During the last 10 years (Italy) Milk production +19% DM intake +6% It has been necessary to change diet formulation in the attempt to full fill energy requirement and prevent metabolic diseases.

Factors affecting DM intake Animal:size, stage of lactation level of milk production,… Environment: temperature, humidity, adaptation to environment,…. Housing condition: free or tie stall, cleanness, social stress, … Feeding management: feeding frequency, feed allowance, group feeding, TMR, …. Diet composition and formulation: level and balance of nutrients, Forage:concentrate, silages vs. hays,….

DM intake regulation mechanisms Physical: it is limited by the volume of the rumen. Animal will eat until the rumen is full. (fresh high producing cows) Metabolic: when animals full fill energy requirement there are mechanisms involving brain receptors which will induce the sensation of satiety

Cellulose + Hemicellulose+ lignin+ silica+ ….. NDF What is it? “Fiber represents the portion of feeds that is bulky and difficult to digest” Mertens, 2002 JAINEE 85 (6) 1205-1424 NDF = fiber Cellulose + Hemicellulose+ lignin+ silica+ ….. We have always to remember that NDF is NOT an anatomical portion of vegetable material or the sum certain cell wall components. Otherwise we shouldn’t find NDF in animal by product. NDF is a portion of feed that define nutritional characteristics of the feed. Cell wall

Lucas principles: The example of NDS (solubles of ND) Ideal nutritional fraction: digestibility of a fraction is proportional to its own content Intercept =-13.9………= metabolic losses NDF was developed to identify an Ideal Nutritional fraction. As a matter of fact this ideal nutritional fraction is NOT NDF, but the remaining part the Neutral Detergent solubles (NDS). Plotting the content of NDS over the NDS digestibility, we would find a very high correlation. The parameter of this regression line are very important: Slope = 0.98 – means NDS is digestibility is 98% Intercept = -13.9 – negative intercept means metabolic losses Slope = 0.98………= digestibility Van Soest, 1994)

“Fiber represents the portion of feeds that is bulky and difficult to digest ” digestibility =20-70% NDF NDS digestibility ~98% + NDF - Milk + NDF + Chetosis - Fertility

Forage charachteristics Main suppliers of long NDF; They stimulate rumination maintaining optimal ruminal conditions; Maintain butterfat level in milk;

Importance of NDF Intake NDF = 1.1-1.2 % BW Mertens, 1987

Effect of meals and rumination on ruminal pH Orts Mastication Allen, 1997

Chewing is key a factor Cows must chew to reduce particle size The greatest buffering capacity is provided by saliva - pH 8.1-8.3 - NaHCO3 equivalents 12.4 g/L; A cow chewing 720 min/d (12h) produce: 270 L of saliva  3.6 kg NaHCO3 equivalents. Cows must chew to reduce particle size To increase digestibility To reduce retention time of particle in the rumen

Physical effective fiber: is there a requirement for fiber? Ruminants need fiber to manintain rumen health Fiber stimulate chewing, dilutes NFC, maintain good good ruminal pH and rumen motility Excessive chopping can reduce effectiveness of fiber in stimulating chewing

Chewing and particle length

Physically effective (peNDF) Animal response: chewing peNDF = pef X NDF Physical effective factor (pef) varies: From 0 when dietary NDF doesn’t stimulate any chewing to 1 when dietary NDF promote maximum chewing Depends on its initial size and the chewing needed to reduce for digestion Its related to ruminal pH and milk butterfat

Factors that affect peNDF content Chewing activity / kg SS Particle size of NDF Chewing per kg of NDF decreases with the reduction of size of the particles Particles < 1.18 mm (vertical shaking) are not retained by the rumen and have little stimulation of chewing

Factors that affect pef value in different forages Class Dimention (in.) Grass hay Grass haylg Corn sil. Alfa hay Alfa sil Long 1.00 Coarse >2 0.95 0.90 Mid-coarse 1-2 0.85 Medium .5-1 0.80 Medium-fine .25-.5 Fine <.25 0.70 Ground >.25 0.40 Finely ground 0.30

Use of pef to measure effectiveness Determination of NDF content Identification of type of feed and class of particle size Determination of the appropriate pef from tables peNDF = NDF X pef Alfalfa Medium-Fine with 40% aNDF peNDF = 32% = 40 X .80

Requirement for peNDF? (Mertens, 1997)

Requirement for peNDF? (Mertens, 1997)

Penn State Particle size separator

Penn State Particle size separator (Penn State 2000) Sieve 19mm 8mm Pan % of diet 5-15% 25-45% 50-65%

Penn State Particle size separator 19 mm 8 mm Pan

Maintaining a good rumen environment Factors that  rumen pH: high DMI intake high NFC intake high rumen deg. abundant meals Factors that  rumen pH: high NDF intake Freq. small meals Chewing

In high producing cow  NDF and  NFC Factors that  rumen pH: high NDF intake Freq. small meals Chewing Factors that  rumen pH: high DMI intake high NFC intake high rumen deg. abundant meals

