Conjugated linoleic acid (CLA) during gestation and lactation does not alter sow performance or body weight gain and adiposity in progeny
Conjugated linoleic acid (CLA) during gestation and lactation does not alter sow performance or body weight gain and adiposity in progeny
Sylvia P. POULOS 0 2
Michael J. AZAIN 1
Gary J. HAUSMAN 0 2
0 US Department of Agriculture, Agricultural Research Service, Animal Physiology Research Unit , Athens, GA 30605 , USA
1 Department of Animal and Dairy Sciences, The University of Georgia , Athens, GA 30602 , USA
2 Department of Foods and Nutrition, The University of Georgia , Athens, GA 30602 , USA
- The objective of this study was to determine the long-term effects of conjugated linoleic acid (CLA) in pigs exposed to CLA during fetal and neonatal growth. Sows were fed a diet with 0.83% soy oil or 0.83% CLA-60 containing 60% active CLA isomers from either d 40 (group 1; CON n = 8, CLA n = 6) or d 75 (group 2; CON n = 8, CLA n = 8) of gestation through weaning on d 28. Within group 1, one male and one female piglet per litter (CON n = 6, CLA n = 5) were sacrificed within 24 hours of birth (d 0) and body weights recorded. Semitendinosus muscle, subcutaneous adipose tissue and organs, including heart, liver, lung, kidney, brain were weighed and tissue samples were frozen. Two average weight barrows and two gilts per litter were weaned and fed standard diets without added CLA until market weight. CLA did not alter sow's feed intake during gestation or lactation, body weight or backfat thickness, and litter size and weight at birth (P > 0.05). CLA decreased newborn pig heart, but not backfat or semitendinosus muscle weights relative to their body weights (d 0). CLA decreased pre-weaning weight in selected piglets but this was not maintained post-weaning. CLA decreased total milk fat by 17% (P < 0.01) and resulted in an increase in the relative amount of saturated fatty acids and a decrease in the relative amount of unsaturated fatty acids in milk on d 21 of lactation (P < 0.05). Decreases in growth rates until d 14 may be due to decreased fat in sow's milk since growth rate and body weight of selected progeny did not differ post-weaning. Serum from newborn CLA pigs suppressed relative preadipocyte number and did not change lipid filling in stromal-vascular cell cultures. The response to this serum was greater in females than in males (PDiet = 0.04; PDiet × Gender = 0.04). Thus, there do not seem to be any long-term effects on growth and body composition of market weight pigs given 0.5% CLA through weaning that would be beneficial in a production scheme.
Résumé – La distribution d’acide linoléique conjugué (CLA) pendant la gestation et la lactation
n’affecte ni les performances des truies ni le gain de poids corporel et l’adiposité de leurs
porcelets. L’objectif de cette étude était de déterminer les effets à long terme de l’acide linoléique
conjugué (CLA) chez les porcs recevant du CLA pendant leur croissance foetale et néonatale. Des
truies ont été alimentées avec un régime à base d’huile de soja (0,83 %, CON) ou de CLA-60 (0,83 %,
CLA) contenant 60 % des isomères actifs de CLA, soit à partir du 40e jour de gestation (groupe 1 ;
CON n = 8, CLA n = 6) soit au 75e jour de gestation (groupe 2 ; CON n = 8, CLA n = 8) jusqu’au
sevrage (28 jours après la naissance). Dans le groupe 1, un porcelet mâle et un porcelet femelle par
portée (CON n = 6, CLA n = 5) ont été sacrifiés à moins de 24 heures de la naissance (d 0) et le
poids corporel des animaux enregistré. Le muscle semitendinosus, le tissu adipeux sous-cutané et
les organes, comprenant le coeur, le foie, le poumon, les reins ainsi que le cerveau ont été pesés, et
des échantillons de tissu ont été congelés. Deux porcelets mâles castrés de poids moyens et deux
jeunes truies par portée ont été sevrés et alimentés avec des régimes standards sans supplémentation
de CLA jusqu’au poids d’abattage du marché. Le CLA n’a pas modifié la quantité d’aliments ingérée
par la truie pendant la gestation ou la lactation, le poids corporel ou l’épaisseur du gras dorsal, et la
taille et le poids de la portée à la naissance (P > 0,05). Le CLA a diminué le poids du coeur du
nouveauné, mais pas le poids du gras dorsal ou du muscle semitendinosus par rapport au poids corporel (d 0).
