Carbohydrates in Dairy Nutrition L.E. Chase and T.R. Overton Dept. of Animal Science Cornell University Used with permission from Dairy Herd Management magazine 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 Feed Additives “Bypass” Protein Minerals and Vitamins Rumen Degradable NFC feeds Protein Grains Byproducts Forages Physical Fiber Carbohydrates Comprise 65 - 75% 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 % of starch (MCP per gram of OM) 100 90 80 70 60 50 40 30 20 10 0 100 86 88 Sucrose Pectin 47 NDF Starch (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 Milk Production as Affected by Hay Quality 100.0 Pre Bloom EarlyBloom MidBloom FullBloom 95.0 90.0 Milk, lbs/day 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0 20 30 40 50 60 % Hay 70 80 90 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 - 1999 DMI & Milk Production 75 70 65 60 High dNDF Low dNDF lbs 55 50 45 40 DMI Milk 4% FCM Summary 1 unit of increased NDF digestibility ( i.e. 45 to 46%)= + 0.37 lbs. DMI + 0.51 lbs. milk + 0.55 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? 40 35 30 25 lbs DM 20 15 40 50 60 10 5 0 0.85 0.95 F-NDF Intake, % of BW 1.05 What About NDF Digestibility? Oba & Allen - 1999 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 75 70 65 60 High dNDF Low dNDF lbs 55 50 45 40 DMI Milk 4% FCM Summary 1 unit of increased NDF digestibility ( I.e. 45 to 46%)= + 0.37 lbs. DMI + 0.51 lbs. milk + 0.55 lbs. 4% FCM This may not be a linear response across all levels of NDF digestibility The relationship between corn silage NDF and digestible NDF 90 Digestible NDF, % 80 70 60 50 40 30 20 25 30 35 40 45 NDF, % 50 55 60 NDF30 Distribution in Corn Silage by Chemistry, CVAS 2008 Mean = 60.0 SD = 6.9 N = 3830 50 60 70 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, coarse 60 min/lb of NDF Bermudagrass 68 min/lb Ryegrass 63 min/lb Oat straw 88 min/lb Corn silage 44 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 r2=0.47 (Mertens, 1997) 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 Fastest Slow e st Source Form W heat Steam flaked B arle y H ig h m oisture O ats D ry g round C orn D ry rolled Sorg hum D ry w ho le Ruminal Feed Carbohydrate Fermentation Profile •oat> wheat>barley> corn>milo •grinding, ensiling, steam •how fast and how much Rate of Fermentation sugars Starches and pectin starches celluloses EAT 1 3 5 7 9 11 13 15 Time after Feeding (h) 17 19 21 23 Rate of ruminal starch digestion of corn % digested 90 fine ground corn 80 cracked corn 60 40 20 0 2 12 hours after feeding 24 If there is too much nonfiber carbohydrates or if it breaks down too fast: rumen pH fiber digestion Acidosis Low milk fat off-feed Healthy rumen performance 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