Peri-Parturient Rise and Genetic Resistance to Haemonchus in Goats

Last Updated: January 17, 2026
Estimated reading time: ~6 minutes
Word count: 1285

While seasonal factors and vaccination offer external methods of control, the host’s internal physiological state plays a decisive role in the severity of Haemonchus contortus infection. A critical phenomenon known as the peri-parturient rise (PPR) describes the temporary relaxation of immunity in female animals around the time of kidding, leading to a massive increase in parasite egg shedding. This biological “loophole” allows the parasite to contaminate pastures exactly when susceptible newborns are beginning to graze.

This educational summary explores the intersection of host physiology and genetics, analyzing how reproductive stress impacts resistance in Jamunapari and Sirohi goats. Furthermore, it delves into the heritability of resistance traits, offering a pathway for breeding animals that naturally withstand this reproductive immune crash.

  • Lactation is the most critical physiological stage for immunity breakdown, with egg counts peaking in early lactation.
  • Jamunapari goats exhibit a more severe peri-parturient rise compared to the resilient Sirohi breed.
  • Heritability estimates ($h^2$) suggest that resistance to Haemonchus is a moderately heritable trait, allowing for genetic selection.
  • Sire selection significantly influences the parasite burden of the progeny, proving that “good genes” can reduce flock infection levels.
  • Nutritional stress during milk production is a primary driver of the immune relaxation observed in does.

Genetic Resistance and Physiological Dynamics of Haemonchus Infection

The Peri-Parturient Rise (PPR) Phenomenon

The immune system of a goat is not a static defense; it fluctuates with the animal’s metabolic demands. The most dramatic fluctuation occurs during the reproductive cycle. This study meticulously monitored the Faecal Egg Counts (FEC) of does through dry, pregnant, and lactating stages. The data confirmed that the stress of producing milk diverts protein and energy away from the immune response, allowing dormant worm larvae to mature and adult worms to increase their egg output.

“The early rise in FEC in Jamunapari goats as compared to Sirohi goats showed that this breed was more likely to affect by loss of immunity. The higher magnitude of FEC in early lactating does… was observed after the anthelmintic treatment” (Agrawal, 2009, p. 107).

The study identified “early lactation” as the period of highest susceptibility. Unlike the “spring rise” often seen in temperate climates, this rise is linked strictly to the physiological event of kidding (birthing). The consequences are twofold: the mother suffers from severe anemia and weight loss due to the sudden explosion of the worm population, and the pasture becomes heavily seeded with eggs, creating a dangerous environment for the unweaned kids. The research highlights that this relaxation of immunity is temporary but potent, requiring targeted management intervention.

Student Note / Exam Tip: The Peri-parturient rise (PPR) is an epidemiological event where faecal egg counts spike in lactating females due to the hormonal and nutritional stress of milk production, specifically a redirection of immunoglobulins and protein.

Physiological StageJamunapari Mean LFECSirohi Mean LFECImmune Status
Dry6.17 ± 0.065.83 ± 0.07Baseline
Early Pregnant6.32 ± 0.155.66 ± 0.20Stable
Early Lactation6.34 ± 0.136.00 ± 0.22Compromised (Peak)
Late Lactation6.21 ± 0.115.99 ± 0.16Recovering

Fig: Least Square Means of Log Transformed FEC across physiological stages (Reformatted from Agrawal, 2009, Table 15).

Professor’s Insight: In clinical practice, you cannot treat a lactating doe as an “adult” in terms of immunity; physiologically, she is as susceptible as a young animal during this window.

Genetic Heritability of Resistance

Beyond physiological stages, the study investigated whether the ability to resist worms is passed from parent to offspring. By analyzing the “sire effect” (the influence of the father), the researcher estimated the heritability ($h^2$) of Faecal Egg Counts. A trait with moderate heritability indicates that selective breeding can effectively improve the trait in the population over time. The results were promising, particularly for the Jamunapari breed.

“The heritability of single measurement analysis for LFEC in Jamunapari breed was 0.18±0.18 for upto 12 months of kids and 0.20±0.07 for adults… However, after pooling all observations heritability was observed as 0.30±0.14” (Agrawal, 2009, p. 105).

A heritability estimate of 0.30 is considered moderate to high in livestock genetics. This implies that roughly 30% of the variation in worm burden among Jamunapari goats is due to their genetics. Therefore, if a farmer selects a buck (male goat) with a consistently low FEC, his offspring are statistically likely to carry that resistance. Interestingly, the Sirohi breed showed much lower heritability (0.08), possibly because the breed is already naturally resistant and has less genetic “variance” to select from, or due to environmental masking effects in the semi-arid study location.

Student Note / Exam Tip: Heritability ($h^2$) is the proportion of phenotypic variation (observed difference) attributable to genetic variation; for nematode resistance in Jamunapari goats, it is approximately 0.30.

Professor’s Insight: Selection for low FEC is a sustainable tool, but it is a slow process; it takes years to shift the herd average, unlike the immediate (but temporary) effect of dewormers.

Breed-Specific Susceptibility Patterns

The interaction between breed genetics and physiological stress provided some of the most practical insights of the thesis. While both breeds experienced a rise in egg counts after kidding, the magnitude and duration differed markedly. The Jamunapari, a larger breed with higher milk production potential, paid a higher “tax” for its productivity in the form of reduced immunity.

