Note: Descriptions are shown in the official language in which they were submitted.
CA 02536548 2006-02-14
Method of Enhancing Reproductive Function of Mammals by Feeding of Conjugated
Linoleic Acids
FIELD OF THE INVENTION
The present invention relates generally to the field of fertility of Mammals
and more
particularly provides compositions and methods for improving the fertility of
lactating
mammals including cattle.
BACKGROUND OF THE INVENTION
Poor fertility in cattle is estimated to cost $1 billion annually in the Us.
It is useful for
fanners to synchronize the estrus of animals such as cattle (both dairy and
beef) sheep, goats,
horses, or the like where artificial insemination is practiced. By way of
example, dairy cows
must be impregnated once a year to maintain a lactation cycle in which milk is
produced for
ten months at a time with two month rest periods in between during which the
cow is dry.
Given the gestation period of a dairy cow, the objective is to impregnate the
cow within 83
days after calving. The efficient management of a dairy herd thus requires
that the cows be
maintained at the peak of fertility to ensure re-impregnation within 83 days.
Accordingly, cattle producers and dairy scientists are continuously searching
for
nutritional supplements that promote dairy cow fertility. Fish oil fatty acids
have become the
focus of numerous research programs that seek to capitalize on their
nutritional and
physiological properties. WO 99/66877 to Amir et al. discloses the use of
omega-3 fatty acids
of fish oil origin to increase fertility in animals including cattle. Among
the omega-3 fatty
acids disclosed are eicosapentaenoic acid (EPA) and docosahexaenoic acid
(DHA).
WO 02/054886 to Lanna et al. provides for improved reproductive function in
cows
which were fed one daily dose of 150 g/day of calcium salts containing 70%
fatty acids.
Conjugated linoleic acid (CLA) isomers make up 60% of the fatty acids
contained within the
calcium salt formulation. Of the total CLA isomers approximately 24% was c/t
9, II; 35%
was c/t 10, 12; 15% was c/t 8, 10; 17% was t11, t13 and the remaining 9% was
others.
Knowing the concentrations of the individual isomers, a calculation of the
amounts of cis-9,
trans-11 and trans-10, cis-12 indicates that the dose used in this reference
was about 15 g of
cis-9, trans-11 and 22 g trans-i0, cis-12 per day. Because the composition
used in this
reference contained significant amounts of several isomers, the effects could
not be attributed
to specific isomers. Additionally, because only a single concentration was
used, there was no
determination of a useful dosage for improvement of reproductive function.
Further, the
CA 02536548 2006-02-14
inventors describe how an improvement in energy balance allowed for the better
reproduction. lt is well known for all mammals that reproductive performance
is
compromised if nutrient intake is inadequate and this can be overcome by
improving energy
balance (Wade et al., 1996, Am. J. Physiol. 270:EI-E19).
Bernal-Santos et al. (2003, .J. Dairy Sci. 86:3218-3228) disclose the
administration of
a single dose of 30 g/day of a CLA mixture comprising a mixture of various
isomers. Of the
total CLA isomers approximately 25.1% was c9, tl 1; 28.9% was t10, c12; 9.2%
was t8, cl 0;
16.1% was cl I, tl 3 and the remaining 20.7% was others. The authors concluded
that no
adverse effects were observed on conception and maintenance of pregnancy.
However, the
authors acknowledge that due to the limited number of animals in their study,
they were
unable to make any definitive conclusions regarding reproductive variables.
SUMMARY OF THE INVENTION
This invention provides compositions and method for enhancing the reproductive
performance of mammals. The present invention is based on the observation that
enhanced
reproductive performance was observed in cows using compositions comprising
specific
isomers of CLA. Thus, the present invention provides a method of improving the
reproductive function of female mammals comprising feeding to the female
mammal a
composition comprising two conjugated linoleic acids (CLA) isomers, cis-9,
trans-11 and
trans-10, cis-12.
In one embodiment, the composition comprises a CLA mixture with a high
proportion
of two isomers: cis-9, trans-11 and trans-10, cis-12. No other isomers of CLA
are required to
be present in this composition in any significant amount for the enhancement
of reproductive
function described herein. A dosage range was also observed for the
enhancement in
reproductive function. Above this dosage range, the enhancement effect is
expected to
diminish based on the observed trend.
