Know when straw is needed in the diet of your dry cows
There has been considerable interest in using straw in dry cow diets in recent years. Firstly, cows have a requirement for 30pc fibre (NDF) in the diet. Silage NDF content ranges from 40pc for excellent quality silage to over 60pc for very poor quality silage.
Therefore, grass silage alone will supply adequate fibre to meet the cow's requirement for fibre.
Secondly, target dietary energy density for dry cows, dried off in optimal condition, is 0.76 UFL/kg DM. This is the equivalent of grass silage with a DMD of 68pc.
Grass silage sampled over the past five years in Ireland typically had a DMD of 66-68pc. The addition of another fibre source like straw, with 68 DMD silage, will only serve to reduce the energy density of the diet and consequently require supplementation with energy and protein to rebalance the diet, adding additional expense and complexity to the feeding system.
Thirdly, work at Moorepark examined the comparative performance of cows offered the standard dry cow diet of grass silage (70 DMD) and pre-calver minerals, compared to a diet of 40pc straw, 25pc maize silage, 25pc grass silage and 10pc soyabean meal.
Relative to a highbre TMR, cows offered grass silage for the duration of the dry period gained moderately more BCS, and had increased milk yield during early lactation. However, there was no difference in health and no persistent effect on milk production.
There are three situations where straw does have a role to play in dry cow diets:
1. Overconditioned cows – use straw or other low digestibility forage to restrict energy intake