We are all aware of the move by a significant portion of the industry to adopt pen housing for gestation sows. It is clear that several major food companies are feeling the social pressure to source pork from production systems that use pen gestation instead of individual sow-gestation crates.

As this proverbial snowball rolling downhill picks up speed, it’s critical that we examine the implications of this change. University of Minnesota scientists have shown that gestating sows housed in pens have increased lameness relative to sows housed in individual stalls.

As sows move to pens, it will require facility modifications. But more importantly management and other factors will need modification to produce a successful outcome, including efficient production. 

Regardless of housing, what are the factors involved and how can we address the issues to provide improved sow comfort and, ultimately, more efficient pork production? There is an ongoing effort by several researchers worldwide to provide some answers.  We must address these issues and correlate how they affect key production areas.

Culling Rates: Even though the industry has experienced improved genetics, nutrition, facilities and management, sow turnover rates continue to rise. Research by Bernie Peet, director, Pig Production Training, revealed that U.S. sow turnover rates increased from 57 percent in 2000 to 63 percent in 2005. In Great Britain those rates jumped from 46 percent to 54 percent. In Canada the move was equally dramatic, going from 50 percent to 60 percent.

How do we make sense of these dramatic increases? It’s difficult to compare numbers across systems or reports because not everyone uses the same terminology or recording methods.  For simplicity sake, all sow replacements, whether due to culling, death or euthanasia, have been combined into one category. The end result is clear: Several factors cause a sow’s early exit from the herd, and it comes at a significant cost to the industry.

If we work backwards from the issue of sow culling, we can begin to identify some contributing factors.  Sows may be removed from the herd for many reasons, but it’s often cited as “poor fertility.” Do we stop to consider if this is accurate?

Iowa State University researchers surveyed eight farms and found that 23 percent of the farm-reported culling classifications were inaccurate. Perhaps each system would be well-served to review and/or change its culling classifications and reinforce training to ensure accurate recording.

Poor Fertility: What leads to “poor fertility” and a sow’s early exit? Is it due to sows and gilts that fail to show estrus or is it due to poor body condition? Either factor can lead to the same conclusion with very different, or perhaps related, etiologies.

Improper body condition can often disrupt the endocrine system, which is necessary for estrus onset.  It also can be responsible for the occurrence of painful shoulder ulcers. Pain and the associated injury elicit a cascade of reactions and physiological compounds in the immune system.

Especially harmful is the impact of an inflammatory response. If the pain response is due to an inflammatory state, there are direct impacts on hormone production and activity of the ovary. (See accompanying graphic.) Pain can decrease the sow’s mobility resulting in more piglets being crushed in the farrowing crate. Unfortunately, there are no labeled analgesic products in the United States for ameliorating pain in swine.

Body Condition: It’s well documented that failure to consume adequate energy and required amino acids can lead to body tissue breakdown.  Australian researchers were among the first to demonstrate the linear relationship between daily feed intake during lactation and increased time required for sows to express estrus after weaning.

Research shows that younger first-litter gilts were more sensitive to negative effects of reduced feed intake during lactation compared with older gilts and multiparous sows.  Most farms attempt to feed lactating sows ad libitum to optimize milk production and maintain body condition.  However, voluntary feed intake of hyperprolific sows can be insufficient, especially in young animals, for them to meet the high nutrient requirements for milk production, maintenance and growth.  Lactation is one of the more energetically expensive and challenging activities that a sow or gilt can undertake.

Low Feed Intake: Research has shown that for each additional kilogram (2.2 pounds) increase in daily feed intake during lactation, an additional 0.11 pigs were born at the subsequent farrowing. Additionally, a high daily feed intake reduced body-weight loss and improved litter-weight gain. It also decreased the probability of a prolonged wean-to-estrus interval by 42 percent for each kilogram increase in average daily feed intake. When young sows have poor daily feed consumption in lactation, a practical outcome of the extended wean-to-estrus intervals is to cull for presumed reproductive failure.  Although young females are often culled for poor reproductive performance, the repeatability of that poor performance is actually lower than what is often suggested.

The interplay between nutrition and the immune system is complicated. Along with the direct impact that immune activation has on decreasing feed intake, an additional challenge is the drain of available nutrients, such as energy and amino acids, for production. At the same time, nutrient needs for immune cell formation and activity are different from normal tissue synthesis and maintenance.  So in a time of immune challenge or inflammatory response, the challenge is not only providing for the immune system’s needs but also to optimize production. 

Studies show that immune system activation alters feed intake, body weight, protein gain and feed efficiency in growing pigs. It also decreases sows’ lactational performance. Immune system activation can directly affect nutrient supply by altering nutrient digestion, absorption and metabolism.  Indirect effects on nutrient utilization and productive and reproductive responses can occur via immune system interaction with the endocrine system to alter hormone production and activity.

Lameness: The claw and foot health of a sow as it relates to lameness issues is critical to improving sow well-being, maintaining sows in the herd for improved longevity and maximizing the economics of pork production.  Information and understanding of lameness is increasing as more research groups are continuing to study the issue. Some examples are:

  • Research from Denmark reported that sows with elongated claws or claw cracks, as well as uneven claws, were much more likely to become lame. Other Danish research showed the main reason to euthanize sows involved locomotive disorders (72 percent).  Euthanized sows had high prevalence of overgrown heels (74 percent), claw-wall cracks (49 percent), sole cracks (77 percent) and white-line cracks (65 percent). Approximately 40 percent of sows in the study were euthanized or died spontaneously before the second parity.
  •  In U.S. sow operations, research has shown that more than 90 percent of all sows had a lesion in the wall and heel. Approximately 50 percent to 75 percent of the sows had overgrown heels, as well as lesions in the white line/heel-sole junction and sole. Heel lesions and overgrown heels were more prevalent in rear feet. However, lesions in the white line/heel-sole junction and sole were more common in front feet.

Counting the Costs: Sow lameness has dramatic implications on herd economics. John Deen, DVM, University of Minnesota, estimates that each incidence of lameness adds $180 in costs. In Europe, where animal disposal costs have risen and salvage values declined, estimates show that lameness may cost more than $500 per case.  Clearly, either estimate is a drain on a sow unit’s production and operating expenses. In addition to animal disposal and replacement costs, medication and labor costs also increase.  Another uncounted cost is lost piglets due to crushing in the farrowing crate, as well as reduced piglet quality.

So, while much work has been done, more research and understanding is needed to further evaluate what makes inflammatory responses from problems such as lameness impact the efficient production in a sow unit. As we focus on the areas that were cited previously and others within the operation, we can better determine the contributors and develop potential solutions to improving profitability.

To contact Terry Ward, Zinpro Corp., e-mail him at tward@zinpro.com.

A Look at Common Claw and Foot Lesions

Sows’ feet take a lot of wear and tear. Research and attention to the topic will provide more insight into which injuries are likely to add to sow lameness challenges. Here is a look at some typical issues:

  • A) Heel and sole cracks
  • B) Heel overgrowth and erosion
  • C) Uneven toes
  • D) Wall crack, horizontal
  • E) Overgrown toes
  • F) White line crack
  • G) Wall crack, vertical

Pathways of Lameness Impact on Reproduction and Removal

Poor fertility is the common denominator for sows that exit the herd early. However, lameness can cause many intermediate factors that lead to poor fertility. While not an easy task, classifying and recording the factors accurately are necessary steps to identifying solutions.