|Olmos Colmenero, J|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2006
Publication Date: 3/1/2007
Citation: Broderick, G.A., Brito, A.F., Olmos Colmenero, J.J. 2007. Effects of feeding formate-treated alfalfa silage or red clover silage on the production of lactating dairy cows. Journal of Dairy Science. 90:1378-1391. Interpretive Summary: Alfalfa forage often is fed to dairy cows as silage rather than hay because silage harvesting requires much less manual labor. Much of the protein in alfalfa silage is broken down in the silo to nonprotein nitrogen (NPN), which is used less efficiently by cows than intact protein. This can lead to increased urinary nitrogen excretion and can contribute to environmental pollution. Previously we found that treating alfalfa silage with formic acid reduced NPN formation and improved its protein value for the dairy cow. An enzyme naturally present in red clover results in this forage yielding silage containing much less NPN than alfalfa. Also, we saw greater energy digestion in red clover than alfalfa in an earlier experiment. Therefore, red clover silage may be better forage for dairy cows than alfalfa silage. Two feeding studies were conducted that compared 2 alfalfa silages (one normal silage and one treated with a solution containing formic acid) to 2 red clover silages (one with the same amount of fiber as alfalfa and one with the same amount of protein as alfalfa). The formic acid treatment reduced NPN in alfalfa silage by 15%; red clover silage had 40% less NPN than alfalfa silage. In the first experiment testing these silages, cows fed formic acid-treated alfalfa produced more milk and milk protein than cows fed the a normal silage or the red clover with the same amount of fiber as alfalfa. In the second experiment, there was no advantage to treating alfalfa with formic acid, but cows produced more milk and milk solids (protein, fat and lactose) when fed either of the 2 alfalfa silages rather than either of the 2 red clover silages. Protein digestibility also was lower on red clover silage in both studies. Although digestibility of the energy and fiber in red clover were 11% and 45% greater than alfalfa, this extra energy was deposited as fat on the cows bodies rather than being used to produce milk. On the other hand, concentrations of ammonia in the rumen (the first compartment of the cows stomach) and urea in milk were lower when cows were fed red clover in both experiments. This means that absorbed protein was being used more efficiently when cows were fed red clover. This research indicates that the protein and energy in red clover silage that are absorbed by the cow are both used more efficiently than that in alfalfa silage. However, digestion of red clover protein is depressed and this may impair utilization of both its protein and energy. If protein digestibility in red clover could be improved, then it might be possible to get more complete utilization of its extra energy. This would improve production efficiency, reducing nitrogen levels in manure and the nutrients lost to the environment from dairy farms.
Technical Abstract: In trial 1, 15 Holsteins were fed 3 total mixed rations (TMR) with 33% neutral detergent fiber (NDF) in 3 x 3 Latin squares (28 d periods). Two TMR contained (dry matter basis): 40% control alfalfa silage (CAS) or 40% ammonium-tetraformate treated alfalfa silage (TAS), 20% corn silage (CS), 33% high-moisture shelled corn (HMSC), 6% solvent-extracted soybean meal (SSBM), and 18% crude protein (CP); the third TMR contained 54% red clover silage (RCS), 6% dried molasses, 33% HMSC, 6% SSBM, and 16.3% CP. Silages differed in NPN and acid detergent insoluble N (ADIN) (% of total N): 50 and 4% (CAS); 45 and 3% (TAS); 27 and 8% (RCS). Replacing CAS with TAS increased intake, yields of milk, fat-corrected milk (FCM), protein, and SNF, and apparent DM and N efficiency. Replacing CAS with RCS increased intake and N efficiency but not milk yield. Replacing CAS or TAS with RCS lowered milk urea N (MUN), increased apparent digestibility, and diverted N excretion from urine to feces. In trial 2, 24 (8 ruminally cannulated) Holsteins were fed 4 TMR in 4 x 4 Latin squares (28 d periods). Diets contained the CAS, TAS and RCS (RCS1) fed in trial 1 plus an immature RCS (RCS2; 29% NPN, 4% ADIN). The CAS, TAS, and RCS2 diets contained 36% HMSC and 3% SSBM and the RCS1 diet contained 31% HMSC and 9% SSBM. All TMR had 50% legume silage, 10% CS, 27% NDF, and 17-18% CP. No differences were observed between cows fed CAS and TAS. Intake of DM and yields of milk, FCM, fat, protein, and SNF, and milk protein content, all were greater on alfalfa silage versus RCS. Blood urea N, MUN, ruminal ammonia, and total urinary N excretion, were lower on the RCS, suggesting better N utilization on lower NPN silage. Apparent N efficiency tended to be higher for cows fed RCS but there was no difference when N efficiency was expressed as kg of milk yield per kg of total N excreted.