Body Condition Scoring II: Using the Net Energy (NE) System to Improve
Body Condition Score
AS-1198,
December 2000
A. Manuel Encinias,
Extension Associate
Co-Products Initiative
Assessing cowherd energy reserves throughout the year is critical
to maintain production efficiency of in
a cow/calf operation. Body condition scoring (BCS) provides a
good estimate of energy status of a cow. Cows are assigned scores from
1 (emaciated and carrying virtually no fat) to 9 (excessively fat). Once
the body condition of the herd has been determined, an increase in
diet quality and energy density in thin cows (BCS 3 and 4) can be used
to increase body condition (BCS
5 or 6).
The purpose of this guide is to help define the most commonly
used system for expressing energy requirements for beef cows
and energy concentration of feedstuffs, as well as using the system
to improve cow body condition through evaluation of pasture or ration
energy availability.
Net Energy
System
A pound of gain on a thin cow is primarily made up of water
and protein (muscle), whereas a pound
of gain in a fat cow is mostly fat.
An added pound of fat requires
2.25 times more energy than an added pound of muscle. Thus, a
thin cow requires less energy to add a pound of gain than a fleshy cow.
The most commonly used system
for expressing energy requirements in beef cattle and energy
concentration of feedstuffs is the net energy (NE) system. This system
expresses units of energy in megacalories (Mcal), separating units of
energy required for daily maintenance
(NEm) from those needed for gain
(NEg). Energy required for varying stages
of production, such as lactation (NEl) and pregnancy (NEp), can
also be accounted for using the
NE system. For practical purposes, the efficiency of using energy
for lactation and pregnancy is similar to using energy to meet
maintenance requirements.
Tables 1 through 3 provide
necessary information for producers to calculate NE requirements
for cows of varying body weight (BW), production status, and body
condition. Data in Table 1 displays NEm requirements at different cow
body weights. This base requirement is
the amount of energy required to prevent weight loss in a
stress-free environment. These values do not include necessary energy
adjustments for environmental stress
from heat, cold, wind, or mud, which increase maintenance requirements.
Stage of production can greatly affect energy requirements and
influences a cow's ability to increase body condition. Table 2 displays
added energy required during critical periods of lactation and pregnancy.
Table 1. Daily net energy of maintenance (NEm) requirements for
mature beef cows.
--------------------------------------------------------------------
Cow Body Weight (lbs)
----------------------------------------------------
1000 1050 1100 1150 1200 1250 1300 1350 1400
--------------------------------------------------------------------
NEm, Mcal/day* 7.52 7.83 8.14 8.45 8.75 9.04 9.33 9.63 9.91
--------------------------------------------------------------------
*Maintenance requirements include allowance for activity, but do not
include added energy for heat, cold, wind, or mud stress.
Table adapted from Buskirk et al., 1992. Journal of Animal Science
Table 2. Daily net energy of production
(NEl and NEp) requirements for beef cows.
-----------------------------------------------
Lactation - Peak Milk (lbs)
--------------------------
Days after
Calving 11 18 24 31 Pregnancy
-----------------------------------------------
------------ Mcal/day --------------
0-21 2.42 3.87 5.32 6.77 --
22-42 3.40 5.44 7.48 9.52 --
43-63 3.58 5.73 7.88 10.00 --
64-84 3.36 5.37 7.39 9.40 --
85-105 2.95 4.72 6.49 8.26 --
106-126 2.49 3.98 5.47 6.96 --
127-147 2.04 3.26 4.48 5.71 0.33
148-168 1.64 2.62 3.60 4.58 0.63
169-189 1.29 2.07 2.85 3.62 1.17
190-210 1.01 1.46 2.19 2.83 2.03
211-240 -- -- -- -- 3.33
241-280 -- -- -- -- 5.17
-----------------------------------------------
Table adapted from NRC, 1996
Table 3. Net energy for gain (NEg) values for mature
beef cows with varying body condition scores (BCS).