Accordingly, this invention also provides a method for enhancing the
reproductive
performance of mammals. The method comprises feeding to mammals, including
mammals
where artificial insemination is practiced, such as lactating cows, a
composition comprising
the two isomers of CLA, cis-9, trans-11 and trans-10, cis-12. Therefore, in
one embodiment,
the method of this invention comprises administering the CLA composition at a
dose of 20
g/day and preferablyI5 g/day or less of each of the two isomers. In another
embodiment, the
two isomers cis-9, trans-11 and trans-10, cis-12 make up at least 65%,
preferably at least 70%
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CA 02536548 2006-02-14
of total CLAs, more preferably at least 80% and still more preferably at least
90% of the total
CLAs. This method can be used for enhancing the reproductive function of
mammals
including cattle (beef and dairy), sheep, goats, horses, pigs, rabbits, dogs
and humans.
BRIEF DESCRIPTION OF FIGURES
Figure I is a graphic representation of the effect of feeding CLA isomers cis-
9, trans-
1I and trans-10, cis-12 to lactating cows on the number of ovulations.
Figure 2 is a graphic representation of the survival analysis of the
maintenance of
pregnancy for cows fed with two CLA concentrations as compared to control.
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention provides a method for improving the
reproductive function of female mammals by administering conjugated linoleic
acid isomers.
Conjugated linoleic acid (CLA) isomers are a mixture of positional and
geometric isomers of
octadecadienoic (linoleic) acid with conjugated double bonds. There are 28
possible isomers
of CLA. These include isomers having double bonds at 7 and 9, 8 and 10, 9 and
II, 10 and
12 or 11 and 13 position and isomers that have the double bond pairs with
geometric
configurations of cis-cis, trans-trans, cis-trans and trans-cis.
This invention is based on the observation that a mixture of CLA isomers
comprising
the two isomers, trans-10, cis-12 CLA and cis-9, trans-11 CLA within a
particular range of
dosage provides enhancement of reproductive function of dairy cows.
Accordingly, in one
embodiment, this invention provides a range of dosage of two CLA isomers which
when fed
to mammals improves their reproductive function. Above this range, the
enhanced effects on
reproductive function are diminished. During the first 6-8 weeks post-partum
the nutrient
intake of cows is less than their nutrient requirements. This is referred to
as a negative
energy balance and extensive research has established that technologies and
practices that
cause improvements in the energy balance of cows in early lactation result in
improvements
in reproductive perfomiance (Butler, 2001, Animal Science Occasional
Publication No. 26
(Vol.1):133-145; Butler, 2003, Livest. Prod. Sci. 83:211-218; Darwash et al.,
2001, Animal
Science 72:539-546). However, at the concentrations useful in enhancement of
reproductive
performance, it was observed that there was no significant effect on net
energy balance.
Therefore, an improvement in reproductive performance with the feeding of CLA
isomers as
described herein is not dependent on an improvement in energy balance.
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CA 02536548 2012-12-19
1
The identification of specific isomers for which a dose dependent enhancement
in
reproductive function is observed, is important because CLA isomers are known
to
sometimes have different or even opposite effects. For example, trans-10, cis-
12 CLA causes
reduction of milk and body fat, whereas cis-9, trans-11 CLA has no effect.
Further, cis-9,
trans-11 CLA is proposed to enhance feed efficiency and growth in young
rodents but trans-
10, cis-12 CLA does not (Pariza et al, 2001, Frog. Lipid Res. 40(4):283-298).
The present invention provides methods for improving the reproductive
performance
of mammals. In one embodiment, the compositions comprise primarily two CLA
isomers
cis-9, trans-11 and trans-10, cis-12 in amounts such that administration or
feeding of the
CLAs to cows will result in a daily dose of less than or equal to 20 g/day for
each isomer. In
one embodiment, the compositions provide a dose of less than or equal to 18
g/day and
preferably less than or equal to 15 g/day for each isomer. In other
embodiments, various
concentrations of the two isomers can be used such that the dose of each is
independently
between 1 and 20 g/day. In another embodiment, the cis-9, trans-11 and the
trans 10, cis-12
isomers can make up greater than 65%. For example, in different embodiments,
the cis-9,
trans-11 and the trans 10, cis-12 isomers can make up 70, 80 or 90% of the
CLAs. In one
embodiment, the combined percentage of 11, 13 isomers, the 8, 10 isomers and
double trans
isomers is less than one percent. In one embodiment, the ratio of the two
isomers, cis-9,
trans-11 and the trans 10, cis-12, is between 1:5 to 5:1. In another
embodiment, the ratio is
between 1:2 to 2:1 and in yet another embodiment, the ratio is approximately
1:1. The
preparation of such compositions is described in U.S. Patent No. 6,015,833 =
In one embodiment, the composition is fed to the cows such that a
dosage of 1-15, preferably 2-14, more preferably 3-13, particularly preferably
4-12 and even
more preferably 5-10 g/day of each isomer is administered. In a more preferred
embodiment,
the daily dose is between 6-14, preferably 7-13, more preferably 8-12g/day for
each isomer.