Formulation guidelines (Varga et al. 1998) Base NDF content = 30%DM Particles retained by the 19mm sieve= 5-10%: - if less then  2% NDF in the diet - if greater then  2% NDF Conc. distr. twice/d:  1.5 % NDF Conc. distributed several times  1.5 % NDF

Maximize intake maintaning the NDF level of the diet To reduce the filling effect, NDF must leave the rumen: escape the rumen to the lower GI tract; digestion; Escape Diet Feces NDF VFA digested

Maximize intake maintaning the NDF level of the diet Increase NDF digestibility; Escape Diet Feces NDF VFA digested

Effect of NDFD on dairy cows High Low P< DMI, kg/d 23.2 21.8 ** Milk, kg/d 31.8 29.9 Fat, % 3.43 3.35 NS Rumen, pH 6.33 6.36 In situ o vitro NDFD, % 62.9 54.5 -- In vivo NDFD, % 54.8 51.5 The table reports the effect of NDFD on cow performances. This review has used 7 research studies and has corrected the results using NDF content of the diets as covariate. The major effect of an increase on NDFD is an increase in DMI and consequently also an increase in milk production. Since this results are obtain correcting for the NDF content, the increase in NDFD also increase the tdNDF and the TDN of the forage. The association of greater energy content of forages and greater DMI allows cows also to produce more milk. One of the interesting consideration of this data set is the fact that there is a large numerical between the the NDFD expected, using in situ or in vitro values and the NDFD actually measured on the animal. The Authors calculated that the increase of 1 unit of NDFD is associated in and in crease of DMI +0.17 kg/d and FCM 4% of + 0.25 kg/d Oba and Allen, 1999

Maturity and NDFD: alfalfa Veget. late bud P< DM intake, kd/d 26.1 24.4 ** Forage intake, kd/d 17.3 11.9 Concentr. Intake kg/d 8.8 12.4 NDF intake, kg/d 8.5 8.0 NDF intake, %/BW 1.23 1.17 * NDFD, % 55.0 48.6 FCM4%, kg/d 30.6 29.3 Llamas Llamas and Combs, 1990

Bmr model Silage comp. bmr Control NDF, %DM 41.4 42.9 Lignin, % DM 1.3 2.0 Starch, %DM 38.3 35.4 IV TDMD 30h, %DM 83.3 78.2 IV NDFD, % NDF 55.9 46.5 The two silages were used to formulate 4 diets, 2 at 29 %NDF and 2 at 37%NDF Oba and Allen, 2000

Bmr model 29% NDF 38% NDF NDFD bmr Contr P Milk, kd/d 36.9 33.5 33.7 30.4 ** FCM, kg/d 35.6 34.3 35.8 32.6 0.06 Fat, % 3.28 3.67 3.86 3.90 * Fat, kg/d 1.22 1.23 1.32 1.20 Ns Protein, % 3.10 3.15 3.09 3.06 ns Protein, kg/d 1.15 1.05 1.04 0.93 Rum. pH, avg 5.62 5.78 5.73 5.90 Milk production was increased by bmr, but fat content was lower particularly when bmr was included in low NDF diets. Oba and Allen, 2000

NDF Digestibility, % of NDF Legume Silage/Hay Grass Silage/Hay Corn Silage 25 30 35 40 45 50 55 60 65 70 75 NDF Digestibility, % of NDF Poor Fair Average Good Excellent The ranges in NDFD reported here included all possible extremes samples. For examples for corn silage this include very mature corn silage samples that have a highly lignified stalks and low NDFD values as well as brown mid rib samples notorious for high NDFD values 20 Ranges of NDF digestibility for common forages. The NDF digestibility ranges and guidelines are based on a 48 h in vitro true dry matter digestibility assay. (Marshfield Soil and Forage Analysis Laboratory, University of Wisconsin-Madison: 2001 Nutrient Requirements of Dairy Cattle).

Review on NDFD 1 unit increase in NDFD: + 0.17 kg/d DM intake + 0.25 kg/d FCM 4% NDFD High Low P< DMI, kg/d 23.2 21.8 ** Milk, kg/d 31.8 29.9 The table reports the effect of NDFD on cow performances. This review has used 7 research studies and has corrected the results using NDF content of the diets as covariate. The major effect of an increase on NDFD is an increase in DMI and consequently also an increase in milk production. Since this results are obtain correcting for the NDF content, the increase in NDFD also increase the tdNDF and the TDN of the forage. The association of greater energy content of forages and greater DMI allows cows also to produce more milk. One of the interesting consideration of this data set is the fact that there is a large numerical between the the NDFD expected, using in situ or in vitro values and the NDFD actually measured on the animal. The Authors calculated that the increase of 1 unit of NDFD is associated in and in crease of DMI +0.17 kg/d and FCM 4% of + 0.25 kg/d Oba and Allen, 1999

What to do in the future? Increase the quality of forages improving their digestibility. If NDF is more digestible,  intake It allows to use more forages and less concentrates in the diet.