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OCR for page 3
~ Dry Matter IntaI`e
Dry matter intake (DMI) is fundamentally important in
nutrition because it establishes the amount of nutrients
available to an animal for health and production. Actual
or accurately estimated DMI is important for the formula-
tion of diets to prevent underfeeding or overfeeding of
nutrients and to promote efficient nutrient use. Underfeed-
ing of nutrients restricts production and can affect the
health of an animal; overfeeding of nutrients increases feed
costs, can result in excessive excretion of nutrients into the
environment, and at excessively high amounts may be toxic
or cause adverse health effects.
Many factors affect voluntary DMI. Individual theories
based on physical fill of the reticulorumen (Allen, 1996;
Mertens, 1994), metabolic-feedback factors (Illius and ;[es-
sop, 1996; Mertens, 1994), or oxygen consumption (Kete-
laars and Tolkamp, 1996) have been proposed to determine
and predict voluntary DMI. Each theory might be applica-
ble under some conditions, but it is most likely the additive
effect of several stimuli that regulate DMI (Forbes, 19961.
Feeds low in digestibility are thought to place constraints
on DMI because of their slow clearance from the rumen
and passage through the digestive tract. The reticulorumen
and possibly the abomasum have stretch and touch recep-
tors in their walls that negatively impact DMI as the weight
and volume of digesta accumulate (Allen, 19961. The neu-
tral detergent fiber (NDF) fraction, because of generally
low rates of digestion, is considered the primary dietary
constituent associated with the fill effect.
The conceptual framework for the metabolic-feedback
theory contends that an animal has a maximal productive
capacity and maximal rate at which nutrients can be used
to meet productive requirements (Illius and hyssop, 19961.
When absorption of nutrients, principally protein and
energy, exceeds requirements or when the ratio of nutri-
ents absorbed is incorrect, negative metabolic-feedback
impacts DMI.
An alternative to the metabolic theory is the theory Kete-
laars and Tolkamp (1996) proposed based on oxygen con-
sumption. This theory suggests that animals consume net
energy at a rate that optimizes the use of oxygen and
minimizes production of free radicals that lead to aging.
In addition to the complexity and interaction of the
physical, metabolic, and chemostatic factors that regulate
DMI is the psychologic and sensory ability of animals (Bau-
mont, 19961. Consistently accurate prediction of DMI in
ruminants has been difficult to achieve because a compli-
cated, diffuse, and poorly understood set of stimuli regulate
DMI. For additional discussions and reviews on intake,
see Baile and McLaughlin (19871; Forbes (19951; Ketelaars
and Tolkamp (1992a,b); Mertens (19941; National
Research Council (19871.
In lactating dairy cattle, milk production (energy expen-
diture) usually peaks 4 to 8 weeks postpartum, and peak
DMI (energy intake) lags until 10 to 14 weeks postpartum
(National Research Council, 19891. It has been debated
whether milk production is driven by intake or intake is
driven by milk production. On the basis of energy intake
regulation theory and others (Baile and Forbes, 1974; Con-
rad et al., 1964; Mertens, 1987; National Research Council,
1989), cows appear to consume feed to meet energy needs,
so intake is driven by milk production.
This increase in energy intake in response to energy
expenditure has been clearly shown in the numerous lacta-
tion studies with bovine somatotropin where DMI follows
milk production (Bauman, 1992; Etherton and Bauman,
19981.
EQUATIONS FOR PREDICTING DMI
Lactating Cows
Earlier editions of Nutrient Requirements of Dairy Cat-
tle used various approaches to predict DMI. The 1971
edition (National Research Council, 1971) simply recom-
mended feeding ad libitum during the first 6 to 8 weeks
of lactation, and then feeding to energy requirements after
that for lactating dairy cows. In 1978 (National Research
3
OCR for page 4
4 Nutrient Requirements of Dairy Cattle
Council, 1978), DMI guidelines were established by using
a set of selected studies to create an interpolation table.
Body weight and 4 percent fat-corrected milk were factors
used to estimate DMI, which ranged from 2 to 4 percent of
bodyweight. The 1989 edition (National Research Council,
1989) predicted DMI on the basis of energy requirement
theory and expressed it simply as
DMI (kg) = NEL required (Meal)
NEL concentration of diet (Mcallkg)
where net energy of lactation (NEL) included requirements
for maintenance, milk yield, and replenishment of lost
weight. Suggested modifications for expected DMI were
an 18 percent reduction during the first 3 weeks of lactation
and DMI reduction of 0.02 kg per 100 kg of body weight
for each 1 percent increase in moisture content of the diet
above 50 percent when fermented feeds were being fed.
