As forages mature, quality decreases. After tame grass plants head out, protein content decreases 1 to 1 ½ % per week and total digestible nutrients (TDN) also declines by the same amount. Native grasses maintain quality longer than tame species but still lose quality later in the year. Fibre levels increase in all plants as they mature.
There comes a point where forage can’t supply 11% protein and 65% TDN that a lactating cow requires to maintain body condition and milk production. Sampling and testing the grasses provides a snapshot of the quality. By the time the results are obtained, the quality has changed. If cow condition is dropping, it has been at least 30 days that nutrient requirements have not been met.
To maintain adequate digestion rates, rumen microbial populations must be high. To achieve this, adequate amounts of protein is needed in the ration. Low protein intake slows microbial reproduction which reduces fibre digestion rates. Feed remains in the rumen longer which reduces the amount of grass consumed per day, and limits nutrient intake.
How do you know when protein is low?
Observing the shape of the manure pats is a good indicator of digestive efficiency.
In the spring, protein levels in the plants is high. The manure pat is flat and runny. This indicates that the feed is passing through the digestive system rapidly. As protein levels decline, the manure becomes firm and takes the shape of a pie. Digestive efficiency and passage rates are good.
When protein is low in the grass, fibre digestion is slowed, and the manure becomes drier and exterior texture becomes rough. It does not flow but rather stacks up on itself and looks like onion rings. If protein is more deficient, the shape changes to a pyramid shape.
When the manure looks like onion rings or a pyramid, higher protein feeds such as a high quality alfalfa grass hay or a pellet should be fed on pasture. The other options are to change pastures or bring the cows home to feed.
For additional information on forage quality and protein levels, contact Barry at 403-741-6032 or firstname.lastname@example.org.
Pyramid shaped manure
Onion shaped manure
Photo credits: Barry Yaremcio