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Energy & Protein
Nutrition
Of Goats |
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John W. Niver
Tennessee Farmers Cooperative
LaVergne, TN
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Presented at the 2005
Nutrition Conference sponsored by Department of Animal
Science, UT Extension and University Professional
and Personal Development The University of Tennessee.
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On a world basis goats
have provided food and fiber for many people for centuries.
This extensive usage of goats to help sustain human
life has provided us with many different breeds and
biotypes adapted to a variety of environments and
production needs. During much of this time goats have
survived and produced due to their own selective intake
of plant materials or with the aid of caretakers who
forced them to consume materials that were not utilized
by man or other economically important animals. At
times they were provided feeds based on scientific
data from other species, that had improved performance.
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The 1981 publication
Nutrient Requirements of Goats (NRC 1981) was one
of the first references to compile known research
into a comprehensive document listing the nutritional
requirements for goats in various stages of production.
This document gained prominence and is still used
as a reference for goat nutritional requirements.
Two statements in the introduction of this publication
illustrate the challenges that existed and still exist
when attempting to address the nutritional requirements
of goats. “It is increasingly evident that despite
similarities to sheep and cattle, goats exhibit significant
differences in grazing habits, physical activities,
water requirements, feed selection, milk composition,
carcass composition, metabolic disorders and parasites,”
Also the authors state “this first NRC report
must be considered within the limits of available
knowledge and refinements are reserved for subsequent
editions as the literature of goats improves”.
Continued study of the Nutrient Requirement of Goats
(NRC1981) establishes that the authors understood
the importance of prioritizing the order of establishing
nutrient requirements and is illustrated by this statement,
“Efficient utilization of nutrients depends
on an adequate supply of energy, which is of paramount
importance in determining the productivity of goats.”
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ENERGY |
Maintenance |
Citing 10 references a value of 101.38 kcal ME/kgW0.75
(424 kJ) was established as the maintenance energy
requirement for goats with no distinction as to
age, stage of growth, maturity or biotype (NRC 1981).
As most of you are aware subsequent editions of
the Nutrient Requirements of Goats have not been
published. Therefore, this value has remained the
U S basis for establishing many feeding programs.
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In a recent publication
Luo et al.(2004) utilized a database which included
80 treatment means representing 466 animals and concluded
that BW0.75 is an appropriate scaler of goat energy
requirements. Utilizing this database he estimated
the ME maintenance requirement of goats consuming
at near or above maintenance to be 431 kJ/kg BW0.75.
We can see that this expanded database has made only
a small increase in the proposed maintenance energy
requirement. However, when Luo et al. (2004b) predicted
energy equirements for maintenance and gain for preweaning,
growing and mature goats by regressing metabolizable
energy intake against average daily gain he arrived
at different values. ME maintenance requirements were
predicted to be 485, 489, 580, 489 and 462 kJ/kg BW0.75
for preweaning, growing meat, growing dairy, growing
indigenous and mature goats. With this information
based on more data and a better understanding that
the biotype of the goat to be fed influences their
maintenance energy needs, we should have a better
opportunity to develop diets to optimize performance.
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Growth |
Dietary energy decisions
when formulating feeding programs for weight gain
have been fairly simple since metabolizable energy
required for weight gain was estimated from three
experimental values and established at 7.25 kcal ME/g
(30.33 kJ) of gain (NRC 1981) for all rates of gain
and with no differentiation as to biotype or growth
stage. Luo et al. (2004b) have also predicted the
metabolizable energy requirements for gain for the
same classes of goats for which they predicted MEm.
Their values are 13.4, 23.1, 23.1, 19.8, and 28.5
kJ/g gain for preweaning, growing meat, growing dairy,
growing dairy, growing indigenous and mature goats.
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These values make
it obvious that growth status and biotype are critical
inputs when establishing energy inputs to attain a
desired level of performance. |
Activity |
“While activity
can have a significant influence on the energy requirements
of animals there is insufficient data available to
make precise estimates of the amount of energy that
will be required for any specific amount of activity”(
NRC 1981). NRC applied percentage increases to the
ME requirement for basic maintenance to account for
the energy costs of activity. For light activity under
intensive managed grazing a 25 percent increment above
maintenance was suggested. In situations with semiarid
range pasture and on slightly hilly land, a 50 percent
increment was used. For mountainous pastures, or grazing
sparsely vegetated grassland increasing the basic
ME maintenance by 75 percent was suggested. In a 2004
publication Sahlu et al. provide a detailed table
with diet quality, distance traveled, terrain, and
grazing plus walking time to suggest multiples of
the ME requirement for maintenance may range from
0.034 to a high of 0.838. However, they state in the
text accompanying this table “there are not
presently published data available to assess the accuracy
of this simple system”. |
Lactation |
Energy requirements for milk production will certainly
be more readily applied to dairy goats since production
is easily measured, but it is also critical for
other biotypes if we are to attain optimum kid weaning
weights from these animals. Again, referring to
the prominent publication Nutrient Requirements
of Goats (NRC 1981) a value of 1246.12 kcal ME/kg
(5213.77 kJ) of 4.0 percent fat corrected milk is
utilized. This value was felt to be valid for milk
with fat ranges from 2.5 to 6.0 percent. Utilizing
data from 44 studies with 243 treatment mean observations,
Nsahlai et al. (2004a) estimated the requirement
and efficiency of use of ME for milk production.