The DMI guidelines in the 1989 publication were based
entirely on energy balance (that is, over the long term,
energy intake must equal energy expenditure). The method
was not designed to estimate daily DMI in the short term.
It required accurate estimates of changes in body tissue
mass (although the equation was based on changes in body
weight, it assumed that body weight changes equaled
changes in body tissue mass) and accurate estimates of the
concentration of NEL in the diet. Because of changes in
gut fill and inaccurate measurements, short-term changes
in body tissue mass and the energy needed or provided
because of those changes are difficult to measure accu-
rately, as is the concentration of NEL in the diet. To
improve the utility ofthis report, the present subcommittee
decided to include an empirical equation to estimate short-
term DMI.
Several DMI prediction equations have been developed
for use in the field, but only a few have been published
in the scientific literature and tested for accuracy (Fuentes-
Pila et al., 1996; Roseler et al., 1997a). The equations
reported in the literature are based on the principle that
animals consume dry matter to meet energy requirements
or are developed by regression of various factors against
observed DMI. DMI prediction equations that include
animal, dietary, or environmental factors have been devel-
oped by Hotter and Urban (1992) and Hotter et al. (19971.
In the approach used to develop DMI prediction equa-
tions in this edition, DMI prediction is based on actual
data with the inclusion of only animal factors, which would
be easily measured or known. Dietary components were
not included in models for lactating cows, because the
approach most commonly used in formulating dairy cattle
diets is to establish requirements and a DMI estimate
before dietary ingredients are considered. Equations con-
taining dietary factors are best used to evaluate postcon-
sumption rather than to predict what will be consumed.
DMI data published in the Journal of Dairy Science
from 1988 to 1998 (see Chapter 16 for references) and
data from Ohio State University and the University of
Minnesota (May, 1994) were used in evaluating and devel-
oping an equation for lactating Holstein dairy cows. The
data set included 17,087 cow weeks (5962 first lactation and
11,125 second lactation or greater cow weeks), a diverse set
of diets, and studies with and without bovine somatotropin
and encompassed a 10-year period from 1988 to 1997.
Weeks of lactation ranged from 1 to 80; most data were
from 1 to 40 weeks. Equations evaluated were those of
Roseler et al. (1997b) and May (1994) and an equation
reported by Rayburn and Fox (1993) based on DMI values
in the 1989 Nutrient Requirements of Dairy Cattle
(National Research Council, 19891. The best overall predic-
tion equation, based on bias ~—0.27 kg/day) and mean
square prediction error (3.31 kg2/day) was a combined
equation of Rayburn and Fox (1993) and an adjustment
for week of lactation developed by Roseler et al. (1997b).
The equation for predicting DMI of lactating Holstein
COWS iS
DMI (kg/d) = (0.372 X FCM
+ 0.0968 X BW075)
X ( 1 — e( - 0 192 X (W0L+ 3 67))) ( 1-2)
where FCM = 4 percent fat corrected milk (kg/day), BW
= body weight (kg), and WOE = week of lactation. The
term 1 _ e(-0.192x(WOL+3.67)) adjusts for depressed DMI dur-
ing early lactation. For early lactation cows, Equation 1-2
was compared to those developed by Kertz et al. (1991)
using the validation data from Kertz et al. (19911. Dry
matter intake predictions for the first 14 weeks of lactation
are shown in Figure 1-1. Equation 1-2 predicts DMI very
closely to the actual DMI for the first 10 weeks of lactation
and then slightly under predicts DMI thereafter compared
to the general overall predictions of Kertz et al. (19911.
-
>~ 20-
-
15 -
`~>~ — NRC-Equation 1-2
KERTZ Equations
_ ACTUAL
0 2 4
6 8 10 12 14
Week of Lactation
FIGURE 1-1 Dry matter intake prediction of early lactation
cows using Equation 1-2 and Kertz et al. (1991) equations.
