the podcast linked to in #756 explains protein's role as building structure - the body and the things in it - as opposed to fuel, which fats and carbs provide.
https://www.backyardchickens.com/th...trad-views-on-nutrition.1567953/post-27005095
On the value of feed companies' advice I urge caution. Yesterday I was reading up on vitamin E and came across (not for the first time, but I'd forgotten it) this in Poultry DVM:
https://poultrydvm.com/condition/vitamin-e-deficiency-in-chickens
“Vitamin E has been shown to be essential for integrity and optimum function of reproductive, muscular, circulatory, nervous, and immune systems. Vitamin E is stored throughout all body tissues, with highest storage in the liver. Vitamin E an essential nutrient for chickens of all ages, and its deficiency causes several disorders…
Nutritional muscular dystrophy,
also known as white muscle disease or nutritional myopathy, is a disease that primarily affects the chicken's striated muscles [emphasis added]. It involves progressive weakness and degeneration of the muscles that control movement. Affected chicks are often unable to stand or walk, and are seen on the ground with their legs spread laterally.
Nutritional Recommendations for Vitamin E in Chickens
Vitamin E levels recommended in the Nutrient Requirements of Poultry (NRC, 1994)
are extremely low and were determined solely based on enhancing productivity traits of broilers and laying hens, and not in relation to immune enhancement and long term health and well-being. Based on latest research studies, vitamin E requirements recommended for chickens at various stages of growth [are much higher]” emphasis added
“
Risk Factors
Feeding chicks starter feed that is more than 2 weeks old
Improperly storing feed
Purchasing poor quality feed
Feeding breeding chickens laying hen feed, without providing additional vitamins and minerals needed for breeding
Feeding vitamins that are past their expiration date
Feeding chicks a diet high in rancid fat
Diet lacking antioxidants”