Le CLA a diminué le poids pré-sevrage des porcelets mais cet effet ne s’est pas maintenu en
postsevrage. La matière grasse totale du lait a été diminuée par CLA de 17 % (P < 0,01), ce qui a eu
pour conséquence une augmentation relative de la quantité d’acides gras saturés et une diminution
de la quantité relative d’acides gras insaturés du lait le 21e jour de lactation (P < 0,05). La diminution
de la vitesse de croissance jusqu’à 14 jours pourrait être due à la faible teneur en lipides du lait des
truies puisque la vitesse de croissance et le poids corporel des porcelets n’ont pas différé en
postsevrage. Le sérum des porcelets nouveau-nés soumis au CLA a diminué le nombre relatif de
préadipocytes et n’a pas modifié le stockage de lipides dans les cellules stromales vasculaires en
culture. Ces observations ont d’ailleurs été plus marquées chez les femelles que chez les mâles (PDiet =
0,04 ; PDiet × Gender = 0,04). Il ne semble pas y avoir d’effets bénéfiques à long terme sur la croissance
et la composition corporelle au poids habituel d’abattage chez les porcs ayant reçu 0,5 % de CLA
acide linoléique conjugué / gestation / lactation / porc / tissu adipeux
Conjugated linoleic acid (CLA), a group
of positional and geometric isomers of
linoleic acid, has many reported biological
activities which alter body composition.
CLA reportedly improves body
composition by decreasing adipose tissue
deposition, increasing leanness, growth, and meat
]. Studies using CLA in rodents
have consistently shown more drastic and
more consistent suppression of adipose
tissue growth and enhanced lean tissue growth
than those in larger animals and humans.
Although studies in gilts have shown no
effect on live body weights [
changes may be occurring, as was seen in
rats which also showed no changes in body
]. Our recent study in rats
showed that 0.5% CLA fed during gestation
and lactation has long-term effects on bone,
muscle and adipose growth, although the
greatest changes in body composition were
evident in animals fed CLA from weaning
into adulthood [
]. In vitro studies using
3T3-L1 cells have shown CLA
supplementation decreases proliferation and inhibits
lipid accumulation [
]. Fat cell
development in pigs begins between 45 d and 75
d of fetal life . Therefore, the objective
of this study was to test the hypothesis that
CLA decreases preadipocyte proliferation,
as was seen in cultured 3T3-L1 cells, and
decreases the propensity to deposit fat. In
addition, we examined the effects of CLA
on sow performance, such as weight loss
during lactation. To determine if CLA
feeding causes changes in circulating factors in
serum that would alter adipocyte
development we evaluated changes in preadipocyte
cell number and lipid filling in primary
porcine stromal-vascular cell cultures.
a CLA-60 (Conlinco, Detroit Lakes, MN) was added to the standard gestation or lactation diet at the rate
of 8.3 g·kg–1 of diet to achieve 0.50% CLA. The same amount (8.3 g·kg–1) of soy oil was added to the diet
fed to the control group. The CLA-60 supplement provided 6.38% palmitic acid, 0.09% palmitoleic acid,
4.37% stearic acid, 21.25% oleic acid, 9.31% linoleic acid, 21.35% cis-9, trans-11 CLA, 25.72% trans-10,
cis-12 CLA and 11.51% unknown fatty acids as determined by gas chromatography.
b The vitamin premix (Animal Science Products, Nacogdoches, TX) provided the following per kilogram
of complete diet: 11000 IU vitamin A, 1650 IU vitamin D, 44 IU vitamin E, 4.4 mg vitamin K, 9.9 mg
riboflavin, 55 mg niacin, 33 mg pantothenic acid, 44 µg vitamin B12.
c The trace mineral premix (Animal Science Products, Nacogdoches, TX) provided the following per
kilogram of complete diet: 165 mg iron, 16.5 mg copper, 39.6 mg manganese, 165 mg zinc, 0.3 mg iodine, and
0.3 mg selenium.
d The sow vitamin pack provided the following per kilogram of complete diet: 551 mg choline, 0.22 mg
biotin, 1.65 mg folic acid and 15.2 mg pyridoxine.