OCR for page 5
Dry Matter Intake 5
Equation 1-2 is based entirely on Holstein cows. No
published DMI data were available for developing or modi-
fying the current equation for use with breeds other than
Holstein. For DMI of Jersey cattle, readers are referred
to Hotter et al. (19961.
No adjustment to the DMI equation for parity is needed.
The bias and mean square prediction error for Primiparous
~—0.16 kg/day and 3.05 kg2/day) and multiparous (0.12 kg/
day and 3.20 kg2/day) were similar and were not different
from the overall combined prediction equation statistics.
However, body weight and milk production data appro-
priate for first and second lactation animals must be used in
the equation to estimate DMI accurately for these animals.
The actual DMI, FCM, and body weight data from
animals used to develop and validate the lactating cow
DMI prediction equation are shown in Figure 1-2. Body
304
~ 25
Z _ 20
I 15
10
45 -
35-
~ a, 25-
O ~
15-
700
650
I
I 600
~ 550
o
m 500
450 ~
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
WEEK OF LACTATION
weight change is based on animals becoming pregnant
by week 17 of lactation, so later weights reflect cow and
conceptus gain during the lactation.
The DMI of lactating cows is affected by environmental
conditions outside the thermal neutral zone (5 to 20°C).
Both Eastridge et al. (1998) and Hotter et al. (1997) have
shown DMI decreases with temperatures above 20°C. The
equation used for predicting DMI of lactating cows (Equa-
tion 1-2) in this edition does not include a temperature or
humidity adjustment factor because of insufficient DMI
data outside of the thermal neutral zone to validate equa-
tion modifiers. However, use of lowered milk production
in Equation 1-2 during heat stress periods will reflect the
reduction in DMI commonly observed during heat stress
periods. Eastridge et al. (1998) suggested the following
changes occur in DMI when temperatures are outside of
a
f
1 ~~,,~ ~- ~7~ · Dry Matter Intake
t ~ ~ (Multiparous Cows)
;) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46
WEEK OF LACTATION
b
----a---- Dry Matter Intake
(Primiparous Cows)
—~ + 4% Fat Corrected Milk
<~w~w"~lR,D,,~ (Multiparous Cows)
----I---- 4% Fat Corrected Milk
(Primiparous Cows)
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46
WEEK OF LACTATION
c
+ Primiparous
· Multiparous
FIGURE 1-2 a) Dry matter intake, b) 4 percent fat corrected milk production, and c) body weight change of Primiparous and
multiparous cows during 48 weeks of lactation.
OCR for page 6
6 Nutrient Requirements of Dairy CattIe
the thermal neutral zone; temperatures >20°C, DMI x
(1 - (~°C—20) x 0.0059221) and temperatures <5°C,
DMI/~1 - (~5 - °C) x 0.00464411. Application of the
Eastridge et al. (1998) adjustment factors to a DMI predic-
tion from Equation 1-2 based on lowered milk production
during periods of heat stress may result in an excessively
low prediction of DMI.
Growing Heifers
Published data on DMI of growing heifers weighing
from 60 to 625 kg are sparse. Most research studies used
fewer than 40 animals with a narrow weight range and
limited experimental observation period. Dry matter intake
equations from Quigley et al. (1986) and Stallings et al.
(1985) and calf equation from the Nutrient Requirements
of Beef Cattle (National Research Council, 1996) were
selected for initial evaluation using data from New Hamp-
shire and Minnesota where dietary composition, heifer
growth, and DMI were measured over several months.
The equation of Quigley et al. (1986) and the Nutrient
Requirements of Beef Cattle equation (National Research
Council, 1996) include dietary energy content and body
weight. An equation based only on animal parameters was
preferred to one including dietary components, however,
the only published heifer DMI equation without dietary
components found was from Stallings et al. (19851. On
evaluation, the limited animal parameter equation of Stall-
ings et al. (1985) was found to have a much larger prediction
error, especially for heifers above 350 kg, than either the
Quigley et al. (1986) or the National Research Council's
Nutrient Requirements of Beef Cattle (1996) equation,
which had similar predictive accuracy (Table 1-11.