Since the value employed for ME maintenance influences
the derived value for ME lactation more than one
source of estimation was evaluated. When he used
the recent ME m derived from estimates of Luo et
al. (2004a), dietary ME for milk production was
5224 and 4882 kJ/kg fat corrected milk without and
with correction for ME required for excretion of
excess nitrogen.
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Pregnancy |
While it is recognized
that the later stages of pregnancy require additional
energy for fetal growth there is very little data
specifically for goats to establish a requirement.
NRC (1981) incorporates a value of 0.80 Mcal ME/day
as a suggested increase during the last two months
of pregnancy. This value includes an additional 20%
allowance for multiple births. Sahlu et al. (2004)
in Table 15 provides estimated daily requirements
of ME for pregnancy in ten day increments from 91
to 150. This table further delineates estimates for
ME needed based on expected birth weight and one,
two or three kids. |
PROTEIN |
Maintenance |
Proteins are the principal
building blocks of the animal body and as such are
needed continuously. We are reminded in (NRC 1981)
that “two types of biologically determined protein
requirements have been reported. These pertain to
minimum and maintenance levels which must not be confused”.
Citing five publications a mean value of 2.03 g of
total protein /kgW0.75 was suggested for maintenance
in the 1981 NRC text. However, this publication utilized
a calorie –to-protein ratio of 1 Mcal DE to
32 g total protein when establishing the recommendations
in Table 1. More recently Luo et al. (2004a) utilized
observations from 73 publications between 1973 and
2003 to determine a requirement for metabolizable
protein for maintenance. By regressing metabolizable
protein intake against ADG these researchers established
a requirement of 3.07g/kgBW0.75 for maintenance of
all biotypes of growing goats. |
Growth |
Using the calorie: protein
ratio described above and the results from three
references, the value of 0.284 grams of total protein
per gram gain was used in the Nutrient Requirements
of Goats (NRC 1981) to develop the protein requirements
for growth shown in Table1. Using regression analysis,
as they did for the protein requirement for maintenance,
Luo et al. (2004b) determined the metabolizable
protein requirement for body weight gain to be 0.404
g/g of gain for meat goats and 0.290 g/g of gain
for dairy and indigenous biotypes. These researchers
further advise that since metabolizable protein
intake may not have been more limiting to growth
than ME intake that these estimates be considered
as maximum requirements rather than averages.
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Activity |
As addressed in the
Nutrient Requirements of Goats (NRC 1981), the energy
requirements for activity have not been determined
experimentally, therefore the levels listed in Table
1 were derived from protein to calorie ratios. Since
energy requirements were established by percentage
increment increases for the three levels of activity,
listed protein requirements for activity follow the
same percentage increases. Recent publications reviewed
do not address the influence of activity on protein
requirement so no additional discussion will be presented.
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Lactation |
Nsahlai et al. (2004) utilized 173 treatment mean
observations of lactating goats to determine metabolizable
protein requirements. As a result these researchers
suggest the requirement for protein for lactation
is 1.45 grams of metabolizable protein per gram
of milk protein.
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The protein requirement for lactation suggested
in the Nutrient Requirements of Goats (NRC 1981)
was based on a digestible crude protein system for
dairy cattle (NRC 1978) due to a lack of adequate
data from studies with lactating goats. This method
of calculation resulted in a suggested requirement
of 72 grams of total crude protein per kilogram
of milk (NRC 1981).
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As shown in Table A, additional data has indicated
a reduction of over 15% in the recommended protein
intake for maintenance for mature goats from the
1981 NRC level.
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However, estimated energy requirements have been
increased almost 9%. These changes can be attributed
to a much larger database for calculating the values
but, also a better understanding of the partitioning
of nutrients to various body functions.
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The nutrient requirements of growing goats (Table
B) show a different trend than those of mature animals.
Protein recommendations increase by over 45% while
energy recommendations increase very little. However,
it must be remembered that energy requirements are
based on minimal activity needed to secure feed
and the actual requirement may very.
