow lifetime productivity (SLP)
- Identifying appropriate early selection strategies for potential replacement gilts
- Validating efficiencies of using purpose-designed facilities for puberty stimulation and heat detection, and key intervention strategies (PG600) to reduce gilt non-productive days
- How research was conducted: The research built on existing collaborations between Holden Farms Inc. (HFI), university-based research groups, and Genus/PIC to identify and validate key management strategies that will allow producers to capture more of the existing genetic potential for excellent SLP. There is compelling evidence that “litter of origin” has a critical impact on developmental potential and SLP. “Litter of origin” effects include the genetic merit (G) for reproductive performance inherited from the sire and dam, plus “environmental effects” (E) of the particular dam and litter that pre-program lifetime growth potential and reproductive performance. The first step in linking litter of origin to SLP was to establish a repeatable birth weight phenotype over three successive parities in Line 3 sows in the production nucleus/multiplication population of HFI.The research team has extensive experience in the use of designated Gilt Development Units (GDUs) that incorporate purpose designed Boar-Estrus Stimulation Areas (BEARS) in the North American industry. Previous collaborations had standardized GDU/BEAR protocols in one off-site GDU and extensive data had already been captures for further analysis. This Preliminary (Phase 1) Trial provided the opportunity to: 1) Validate the impacts of final gilt selection and pre-breeding programs on SLP in a large commercial system (Phase 1). 2) To apply standardized programs of gilt selection and pre-breeding management, to determine the impacts of “litter of origin” on SLP.
- Research findings:
3.i. Extensive collection of data on litter birth weight phenotypes has been a key part of the Preliminary (Phase 1) Trial and involved weighing successive litters born to over 1,000 Line 3 sows. In turn, this provided the background data to allow the ongoing weighing and tagging of individual replacement gilts born to sows with established litter birth weight phenotypes.
3.ii. Preliminary analysis of litter of origin effects on gilt selection programs suggests:
- Large variations in the proportion of gilts selected from particular litters.
- Using existing selection criteria, in some 15% of litters born, between 50 and 75% of gilts are designated as “non-select” at weaning or around 140 days of age, on the basis of relatively poor growth performance and our prediction is that these gilts are born to sows with a repeatable low birth weight phenotype.
3.iii. Validation and application of efficient programs of gilt selection and pre-breeding management. Data collected included information on vulval development scores, observed standing heat, and estimated weights on over 3,000 naturally cyclic gilts and on over 1,000 gilts that were induced to cycle using PG600 treatment. Outcomes included:
- Standardized protocols for gilt exposure to boar stimuli and remixing, and if required for to treatment with PG600, to induce pubertal estrus.
- Objective scoring of gilts responses using wall charts and data recording sheets.
- Demonstrated value of moving gilts to breeding farms based on a recorded “heat-no-serve” event, and at a recorded weight, followed by controlled pre-breeding management programs.
- A comparison of SLP in naturally cyclic vs PG600-induced gilts that established excellent breeding and farrowing rates in naturally cyclic gilts and retention above industry benchmarks to parity 3. PG600-induced puberty was resulted in slightly lower percentages of gilts bred and farrowing but still resulted in retention to parity 3 that surpassed industry benchmarks.
- Established standardized protocols at the GDU and breeding farm that will optimize our efforts to link “litter of origin” traits to differences in SLP.
- Industry implications4.ii. Gilt selection efficiency:
- Retention of sows producing relatively few replacement gilts in the nucleus/multiplication farm leads to inefficiencies in replacement gilt production. One possibility is to designate complete litters as “non-select” at processing on the basis of a low litter average birth weight. Additionally, Line 3 sows with a repeat low birth weight phenotype should be aggressively culled and not used to generate Line 3 replacements, or Camborough replacement gilts at multiplication level.
- However, as data from other recent NBP SLP trials suggests that growth performance of most gilts will meet the minimal lifetime growth requirement (0.55 kg.d) for attainment of pubertal estrus, this begs the question whether the smaller gilts in low birth weight litters should actually be designated as “non-select” on the basis of relative size.
- Linking the complete range of litter birth weight phenotypes to gilt selection rates and SLP will, therefore, be a critical outcome of Project# 14-149.
4.iii. GDU and pre-breeding management
- Well managed GDU/BEAR facilities and protocols allows up to 80% of gilts entering the GDU to be identified as “breeding eligible” (known HNS and weight) before moving to the sow farm.
- These targets can be met in a 28 to 30 day selection program.
- Meeting these targets minimizes gilt non-productive days, results in excellent breeding and farrowing rates at parity 1 and excellent retention to parity 3.
- High quality GDU/pre-breeding programs are a major first step to achieving NPB targeted improvements in SLP.