Because of more current evaluation and a much larger
validation data set than Quigley et al. (1986), the equation
for beef calves from the 1996 Nutrient Requirements of
Beef Cattle (National Research Council, 1996) was further
validated using a data set from Purina Mills, St. Louis,
Missouri. This data set included 2727 observations on
growing heifers ranging from 58 to 588 kg and dietary
net energy-maintenance concentrations from 1.24 to 1.55
Mcal/kg. Based on the fit of the data from the initial evalua-
tion and the validation (Figure 1-3), the National Research
TABLE 1-1 Validation Statistics for Prediction of Dry
Matter Intake by Heifers
Bias, kg/d MSPE,a kg2/d
Equation source
Quigley et al. (1986) - 0.32
Stallings et al. (1985) - 1.32
National Research Councilb (1996) Calves —0.51
1.47
1.90
1.48
aMean square prediction error.
b Nutrient Requirements of Beef Cattle (National Research Council, 1996).
Council equation for beef cattle is recommended for pre-
dicting DMI of growing, nonlactating Holstein heifers.
DMI (kg/d) = (BW075 x (0.2435 x NEM
— 0.0466 x NEM2
— O. 1128~/NEM)
(1-3)
where BW = body weight (kg) and NEM is net energy of
diet for maintenance (Meal/kg).
No adjustments for breed, empty body fat, feed addi-
tives, or anabolic implant were made. There is a consider-
able difference in the DMI predicted from the growing
heifer equation (Eq. 1-3) during late gestation and the
equation used to predict DMI of heifers the last 21 days
of gestation (Eq. 9-1, Chapter 91. To avoid a large discon-
nect in DMI between days 260 and 261 in the model, the
following adjustment factor for Equation 1-3 based on days
of gestation is applied to Equation 1-3: L1 + (~210—DG)
x 0.002514; where DO = day of gestation. The adjustment
is applied for utility in model usage and is not validated.
Reported information on DMI of growing heifers during
the last trimester of pregnancy is nonexistent.
Data for predicting DMI of growing heifers for breeds
other than Holstein or adjusting Equation 1-3 to fit other
breeds was not found. Likewise, there is a dearth of infor-
mation for developing adjustments to Equation 1-3 for
temperature and other environmental factors. Fox and
Tylutki (1998) modified the temperature and mud adjust-
ments listed in the Nutrient Requirements of Beef Cattle
(National Research Council, 1996) for growing dairy heif-
ers, but did not validate the adjustments because of the
lack of data. Hoffman et al. (1994) have shown that season,
type of housing, muddy conditions, length of hair, and body
condition all affect average daily gain; and adjustments to
energy requirements for gain were suggested, but effects
on DMI were not evaluated.
a
NUTRIENTS AND FEEDING
MA N A G E M E N T R E LAT E D T O D M I
OF LACTATING DAIRY COWS
Moisture
Studies reviewed by Chase (1979) and included in the
1989 Nutrient Requirements of Dairy Cattle (National
Research Council, 1989) indicate a negative relationship
between DMI and diets high in moisture content. A
decrease in total DMI of 0.02 percent of body weight for
each 1 percent increase in moisture content of the diet
above 50 percent was indicated when fermented feeds
were included in the ration. In a study using alfalfa silage
to vary dietary DM, Kellems et al. (1991) found a trend
of reduction in DMI with increasing moisture in the diet.
Hotter and Urban (1992) summarized data on 329 lactating
OCR for page 7
Dry Matter Intake 7
~ 12
11
|~ 10
7
5
3-
Prec feted Dry flatter I re~ke
(key d~Y)
FIGURE 1-3 Observed versus predicted dry matter intake of
growing daily heifers using beef calf equation from Nutrient
Requirements of Beef Cattle (National Research Council, 1996~.
cows fed diets ranging from 30 to 70 percent DM and
found that DMI was not decreased when dietary DM
decreased to below 50 percent. Most high moisture feeds
are fermented, and the decrease in DMI when they are
fed is generally thought to result from fermentation end
products and not water itself. When cows were given diets
identical in composition except for the addition of water
(78, 64, 52, or 40 percent DM in diets), DMI of cows
increased linearly (P ~ 0.01) as percentage DM in the
ration increased (Lahr et al., 19831. However, DMI was
not affected by soaking grain mixes in water to achieve a
dietary DM of 35, 45, or 60 percent (Robinson et al., 19901.
Published reports on the relationship between dietary DM
content and DMI are conflicting and no optimum DM
content of the diet for maximum DMI is apparent.
