Effects of corn silage particle size, supplemental hay, and forage-to-concentrate ratio on rumen pH, feed preference, and milk fat profile of dairy cattle

May 11, 2015Journal of dairy science

How Corn Silage Size, Extra Hay, and Forage-to-Concentrate Ratio Affect Stomach Acidity, Feed Choice, and Milk Fat in Dairy Cows

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Abstract

Feeding long corn silage total mixed rations resulted in an acetate-to-propionate ratio in the rumen maintained above 2 during a grain-induced acidosis challenge.

Cows fed long corn silage diets experienced lower milk fat concentration on day three of the challenge phase.
Cows fed short corn silage diets had lower milk fat concentration on the final day of the challenge compared to baseline.
Supplementing diets with hay prevented acidosis when cows were challenged with a high-grain diet.
Both diets supplemented with hay saw substantial decreases in milk fat concentrations during the challenge phase.
Cows showed a preference for shorter particle sizes over longer ones even during the rumen challenge.
Feeding long corn silage or supplementing with grass hay improved rumen pH and accelerated recovery from subacute ruminal acidosis.

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Two experiments (Exp.) were conducted to study effects of feeding long or short corn silage total mixed rations (TMR) on rumen pH, feed preference, and dairy cow performance and to determine the rate of recovery from grain-induced subacute ruminal acidosis (SARA). Both experiments utilized a crossover design with 12 lactating, multiparous, Holstein cows each (including 4 ruminally cannulated cows) and consisted of two 26-d periods. Each period consisted of 12d of adaptation followed by 14d of data collection. Each period was divided into 4 phases: adaptation, d 1 to 12; baseline, d 13 to 14; challenge, d 15 to 19; and recovery, d 20 to 26. Treatments in Exp. 1 were TMR based on corn silage with long (L) or short (ST) particle size in a 65:35 forage-to-concentrate (F:C) diet. Treatments in Exp. 2 were TMR based on corn silage with short (SH) or long (LH) particle size in a 65:35 F:C diet with 3.3% (DM basis) orchardgrass hay offered as a supplement to the diet. In both experiments, during the challenge phase cows received a 50:50 F:C diet to initiate SARA. Animals were housed individually, milked twice per day, and fed once per day for 10% refusal rate on an as-fed basis. Data were analyzed using PROC MIXED of SAS. Feeding L and LH diets increased acetate-to-propionate ratio in the rumen, which resulted in the maintenance of a ratio >2 from the start of the SARA challenge through recovery. In Exp. 1, feeding long corn silage TMR resulted in lower milk fat concentration on the third day of the challenge, whereas cows fed short corn silage TMR had lower milk fat concentration on the final day of the challenge compared with d 13. Providing supplemental hay to cows fed TMR based on long or short corn silage in Exp. 2 prevented acidosis when cows were challenged with a high-grain diet. Milk fat concentrations substantially decreased during the challenge phase in both diets supplemented with hay, but feeding LH did not lower milk fat concentrations until d 20 compared with d 17 for cows fed SH. Under the conditions of these experiments, cows selected for shorter particles compared with longer particles, despite the rumen challenge. However, when feeding a 50:50 F:C diet, feeding long corn silage TMR or supplementing the diet with grass hay increased rumen pH, acetate-to-propionate ratio in the rumen, and rate of recovery from SARA.

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Effects of corn silage particle size, supplemental hay, and forage-to-concentrate ratio on rumen pH, feed preference, and milk fat profile of dairy cattle

Abstract

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