2. MATERIALS AND METHODS
2.1. Animals and diet
Parity matched, gestating sows (CON,
3.6; CLA, 4.1; Pooled SEM, 0.6; P = 0.46;
Yorkshire × Hampshire × Landrace) in the
University of Georgia herd were fed corn
and soybean meal based diets (Tab. I) that
were supplemented with either 0.83% soy
oil (CON) or 0.83% CLA-60, (CLA,
Conlinco, Detroit Lakes, MN, USA). Sows in
two farrowing groups began diet treatment
on either d 40 (group 1; CON n = 8, CLA n =
6) or d 75 (group 2; CON n = 8, CLA n = 8)
of gestation through d 28 of lactation. As
expected, CON diets contained low
amounts of the cis-9, trans-11 and the
trans10, cis-12 CLA isomers (0.2–0.3 mg·g–1)
while the CLA supplement diets contained
5–6 mg·g–1 CLA. The minimal amount of
CLA present in the CON supplemented diet
is likely due to the animal fat in the diet.
Sows were limit fed 2.0 kg·d–1 during
gestation and fed ad libitum during lactation.
The day of farrowing was designated as d 0.
Within 24 h of birth, sow, pig, and litter
weights were recorded. Backfat thickness
at the tenth rib was determined on sows on
d 0 and at weaning (28 d) using a
LeanMeater (Renco, Minneapolis, MN, USA).
Milk samples from each sow were collected
from several teats without removing piglets
and without the use of oxytocin on d 21
(groups 1 and 2) of lactation. Milk samples
were frozen at –20 °C for determination of
milk fat content and fatty acid profile. Litter
records including number of pigs per litter
and litter weight at birth, d 7, d 21 and
weaning were maintained.
Between 8 and 16 h of birth, one male
and one female piglet from CON fed (n = 6)
and CLA fed (n = 5) litters in group 1 were
sacrificed to determine the effects of CLA
during gestation. Piglets were injected
intraperitoneally with 30 mg·kg–1
5-bromo2’-deoxyuridine (BrdU, Boehringer
Mannheim Corp., Indianapolis, IN, USA) to
determine rates of cell proliferation. Piglets
were sacrificed one hour later using
intraperitoneal injections of sodium
pentobarbitol. Several litters were excluded (CON n = 2;
CLA n = 3) because pigs could not be
collected between the 8–16 h time window
used in this study. Brain, heart, lung, liver,
kidney, semitendinosus muscles, and
subcutaneous adipose tissue collected from the
piglet’s back were weighed and samples
were snap frozen and stored at –70 °C for
further analysis. Blood was collected via
cardiac puncture, serum collected and
frozen at –70 °C. All other piglets remained
with sows until weaning (d 28) and had free
access to the sow’s diet but were not offered
creep feed. At weaning (d 28) 2 barrows and
2 gilts per litter that were closest to the
average weight of the litter were selected and
blood samples were collected. After
weaning these selected pigs were fed diets that
met or exceeded the NRC requirements for
growing pigs and were maintained until
they were approximately 110 kg body
weight. At this time, images of the loin
muscle and backfat at the tenth rib taken with
an Aloka 633 ultrasound unit (Corometrics
Medical Systems, Wallingford, CT) were
used to determine backfat depth and loin
muscle area. Previous studies have validated
the use of ultrasound measures of loin area
and backfat thickness [
thickness, loin eye area, percent lean, and days
to 113 kg were determined using National
Swine Improvement Federation Guidelines
All animal procedures were conducted in compliance with established guidelines from The University of Georgia Institutional Animal Care and Use Committee.
2.2. Serum assays
Blood was collected and kept at 4 °C for
12 h before centrifugation at 1800 × g for
20 min. Serum was stored at –70 °C until
assayed. Serum leptin concentrations were
determined using a multi-species RIA kit as
previously described [
] (Linco Research,
Inc., St. Charles, MO, USA). Assay sensitivity
was 0.1 ng per tube. Insulin-like growth
factor-1 (IGF-1) concentrations of serum were
determined via RIA using rabbit IGF-1
antiserum UBK487 [
] (distributed by the
National Hormone and Pituitary Program,
Bethesda, MD, USA) and recombinant
human IGF-1 (Amgen Biologicals,
Thousand Oaks, CA, USA) as the standard. The
specific radioactivity of the 125I-IGF-1
(Dupont NEN Research Product, Boston,
MA, USA) was 345 µCi × µg–1.