Neutral Detergent Fiber
Mertens (1994) suggested that NDF be used to define
the upper and lower bounds of DMI. At high NDF concen-
trations in diets, rumen fill limits DMI whereas, at low
NDF concentrations energy intake feedback inhibitors
limit DMI. D ado and Allen (1995) demonstrated the fill
relationship in cows during early lactation: 35 percent NDF
diets restrict DMI because of feed bulkiness and rumen
All, but DMI was not limited when 25 percent NDF diets
were fed with or without inert bulk in the rumen. In a
review on feed characteristics affecting DMI of lactating
cattle, Allen (2000) summarized 15 studies and showed a
general decline in DMI with increasing NDF concentra-
tions in diets when diets exceeded 25 percent NDF. At
any particular NDF concentration in the diet, however, a
considerable range in DMI was observed suggesting the
source or sources of NDF in the diet as affected by particle
size, digestibility, and rate of passage from the reticulo-
rumen affect DMI.
The use of NDF as a variable in DMI prediction models
has been reviewed in two studies. Rayburn and Fox (1993)
concluded that DMI prediction was most accurate and
least biased when dietary NDF, particularly from forages,
was included in a model with BW, FCM, and days in milk.
However, in models for predicting DMI of lactating cows
fed high energy diets ranging in NDF from 25 to 42 percent
of DM, less than 1 percent of the variation in DMI was
accounted for by dietary NDF (Roseler et al., 1997a).
Forage to Concentrate Ratio
The ratio of forage to concentrate (F:C) in lactating dairy
cow diets has been reported to affect DMI. Many of the
study results are probably associated with the amount and
digestibility of forage fiber and a propionate limiting effect
on DMI as discussed by Allen (2000), rather than a specific
ratio of forage to concentrate. In alfalfa or orchardgrass
based diets, cows fed concentrate as 20 percent of the
dietary DM produced less milk (P ~ 0.01) than cows fed
diets that contained 40 or 60 percent concentrate (Weiss
and Shockey, 19911. The DMI increased linearly (P ~
0.01) with increasing concentrate in diets regardless of
forage type. Digestible DM also increased linearly (P ~
0.01) with increasing concentrate in the diet. Because
intake of undigested DM was not affected by the amount
of concentrate, rates of passage and digestion and physical
characteristics of the foodstuffs are probable causes of dif-
ferences in DMI.
Llamas-Lamas and Combs (1991) fed diets with three
ratios of forage (alfalfa silage) to concentrate (86:14, 71:29,
and 56:441. DMI was greatest for the diet highest in con-
centrate but similar for the other two diets. Petit and Veira
(1991) fed concentrate at either 1.3 or 1.8 percent of BW
and alfalfa silage ad libitum (F:C, 63:37 and 54:46) to
Holstein cows during early lactation. Both groups of cows
ate similar amounts of silage, but cows consuming the high-
concentrate diet gained weight, and animals consuming
the low-concentrate diet lost weight. Similar results were
observed by Johnson and Combs (19921: cows fed a 74
percent forage diet (2:1 alfalfa silage to corn silage) con-
sumed 2.7 kg less DM per day than cows fed a diet contain-
ing 50 percent forage. In general, increasing concentrate
in diets up to about 60 percent of the DM increased DMI.
Fat
Assuming that cows consume DM to meet their energy
requirements (Baile and Forbes, 1974; Mertens, 1987;
National Research Council, 1989), often less DM is con-
sumed when fat replaces carbohydrates as an energy source
OCR for page 8
8 Nutrient Requirements of Dairy CattIe
in diets (Gagliostro and Chilliard, 19911. Fats may also
decrease ruminal fermentation and digestibility of fiber
(Palmquist and Jenkins, 1980; Chalupa et al., 1984, 1986)
and so contribute to rumen fill and decrease the rate of
passage. Allen (2000) also indicated fats may contribute to
decreased DMI through actions on gut hormones, oxida-
tion of fat in the liver and the general acceptability of fat
sources by cattle.
The response in DMI to the addition of fatty acids in
lactating dairy cattle diets is dependent on the fatty acid
content of the basal diet and source of added fatty acids
(Allen, 20001. For the diets containing 5 to 6 percent total
fatty acids, the addition of oilseeds and hydrogenated fatty
acids to diets resulted in a quadratic effect on DMI with
minimums occurring at 3 and 2.3 percent added fatty acids,
respectively. Additions of tallow, grease, and calcium salts
of palm fatty acids to diets resulted in a general negative
linear decrease in DMI. Smith et al. (1993) reported rumi-
nally active fats have a greater negative effect on DMI,
ruminal fermentation, and digestibility of NDF when diets
are high in corn silage than when they are high in alfalfa hay.
