I don't think it really matters. I think Purina is trying to say that the blocks are not meant for caged birds. We use them as a supplement in the barn in the dead of winter when there is no pasture available for our flock.
According to the label I have in front of me...
Purina Flock Block - Whole Grain Enrichment Supplement
-For free-ranging poultry and game birds
-Encourages natural pecking instincts to help reduce cannibalism
-Contains oyster shell and grit
Guaranteed Analysis:
Crude Protein not less than 8.0 %
Lysine not less than .30%
Methionine not less than .25%
Crude Fat not less than 2.5 %
Crude Fiber not more than 4.0 %
Calcium (Ca) not less than 2.3 %
Calcium (Ca) not more than 2.7 %
Phosphorus (P) not less than .65%
Salt (Nacl) not less than .70%
Salt (Nacl) not more than 1.2 %
Sodium (Na) not more than .35%
How to Feed:
Flock Block supplement is designed to supplement the diet of poultry 18 weeks and older. This is not intended to be the sole ration. Place blocks on the ground, free-ranging poultry and game birds will regulate their consumption according to the availability of natural diet. A feeding program is only as effective as the management practices followed and should only be used in combination with good conservation practices.
Caution:
Use only as directed. Store in a dry area away from rodents and insects. Do not feed moldy or insect-infested feed to animals as it may cause illness or death.
In respnse to the milk jug feeder: I leave it intact, but cut long (tall) arches on the two sides away from the handle. This leaves the pouring spout and lid in place for more stability. That way there is not way for them to get on or in the feeder. 1/2 gallons are perfect for grit and oyster shell.
This is sort of a hanging treat - I planted "climbing spinach" in my garden, which shares a wire fence with the chicken yard and it grows all over - the girls keep it trimmed on their side. I have seen them hopping up to get as far as they can. I sometimes cut long vines of spinach and toss in their coop. They love it and gives them lots of exercise and interest. It grows in TX - even thru this summer which was long, hot and dry! All my other veggies suffered terribly, but this stuff grew and grew. The tag that came with it says: Climbing Spinach (considered a herb) Glossy-leaved vine grows fast in Summer. Train against fence or wall. Young leaves can be cut through Summer. uses: cooked or fresh in salad. Botanical name is: Malabar Basella Alba