-----------------------------------------------------------
Desired BCS
Present --------------------------------------------------
BCS 1 2 3 4 5 6 7 8 9
-----------------------------------------------------------
------------------- Mcal/lb of gain ---------------
1 -- 1.14 1.31 1.47 1.64 1.8 1.97 2.13 2.29
2 -- 1.47 1.64 1.80 1.97 2.13 2.30 2.46
3 -- 1.80 1.97 2.13 2.30 2.46 2.62
4 -- 2.13 2.29 2.46 2.62 2.79
5 -- 2.46 2.62 2.79 2.95
6 -- 2.79 2.95 3.12
7 -- 3.12 3.28
8 -- 3.45
9 --
-----------------------------------------------------------
Table adapted from Buskirk et al., 1992. Journal of
Animal Science
Practical Application of NE System
This section provides practical application of the NE system to evaluate current and develop future nutritional
programs to ensure energy requirements are met.
Scenario
- Mature British cow (1170 lbs BW)
- Peak milk = 24 lbs/day
- BCS 3 at calving
- Breeding season begins in 80 days
- Desire a BCS 5 at beginning of breeding season
- After calving diet consists of: 80% high quality grass hay,
20% wheat midds
Procedure
1. Determine average BW of cow over the period evaluating:
a. Calculate total gain necessary to increase from BCS 3 to 5
1 BCS change=80
lbs.
2(80 lbs)=160 lbs.
b. Calculate desired BW at breeding
initial BW + total gain to increase BCS = breeding BW
1170 lbs + 160 lbs = 1330 lbs
c. Calculate average BW for period
(initial BW + end BW)/2 = average BW
(1170 lbs + 1330) /2 = 1250 lbs
2. Calculate ADG required to achieve desired BCS.
lbs to BCS 5 + period length (days) = ADG
160 lbs + 80 days = 2 lbs/day
3. Find NEm requirement for average cow body weight (1250 lbs)
from Table 1.
NEm=9.04
Mcal/day
4. Determine average NEl required for lactation (based on peak
milk production = 24 lbs) in Table 2.
(initial period NEl + final period
NEl) :_ 2 = average
NEl
requirement
(5.32 Mcal/day + 7.39
Mcal/day)
:_ 2 = 6.36 Mcal/day
5. Calculate total maintenance requirements for period.
(NEm + NEl)=daily
NEm requirement
(9.04 Mcal/day+6.36 Mcal/day)=15.4
Mcal/day
6. Locate NEg to achieve desired BCS from Table 3 and determine
NE required for calculated ADG for period.
NEgXADG=average
NEg required
1.97 Mcal/lbX2.0 lbs/day=3.94
Mcal/day
7. Calculate dietary concentration of
NEm and NEg.
--------------------------------------------------
Feedstuff DM CP NEm NEg
--------------------------------------------------
% of diet % % Mcal/lb Mcal/lb
--------------------------------------------------
Grass Hay* 80 90 10.8 0.52 0.29
Wheat Midds** 20 90 17.2 0.78 0.53
--------------------------------------------------
*Values converted to as-fed basis from Stock et al.,
1995. Nebraska Cooperative Extension G91-1048-A
**Values converted to as-fed basis from Lardy and
Anderson, 1999. NDSU Extension Service AS-1182
a. Calculate diet NEm and diet
NEg
Feedstuff NEmX% in
diet=NEm/lb of diet
0.52X0.80 = 0.42 Mcal/lb (grass hay contribution)
0.78X0.20 = 0.16 Mcal/lb (wheat midds contribution)
= 0.58 Total Mcal
NEm/lb of diet
Feedstuff NEg X % in diet =
NEg/lb of diet
0.29X0.80 = 0.23 Mcal/lb (grass hay contribution)
0.53X0.20 = 0.11 Mcal/lb (wheat midds contribution)
= 0.34 Total Mcal
NEg/lb of diet
b. Pounds of ration to meet
NEm and NEg requirement
Daily NEm
requirement � dietary NEm concentration=
lbs of diet for maintenance
15.4 Mcal/day � 0.58
NEm Mcal/lb=
26.5 lbs/day for maintenance
Daily NEg
requirement :_dietatry NEg concentration=
lbs of diet for gain
3.94 Mcal/day :_ 0.34
NEg Mcal/lb = 11.6 lbs/day for gain
lbs for maintenance+lbs for gain=Total lbs
of diet needed/day to achieve BCS 5 at breeding
26.5 lbs+11.6 lbs=38.1 lbs of diet
c. Calculate total feedstuffs fed per day
lbs of dietX% of feedstuff in diet=
lbs of feedstuff fed/day
38.1 lbsX0.80 grass hay=30.5 lbs grass hay
38.1 lbsX0.20 wheat midds=7.6 lbs wheat midds
Summary
To achieve BCS 5 by the start of the breeding season
in this example, a cow must consume 38.1 lbs of
the previous ration per day. |
Considerations
Under certain circumstances the required ADG and ration
calculated with the NE system to alter body condition may not work in a
production setting. An animal may be unable to achieve desired gains
or consume enough of the calculated ration in a given time period,
so reformulation with more energy dense feedstuffs may be
necessary. However, also consider that daily gains above 2.5 lbs are difficult
to achieve in a practical setting. In such cases where reformulation is not
the solution, more time is necessary
for the desired condition change
to occur. This further reemphasizes
the importance of evaluating cow body condition throughout the
year so timely changes can be made.
