Effects of silage pH on voluntary intake of corn silage

We evaluated effects of silage pH on corn silage intake. Sixteen Holstein heifers (292 kg) were fed control corn silage during a 2-wk preliminary period. This was followed by an 8-wk experimental period in which animals were fed silage neutralized with 0, 2, 4, or 6% sodium bicarbonate (dry matter) added prior to feeding with corresponding pH's 3.72, 4.46, 5.62, and 8.05. Organic matter intake was increased 1.0 and 1.2 kg/day by addition of 2 and 4% sodium bicarbonate versus controls whereas 6% sodium bicarbonate reduced intake .7 kg/day. An equation developed to predict organic matter intake from silage pH was: Y = 3.20 + 3.92 (pH) -.35 (pH)2 with coefficient of determination .66. This equation predicted maximum organic matter intake at pH 5.6. It appears that silage pH is a factor that affects voluntary consumption of corn silage and that pH 5 to 6 is optimum, whereas silage pH above and below may reduce intake.