Triacylglycerol (352; INT 336; Sigma Diagnostics,
St. Louis, MO, USA) and blood urea
nitrogen (BUN, 535-A; Sigma Diagnostics, St.
Louis, MO, USA) concentrations of serum
were determined via colorimetric assays.
2.3. Tissue and milk composition
Dry matter and lipid content of adipose,
cerebellum, heart, kidney, liver, lung, and
semitendinosus muscle tissues were
determined. Approximately 1–1.5 g of each
tissue was frozen and dried under vacuum in
a freeze dryer (Labconco, Kansas City,
MO). Lipids were extracted from freeze-dried
tissues using chloroform and methanol
(1:2 v/v) followed by chloroform and 1M
KCl (1:1 v/v).
Fatty acid composition of milk and tissue
samples was determined with gas
chromatography using with a flame ionization
detector (Shimadzu, Model 14A,
Columbia, MD, USA). Approximately 1–1.5 g of
lung, liver, kidney, heart and 0.5 g each of
cerebellar and adipose tissue from each
piglet and 1 mL of sow’s milk were frozen at
–20 °C until fatty acid composition was
determined. Fatty acids were saponified
and methylated as previously described
]. Fatty acid methyl esters were
separated on a Supelcowax-10 fused capillary
column (60 m × 0.53 mm, 0.50 µm film
thickness; Supelco, Bellefonte, PA, USA)
under isothermal conditions at 240 °C.
Sample size was 0.5 µL and helium was the
carrier gas. Peaks were identified by
comparison of retention times of known
standards, including pure samples of CLA
isomers (Matreya, Pleasant Gap, PA, USA).
CLA isomers separated were cis-9, trans-11
CLA and 10-trans, 12-cis CLA.
Quantification was corrected for recovery of the
internal standard and is based on the
Subcutaneous adipose tissue, kidney,
liver, and lung tissues form newborn pigs
were homogenized and lysed with 1X lysis
buffer containing 60 nmo·L–1 Tris (pH 6.8)
and 10 g·L–1 SDS. The lysate was
centrifuged (12 000 × g, 10 min) and the protein
concentration was determined using the
Bio-Rad protein assay (Bio-Rad
Laboratories, Hercules, CA, USA). One hundred
micrograms of protein from adipose tissue
was diluted in SDS-sample buffer, boiled
for 5 min, and placed on ice for one min.
This was followed by electrophoresis and
separation of adipose tissue proteins on
16 cm, 12.5%, SDS-polyacrylamide gels at
100V and a one h transfer, at 100V, to
Immobilon-P protein sequencing membrane
(Millipore Corp., Bedford, MA, USA). One
hundred micrograms of protein from kidney,
lung, and liver tissue was placed directly
onto Immobilon-P protein sequencing
membrane (Millipore Corp., Bedford, MA,
USA) using a Minifold II slot blot system
(Schleicher and Schuell, Keene, NH, USA).
Membranes were blocked for nonspecific
binding sites using a 50 g·L–1 nonfat
powdered milk solution for one h. Adipose
tissue proteins were then probed for CCAAT/
enhancer binding protein α and CCAAT/
enhancer binding protein δ (C/EBPα,
catalog # sc-61; C/EBPδ, catalog # sc-151;
Santa Cruz Biotechnology, Santa Cruz,
CA, USA) for one h followed by a one h
incubation with horseradish polypeptidase
conjugated secondary anti-rabbit
immunoglobulin G (Amersham, Arlington Heights,
IL, USA). Both C/EBPα and C/EBPδ are
rabbit polyclonal antibodies corresponding
to rat proteins and are mouse, rat, and human
reactive. Antibody dilutions were 1/500,
1/500, and 1/4000 respectively. Membranes
containing kidney, liver, and lung tissue
were probed for anti-bromodeoxyuridine
(1/1000 BrdU; Affinity Bioreagents Inc.,
Golden, CO, USA) for one h followed by a
one h incubation with horseradish
polypeptidase conjugated secondary anti-mouse
immunoglobulin G (1/5000; Amersham; Arlington
Heights, IL, USA). Immunoreactive
polypeptides were visualized using ECL
chemiluminescence (Amersham, Piscataway, NJ,
USA). Protein band density was determined
using a densitometer to compare protein
amounts (Molecular Dynamics, Sunnyvale,
CA, USA). To ensure the specificity of these
results, blots were exposed to the secondary
antibody alone and used as negative controls.