“Sirohi breed showed a sharp decline in faecal egg count in early lactation period while Jamunapari breed showed a gradual decline in their FEC during this period” (Agrawal, 2009, p. 107).

The Sirohi does demonstrated a unique resilience. Even when their immunity dipped, they recovered (“self-cured”) much faster than the Jamunapari does. The Jamunapari animals maintained high infection levels well into late lactation. This suggests that the Sirohi breed possesses a more elastic immune response, capable of bouncing back quickly after the initial stress of kidding. This makes the Sirohi a superior choice for low-input systems where veterinary care (like frequent deworming during lactation) might be scarce.

Student Note / Exam Tip: High-producing breeds like Jamunapari often exhibit a trade-off between productivity (milk/growth) and disease resistance, making them more susceptible to the peri-parturient rise.

Reviewed by the Professor of Zoology editorial team. Direct thesis quotes remain cited; remaining content is original and educational.

Real-Life Applications

  • Targeted Selective Treatment (TST): Instead of deworming the whole flock, farmers should focus strictly on does in early lactation, as the study proves they are the primary “contamination factories” on the farm.
  • Buck Selection: Breeders should record FEC data for potential sires. Choosing a Jamunapari buck with a documented low FEC can genetically upgrade the herd’s resistance within 1-2 generations.
  • Nutritional Buffering: Since the PPR is driven by protein scarcity (milk vs. immunity), providing high-protein concentrates specifically during the last 2 weeks of pregnancy and first 4 weeks of lactation can mitigate the immune crash.
  • Breed Deployment: In regions with heavy rainfall and high parasite loads, introducing Sirohi genetics may be more sustainable than struggling to keep purebred Jamunapari healthy without excessive drug use.

Key Takeaways

  • The peri-parturient rise (PPR) is a temporary loss of immunity to parasites occurring around the time of birth and lactation.
  • Early lactation is the period of maximum vulnerability and highest pasture contamination.
  • Resistance to Haemonchus contortus is a heritable trait ($h^2 \approx 0.30$ in Jamunapari), enabling genetic selection.
  • Sirohi goats recover immunity faster after kidding than Jamunapari goats, demonstrating better resilience.
  • There is a significant Sire Effect, meaning the father’s genetics play a major role in the offspring’s parasite burden.

MCQs

1. At which physiological stage did the goats exhibit the highest Faecal Egg Counts (LFEC)?
A) Dry period
B) Early Pregnancy
C) Early Lactation
D) Late Pregnancy

  • Correct: C
  • Difficulty: Easy
  • Explanation: The data indicates that FEC peaks during early lactation (6.34 in Jamunapari) due to the physiological stress of milk production (Agrawal, 2009, p. 107).

2. What was the estimated heritability ($h^2$) of Faecal Egg Counts in the pooled data for Jamunapari goats?
A) 0.05
B) 0.30
C) 0.80
D) 0.00

  • Correct: B
  • Difficulty: Moderate
  • Explanation: The thesis reports the pooled heritability estimate for Jamunapari goats as 0.30 ± 0.14, indicating a moderate genetic component (Agrawal, 2009, p. 105).

3. Why do lactating does experience a rise in parasite egg counts?
A) They eat more grass.
B) The parasites reproduce faster in spring.
C) Nutritional resources are diverted from immunity to milk production.
D) The kid suppresses the mother’s immune system.

  • Correct: C
  • Difficulty: Moderate
  • Explanation: The “relaxation of immunity” is attributed to the metabolic priority of lactation, where protein is used for milk rather than maintaining antibodies and immune cells against worms.

FAQs

Q: What is the peri-parturient rise?
A: It is a sharp increase in parasite egg shedding by female animals around the time of giving birth (parturition) and during lactation, caused by a temporary drop in immune resistance.

Q: Can we breed goats to be resistant to worms?
A: Yes. The study showed that resistance (measured by low FEC) is heritable, especially in the Jamunapari breed, meaning you can select resistant sires to produce resistant offspring.

Q: Which breed is more suited for high-parasite areas based on this study?
A: The Sirohi breed. They naturally shed fewer eggs and recover their immunity faster after giving birth compared to the Jamunapari breed.

Q: Does the father (sire) affect the worm burden of the kid?
A: Yes. The study found a significant “random effect of sires,” meaning some fathers consistently produced offspring with better resistance (lower egg counts) than others.

Lab / Practical Note

Sampling Timing: When collecting faecal samples to assess herd resistance or PPR, ensure you record the exact reproductive status of each doe (e.g., “Lactating-Week 2” vs “Dry”). Mixing these groups will skew your data and hide the epidemiological spike associated with kidding.

External Resources

Sources & Citations

Thesis Citation:
Comparative Study on Immune Response and Resistance Status in Indian Goat Breeds Against Haemonchus contortus Infection, Ms. Nimisha Agrawal, Supervisor: Dr. D.K. Sharma, Central Institute for Research on Goats (CIRG), Makhdoom, Mathura, 2009, pp. 65, 88–93, 104–108.

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Author Box

Author: Ms. Nimisha Agrawal (PhD Candidate/Scholar at time of publication)
Affiliation: Central Institute for Research on Goats (CIRG), Makhdoom, Mathura, India.

Disclaimer: This content is an educational summary of a specific scientific thesis and does not constitute veterinary medical advice.

Reviewer: Abubakar Siddiq
Note: This summary was assisted by AI and verified by a human editor.


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