Straw in total mixed rations may affect milk yield

Feeding straw in a TMR mix to lactating dairy cows could reduce feed intake and milk yield, Reading University’s Chris Reynolds told delegates at this year’s British Society of Animal Science Conference, Belfast.

Dr Reynolds said there was little scientific evidence about including straw in milking rations. “While the concept of including limited amounts of straw in milking rations is accepted as being nutritionally sound, there is little scientific evidence available. So for this reason we decided to look at whether straw and it’s method of inclusion affected production and eating behaviour in lactating cows.”

Cows were fed either a control TMR (37% maize silage, 18% grass silage and 45% concentrates), or one of two diets containing 4% straw mixed with a horizontal mixer or the same diet mixed with a vertical mixer which gave a longer chop length.

“We found cows fed straw spent more time eating and as a consequence had a lower eating rate compared to the control diet and these effects were greater for straw diets with longer chop length. Milk yield was also lower where straw was fed.”

And although this confuses what farmers may have been previously told, Dr Reynolds advised farmers to look at fibre levels in the base diet before deciding whether to include straw. “Fibre is vital in a diet and you can get effective fibre from straw. This study may not have seen benefits from straw because NDF in the control was sufficient.”