2.5. Cell culture
Bioactivity of serum from CLA fed
piglets was determined by evaluating changes
in primary stromal-vascular cell cultures
from 75 d old fetal pigs (n = 3). Primary
stromal-vascular cells were isolated as
previously described [
]. Cells were
resuspended in Dulbecco’s Modified Eagle’s
Medium (DMEM) supplemented with 5%
serum from each of 22 piglets (12 CON,
10 CLA) and 1 × 105 cells were plated on
each of three 35 mm culture dishes. Fresh
media containing 5% pig serum was added
3 d post plating thus cultures were exposed
to serum from each pig for 6 d. Six d post
plating (D6), immunocytochemistry for
AD-3, a preadipocyte cell surface antibody,
followed by Oil-Red-O and hematoxylin
staining was performed. Briefly, culture
dishes were rinsed in 0.01M PBS, fixed in
4% paraformaldehyde, rinsed, incubated
with AD-3 antibody (1/50 dilution), rinsed,
incubated with an ExtrAvidin peroxidase
staining kit as instructed (Sigma-Aldrich
Co. St. Louis, MO, USA), incubated with
AEC color substrate, and rinsed. Dishes
were then stained with a 60% Oil-Red-O
solution for 10 min, rinsed, stained with
hematoxylin for 2 min, rinsed, covered, and
mounted with glycerol gelatin
(SigmaAldrich Co. St Louis, MO, USA). Three
photomicrographs of each culture dish at a
10X magnification were used to determine
total cell number, preadipocyte cell number,
and lipid containing cell number. Computer
assisted image analysis (Image-Pro Plus,
Media Cybernetics, Inc., Silver Spring, MD,
USA) was used to quantify lipid droplet area.
2.6. Statistical analysis
Data were analyzed by the PROC GLM
procedure in SAS. Values are reported as
least square mean ± SEM. In most cases,
sow or litter was considered the
experimental unit. The effects of diet on sow and litter
performance and sow milk fatty acid profile
were determined using the PROC GLM
procedure in SAS with the main effects of
diet, group and their interaction. The
significance of effects of maternal diet on
progeny was tested using a model with the main
effects of diet, litter nested within diet and
group. Pig nested within litter and diet was
used as the error term.
3. RESULTS AND DISCUSSION
Improved body composition or
performance is a way of increasing the
cost-effective production of highly desirable meats. A
number of studies investigating the
effectiveness of CLA supplemented diets in
improving swine production have shown
variable responses in lean tissue mass and
adipose accumulation [
1, 9, 12, 32
Reports in swine indicate gender [
] influence CLA’s apparent effects
more than genotype [
] and that 5 g CLA
per kg diet was an effective dose for
reducing lipid accretion and subcutaneous fat
]. Thus, the goal of this study
was to determine if CLA supplementation
of a sow’s diet during critical periods of
fetal adipose tissue development would
induce changes resulting in leaner animals
with higher consumer appeal. We chose to
include CLA in maternal diets prior to
adipocyte differentiation and during the early
phase of endocrine responsiveness of
developing adipocytes [
Diet treatments beginning on d 40 (group 1)
or on d 75 (group 2) of gestation did not
affect sow or litter performance thus results
of these two groups have been combined
and summarized in Table II. As previously
reported in pigs and rats [
] there was
no significant difference in body weight or
litter weight of progeny at birth. CLA
tended to decrease body weight at d 7
compared to control pigs selected to remain in
the study until market weight. This
difference in weight was significant by d 14
(CON-F, 4.51 ± 0.20 kg; CON-M, 4.43 ±
0.20 kg; CLA-F, 3.88 ± 0.27 kg; CLA-M,
3.87 ± 0.27 kg; P Diet < 0.05) but was not
maintained post-weaning. The effect of
suppressed pre-weaning growth is likely
due to the sample of pigs selected to remain
in the study as the weights of all piglets did
not differ among treatment groups. In pigs
sampled from group 1, maternal CLA
consumption beginning on d 40 of gestation
decreased relative heart weights (PDiet =
0.006, PDiet×Gender = 0.09; g tissue per 100 g
body weight) and tended to decrease
relative kidney weight (PDiet = 0.09) in
newborn pigs while male piglets tended to have
smaller lungs (PDiet = 0.07) compared to
females (Tab. III). Percent dry matter and
1 Results are least squares means for two consecutive farrowing groups of 7–8 sows per group on each
diet. Group 1 was started on test diets on day 40 of gestation, while group 2 was started on diets on day
75 of gestation. There were no differences in response to diet between groups so the data were pooled.
