Anatomy and
Physiology
Content:
Feline Pregnancy
In feline reproductive management, understanding the intricacies of the reproductive cycle is paramount. Queens are seasonally polyestrous, with cyclicity linked to photoperiods, where exposure to 14 hours of artificial lighting can induce and sustain cyclicity, while a decrease to 8 hours prompts anestrus. As induced ovulators, queens require coital stimuli for ovulation, with spontaneous ovulation observed in a subset, influenced by the proximity of an intact male and increased body weight.
Gestation in felines averages 65.6 days, with notable breed variation. Implantation occurs approximately 14 days post-fertilization, with palpable deciduomata by day 21.
Diet during gestation demands increased protein intake, with arginine, lysine, and tryptophan being critical. An optimal diet comprises a minimum of 32% protein and 18% fat to support the queen's weight gain, which should be between 12-38% of pre-pregnancy weight.
Progesterone, pivotal for maintaining pregnancy, peaks between days 13 and 21, subsequently declining to baseline by day 65 post-mating. The luteal phase, if not followed by pregnancy, leads to pseudopregnancy lasting about 40-45 days, with a subsequent inter-estrus interval of approximately 17±4 days. Extended progesterone exposure due to mating with sterile or subfertile toms can induce uterine pathology, adversely affecting fertility.
Ultrasonography plays a crucial role in gestational management. Initial detection is feasible as early as 10 days post-mating with embryonic visualization by day 17. Structural developments like the urinary bladder and stomach can be discerned around day 30, kidneys by day 39, and bowel by day 40. Gestational age estimation via ultrasound relies on measurements such as inner chorionic cavity diameter early in gestation and biparietal diameter later on. The deep portion of the foetal diencephalo-telencephalic vesicle becomes measurable between days 35 to 58. Accurate parturition prediction is attainable with species-specific formulae applied to these ultrasonographic parameters.
REFERENCES:
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Johnson, AK. Normal Feline Reproduction. The Queen. Journal of Feline Medicine and Surgery (2022) 24, 204-211.
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Root, MV. Clinical management of pregnancy in cats. Theriogenology 66 (2006) 145-150.
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Beccaglia, M. Determination of gestational time and prediction of perturbation in dogs and cats: an update. Reprod Dom Anim 2016; 51: 12-17.
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Davidson, AP. Pregnancy Determination in Dogs and Cats. Merck Veterinary Manual.
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Sheep and Goat Pregnancy
Managing sheep and goat pregnancies effectively requires a thorough understanding of various diagnostic techniques and potential complications. The average gestation period for both sheep and goats is approximately 150 days (5 months).
For goats, pregnancy can be detected as early as 30 days post-breeding using real-time ultrasonography, with transrectal ultrasound offering early diagnosis at around 20 days. Ultrasonography is also useful for embryo or fetus counting and sex determination. Radiography becomes a reliable diagnostic tool after 70 days of gestation. Hormonal assays, including progesterone levels in milk or serum and estrone sulfate tests in plasma or urine, are utilized for pregnancy confirmation. However, progesterone cannot differentiate between true pregnancy and pseudopregnancy. Pregnancy-specific protein B (PSPB) is detectable via ELISA from 25-30 days post-breeding. Hydrometra, or pseudopregnancy, is a condition in goats diagnosed by excluding pregnancy and is treatable with prostaglandin.
Abortions in goats can result from infections like Chlamydia psittaci, Toxoplasma gondii, and Coxiella burnetii. Diagnostic evaluations are essential for managing abnormal abortion rates, with prevention strategies including stress reduction, biosecurity, and vaccinations.
In sheep, pregnancy determination methods include observing ewes not returning to estrus, transabdominal real-time ultrasonography, rectoabdominal palpation, and plasma progesterone concentration measurements. Ultrasonography, especially transrectal in the early stages (20-40 days), is highly sensitive and enables efficient examination of a large number of ewes. This precise diagnosis aids in the differential management of pregnant ewes, enhancing nutritional supplementation strategies and lambing supervision.