Palmquist and Jenkins (1980) indicated that increased
saturation of fatty acids usually reduces the negative rumi-
nal effects associated with fats. However, Allen (2000)
found that as the proportion of unsaturated fatty acids in
the fat source increased, DMI generally decreased. Most
all of the studies that Allen (2000) cited fed the calcium
salts of palm fatty acids. However, total digestible energy
intake in many of the studies was not reduced, as digestibil-
ity of the calcium salts of palm fatty acids was high and
greater than hydrogenated palm fatty acid comparisons.
While the trend is for a reduction in DMI with the
addition of fatty acids to diets (Allen, 2000; Chan et al.,
1997; Elliot et al., 1996; Garcia-Bojalil et al., 1998; Jenkins
and Jenny, 1989; Rodriguez et al., 1997), some studies
(Pantoja et al., 1996; Skaar et al., 1989) have reported
increases in DMI. Potential reasons for increased DMI
with fat addition is a lower heat increment during periods
of heat stress and/or a reduction in propionate inhibition
on DMI when fat is substituted for grain (Allen, 20001.
COW B E HAVIO R. MANAGE ME NT. AN D
ENVIRONMENTAL FACTORS AFFECTING
FEED INTAKE
Eating Habits and Cow Behavior
D ado and Allen (1994) studied eating habits of lactating
dairy cows housed in a tie-stall barn. Twelve Holstein cows
ranging in milk production from 22 to 45 kg/d were moni-
tored during the ninth week of lactation. The six highest-
producing cows averaged 11 kg more milk per day and
consumed about 6 kg more DM per day than the lowest-
producing six cows. The time spent eating (average, 300
minutes/day) and the number of meals (average, 11/day)
did not differ between the two groups, but the high-pro-
ducing cows consumed more DM per meal than did the
low-producing cows (2.3 vs. 1.7 kg). High-producing cows
ruminate fewer times per day (13 vs. 14.5 times/day) but
ruminate an average of 5 min more per rumination period
than low-producing cows.
Grouping cows according to their nutrient requirements
can decrease the variation in DMI among cows within
the group. The DMI shown in Figure 1-2 illustrates the
difference between primiparous and multiparous cows in
total DMI and pattern of DMI during lactation. Primipa-
rous cows do not peak in DMI as early in lactation, but they
are more persistent in DMI after peak than are multiparous
cows. Thus, primiparous and multiparous cows should be
grouped separately because of differences in DMI and
social hierarchy. Primiparous cows are usually more timid
and of lower social rank in the herd initially, but they
gradually rise in social rank as more cows enter the herd
or as older cows leave (Wierenga, 19901. Phelps and Drew
(1992) reported an increase of 725 kg in milk over a 305-
day lactation for f~rst-lactation animals when grouped sepa-
rately instead of being mixed in with older cows.
Behavior at the feed bunk is often affected by social
dominance. Dominant cows, usually older and larger, tend
to spend more time eating than do cows with a lower social
rank in a competitive situation, such as when bunk space
is restricted (Albright, 19931. Socially dominant animals,
not necessarily the highest producers, tend to consume
more feed at the bunk in these situations (Friend and
Polan, 19741. In a situation of competition for feed, cows
consume slightly more feed but do it in less time per day
than when there is no competition and access to feed is
ample (Olofsson, 19991.
In 1993, Albright (1993) recommended at least 46 cm
of bunk space per cow. Friend et al. (1977) evaluated bunk
spaces of SO, 4O, SO, SO, and 10 cm per cow, for early
lactation cows with mature equivalent productions of 7,700
to lO,000 kg/year. Average time spent at the feed bunk
(3.7 hours/day) did not decrease until only 10 cm of space
per cow was available (Table 1-21. When there was 20 or
10 cm per cow, the correlation of dominance to duration
of eating periods increased. The optimal or critical feed
bunk space needed is probably not a constant number
and will depend on competition between cows, the total
number of cows having access to the feed space, and the
availability of feed over a 24-hour period.