Differences were considered significant if P < 0.05.
2 Piglets taken from sows within 24 h were not included in calculations for the number of pigs live at birth,
dead at birth, number weaned, or % survival.
percent lipid of semitendinosus muscle,
liver, heart, lung and kidneys were not
influenced by maternal CLA consumption
(P > 0.05).
Reports using cell culture systems
suggest CLA may alter proliferation and
differentiation of 3T3-L1 adipocytes [
]. Human preadipocytes cultured in the
presence of trans-10, cis-12 isomer had
decreased differentiation and peroxisome
proliferator-activated receptor (PPARγ)
expression, whereas those cultured with the
cis-9, trans-11 isomer had increased PPARγ
]. However, treatment with the
cis-9, trans-11 or the trans-10, cis-12 isomers
did not change PPARγ expression in
cultures of primary porcine stromal-vascular
]. In vivo studies have shown
dietary CLA increases C/EBPα protein [
and the expression of several metabolic
genes in adipose tissue in swine [
Because of these conflicting reports,
proliferation and differentiation in adipose tissue
and primary cultured cells was assessed in
this study. Several markers of adipose tissue
development were not influenced by CLA
including adipose tissue weight, cell
proliferation as measured by BrdU incorporation,
1 Values are least square means. Differences were considered significant if P < 0.05. Abbreviations:
control female, CON-F; CLA female, CLA-F; control male, CON-M; and CLA male, CLA-M.
2 Organ weights are expressed relative to warm carcass weight.
and cell differentiation as measured by C/
EBPα and C/EBPδ protein expression. C/
EBPα and C/EBPδ expression in adipose
tissue from newborn CLA pigs relative to
CON pigs was not influenced by maternal
CLA consumption or gender (P > 0.05).
There was also no influence of CLA intake
on BrdU incorporation in kidney, liver, or
lung tissue from newborn pigs, suggesting
there was no difference (P > 0.05) in rates
of cell replication at birth. The possibility
that CLA alters circulating factors was tested
by exploring the effects of serum from these
pigs on primary stromal-vascular cultures
from fetal adipose tissue. Studies of
stromal-vascular cells isolated from 75 d old
fetuses grown in serum collected from
newborn CLA pigs showed that CLA suppressed
relative preadipocyte number though no
differences in lipid filling were observed
(Tab. IV). The response to this serum was
greater in females than in males (PDiet =
0.04; PDiet × Gender = 0.04). These results
show that serum from CLA exposed pigs
affects cell growth by decreasing relative
preadipocyte number. This suggests CLA
may affect the nonadipogenic cells present
in adipose tissue and may alter circulating
adipogenic factors. Dietary CLA has also
been shown to decrease serum
concentrations of several factors with key roles in
adipogenesis including triacylglycerol, leptin,
non-esterified fatty acids, and glucose in
]. We observed changes in serum
triacylglycerol which may be an avenue of
circulating factors affecting tissue growth.
