Carbohydrates in Dairy Nutrition

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

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

3. 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 Fat Suppl. “Bypass” Protein Minerals and Vitamins Rumen Degradable Protein NFC feeds Grains Byproducts Forages Physical Fiber

4. 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

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

6. What Does Your Forage Customer Want?

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

8. 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

9. JDS: 66, Suppl. 1, 181

10. 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

11. 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

12. DMI & Milk Production

13. 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

14. 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)

15. 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

16. How Many lbs. of Forage DM to Feed?

17. What About NDF Digestibility?

18. 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%

19. DMI & Milk Production

20. 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

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

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

24. 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)

25. 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

26. Two Basic Methods for Measuring Physical Fiber (Particle Size) 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 Penn State Particle Separator (moist, as-fed samples) 19, 8, 1.18 mm, pan; 40 horizontal shakes On-Farm evaluation

27. peNDF (dry sieving) and cow response: chewing activity r2=0.47 (Mertens, 1997)

28. peNDF and Ruminal pH

29. 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

30. 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

31. 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

32. Rumen Degradability of CHO Sources

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

34. Rate of ruminal starch digestion of corn fine ground corn 90 80 60 40 20 0 cracked corn % digested 2 12 24 hours after feeding

35. 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

36. 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