Nutrition Update
Volume 16 No.2, November 2005

Manitoba cattle producers generally do an excellent job of putting up good quality silage. Silage is chopped to the recommended length, silos are well packed and covered when full, and feed-out is managed well. All these things are done with an eye towards minimizing the spoilage which we know can significantly decrease dry matter and nutrient recovery from a silo. Despite the best of intentions, occasionally some silage does become spoiled and research from Kansas State University (KSU) shows that spoiled silage should be discarded as it can have a big negative impact on performance.

Corn was harvested and placed in a bunker silo. The top 3 feet of the corn silage was allowed to spoil. The top 18” of the spoilage was black, with a mud-like texture and a foul odour – typical signs of silage which had not been sealed. The bottom 18” was yellow-orange in color and had a strong acetic acid smell. The spoiled silage was incorporated into steer diets consisting of 90% silage and 10% supplement. Of the 90% silage, treatment groups consisted of 100% good silage, 75% good silage: 25% spoiled silage; 50% good : 50% spoiled and 25% normal : 75% spoiled. Steers were fitted with ruminal cannulas which allowed samples of digesta to be taken directly from the rumen.

The addition of spoiled silage to the diet resulted in drops in feed intake and digestibility.

Decreases in organic matter, protein and NDF digestibilities meant the steers were not able to utilize the available nutrients as efficiently. The addition of the first 25% spoilage caused the largest drop.  When samples of rumen digesta were examined, it was found that the spoiled silage had destroyed or partially destroyed the forage mat in the rumen.

Using this information, KSU researchers went on to determine the effects that spoiled silage might have on milk production.  Using a software program called Milk 2000, which calculates milk production based on various aspects of forage quality, they estimated a loss of 7.5 lbs of milk/cow/day when feeding 25% spoilage.  If we use a more moderate loss of 4 lbs/cow/day and Manitoba milk prices, this equals close to 6 hectolitres of milk per lactation and $360 of lost profit.

Most dairy producers will not feed spoiled silage to milk cows and the above information shows why this is a good management practice.  However, does this discarded material make its way into the diets of heifers or dry cows?? The KSU work showed a drop in feed intake of almost 10% when 25% spoiled silage was incorporated into the diets of the steers.  This could have negative impacts on heifer and dry cow productivity.

Reference: Kansas State University Silage Team.  2002. www.oznet.ksu.edu/pr_silage.