swine health blackbelt Oct 24, 2023

Inspired by Episode 65 of The Swine Health Blackbelt with Dr. Lauren Glowzenski


Summer, a season synonymous with vibrance and vitality, paradoxically brings a unique set of challenges for sow farms across the United States. When the sun reaches its zenith, casting an intense blanket of heat across the farms, the sow’s journey from weaning to service - a crucial indicator of a farm’s reproductive efficiency - becomes arduous. When the temperature goes north of 70 degrees Fahrenheit, the unforgiving heat stress kicks in, leading to a discernible drop in the sow's feed intake and subsequently extending the weaned-to-service interval (WSI).

Understanding this key variable, WSI is quintessential. It represents the number of days between the weaning of a sow and her first artificial insemination service succeeding the weaning. A minimized WSI is emblematic of high reproductive efficacy, a cornerstone in the prosperous management of sow farms.


Succumbing to the Summer Heat: The Struggles of the Sow

Heat stress is more than a mere inconvenience; it is a formidable adversary in pursuing optimal swine health. It curtails the sow's appetite, diminishing their energy reserves and complicating the intricate road from weaning to service. This reactionary decrease in lactation intake spells a delay in the WSI, making it a pressing concern that necessitates immediate and effective management strategies.


Harnessing Lactation: The Dual Strategy

Lactation, in its essence, holds a mirror to the health and readiness of a sow post-weaning. The length of lactation, paired with the lactation intake, emerges as the two paramount facets that require meticulous management to maneuver through the summer heat successfully.

An abbreviated lactation period, particularly those short of 16 days, throws a wrench in the works. It denies the uterus the essential recovery period post-farrowing, inadvertently causing an elongation in the WSI. The prevailing practice leans towards a weaned age oscillating between 20 to 24 days, an approach bearing significant implications on the WSI outcomes.

Similarly, a sow’s lactation intake is a robust influencer of the available energy reservoirs during lactation and, consequentially, follicular development. A bountiful intake augments the sow’s condition, but the scorching summer temperatures wield the power to subdue the sow’s intake.


Meticulous Management: A Symphony of Strategies

Navigating through the summer necessitates a tapestry of nuanced strategies, expertly woven with the threads of fundamental understanding of sow needs and environmental interactions. Central to this tapestry is water, the lifeblood of swine health. Summer’s embrace causes a surge in the sow’s water consumption, reaching pinnacles of up to 16 gallons, a marked increase from the customary 5 to 10 gallons during less intense seasons. This increased water consumption is pivotal in bolstering feed intake, thus subtly enhancing reproductive performance.

Feed, the energy architect, demands a thoughtful recalibration during the summer months. The objective remains clear: augment the caloric intake per bite to sustain energy levels amidst reduced feed consumption. A tangible manifestation of this strategy could be incorporating enriched elements like a choice of white grease or vegetable oils.

Air, the invisible sustainer of life, takes center stage in the mitigation strategies. A conducive ambient temperature, complemented by a well-oiled ventilation system, emerges as non-negotiable for sustaining swine health during the intense summer heat. The arsenal to achieve this includes cool cells, inlet fans, and misters, all synchronizing to ensure an environment conducive to sow well-being. 


Special Focus: First Parity Sows

Delving deeper into the management strategies unveils a sector requiring particular attention: the first parity sows. These sows frequently find themselves in the unenviable position of facing exacerbated challenges in their WSI. Resorting to hormonal strategies, such as the introduction of PG 600 at weaning, unveils a pathway to invigorate their hormonal cycles. This revitalization facilitates a more rapid recovery post their inaugural farrowing.

However, it is not solely hormonal assistance that warrants attention. A sow’s body condition score emerges as a crucial player in the theatre of WSI management. An ideal state of moderation in the body condition emerges as the coveted goal, steering clear from the extremities of under-condition and over-condition that both bear their unique set of complications.



Navigating the tumultuous waters of summer, laden with the intrinsic challenges of heat stress, requires a compass finely tuned with strategies focused on optimizing the lactation variables and environmental conditions. The tapestry of success is woven with threads of meticulous management strategies, each contributing to mitigating the impacts of heat stress and optimizing the weaned-to-service interval in sows.



Effectively managing the non-productive days of sows - Lauren Glowzenski. Swine Campus, 2023. Available at: <https://www.swinecampus.com/blog/65>. Access on October 20th, 2023.