TECHNICAL ARTICLES Dairy

Fibre for Rumen Health

Forage dry matter consumption should be near 2 percent of the cow’s body weight (BW). Example: 1,350 pound cow x 2 percent = 27 pounds dry matter from forages.

Provide at least 19 to 21 percent acid detergent fiber (ADF) in the total ration. Levels at 17 percent are adequate for high-corn-silage-based rations or herds using total mixed rations.

Provide at least 28 to 30 percent neutral detergent fiber (NDF) levels in the total ration.

Make sure that forages provide at least 21 percent NDF in the total DM. Boost this to 24 percent if corn silage makes up more than one-fourth of total forage dry matter.

Example: If forages in the ration average 44 percent NDF, then 21% / 44% = 47% of the total ration DM should come from forages.

Forage NDF should be about 0.9 percent of body weight. Example: 1,350 pound cow x 0.009 = 12.15 pounds of ration NDF supplied by forages.

Make sure that 65 to 75 percent of the total ration NDF is supplied by forages.

The maximum pounds of total ration NDF should be about 1.25 percent of BW.

Example: 1,350 pound cow x 1,25% = 16.8 pounds NDF, 16.8 pounds/total DMI = upper % NDF in the ration. 16.8 pounds NDF/54 pounds typical DMI = 31% upper limit for %NDF in the total ration. Exceeding these NDF levels may result in lower dry matter consumption.

Provide at least 5 pounds of fiber per day (by weight) that is more than 1-1/2 inches long. Underfeeding of “effective” fiber can cause off-feed and milkfat test problems.

Rumen pH should be above 6.0. A lower pH (more acid) could limit fiber digestion and protein synthesis, and the potential for acidosis could cause reduced feed intake.

Fiber particles should be long enough to stimulate 15 minutes of cud-chewing time per pound of dry matter. This will provide a cow eating 50 pounds of dry matter with 35 to 40 gallons of saliva production to buffer the rumen environment.

Silages should be chopped at 3/8 to 1/2 inch theoretical length of cut (TLC) to ensure that 15 to 20 percent of the silage particles are more than 1-1/2 inches long. Finer chopped silages do pack better in storage structures, but high silage-based rations need adequate particle length to stimulate rumen buffering from cud chewing.

Sodium bicarbonate, or its buffer equivalent, should be added at 0.75 percent of the total ration dry matter, especially in high-corn-silage or high-moisture-corn rations.

Example: 50 pounds dry matter x 0.75% = 0.375 pounds or 6 ounces.

To meet energy needs

Energy density of your top cow ration should be up to 0.78 megacalories (Mcal), net energy of lactation (NE-1) per pound of dry matter in rations containing no added fat, up to 0.80 Mcal NE-1 for rations with added fat and up to 0.82 for rations adding ruminally inert (bypass) fat.

If you’re lead feeding, cows should be eating 6 to 8 pounds of grain at calving. Boost grain 1 to 2 pounds per day, from three days after freshening until you have reached desired grain levels.

Don’t feed more than 5 to 7 pounds of grain at any feeding. This reduces the changes in rumen acidity and prevents off-feed problems.

At less than 40 pounds milk, grain intake for Holsteins and Brown Swiss should be about 1 pound grain (as fed) per 4 pounds milk, between 40 and 70 pounds it should be near 1 pound grain for each 3 pounds milk and above 70 pounds it should be about 1 pound grain for each 2.5 pounds milk. Higher-solids breeds should be receive about 1 pound grain per 3 pounds milk (up to 30 pounds milk), 1 pound grain per 2-1/2 pounds milk (31 to 60 pounds) and 1 pound grain per 2 pounds milk (over 61 pounds).

Grain intake should not exceed 60 percent of ration dry matter.

If too much corn passes undigested into the manure, check grain level, extent of processing and harvest maturity (harvest corn silage at 1/2 to 2/3 milkline). Also check levels of DIP and SIP protein (important to rumen bacteria) and amount of fiber intake that’s more than 1-1/2 inches long (important for the rumen mat).

Provide nonfiber carbohydrate (NFC) levels of 35 to 42 percent in the total ration. NFC (by difference) = 100 – (% crude protein + %NDF + % fat + % ash). Providing excess sugars and easily fermented carbohydrates can result in acidosis and fat test problems.

Provide between 30 to 40 percent starch in the total region.

Manure pH levels should not be less than 6.0. Lower pH (more acid) means excess starch is escaping the rumen and being fermented in the small intestines.

Consider feeding added fat to cows milking more than 75 pounds of 4 percent FCM milk per day (79 pounds, 3.7 percent). As production rises, it becomes more difficult for cows to physically consume enough feed to meet energy requirements. Older cows generally will respond better than 2-year-olds. Fat levels in excess of 5 to 6 percent of the ration are not recommended during the first five weeks of lactation. Supplement the first 1/4 pound in the transition ration, up to a pound at freshening and, if needed, additional fat after five weeks in milk.

Limit total fat to no more than 7-1/2 percent of the ration dry matter.

Example: 4 pounds total fat in the ration per 55 pounds typical DMI = 7.2 %. Too much fat interferes with fiber digestion and lowers fat test.

Provide the same amount of fat in the ration as pounds of milkfat produced.

Example: 100 pounds milk per day x 4% fat = 4 pounds milkfat and 4 pounds total fat in the ration.

Date published: 1993-06-25

Author:
Hoard’s Dairyman

Publication:
N/A