The method of the present invention comprises providing a composition
comprising
primarily of cis-9, trans-11, and trans-10, cis-I2 isomers and feeding the CLA
composition to
mammals (including, but not limited to, dogs, horses, pigs, rabbits and
humans), preferably
ruminants like cows, sheep or goats, more preferably lactating ruminants like
dairy cows or
beef cows. The animals are fed feedstock containing the above described
conjugated linoleic
acids at concentrations such that upon feeding of the feedstock to the cows,
the reproductive
performance of the animals is increased preferably at concentrations between 6-
14, preferably
7-13, more preferably 8-12g/day for each isomer.
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For human applications, the CLA isomers can be provided in a variety of fonns.
The
dosage will depend upon the weight and metabolic rate of the individuals.
Based on the
guidance provided herein, those skilled in the art can determine the
appropriate dosage. The
administration may be oral wherein the CLA isomers are formulated with
suitable carriers
such as starch, sucrose or lactose in tablets, pills, dragees, capsules,
solutions, liquids,
slurries, suspensions and emulsions. CLA isomers may also be administered by
other routes
such as by intravenous, intramuscular, transdermal, subcutaneous,
intraperitoneal, or mucosal
routes. Such administration regimes can be found in Remington's Pharmaceutical
Sciences
(Maack Publishing Co., Easton, Pa.).
By improved reproductive function or an enhanced fertility is meant an
improvement
is observed in one or more of the following: interval between calving and
first ovulation;
improvement in maintenance of pregnancy; increased embryonic survival or the
percentage
of female mammals, preferably cows in a herd that become pregnant; period of
time
(interval) until the mammals get pregnant; decreased services per conception,
and early
embryo survival.
For ruminants, the CLA compositions can be delivered by infusing directly into
the
abomasum as a convenient experimental approach to avoid possible alterations
by rumen
bacterial fermentation. However, in commercial practice this is not feasible,
so the dietary
supplement of CLA has to be formulated in a manner so that it is protected to
minimize its
metabolism by rumen bacteria and can pass directly to the abomasum. Exemplary
methods
for rumen-protection of CIA to minimize its metabolism by rumen bacteria
include, but are
not limited to, encapsulation in a lipid-protein matrix or with water
insoluble lipids;
formaldehyde treatment; formation of calcium salts; and linkage by amide
bonds.
Fomialdehyde protection, encapsulates lipid in a matrix of protein and through
cross-
linkages are formed between the formaldehyde and protein which confer
resistance to
microbial attack in rumen (Scott and Cook, 1975, pp 510-523 in Digestion and
Metabolism in
the Ruminant. I. W. McDonald and A. C. I. Warner, ed. The University of New
England
Publishing Unit, Sydney, Australia). The mechanism whereby calcium salts
provide
"protection" is related to the inertness of the calcium-fatty acid complex on
rumen digestion;
it does not appear to be related to protection from rumen biohydrogenation.
Microencapsulation is a lipid based protection method that either embeds the
active
ingredient in a lipid matrix or produces small spheres of the nutrient which
are encapsulated
(Wu and Papas, 1997, Advanced Drug Delivery Reviews 28:323-334).
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CA 02536548 2006-02-14
A number of recent studies have shown that all four methods mentioned above
provide protection for CLAs when fed to lactating dairy cows and were
effective based on the
absorption and incorporation of the CLA isomers into milk fat (Bernal-Santos
et al., 2003,
Moore et al., 2004, J. Dairy Sci. 87:1886-1895; Perfield et al., 2004, J.
Dairy Sci. 87:3010-
3016, and de Veth et al., 2005, J. Dairy Sci. 88:1685-1693). Determination of
level of
protection using other methods can be done by routine methods and is well
within the
purview of those skilled in the art.
A commercially available type of rumen protection used for the supplement is
lipid
encapsulated CLA (BASF, Ludwigshafen, Germany; Balchem Encapsulates, USA).
