Vitamin A is a group of substances with vitamin A biological activity. The vitamin A commonly referred to is retinol and dehydroretinol. Vitamin A plays a vital role in cats' bodies; it is an essential element for healthy vision, especially night vision. Vitamin A also participates in the synthesis of reproductive hormones, proteins, and regulates skin cell growth and sebum production.
Vitamin A exists in many forms, the most common being retinol, retinaldehyde, retinoic acid, dehydroretinol, and palmitate retinoic acid. 
I. The main functions of Vitamin A for cats:
1. Maintaining normal visual function; 2. Maintaining the health of epithelial tissue cells; 3. Maintaining normal bone growth and development; 4. Promoting growth and reproduction; 5. Immune function. All of these functions can be maintained by retinol and retinal in the diet.
II. Clinical symptoms of vitamin A deficiency:
Sick cats exhibit sparse fur, loss of appetite, and weight loss, which can further progress to follicular keratosis, increased dandruff, conjunctivitis, photophobia, and tearing. Secondary bacterial infections can lead to corneal ulcers and even perforation. Male affected cats show testicular atrophy and low or absent sperm count in their semen. Mildly affected female cats may still experience estrus and pregnancy, but are prone to abortion, stillbirth, weak offspring, or retained placenta. Severely affected cats may not exhibit estrus.
Kittens that survive birth often exhibit ataxia, tremors, and spasms, eventually leading to paralysis. Young kittens show signs of stunted growth, lethargy, anorexia, unsteady gait, delayed tooth replacement, and digestive problems. Sometimes, affected cats also develop anemia, diarrhea, weakness, and are prone to secondary respiratory illnesses.
III. Causes of Vitamin A Deficiency:
1. Vitamin A mainly exists in the form of carotene in various feeds. When cat owners feed their cats only extruded dry food for a long period of time, it can cause vitamin A deficiency.
2. Improper feed processing (such as heating, pressurization, and humidity during pelleting affecting vitamin stability) can also destroy vitamin A in feed;
3. Increased need for vitamin A. Cats require significantly more vitamin A during pregnancy than usual.
4. Secondary deficiency. Even if the diet contains sufficient vitamin A or carotene, a cat's poor appetite leading to reduced food intake, or stress and illness that can disrupt digestion, absorption, and metabolism, can result in vitamin A deficiency at the tissue level.
IV. Prevention and treatment of vitamin A deficiency:
For cats deficient in vitamin A, vitamin A preparations should be administered immediately at a dose of 10-20 times the daily requirement. Providing vitamin A-rich feed or carrots can effectively prevent vitamin A deficiency. During pregnancy, lactation, and growth and development, cats generally require 50%-100% or more of the minimum requirement for vitamin A. Therefore, it is important to supplement vitamin A during these stages.
V. Vitamin A requirements for cats:
The minimum requirement for vitamin A in cats during their growth period is 9000 IU per kilogram of dry matter in their diet, while the minimum requirement for adult cats during their maintenance period is 5000 IU per kilogram of dry matter in their diet, and the maximum requirement is 750000 IU.
Animal liver contains a significantly higher amount of Vitamin A than many other foods, making it a good source of Vitamin A for cats when given some. However, it's crucial to ensure the liver is fresh and safe, and to prepare it properly, such as adding seasonings according to the cat's preference. Because of its high Vitamin A content, owners must carefully control the amount fed to avoid Vitamin A poisoning in their cats.
When feeding eggs to cats, owners should consider their individual cat needs. Some cats may experience adverse reactions after eating eggs, so owners should avoid feeding them eggs. In fact, some cats may even ignore eggs altogether, in which case owners can supplement their nutrition through other means.
Milk and dairy products also contain a certain amount of vitamin A. Some owners may feed their cats milk, but not all cats are suitable for drinking milk. Some cats may experience diarrhea after drinking milk, so owners should be cautious when feeding them milk.
Plant-based carotene can be converted into vitamin A in cats' bodies, so foods such as carrots can be provided to cats in moderation.
VI. Symptoms and treatment of vitamin A poisoning in cats:
Vitamin A poisoning can occur when cats are fed excessive amounts of vitamin A over a long period, especially during treatment or when they are fed animal liver or fish viscera. Clinical manifestations of poisoning include lethargy, gingival congestion and edema, decreased appetite, abdominal distension, constipation, stunted bone growth and development, exostosis around the joints of the cervical vertebrae and forelimbs, neck stiffness, fusion of bones in the elbows and wrists of the forelimbs, difficulty walking, and lameness. When the vertebrae of a cat are fused, spinal curvature becomes difficult, and the cat cannot groom itself. Some cases also present with gingivitis and tooth loss, affecting eating and chewing.
If poisoning is detected, adjust the diet immediately. Those with mild symptoms may recover on their own; however, in severe cases, the skeletal changes are generally difficult to reverse.