For growing dairy heifers, feed-bunk space requirement
varies with age. Longenbach et al. (1999) found that rapid
growth in growing heifers fed a total mixed diet could be
maintained in young heifers (4 to 8 months old) with 15
cm of bunk space. But, by the age of 17 to 21 months,
OCR for page 9
Dry Matter Intake 9
TABLE 1-2 Effect of Bunk Space Per Cow on
Feeding Behavior and Intake of Early Lactation Cowsa pock, ~ A fib).
Feed Bunk Length Per Cow (cm)
40 30
20
10
Time at feed bunk, h
Correlation of time with
social dominance
Percentage of time at feed
bunk, %
Dally feed intake, kg of DM
3.82 3.73 3.73
0.46 0.32 0.30
21.5 26.9 34.6
17.5
17.6 17.8
3.76
o.67c
51.9
16.9
2.57b
0. 71d
70.6
15.7
a From Fnend et al. (1977).
b Differs from 50 cm feed bunk/cow.
CDiffers from zero (P < 0.05).
Differs from zero (P < 0.01).
feed bunk space needed to be similar (47 cm) to that
recommended for lactating cows.
Cattle prefer mangers that allow them to eat off a smooth
surface in a natural grazing position. Albright (1993) cited
evidence showing cows eating with their heads down pro-
duce 17 percent more saliva than cows eating with their
heads in a horizontal position. Feed-wasting activities asso-
ciated with elevated bunks, such as feed tossing, are elimi-
nated when cows eat with their heads down (Albright,
1993~.
Weather
The thermal neutral zone of dairy cattle is about 5 to
20°C, but it varies among animals. Temperatures below or
above the thermal neutral range alter intake and metabolic
activity. Young (1983) stated ruminants adapt to chronic
cold stress conditions by increasing thermal insulation,
basal metabolic intensity, and DMI. Rumination activity,
reticulo-rumen motility, and rate of passage are also
increased (Young, 1983~. However, in extreme cold, DMI
does not increase at the same rate as metabolism, so animals
are in a negative energy balance and shift energy use from
productive purposes to heat production.
A rise in ambient temperature above the thermal neutral
zone decreases milk production because of reduced DMI.
Hotter et al. (1997) found pregnant multiparous middle-
to late-lactation Holstein cows decreased DMI more (22
percent) than primiparous cows (9 percent) at the same
stage of lactation and pregnancy when subjected to heat
stress. A decrease in DMI up to 55 percent of that eaten
in the thermal neutral zone along with an increase of 7 to
25 percent in maintenance requirement has been reported
for cows subjected to heat stress (National Research Coun-
cil,1981~. Water consumption of cattle increases as ambi-
ent temperature increases up to 35°C, but further tempera-
ture increases decrease water consumption because of
inactivity and low DMI. Similar effects as those observed
under high temperature conditions can be seen in cattle
at temperatures as low as 24°C with high humidity (Cop-
1 ~ Berm\
Feeding Method Total Mixed Ration vs. Individual
Ingredient
The goal of any feeding system or method is to provide
the opportunity for cows to consume the amount of feed
specified in a formulated diet. Considerations in the choos-
ing of a feeding system should include housing facilities,
equipment necessities, herd size, labor availability, and
cost. Nutrients can be effectively supplied by feeding either
a total mixed ration (TMR) or individual ingredients. A
TMR allows for the mixing of all feed ingredients together
based on a prescribed amount of each ingredient. When
consumed as a TMR without sorting of ingredients, more
even rumen fermentation and a better use of nutrients
should occur than feeding of separate ingredients. Compu-
terized or electronic feeders reduce the labor involved in
individual-concentrate feeding and provide an opportunity
to control and regulate concentrate feeding to cows
through several small amount feedings each day. Limita-
tions to feeding forages and concentrates separately are
the forages as they are usually provided free-choice and
the amount fed is usually unknown or individual cow
amounts are calculated from a group average intake. Maltz
et al. (1992) reported that cows fed a TMR or concentrate
by computer feeders did not differ in milk production (32.7
vs. 32.7 kg/d) or differ much in DMI (19.7 vs. 20.4 kg/d)
during the first 20 weeks of lactation. Allocation of concen-
trates through a computer feeder based on milk yield per
unit of body weight was more successful in economizing
on concentrate feeding without losses in milk production
and management of body weight than allocation only by
milk yield.
