The occurrence of late weaners is one of the variables that should be reviewed, understood and fixed when the incidence rate increases or the interval becomes extended. In many situations the cause and subsequently, the solution, can be identified and targeted for improvement. The goal of this article is to provide definitions to better understand the implications of a longer weaning-to-service interval and also provide a set of practical interventions.

Introduction

A deep understanding of the cost structure, at every production phase, is required to thrive in volatile times. It is well known that after feed cost the second biggest input cost of the market pig is the cost of the weaned pig. Late weaners and procedures including skipping a heat increase the number of non-productive-days, negatively affecting the number of litters per sow per year, which in turn can decrease throughput and increase the cost of producing a weaned pig.

Definition

A late weaner is a sow that does not show estrus within the first 7 days after weaning. It becomes an issue when its prevalence is > 1% of the average sow inventory at any given time, when breed back is < 90% or when the farm average wean-to-service interval is consistently > 7 days. Seasonality may play a role by depressing feed intake. When this reduction of intake is found, younger parity females are especially vulnerable to delayed return to estrus and subsequently, may increase the occurrence in this group.

System Review

The table below summarizes the most relevant points that should be reviewed and a set of meaningful interventions to address the issue:

Management Strategy	Standard
Boar exposure & heat detection	Sow to boar ratio: <200 Boar quality: older than 11 months; high libido Begin from: day of weaning Frequency: 7 days a week Man-power: enough for 1 full time employee to spend 1 hour/day per every 120 farrowings per week
Management decisions	Farms can skip sows after breed target is achieved and they are worth retaining There is no KPI for skip-a-heat, but a lower number is always better Quantify the cases and understand why females are skipped
Estrus in farrowing	Target is none<200 Potential cause: Poor lactation cycle associated with low litter sizes and/or low number of pigs nursed Potential cause: Poor lactation cycle associated with nursing disruptions, generated by scours and too many untimely fostering events
Feed usage and body weight dynamics	Targeted feed usage depends largely on lactation length and nutritional profile. Assuming typical US diets, gestation feed usage range goes from 1,500 to 1,700 lb/sow/year, while lactation feed usage is 600 to 1,000 lb/sow/year (range from 20 to 28 day lactation) Body weight in gilts at first breeding: 300 to 350 lbs Body weight at first farrowing: 350 to 400 lbs (net weight so piglets and placenta excluded) Body weight loss in lactation (P1) <5% Fresh water always available. Flow rate in farrowing drinkers >½ gal per minute. Free access in weaning area Full feed from farrowing to next breeding
Stress avoidance	Vaccinations in lactation and weaning-to-service period must be avoided P1 grouped together both in farrowing and weaning area Water and feed available in quantity and quality Breeding area should be cool and dry
The wild cards	Mycotoxins in feed Ovarian pathology can be associated to individual cases but seldom to a massive incidence of late breeders

Justification & Interventions

A longer wean-to-service interval negatively impacts the litters farrowed per sow per year. The financial impact of this delay is strongly dependent on the geography, as it creates variations in feed, labor and facilities costs. Our experience suggests a decrease of 0.02 litters per sow per year with every additional day added to the wean-to-service interval for the farm. In terms of increased wean pig cost, and not considering the impact of the lost opportunity profit from unrealized pigs, the cost per inventoried sow is up by $7 to $10 per year, per every 10% of weaned sows that are late breeders.

Management Strategy	Standard
Boar exposure & heat detection	Plan annual boar replacement to have enough boars older than 11 month of age. Keep boars in good physical shape by not overfeeding them Maintain boar libido Do heat detection as early in the morning as possible Make sure heat exposure and detection is getting done over weekends and holidays, starting same day of weaning
Management decisions	Achieving breed target: (a) Consider culling every P3+ that has not cycled after day 7 post-weaning;(b) high performing farms could consider culling every late breeder, if cost-effective If approved by law and available in your region, pharmacological interventions can be utilized during critical season at weaning in P1s (ask your herd veterinarian)
Estrus in farrowing	Load P1s with 14+ piglets from farrowing Fostering done within day 1 and later around day 3-5 to take care of poor doing piglets As much as possible, avoid fostering events after day 7 and minimize partial weanings or bump weanings
Feed usage and body weight dynamics	Make sure feed ins always fresh and available Flush water lines periodically during the hot weather Wet feeding can be a good tool to increase feed intake in lactation but has to be well managed to prevent issues with feed quality When facilities and flow allow, wean younger females to common barn areas that allow for specialized management and feeding Check rectal temperature and aggressively treat fever in sows after farrowing
Stress avoidance	Receive weaned sows in clean spaces Individual treatment of any sow with condition that might impact feed intake (rubber mats, bedding material) Minimize/avoid vaccinating sows when feed intake needs to be maximized (sows in lactation and weaned sows)
The wild cards	Use mycotoxin binder when having diets with high level of mycotoxins. For reference http://www.extension.umn.edu/agriculture/swine/effects-of-mycotoxins http://www.food.gov.uk/business-industry/farmingfood/crops/mycotoxinsguidance/animalfeed/ Weaned sows should get min 14 hours at >250 lux of light