The present method can be used for enhancing reproductive performance of
mammals
including ruminants such as cows (including beef and dairy cattle), goat and
sheep. While
specific examples and dosages are presented herein with respect to cows, it
will be
appreciated by those skilled in the art, that based on the information
provided herein,
appropriate dosages for other ruminants as well as other mammals can be easily
determined.
The feeding of CLA composition to mammals can begin prior to calving or at
calving
and can be continued for period of at least 2 weeks. In further embodiments,
the feeding can
continue for a period between 50 to 75, for a period of 76 to 100, for a
period of 101 to 125,
for a period of 126 to 150, or for a period of 151 to 200 days after calving.
The treatment can
also be continued beyond 200 days after calving. For example, the feeding of
CLA can begin
about 2 weeks prior to calving. Although it is preferred that the dairy cows
are fed the
composition daily such that a dosage of 1-20 g/day and more preferably between
1-18 g/day
and even more preferably 1-15 g/day of each of eis-9, trans-11 CLA and trans-
10, cis-12
CLA is delivered to the animal, those skilled in the art will recognize that
the feeding
schedule includes instances wherein the composition is inadvertently or
intentionally (such as
because of a temporary medical condition) deleted from the daily diet during a
short period of
time during the administration period. It is preferable that such break in CLA
administration
does not exceed 14 consecutive days and more preferable that it does not
exceed 7
consecutive days.
While the present invention is illustrated by way of the following examples,
the
examples are meant only to illustrate particular embodiments of the present
invention and are
not meant to be limiting in any way.
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EXAMPLE 1
This example describes the effect of a CLA isomer mixture administered at two
doses
on the reproductive performance of cows. All procedures involving animals were
approved
by the Cornell University Institutional Animal Care and Use Committee.
Multiparous
Holstein cows (n = 48) from the Cornell University Dairy Teaching and Research
facility
were blocked by parity and by 305-day mature equivalent milk production in the
previous
lactation and assigned in a randomized complete blocked design to one of the
following 3
dietary treatments: 1) control, consisting of 271 g/d of Ca salts of palm
fatty acid distillate
(EnerGII; Bioproducts Inc., Fairlawn, OH); 2) conjugated linoleic acid dose 1
(CLA-1),
consisting of 147 g/day of Ca salts of mixed isomers of CLA (Bioproducts Inc.)
and 136
g/day of Ca salts of palm fatty acid distillate; or 3) conjugated linoleic
acid dose 2 (CLA-2)
consisting of 295 g/day of Ca salts of mixed isomers of CLA. The weight of the
lactating
Holstein cows is generally between 500 to 700 kg.
Supplements of Ca salts of palm fatty acid distillate and Ca salts of CLA
contained 85
and 78% fat, respectively. The 3 supplements provided the same intake of fat
(230 g/day) and
were top-dressed once daily on the total mixed rations (TMR) from 21 day
before expected
day of calving to 63 days in milk (DIM). The CLA-1 and CLA-2 treatments
provided 31.6
and 63.2 g/dayof CLA isomers, respectively. The 4 predominant CLA isomers in
the
supplements were trans-8, cis-10 (21.2%), cis-9, trans-11 (21.8%), trans-10,
cis- 12 (29.0%),
and cis-11, trans-13 (28.0%). Thus, CLA-1 provided 6.8 g/day of cis-9, trans-
11 CLA and
9.2 g/day of trans-10, cis-12 CLA whereas CLA-2 provided twice these amounts.
The
predominant fatty acids in the Ca salts of palm fatty acid distillate were
palmitic (42.6%),
oleic (40.6%), and linoleic acids (10.1%).
Cows were housed in tie stalls and fed at ad libitum intake to allow about 10%
orts.
Individual feed intake was recorded from 14 days before the expected date of
calving to 63
DIM. During the post-treatment period (64 to 126 DIM), cows were combined in
groups
independent of treatment and fed a common diet. Water and mineral blocks were
available
throughout the study. Body weight and body condition score (BCS) (5-point
system;
Wildman et al., 1982, J. Dairy Sci., 65:495-501) were recorded weekly after
the morning
milking. After calving, cows were milked 3x/day, and milk weight was recorded.