Feeding Frequency
It has been suggested that increasing the frequency of
offering feed to cows increases milk production and results
in fewer health problems. Gibson (1981) concluded in a
review on feeding frequency that changing from one or
two offerings of feed per day to four increased average
daily gain of cattle by 16 percent and increased feed use
by 19 percent. Improvements in gain or feed use were
greatest when cattle were fed high-concentrate diets. In a
review of 35 experiments on feeding frequency in lactating
dairy cows, Gibson (1984) reported that increasing feedings
to four or more times per day compared to once or twice
increased milk fat percentage by an average of 7.3 percent
and milk production 2.7 percent. Higher milk fat concen-
tration with increased feeding frequency also was reported
by Sniffen and Robinson (19841. The benefit of increased
feeding frequency might be more stable and consistent
OCR for page 10
10 Nutrient Requirements of Dairy Cattle
ruminal fermentation. When Robinson and McQueen
(1994) fed a basal diet two times per day and then a protein
supplement two or five times per day, production and
composition of milk were not affected by the frequency of
feeding protein supplement, but both pH and propionate
concentration in the rumen were higher with five than
with two feedings per day. Klusmeyer et al. (1990) reported
that ruminal fermentation pattern and production of milk
and milk components were not improved by increasing
feedings from two to four times per day. Similar results
were found with the feeding of concentrate two or six times
per day as milk production, milk-component yield, DMI,
or ruminal fermentation characteristics were not affected
(Macleod et al., 19941. Fluctuations in diurnal patterns
of ruminal metabolites probably have to affect microbial
growth and fermentation adversely before a benefit of
increasing feedings to more than two times per day will
be seen.
All of the studies reviewed for feeding frequency
involved the actual offering of new feed to cattle and not
the pushing in of existing feed to the manger. Whether
the act of pushing feed in stimulates the same effects as the
offering of new feed is unknown. In the study of Macleod et
al. (1994), whenever fresh concentrate was offered to the
cows fed concentrate six times per day, cows fed concen-
trate only twice per day would begin eating also, suggesting
the act of feeding, or maybe pushing in feed, has a stimulat-
ing affect on eating.
Sequence of Feeding
Sniffen and Robinson (1984) hypothesized the following
reasons for feeding forages as the first feed offered in
the morning before concentrates. The feeding of highly
fermentable carbohydrates to cows that have been without
feed for over 6 hours could cause acidotic conditions in the
rumen depressing feed intake and fiber digestion. Feeding
foragers) as the first feed in the morning before other
foodstuffs would allow for the formation of a fiber mat in
the rumen and provide buffering capacity in the rumen
from both the forage and the increased salivation associated
with forage consumption. Forages of medium to long chop
length were advocated as they should prolong eating and
thereby increase salivation and reduce particle passage
from the rumen. However, evidence to support this
hypothesis is lacking. In two studies (Macleod et al., 1994;
Nocek, 1992) where legume forages were fed before con-
centrates, no effects on rumen fermentation characteris-
tics, rumen pH or milk production were found. In both
studies, feeding forage after concentrates resulted in a
numerical increase in DMI compared to feeding forage
before concentrate.
Access to Feed
Maximal DMI can only be achieved when cows have
adequate time for eating. Data from D ado and Allen (1994)
indicated early lactation cows (63 days in milk) producing
23 to 44 kg of milk per day fed a TMR ad libitum ate an
average of 5 hours per day. Feed intake occurred during
9 to 13 (average of 11) eating bouts per day that averaged
29 minutes per bout. Mean DMI at each eating bout was
about 10 percent of the total daily DMI, which ranged
from 15 to 27 kg/day. Cows in this study (Dado and Allen,
1994) were housed in tie-stalls and had access to feed 22
of 24 hours per day. This study demonstrates there is a
considerable difference in eating behavior between cows
in a non-competitive feed environment and that the acces-
sibility of feed must be considerably more than the 5 hours
of actual eating time per day. Martinsson (1992) and Mar-
tinsson and Burstedt (1990) found that limiting the access
of feed to 8 hours a day decreased milk production of cows
averaging about 25 kg/day by 5 to 7 percent compared
with cows that had free-choice access to feed.
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Representative terms from entire chapter:
dairy cows