Maternal CLA consumption beginning on
day 40 of gestation did not alter serum blood
urea nitrogen, insulin-like growth factor 1,
or leptin concentrations in newborn pigs
(Tab. IV). Studies of cultured cells exposed
to a combination of both CLA and linoleic
acid have shown linoleic acid can partly
restore triacylglycerol accumulation in
3T3-L1 cells [
] suggesting cells require
the presence of several fatty acids for
appropriate development. Thus, changes in the
types and amounts of fatty acids present in
tissue may play a role in CLAs affects on
In the present study, CLA was not
consistently incorporated into tissues from
CON-F CLA-F CON-M CLA-M
1 Differences were considered significant if P < 0.05. Abbreviations: control female, CON-F; CLA
female, CLA-F; control male, CON-M; and CLA male, CLA-M.
newborn pigs from CLA fed sows (Tab. V).
The failure to observe consistent changes in
tissue CLA content of pigs sampled at birth
leads one to question whether there is
placental transfer. Heart, kidney, and adipose
tissues did show changes in fatty acids but
these patterns were not similar to those
previously described in other animal models
]. CLA accretion was observed in the
kidneys and hearts of newborn pigs from CLA
fed sow’s indicating CLA did transfer
across the placenta to fetal tissues.
Interestingly, these were the tissues which showed
differences in relative weight as relative
heart weight and relative kidney weight
tended to be decreased when compared to
CON pigs. Fatty acid profiles from samples
of cerebellum and lung from CLA pigs
showed no significant differences when
compared to tissues from CON pigs (data not
shown). CLA has been shown to decrease
∆ 9 desaturase activity resulting in decreased
16:1 and 18:1 [
]. Changes in
monounsaturated fatty acids were not consistently
1 Values are least square means for CON-F (n = 6), CLA-F (n = 5), CON-M (n = 6), and CLA-M (n = 5)
pigs. Abbreviations: control female, CON-F; CLA female, CLA-F; control male, CON-M; and CLA
2 g per 100 g total extractable saponafiable fatty acids.
3 The following fatty acids were included in statistical analysis but were excluded from this table: 14:0,
18:3, 20:0, 20:1, 20:4 n-3, 22:0, 20:5 n-3, 22:1, 24:0, 22:5.
4 P-value symbols: D represents a main effect of diet, G represents a main effect of gender, and D × G
represents an interaction of diet and gender. Differences were considered significant if P < 0.05.
observed among all tissues. Significant
increases in saturated fatty acids were
observed in several tissues including
adipose tissue (16:0; P Diet = 0.01) and hearts
(18:0, PDiet = 0.01, PDiet × Gender = 0.05).
CLA feeding also resulted in differences in
polyunsaturated fatty acids. CLA
accumulation in adipose, brain, and liver was not
elevated due to maternal CLA consumption.
It is possible that CLA increased energy
availability for growing tissues after the
onset of the study and, therefore, after much
1 Values are least square means.
2 Results are expressed as g of each fatty acid per 100 g fatty acid.
3 Differences were considered significant if P < 0.05.
of the organ development has occurred.
However, it is also possible that CLA is
affecting organ development in the fetus as
it has been shown to increase body weight
and muscle mass independently of its effects
on adipose tissue [
]. In contrast, CLA
was elevated in milk samples collected on
d 7 (not shown) and 21 of lactation.
CLA accumulation in tissue of
postweaning animals appears to be markedly
increased as compared to fetal animals [
After birth, maternal triacylglycerols are
used for milk synthesis and are available to
the newborn [
]. In the present study,
maternal milk samples did show
significantly higher amounts of CLA in CLA fed
versus control fed sows which is similar to
that reported by Bee [
]. Milk, collected
from sows in both groups on d 21 of
lactation, showed CLA incorporation into milk
(Tab. VI) as determined by analysis of fatty
acid composition. Total fat was decreased
17% (P < 0.01) in milk from sows fed CLA
(CON, 74.5 g·L–1; CLA, 61.7 g·L–1). On a
percentage basis, feeding CLA resulted in
an increase in the amount of saturated and
a decrease in the amount of unsaturated
fatty acids. There was some endogenous
cis-9, trans-11 CLA but no trans-10, cis-12
CLA detected in the milk of control sows.