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While the 2004 data increases the information
available to make decisions concerning expected
performance from a wide variety of feeding conditions.
It also enhances our understanding of goat biotype
influence on energy and protein requirements it
also highlights the need to better understand the
feeds we are using if we expect growth performance
from meat type goats. Recent published and unpublished
data establishes this need more dramatically.
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Moore et al. (2002) reported in a study evaluating
by-product feeds for meat goats that animals with
an initial weight of 24.7 kg consuming orchardgrass
hay averaged 905 g per day (3.2%BW) of dry matter
(DM) intake. These animals were fed for 72 days
and had an ADG of 33 g. The orchardgrass hay which
contained 10.7% crude protein (C P) and 36.8% ADF
on a
DM basis was supplemented with soybean meal to bring
the consumed C P to 12.25%. This is in contrast
to a more recent study (Hall 2005) in which meat
type goats consumed a mixed grass hay containing
10.6% C P and 39.9% ADF at 2.5% BW. Their ADG was
109 g.
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The 1981 NRC has been an excellent source of information
concerning goat nutritional requirements and should
not be ignored. However, the tremendous amount of
information, based on additional data, available
in the 2004 publications referenced should be considered
when evaluating or developing new goat feeding programs.
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| Table A. Energy & protein
requirements of a 70 kg mature goat |
NRC |
1981 |
2004 |
ME mJ
Crude Protein g
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10.26
96.3 b
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11.18a
81.7c |
a based on Luo et al. (2004a)
value of 462 mJ ME/ kgW0.75
b NRC (1981) C P requirement = Mcal DE * 32
c table 7 Sahlu (2004) converted to crude protein utilizing
NRC 1996 |
| Table B. Energy & protein
requirements a of a 20 kg growing kid |
| NRC |
1981 |
2004 |
ME mJ
Crude Protein g |
5.53
51.76
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5.69 b
76.5 c |
a 50 g gain
b 2004 requirements for energy based on doelings and
wethers
c metabolizable protein converted to crude protein utilizing
NRC 1996 |
Literature Cited |
Hall, R. E. 2005. Personal communication.
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Moore, J. A., M. H. Poore, and J. M. Luginbuhl.
2002. By-product feeds for meat goats: Effects on
digestibility, ruminal environment and carcass characteristics.
J. Anim. Sci. 82: 1752-1758.
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NRC, 1978. Nutrient Requirements of Dairy Cattle
5th ed. National Academy Press, Washington D.C.
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NRC, 1981. Nutrient Requirements of Goats: Angora,
Dairy and Meat Goats in Temperate and Tropical Countries.
National Academy Press, Washington D.C
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NRC, 1986. Nutrient Requirements of Beef Cattle.
7th ed. National Academy Press, Washington D.C.
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Luo, J., A. L. Goetsch, I. V. Nsahlai, Z. B. Johnson,
T. Sahlu, J. E. Moore, C.L. Ferrell, M. L. Galyean
and F. N. Owens. 2004, Maintenance energy requirements
of goats: predictions based observations of heat
and recovered energy. Small Ruminant Research 53,
221-230.
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Luo, J., A. L. Goetsch, I. V. Nsahlai, T. Sahlu,
C.L. Ferrell, F. N. Owens, M. L. Galyean J. E. Moore
and Z. B. Johnson. 2004a, Metabolizable protein
requirements for maintenance and gain of growing
goats. Small Ruminant Research 53, 309-326.
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Luo, J., A. L. Goetsch, T. Sahlu, I. V. Nsahlai,
Z. B. Johnson, J. E. Moore, M. L. Galyean, F. N.
Owens and C.L. Ferrell. 2004b. Prediction of Metabolizable
energy requirements for maintenance and gain of
preweaning, growing and mature goats. Small Ruminant
Research 53, 231-252
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Nsahlai, I. V., A.L. Goetsch, J. Luo, Z. B. Johnson,
J. E. Moore, T. Sahlu, C.L. Ferrell, M. L. Galyean
and F.N. Owens. 2004. Metabolizable protein requirements
of lactating goats. Small Ruminant Research 53,
327-337.
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Nsahlai, I. V., A.L. Goetsch, J. Luo, Z. B. Johnson,
J. E. Moore, T. Sahlu, C.L. Ferrell, M. L. Galyean
and F.N. Owens. 2004a. Metabolizable energy requirements
of lactating goats. Small Ruminant Research 53,
253-273.
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Sahlu, T., A. L. Goetsch, J. Luo, I. V. Nsahlai,
J. E. Moore, M. L. Galyean, F.N. Owens, C. L. Ferrell
and Z. B. Johnson. 2004, Nutrient requirements of
goats: developed equations, other considerations,
and future research to improve them. Small Ruminant
Research 53, 191-219.
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