A milk
sample from each milking was taken 1 day/week, and a composite was formed
based on
proportion of daily yield. Composite milk samples were stored at 4 C with a
preservative
(bronopol tablet; D& F Control System, San Ramon, CA) until analyzed for fat,
true protein,
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and lactose (Dairy One Cooperative Inc., Ithaca NY) Blood samples were taken
at 10 and 5
days prepartum, 3x/week during the first 11 wk of lactation, and once weekly
from week 12
to 18 postpartum. Blood (10 mL) was obtained via coccygeal venipuncture and
was collected
in vacuum tubes (Becton Dickinson Vacutainer Systems, Franklin Lakes, NJ)
containing
sodium heparin (100 U/mL of blood). Plasma was harvested within 20 min after
collection by
centrifugation (2800 x g for 15 min at 4 C) and stored at ¨20 C until
metabolite and
hormone analysis.Estrus was synchronized with an intramuscular injection of
100 mg of
GnRH analogue (Cystorelin; Abbott Laboratories, North Chicago, IL) at d 70 3
(mean
SD) postpartum; 7 days later, cows received an injection of 30 mg of PGF2a
analogue
(Lutalyse; Pharmacia & Upjohn, Kalamazoo, MI); 48 hours later, they received
an injection
of 100 mg of GnRH and were inseminated 4 to 8 h later. Pregnancy was diagnosed
by rectal
palpation at 42 days after insemination. After the experimental period (>126
DIM),
nonpregnant cows were resynchronized or inseminated when estrus was visually
detected; if
conception occurred before 185 d postpartum, this was recorded and used for
statistical
analysis.
A total of 46 of the 48 cows completed the treatment period. One cow from each
CLA
treatment group was excluded (all analysis) because of health reasons (chronic
laminitis). In
addition, 2 cows in the CLA-1 treatment group completed the treatment period
but not the
post-treatment period because of chronic laminitis and death caused by a
respiratory problem.
Net energy balance was computed for each cow in the experiment according to
the
equations published by the National Research Council (NRC, 2001, in Nutrient
Requirements
of Dairy Cattle, 7th Revised Ed., National Academy Press, Washington, D. C.).
The estimate
is calculated from the difference between total energy intake (dry matter
intake multiplied by
the net energy value of the diet) minus the sum of energy requirements for the
cow's
maintenance and her milk production. The energy requirement for maintenance is
based on
the cow's size (body weight), and the energy requirement for milk production
is based on the
daily milk yield and the composition of the milk (fat, protein and lactose).
There was no
difference in net energy balance among the treatments (P value = 0.54)
Plasma concentrations of progesterone and estradiol were determined by
radioimmunoassay (Elrod and Butler, 1993, J. Animal Sei. 71:694-701; Beam and
Butler,
1997, Biol. Reprod. 56:133-142). Progesterone was analyzed on the plasma
samples obtained
3x/week during the first 11 weeks of lactation, whereas estradiol was analyzed
on the plasma
samples from the first 3week postpartum. Ovulation was determined based on
temporal
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pattern and concentration of plasma progesterone according to the criteria
described by Butler
et al. (1981). The results of the study are shown in Table 1. The mean and
median days to
first ovulation were lower for cows supplemented with CLA-1 (P = 0.05). The
proportion of
cows pregnant before 185 days differed among treatments (P = 0.07), with thc
highest value
observed for the CLA-1 group. The percentage of cows pregnant before 126 DIM
of the 2
CLA groups was similar (31.1 and 33.3%) and numerically greater than the
control group
(18.7%). As shown in the survival analysis (Figure 2) the CLA-1 dose
dramatically increased
the percent cows pregnant in the interval beyond 135 days postpartum. These
results suggest
that the CLA-1 supplement reduced embryonic mortality thereby resulting in a
marked
enhancement of pregnancy survival rates.
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Table 1. Reproductive performance data for Example 1.
Treatment I
Variable Control CLA-1 CLA-2 P-
value
Days to first ovulation
Mean 32.6 27.3 41.4 0.05
Median 34.03h 21.5h 41.33 0.05
Days to pregnancy
Mean2 160 135 151 0.81
Median3 146 137 124 0.54
Ovulation before 1.6 1.7 1.5 0.63
synchronization4' 5
Cows pregnant before 18.7 31.3 33.3 0.63
126 DIM, %
Cows pregnant bethre 43.7 81.3 53.3 0.07
185 DIM, %
Services per conception 9.5 2.1 1.0 0.57
Proportion of cows with estrogen
active follicles in the first 21 73.3 57.1 60.0 0.63
DIMh, %
Proportion of cows with
ovulation in the first 21 18.8 46.7 7.1 0.63
DIM, %
Progesterone peak at first 7.7 6.5 6.8 0.58
ovulation, ng/d1
Cows received a dietary fat supplement consisting of Ca salts of palm fatty
acid distillate (271 g/day)
(control treatment), Ca salts of a mixture of conjugated linoleic acid isomers
(147 glday containing 32
g/dayCLA isomers; 9 g/day of CLA trans-10, cis-12) plus paltn fatty acid
distillate (136 g/day) (CLA-
1), or Ca salts of a mixture of conjugated linoleic acid isomers (295 g/day
containing 63 g/day CLA
isomers; 18 aid of CLA trans-10, cis-12) (CLA-2).
