Modern swine production is a science-driven enterprise that demands precision at every stage—from gilt development to farrowing and lactation. Among the numerous tools supporting this precision, Veterinary ultrasound has become indispensable for monitoring sow health, evaluating reproductive performance, and making informed management decisions. In particular, ultrasound offers a non-invasive, real-time view into the sow’s body condition, ovarian activity, fetal development, and response to dietary and hormonal interventions.
This article explores how veterinary ultrasound is used to evaluate the effects of feeding levels, flushing, and hormone treatments on sows, particularly during gestation and the breeding cycle. Drawing from global practices, it underscores how ultrasound enhances reproductive efficiency and herd management across diverse farming systems.
Ultrasound Evaluation of Feeding Level During Gestation
Why Sow Nutrition Needs Change During Pregnancy
Sow nutrition during pregnancy is not static. Nutrient requirements evolve as the sow progresses through different stages of gestation. In early gestation (0–85 days), sows require moderate energy and protein levels to support maternal tissue growth and early embryonic development. In late gestation (86–114 days), fetal growth accelerates, demanding higher nutrient intake.
A one-size-fits-all feeding approach—providing the same ration throughout gestation—can lead to nutritional imbalances. Excess energy intake in early gestation may cause excessive fat deposition, while insufficient intake in late gestation may result in fetal underdevelopment and poor lactation performance.
Using Ultrasound to Detect Overfeeding and Underfeeding
Veterinary ultrasound, particularly B-mode scanners, provides a valuable tool for tracking these nutritional effects in real time. By measuring backfat thickness, farmers and veterinarians can detect overfeeding in early gestation—usually evident through a noticeable increase in subcutaneous fat layers.
Conversely, during late gestation, insufficient feeding can be identified by reduced fetal size and poor placental development, both visible during routine ultrasound scans. In some cases, fetal death or developmental abnormalities can be detected, signaling the urgent need for dietary adjustment.
International Practices: Stage Feeding vs. Constant Feeding
In many parts of the world, particularly in Europe and North America, stage feeding is widely adopted. This method divides pregnancy into distinct phases and adjusts nutrient supply accordingly. Ultrasound supports this practice by verifying that backfat remains within target ranges—typically 16–20 mm at farrowing.
Stage feeding has been shown to reduce excessive backfat gain in early gestation while supporting fetal growth later. Studies in Denmark and Canada report that stage-fed sows maintain more stable body condition and demonstrate improved farrowing outcomes compared to sows fed a constant ration throughout gestation.
Interestingly, even in farms practicing constant feeding, veterinary ultrasound plays a corrective role. If excessive backfat is detected mid-pregnancy, feed can be adjusted downward. Likewise, ultrasound can confirm whether energy reserves accumulated early in gestation are being mobilized appropriately in later stages.
Ultrasound as a Decision Tool for Feeding Adjustments
Ultrasound allows for real-time, individual-level decisions rather than relying solely on group averages. On-farm data gathered via ultrasound helps adjust rations dynamically, reducing feed waste and enhancing sow welfare. This tailored approach is especially beneficial in systems aiming for higher productivity and reproductive efficiency.
Supplemental Feeding (Flushing) and Sow Reproductive Response
Understanding Flushing and Its Timing
Flushing refers to short-term increased feeding before and during estrus, typically applied to weaned sows or gilts to enhance ovulation rate and conception probability. The strategy is based on the idea that improving the sow’s metabolic state boosts reproductive hormone secretion and follicular development.
Ultrasound’s Role in Monitoring Flushing Effects
Using ultrasound, the direct impact of flushing can be observed by measuring follicle size and number. Within 5–7 days of initiating supplemental feeding, ultrasound scans often reveal an increase in the number of large, mature follicles, indicating improved readiness for ovulation.
Global Observations: Flushing Efficacy in Practice
In the U.S. and Europe, studies have shown that flushing sows with energy-rich diets for 7–10 days post-weaning increases ovulation rate by 1–3 oocytes, which directly contributes to larger litter sizes. In Brazil and China, trials using high-protein and high-fat flushing diets, coupled with ultrasound tracking, showed better follicular development and reduced anestrus incidences among multiparous sows.
Ultrasound helps distinguish between sows with a strong response to flushing—indicated by robust follicular growth—and those with poor ovarian activity. For the latter, reproductive management can be escalated to include hormone intervention.
Preventing Nutrition-Related Reproductive Disorders
One of the strengths of ultrasound is its ability to detect reproductive disorders that may otherwise go unnoticed. For example, sows that are too thin or too fat may experience cystic ovaries or persistent corpora lutea, conditions visible on ultrasound. Regular backfat monitoring ensures that nutritional extremes do not impair reproductive performance.
Hormonal Treatments: Synchronizing Estrus and Enhancing Fertility
Common Hormonal Agents and Their Uses
In practice, several hormonal products are used to manage sow reproduction:
PMSG (Pregnant Mare Serum Gonadotropin): Stimulates follicle development.
hCG (Human Chorionic Gonadotropin): Triggers ovulation.
PGF2α analogs (e.g., Cloprostenol): Induce luteolysis, allowing for controlled estrus synchronization.
These hormones are frequently used in artificial insemination programs, particularly in large-scale or synchronized breeding systems.
Ultrasound Monitoring of Hormone Effects
Veterinary ultrasound provides visual confirmation of hormone efficacy. For instance, after administering PMSG or hCG, ultrasound can track follicular development and confirm ovulation. When using PGF2α analogs to dissolve the corpus luteum, ultrasound checks whether the luteal tissue regresses appropriately.
In cases where cloprostenol sodium appears ineffective—evident when the corpus luteum remains unchanged—ultrasound findings suggest the treatment timing might be suboptimal. Studies show that luteal tissue becomes resistant to PGF2α around day 12 of the estrus cycle. Therefore, proper timing and repeat dosing may be necessary for effective luteolysis.
Protocols Combining Hormones and Ultrasound
Advanced breeding programs in the Netherlands, the U.S., and Australia increasingly use combination protocols:
Day 1: Cloprostenol sodium
Day 14: Repeat cloprostenol
Day 17: Administer hCG
Day 18–19: Artificial insemination
Ultrasound scans at multiple intervals ensure follicles are maturing and ovulation is imminent. This approach increases breeding precision and litter size while reducing non-productive sow days.
Benefits of Ultrasound in Reproductive Management
Non-Invasive and Stress-Free
Ultrasound imposes minimal stress, making it ideal for routine monitoring.Real-Time Decision-Making
Changes in backfat thickness, ovarian status, or fetal viability can be identified quickly, allowing timely intervention.Reduced Hormonal Waste
By confirming whether a hormone has taken effect, ultrasound minimizes unnecessary repeat dosing.Enhanced Reproductive Efficiency
Ultrasound helps improve farrowing rates, reduce stillbirths, and optimize litter uniformity.
Conclusion
Veterinary ultrasound has revolutionized sow management by providing detailed insight into how sows respond to feed level, supplemental nutrition, and hormone treatments. Around the world, producers use this technology to make smarter decisions that improve productivity, animal welfare, and economic outcomes.
Whether adjusting gestation rations, evaluating follicular response to flushing, or tracking hormonal treatments, ultrasound serves as a reliable and essential tool. As swine production continues to evolve, the integration of precision imaging and nutrition will remain at the core of reproductive efficiency and sustainability.
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