Carbohydrates in Dairy Nutrition L.E. Chase and T.R. Overton Dept. of Animal Science Cornell University

Used with permission from Dairy Herd Management Used with permission from Dairy Herd Management magazine

Forages Physical Fiber Rumen Degradable Protein NFC feeds Grains Byproducts Minerals and Vitamins “Bypass” Protein Fat Suppl. Feed Additives The Feed Pyramid (Rick Lundquist, 1995) Use the Feed Pyramid to think about how rations should be formulated and cows fed. A basic ration with high quality forages (bottom three sections of pyramid) should support up to 75 lbs (or more) of milk per day. Fats, bypass proteins and feed additives are needed by higher producing cows and should top off the base ration

Carbohydrates Comprise % of the total dry matter consumed by the cow Most important source of energy for rumen bugs Carbohydrates are essential in maximizing microbial protein Provide the major component of NE-l

Maximum Microbial CP Yield (MCP per gram of OM) (Hall and Herejk, 2001)

What Does Your Forage Customer Want?

What Does Your Forage Customer Want? A consistent supply of - High quality - High digestibility - “Effective” physical fiber - Palatable - Well-fermented silage

How Important is Forage Quality? Kawas et. al., Univ. of Wisconsin Used alfalfa hay 4 stages of maturity 4 levels of grain feeding Short-term trial

JDS: 66, Suppl. 1, 181

Alfalfa Maturity - Conclusions Feeding increased grain could not overcome the effects of lower forage quality Milk decreased about 1 lb./day for each day increase in maturity after prebloom Milk decreased by 1 lb./day for each 1% increase in alfalfa NDF content

How Important is Forage Digestibility? Data from 23 research trials Alfalfa hay, alfalfa silage, corn silage, timothy silage, wheat silage Reported NDF dig. (in situ or in vitro) High NDF dig. = 62.9% Low NDF dig. = 54.5% Oba & Allen – Michigan State

DMI & Milk Production

Summary - 1 unit of increased NDF digestibility ( i.e. 45 to 46%)= lbs. DMI lbs. milk lbs. 4% FCM This may not be a linear response across all levels of NDF digestibility

Using NDF to Determine Forage in the Ration NDF is currently the best method to use to set the quantity of forage to be fed. Guideline is between 0.85 and 1.1% of body weight as forage NDF (F-NDF)

Example 1400 lb. cow 0.85% BW = 11.9 lbs. of F-NDF 1.1% BW = 15.4 lbs. of F-NDF Typically, I use about 1% of BW as a starting point

How Many lbs. of Forage DM to Feed?

What About NDF Digestibility?

Oba & Allen Data from 23 research trials Alfalfa hay, alfalfa silage, corn silage, timothy silage, wheat silage Reported NDF dig. (in situ or in vitro) High NDF dig. = 62.9% Low NDF dig. = 54.5%

DMI & Milk Production

Summary - 1 unit of increased NDF digestibility ( I.e. 45 to 46%)= lbs. DMI lbs. milk lbs. 4% FCM This may not be a linear response across all levels of NDF digestibility

NDF30 Distribution in Corn Silage by Chemistry, CVAS 2008 Mean = 60.0 SD = 6.9 N = 3830

Physically effective NDF peNDF  Related to physical properties of NDF that stimulate chewing and establish rumen digesta mat Animal response = chewing activity

peNDF and Chewing Activity (cont.) Cows only chew ~10-11 h/d (Welch, 1982) 88 min to chew 1 lb of NDF from oat straw  Or, 1.5 h Only takes 6.8 lb straw NDF to reach cow’s capacity (or, 8 lb of straw DM)! Explains response to 1 lb supplementation (or to bedding)

Importance of NDF and Chewing Activity Chewing data set (Mertens, 1997)  Equivalent particle length  Alfalfa, coarse60 min/lb of NDF  Bermudagrass 68 min/lb  Ryegrass63 min/lb  Oat straw88 min/lb  Corn silage44 min/lb

Two Basic Methods for Measuring Physical Fiber (Particle Size) Penn State Particle Separator (moist, as-fed samples) 19, 8, 1.18 mm, pan; 40 horizontal shakes On-Farm evaluation Dry sieving Ro-Tap (dried sample, standard procedure for peNDF) 19, 13, 9.5, 6.7, 4.75, 3.35, 2.36, 1.18, 0.6 mm; shakes for 10 min Laboratory procedure

peNDF (dry sieving) and cow response: chewing activity (Mertens, 1997) r 2 =0.47

peNDF and Ruminal pH

Positive Impacts of Digestible NDF Increased DMI Increased Energy Intake Higher ruminal pH Increased A:P No lactic acid Greater MCP production Less need for RUP supplements More constant supply of absorbed nutrients

NFC (Non-Fiber Carbohydrates) 4 basic categories Organic acids (no energy for bugs) Sugars Starch Neutral-detergent soluble fiber (pectin's, beta-glucans, fructans, etc.) Is a calculated value

Nonfiber Carbohydrates All NFC are NOT created equal! Chemically & nutritionally diverse Different effects on cow health and performance NFC = 100 – (NDF+CP+EE+Ash) NFC = 100 – ((NDF-NDICP) +CP+EE+Ash) NSC = sugars + starch  directly measured General recommendation for NFC 37 to 42% of DM

Rumen Degradability of CHO Sources

sugars Starches and pectin starches celluloses oat> wheat>barley> corn>milo grinding, ensiling, steam how fast and how much

Rate of ruminal starch digestion of corn fine ground corn cracked corn hours after feeding % digested

rumen pH fiber digestion Acidosis Low milk fat off-feed Healthy rumen performance If there is too much nonfiber carbohydrates or if it breaks down too fast:

Summary Carbohydrates are the key to providing energy for both microbial bug growth and energy for the cow Structural (fiber) carbohydrates stimulate chewing and rumination Non-structural (sugars, starch) provide rapidly available energy in the rumen but can also lower rumen pH