|Hymes Fecht, Ursula|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2012
Publication Date: 1/15/2013
Citation: Hymes Fecht, U.C., Broderick, G.A., Muck, R.E., Grabber, J.H. 2013. Replacing alfalfa or red clover silage with birdsfoot trefoil silage in total mixed rations increases production of lactating dairy cows. Journal of Dairy Science. 96(1):460-469.
Interpretive Summary: Because of its high total protein content, alfalfa is the major legume forage fed to U.S. dairy cows. Alfalfa is increasingly harvested as silage rather than dry hay because ensiling is faster and requires less physical labor than hay-making. Birdsfoot trefoil is a legume forage with similar protein content as alfalfa. Birdsfoot trefoil also contains condensed tannins that bind plant proteins, reducing protein breakdown in both the silo and the rumen, the first compartment of the cow’s stomach. Presence of tannis suggests that birdsfoot trefoil could be harvested as silage and, when fed to dairy cows, result in more efficient use of the dietary protein. Red clover is a third legume forage that has been reported to produce silage with better protein and energy utilization than alfalfa silage. Improving protein efficiency in milk production would reduce both feed costs and nitrogen pollution of the environment. Silages were made from harvested birdsfoot trefoil that contained three different levels of condensed tannins. These were compared to alfalfa and red clover silages as the main dietary forage for lactating dairy cows. The five experimental diets contained similar amounts of all ingredients except the legume silage. Cows ate the same amount of feed, regardless of the forage source in the diet. However, cows yielded more milk, energy-corrected milk, fat, protein, and lactose (milk sugar) when fed a diet containing one of the birdsfoot trefoil silages compared to alfalfa or red clover silage. Moreover, protein efficiency (milk protein/protein consumed) was 26% when cows consumed birdsfoot trefoil compared to 21% when they consumed alfalfa or red clover silage. Milk urea, higher concentrations of which indicate lower protein utilization, was lowest on the two birdsfoot trefoils with highest tannin content. This research indicates that replacing silage made from alfalfa or red clover with birdsfoot trefoil silage will increase production of milk and milk components by lactating dairy cows. This research also indicates that the presence of condensed tannins in birdsfoot trefoil reduces excessive protein breakdown in both the silo and the rumen, thus improving protein utilization by the dairy cow. Dairy farmers feeding birdsfoot trefoil silage will benefit from improved protein efficiency and will spend less money on supplemental feeds. Moreover, greater protein efficiency in dairy production means less nitrogen will be lost to the environment and dairy production will be more sustainable in the U.S. landscape.
Technical Abstract: The objective of this study was to compare effects of feeding silage made from birdsfoot trefoil (BFT), selected for low (LBFT), normal (NBFT) and high (HBFT) levels of condensed tannins (CT), to feeding silage made from alfalfa (AL) or red clover (RC) on milk production and nutrient utilization in dairy cattle. Twenty-five multiparous Holstein cows (5 fitted with ruminal cannulae) were blocked by days-in-milk and randomly assigned within blocks to incomplete 5 x 5 Latin squares. Diets contained (dry matter [DM] basis) about 60% AL, 50% RC, or 60% of one of the 3 BFT; the balance of dietary dry matter (DM) was largely from high-moisture corn plus supplemental crude protein (CP) from soybean meal. Diets were balanced to approximately 17% CP and fed for four 3-wk periods: production data were collected during the last wk of each period. There were no differences in DM intake or milk composition due to silage source, except milk protein content was lower on RC. Yields of milk, energy-corrected milk, fat, protein, lactose, and SNF were all greater on the 3 BFT diets than on diets containing AL or RC. Moreover, milk-N/N-intake was higher on BFT silages (mean: 26%) than AL and RC (mean: 21%). Concentrations of milk urea nitrogen were lower on NBFT and HBFT. Urinary urea-N excretion was highest on AL, lowest on NBFT, and intermediate on the other silages. Apparent digestibility of DM, organic matter, neutral detergent fiber, ADF and hemicellulose were all highest on RC; ruminal concentrations of ammonia and free AA were the lowest. Ruminal branched-chain volatile fatty acid levels were lowest on RC and HBFT and highest on AL. Greater nutrient digestibility on RC silage did not translate into higher yields in this trial. Overall, diets containing BFT silage supported greater production than diets containing silage from AL or RC. The results indicated that feeding BFT, or other legume silages containing CT, can enhance performance and N utilization in lactating dairy cows.