R. E. McQueen1
(Partner: Atlantic Dairy & Forage Institute Inc.)
Abstract: Although unimproved stands of forage consisting of timothy, many other grasses and weeds provide feed for significant numbers of dairy and beef cattle in New Brunswick, little research has been done to assess the nutritive potential of such crops. Silages made from unimproved grass stands or corn were compared as forage sources for lactating dairy cows. Three total mixed rations (TMR) with 50 percent forage and 50 percent concentrate were used where all of the forage was unimproved grass silage (A), 30 percent of the unimproved grass silage was replaced by corn silage (B) and 60 percent of the same grass silage replaced by corn silage (C). The experiment was a 3 X 3 Latin square design with diets A, B and C and three periods of 28 days. One week was allowed for adaptation to each diet. Twenty-four dairy cows in mid to late lactation with an average milk production of 30 kg/day were used with eight cows per treatment. Total milk yield and percent fat, protein and lactose were not affected by increasing the proportion of corn silage in the TMR. Similarly the yield of these components was not affected by feeding corn silage. Total feed dry matter intake also was not influenced by type of silage fed. Cows gained body weight throughout the trial but with no effect due to silage type. Total net energy (Mcal/kg dry matter) derived by the cows from the three diets was A: 1.53, B: 1.47, C: 1.48 with no response due to replacing the grass with corn silage. Milk urea nitrogen values indicated that diet C may have promoted more efficient protein utilization but no response was detected in total milk or its protein component. Unimproved grass forage with proper fertilization is nutritionally comparable to corn silage in TMRs for milk production by cows in mid to late lactation.
1Atlantic Dairy & Forage Institute Inc., 115 Sunbury Drive, Fredericton Junction, NB E0G 1T0