A variety of regional co-product feedstuffs (Table 4) are available
as energy and protein supplements to offset energy deficiencies in
cow diets. Many of these feedstuffs may prove to be less expensive
than common or commercial energy supplements at certain times
during the year.
Table 4. Feedstuffs to use as energy supplements in
cow diets.
----------------------------------------------------------
Feedstuff* DM TDN CP NEm NEg
----------------------------------------------------------
% % % Mcal/lb Mcal/lb
Beet pulp, dried sugar 90 65.0 8.2 0.69 0.44
Beet pulp, wet sugar 25 20.0 2.3 0.19 0.12
Canola seeds** 92 105.9 19.3 1.23 0.89
Canola meal, expeller 90 68.4 36.9 0.72 0.47
Canola meal, solvent 90 62.1 39.2 0.66 0.41
Concentrated separator
byproduct 66 44.2 13.2 0.50 0.28
Corn gluten feed, wet 43 37.8 9.2 0.43 0.29
Corn gluten feed, dry 90 74.7 19.4 0.83 0.56
Field peas, grain 88 79.2 20.8 0.90 0.62
Safflower seeds** 93 84.8 16.3 0.93 0.60
Safflower meal, solv. 92 52.4 23.4 0.51 0.27
Sunflower meal 90 57.6 35.0 0.59 0.32
Sunflower seeds, oil** 95 115.0 17.0 1.35 0.98
Wheat middlings 90 74.7 17.2 0.78 0.53
----------------------------------------------------------
*Values expressed on as-fed basis.
**Whole seeds should be limited to 15 percent of ration.
Table adapted from Lardy and Anderson, 1999. North Dakota
Cooperative Extension AS-1182
Conclusion
The NE system can be a viable option for producers to evaluate
and adjust cow energy reserves throughout the year. Net energy values
for feedstuffs are estimates. Responses such as cow body condition
provide a clearer picture of actual energy concentration in the current
nutrition program and its effects on energy status under certain production
and environmental conditions. When energy supplementation is
necessary, less expensive co-product feedstuffs may prove
economically beneficial in certain regions.
Literature Cited
Buskirk, D.D., R.P. Lemenager, and L.A. Horstman. 1992. Estimation of
net energy requirements(NEm and
NEg)
of lactating beef cows. J. Anim. Sci. 70:3867-3876.
Corah, L.R., R.P. Lemenager, P.L. Houghton, and D.A. Blasi. 1991.
Feeding your cows by body condition. C-842. Kansas State
University Agricultural Experiment Station
and Cooperative Extension Service.
Lardy, G.P. and V. Anderson. 1999. Alter-native feeds for ruminants.
AS-1182. North Dakota State University.
Mathis, C.P. and J.E. Sawyer. 2000.
Beef cow efficiency in the Southwest. GB-217. New Mexico State University.
National Research Council. 1996. Nutrient Requirements of Beef Cattle.
National Academy Press, Washington, DC.
Stock, R., R. Grant, and T. Klopfenstein. 1995. Average composition of
feeds used in Nebraska. G91-1048-A. University of Nebraska.
AS-1198,
December 2000
|