2 Pregnancies recorded before 185 days postpartum.
3 Cows were removed if they were not pregnant before 185 days postpartum (3
from CLA-1 group, 5
from CLA-2 group and 8 from control group).
4 Synchronization occurred at 67 days postpartum.
Ovulation detennined when plasma progesterone levels were above 0.5 ng/ml for
at least five
consecutive satrapies, and exceeded 2 ng/m1 for at least two successive
samples.
6 Follicular activity during the first 21 day postpartum was assumed when
estrogen level > 2 pg/ml.
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A similar effect was seen when the cows were fed with a composition in which
the
two isomers - cis-9, trans-11 CLA and trans-10, cis-12 CLA made up more than
90% of the
total CLA.
EXAMPLE 2
This example describes the effect of two CLA isomers on reproductive function
and
establishes a cutoff dose for observing enhanced reproductive function. By
using different
doses of the two isomers, a dose dependent effect on reproductive function was
observed.
The effects of rumen protected CLA on reproductive performance was studied
using 4 doses
of rumen-protected CLA supplement (BASF, Ludwigshafen, Germany). The type of
rumen
protection used for the supplement was lipid-encapsulation commercially
obtained from
Balchem Encapsulates, New Hampton, NY. The supplement contained 20% CLA
isomers.
Of the total CLA isomers, 50% was cis-9,trans-11 and 50% was trans-10, cis-12
CLA and the
four treatment levels provided 0, 5, 10 and 15 g/day of each CLA isomer. The
supplement
was fed once daily by top-dressing over the basal diet (fed ad-libitum), with
cows receiving
an additional concentrate supplement. The experiment started at calving and
dietary
supplements of CLA continued until all cows were 91 days into lactation.
Animals were also
monitored after the treatment period so that effects of CLA treatment on
reproductive indices
could be fully determined.
The net energy balance and reproductive performance were estimated as
described in
Example 1. No change in net energy balance was seen as dose increased from 0
to 15 g/d of
each isomer (P value = 0.20). Results demonstrate that CLA treatment improved
overall
conception rate (P = 0.03) and reduced the median number of days until
pregnancy (P =
0.07) (Table 1). The effect seen was a quadratic response to dose. The
quadratic relationship
indicates that as the dose of CLA is increased, the reproductive performance
improves, but as
the dose is increased beyond a certain level the beneficial effects on
reproductive
performance are diminished. The quadratic relationship also shows that
although for the high
CLA sometimes the reproductive performance appears to be better than the
control
(numerically) that in fact the performance is diminished at this high dose.
This enables the
determination of a dose range for enhancement of reproductive performance
whereby the
greatest improvement in reproductive performance occurred at the low and
medium doses (5
and 10 Wday of each CLA isomer). Additionally, there was a reduction in the
number of
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CA 02536548 2012-12-19
services per conception (Table 2) and fewer ovulations per cow (recorded as
number of estrus
cycles prior to pregnancy; Figure 1) at the low and medium dose levels,
however, at thc high
treatment level (15 g/day of each CLA isomer) a trend toward reduction of the
effect was
seen. Similar to Example 1, the pattern of reproductive variables indicates
that embryonic
survival is improved with the low and medium doses of CLA.
Table 2. Reproductive performance of cows receiving four doses of CLA
Treatment
Control Low Med High Quadratic
CLA CLA CLA
Services per 2.1 1.7 1.5 2.0 0.25
conception
Days until 136 110 92 100 0.07
pregnancy, median
Conception rate % 64 87 100 80 0.03
These results show that a CLA supplement that is fed to provide cis-9, trans-
11 and
trans-10, cis-12 CLA doses between 5-15 g/day (of each isomer) will improve
reproductive
performance. At doses above this range 15 g/day of each isomer) the beneficial
effects on
reproductive performance may be reduced.
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