Is it a bit of a stretch to improve waste management through better feed efficiency? Perhaps not.
What would be the cost of additional storage if your cows ate more feed and produced more manure? Even worse, what if they produced more manure without producing more milk?
Quantity of feed.
Let's compare two herds that are each producing 80 lb. of milk/cow/day. The first herd has a dry-matter efficiency (DME) of 1.6 lb. of milk per pound of dry matter (DM), while the second herd has a DME of only 1.4. Herd 1 needs to consume only 50 lb. of DM/day (80/1.6=50), but herd 2 eats more than 57 lb. of DM/day (80/1.4=57.1). That's a 14% increase in DM feed consumption for the same amount of milk!
Since there are many factors that control the volume of manure produced per cow per day, we cannot assume a one-to-one relationship of increased intake to increased manure production. However, we can safely assume that the cow eating more feed will not produce less manure than the more efficient animal!
Quality of feed.
Common sense indicates poor-quality feeds tend to result in lower DME than high-quality feeds. Concentrating on highly digestible feeds will support increased feed efficiency while decreasing the need to overfill bunks due to sorting and feed refusal.
Feed nutrient content.
There are many feeds that may lead to nutrient excesses in manure. Two common nutrients are phosphorus and sulfur. Overfeeding a poorly balanced diet simply adds to the problem of increased feed needed to produce milk, resulting in excess manure produced per pound of milk produced.