Feeding CLA increased the content of both
isoforms of CLA in milk. Milk was
collected from sows in group 1 on d 7 of
lactation as well and the profile was similar to
that on d 21 (not shown). In our study milk
samples also showed a marked suppression
in total fat content though not as dramatic
as the ~50% decrease in milk fat content
observed in dairy cattle [
]. Changes in the
milk fat and the proportion of saturated and
unsaturated fatty acids are similar to that
noted for the effect of CLA on body fat
stores and is consistent with the inhibition
of porcine desaturase activity by CLA [
Previous work has shown that suppressing
milk fat should induce growth suppression
and decrease body weights [
]. It has been
shown that the amount of saturated fatty
1 Results represent data from 2 barrows and 2 gilts per litter. Abbreviations: control female, CON-F; CLA
female, CLA-F; control male, CON-M; and CLA male, CLA-M.
2 Backfat thickness, loin area, days to 113 kg and percent lean were calculated using National Swine
Improvement Federation Guidelines.
3 Differences were considered significant if P < 0.05.
acids in a diet can also influence pig growth
], thus the increase in the amount of
saturated fatty acids and the decrease in the
amount of unsaturated fatty acids in sow’s
milk observed in this study may affect
growth. Interestingly, the pigs in this study
showed a significant difference in body weight
on d 14 but body weights at weaning were
similar. Though not measured in this study,
milk yield and milk protein content remained
unchanged with CLA supplementation in
dairy cattle [
], suggesting the short
term suppression of growth may be due to
limited fat availability to the newborn. This
may be an interesting avenue for future
investigation in regards to promoting health
of neonates which require artificial rearing.
At weaning, 2 barrows and 2 gilts were
selected from each of 28 litters (15 CON, 13
CLA) and 104 of these pigs were monitored
until market weight (110 kg). In this group
of pigs, body weights at day 14 and weaning
and growth rate from birth to weaning was
less in pigs from sows fed CLA (P < 0.05,
Tab. VII). However, final body weight and
calculated days to 113 kg was not different
between groups. There was no effect of
CLA on post-weaning growth rate or
subcutaneous fat thickness or loin muscle area
at the tenth rib as determined by ultrasound
at 110 kg. Expected differences between
barrows and gilts were observed (not
shown) including increased growth rate and
carcass fat for barrows. Several studies
supplementing swine diets with CLA have also
shown no significant difference in average
daily gain [
], live weight, or growth
rate though others have demonstrated
improvements in body composition and
feed efficiency in swine . Dietary CLA
affects lipid composition in several tissues
] while de novo lipogenesis was
unaltered in pigs . Dugan et al. [
a reduction in subcutaneous adipose tissue
and an increase in lean commercial cuts
without seeing a significant difference in
average daily gain, feed intake, or feed
conversion efficiency. Examples of this can
also be seen in humans whose diet was
supplemented with CLA. Sixty-four days of
supplementation resulted in no differences
in fat-free mass, fat mass, percent body fat,
energy expenditure, or body mass index in
human subjects [
]. Mice fed CLA for four
weeks and placed on control diets showed
the cis-9, trans-11 CLA isomer is removed
from tissue over time in a tissue specific
manner and that the isomer was
undetectable in liver after two weeks, fat after four
weeks, and muscle after eight weeks [
It seems the withdrawal of CLA from these
tissues also results in a loss of beneficial
response since there were no significant
differences in whole body fat, protein, water,
or ash, two weeks after CLA was
withdrawn from the diet [
]. The pigs in our
study were only given CLA through
weaning and failed to show any differences in
body weight, backfat thickness, loin eye
area, or gain:feed at the end of the study.
These results suggest that exposure of the
fetus to CLA during the time of fat cell
differentiation had little effect on subsequent
fat cell development. Combined, these
studies [22, present study] suggest CLA
may have long-term benefits only if
maintained in the diet. Similarly, the effect of
somatotropin treatment of pregnant dams
on growth of the offspring is not maintained
through market weight [
]. Though it may
be impractical to suggest producers include
CLA enhancers in diets of gestating sows in
hopes of permanent benefits in body
composition, these results suggest that
mechanisms of CLA’s actions are dependant on
the continual presence of CLA in growing
swine. This may be because of changes in
fatty acid composition or cellular
membrane fluidity which would be corrected
once CLA is no longer present in the tissue.
CLA’s mechanisms of action have yet to be
determined but seem to warrant continued
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