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References:
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Veterinary Merck Manual. Management of Reproduction Sheep.
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Veterinary Merck Manual. Management of Reproduction Goat.
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Gizzard in Chickens
The gizzard, also known as the ventriculus, is an integral part of a chicken's digestive system, functioning as a mechanical stomach. This muscular organ uses ingested grit and small stones to grind down food, compensating for the absence of teeth in birds. The gizzard's robust muscles and thick lining allow for the effective breakdown of hard materials like seeds, playing a crucial role in the bird's ability to digest and utilize nutrients from its diet.
Gizzard impaction, a condition where indigestible material obstructs the gizzard, poses a significant health risk, particularly in free-ranging chickens that may ingest long grass or foreign objects. Symptoms include reduced feed intake and potential for starvation due to obstruction of food passage into the duodenum. Management strategies to prevent impaction include providing grit supplementation and ensuring birds are kept on short, fresh grass to minimize ingestion of fibrous materials.
In cases of hardware disease, metal objects ingested by chickens can penetrate the gizzard wall, leading to severe conditions such as peritonitis secondary to ventricular perforation. Veterinary intervention may include treatments to facilitate the passage of ingested material or, in severe cases, surgical removal of the objects.
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REFERENCES:
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Extension. Small and Backyard Poultry. Avian Digestive System.
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University of Kentucky. Animal and Food Services.
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Texas A&M Veterinary Medical Diagnostic Laboratory. Hardware Disease in Backyard Chickens.
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Bovine Estrous Cycle: Detection, Management, and Insights
Environmental Conditions Affecting the Estrous Cycle:
The estrous cycle in bovines is influenced by environmental conditions such as photoperiod, temperature, nutrition, and stress. Optimal conditions can promote regular cyclicity, whereas adverse conditions may lead to irregular estrous cycles or anestrus.
Signs and Duration of the Estrous Cycle:
The average duration of the bovine estrous cycle is 21 days, with a range of 18 to 24 days.
It comprises several phases:
- Proestrus: Transition phase leading up to estrus, characterized by the formation of the dominant follicle and increasing estrogen levels.
- Estrus (Heat): Sexual receptivity, marked by standing to be mounted behavior, vulvar swelling, and mucous discharge. Lasts approximately 18 to 24 hours.
- Metestrus: A short phase following estrus, associated with ovulation and initial formation of the corpus luteum (CL).
- Diestrus: The longest phase, dominated by the presence of the CL and progesterone production, crucial for maintaining pregnancy if fertilization occurs.
- Anestrus: A period of sexual and hormonal inactivity, more common in certain seasons or due to stress, poor nutrition, or lactation.
Detection and Diagnostic Tests:
Detecting estrus and determining the cycle phase can be achieved through:
- Visual Observation: Noting behaviors such as mounting and standing to be mounted.
- Vaginal Mucus Examination: Changes in quantity and consistency of vaginal mucus.
- Telemetry Devices: Automated heat detection systems that monitor activity levels.
- Ultrasound: Used to visualize changes in ovarian structures such as follicles and CL.
- Hormone Assays: Measuring levels of estrogen and progesterone in blood or milk to determine the cycle phase.
Management and Interventions:
To optimize reproductive efficiency, various interventions may be employed:
- Estrous Synchronization: Utilizing hormonal treatments such as prostaglandins, GnRH, and progesterone-releasing devices to synchronize estrus in a herd.
- Environmental and Nutritional Management: Ensuring optimal conditions for regular cyclicity through adequate nutrition, minimizing stress, and adjusting light exposure.
- Reproductive Technologies: Artificial insemination (AI) timed with detected estrus or following synchronization protocols enhances breeding success rates.
References:
The Cattle Estrous Cycle and FDA-Approved Animal Drugs to Control and Synchronize Estrus—A Resource for Producers
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