1. 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.

2. 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,….

3. 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

4. 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)
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

5. 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 = – negative intercept means metabolic losses
Slope = 0.98………= digestibility
Van Soest, 1994)

6. “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

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

8. Importance of NDF
Intake NDF = % BW
Mertens, 1987

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

10. Chewing is key a factor Cows must chew to reduce particle size
The greatest buffering capacity is provided by saliva - pH 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

11. 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

12. Chewing and particle length

13. 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

14. 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

15. 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

16. 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

17. Requirement for peNDF?
(Mertens, 1997)

18. Requirement for peNDF?
(Mertens, 1997)

19. Penn State Particle size separator

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

21. Penn State Particle size separator
19 mm
8 mm
Pan

22. 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

23. 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

24. 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

25. 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

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

27. 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 kg/d and FCM 4% of kg/d
Oba and Allen, 1999

28. 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

29. 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

30. 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

31. 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).

32. Review on NDFD 1 unit increase in NDFD: + 0.17 kg/d DM intake
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 kg/d and FCM 4% of kg/d
Oba and Allen, 1999

33. 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.