Received: 23/11/2024 Accepted: 02/01/2025 Published: 04/03/2025 1 of 8
https://doi.org/10.52973/rcfcv-e35577 RevistaCientíca,FCV-LUZ/Vol.XXXV
ABSTRACT
Conjugated linoleic acid (CLA) is a constituent of bovine milk that
has been shown to possess protective effects against various
diseases, including cancer. Therefore, there is a compelling rationale
for increasing the content of CLA in milk. The feeding of cows in
pastures has been demonstrated to increase CLA, as pastures
typically have higher concentrations of linoleic and α–linolenic
acids, which serve as precursors of CLA in the process of ruminal
biohydrogenation. The enhancement of linoleic and α–linolenic
acids can be achieved through management techniques that
promote rapid vegetative growth, such as nitrogen fertilization.
An experiment was conducted on a ranch in the state of Tabasco,
Mexico, to determine the effect of nitrogen fertilization on the
milk. The experimental design involved two plots, one of which was
fertilized with urea (150 kg·ha
-1
), while the other served as a control.
randomized complete block design. An intensive rotational grazing
system was used, and grass and milk samples were taken on days
14, 21, and 28 of the experimental periods. Nitrogen fertilization of
the grass increased (P
fertilization of the grass increased (P
P>0.05) the protein and lactose content
or the content of CLA. A positive linear relationship was found
(P
concentration of CLA in milk. The nitrogen fertilization of Cayman
Blend grass increases forage production, the crude protein content
in the grass, and the fat content in milk without affecting the content
of conjugated linoleic acid and other fatty acids.
Key words: Conjugated linoleic acid; grazing; forage; lipids; tropics
RESUMEN
El ácido linoleico conjugado (ALC) presente en la leche bovina tiene
efectos protectores contra diversas enfermedades incluyendo
el cáncer, por lo que es importante incrementar su contenido en
leche. La alimentación de las vacas bajo pastoreo incrementa
el CLA ya que los pastos tienen mayor concentración de ácidos
linoleico y α–linolénico, precursores del ALC en la biohidrogenación
ruminal. Tanto linoleico y α–linolénico pueden incrementarse a
través de técnicas de manejo que promuevan un rápido crecimiento
vegetativo, tal es el caso de la fertilización a base de nitrógeno. En
un rancho del estado de Tabasco, México se realizó un experimento
con el objetivo de conocer el efecto de la fertilización nitrogenada
y de la leche bovina. Se utilizaron dos parcelas con pasto Cayman
Blend y sólo una de ellas se fertilizó con urea (150 kg·ha
-1
) y a
cada parcela se le asignó un grupo de cinco vacas en producción
mediante un diseño de bloques completos al azar. Se utilizó un
pastoreo rotacional intensivo y se tomaron muestras de pasto y
leche los días 14, 21 y 28 del periodo experimental. La fertilización
nitrogenada aumentó (P
El pasto fertilizado aumentó (P
P>0,05) los contenidos
de proteína, lactosa y CLA. Se encontró relación lineal positiva
(P
concentración de CLA en leche. La fertilización nitrogenada del
pasto Cayman Blend aumenta la producción de forraje, el contenido
de proteína bruta en el pasto y el contenido de grasa en leche sin
afectar al contenido de CLA y otros ácidos grasos.
Palabras clave: Ácido linoleico conjugado; pastoreo; forraje;
lípidos; trópicos
Nitrogen fertilization of Cayman Blend grass (Urochloa hybrid cv.
GP0423 + GP4467) on the chemical composition and fatty acid prole
in milk from grazing cows
Fertilización nitrogenada del pasto Cayman Blend (Urochloa híbrida cv. GP0423 + GP4467)
sobre la composición química y el perl de ácidos grasos en leche de vacas en pastoreo
Isabel Cristina Acosta–Balcazar
1
, Yuridia Bautista–Martínez
1
, Benigno Estrada–Drouaillet
2
, José Felipe Orzuna–Orzuna
3
,
Miguel Ruíz–Albarran
1
, Jorge David Guiot–García
4
, Lorenzo Danilo Granados–Rivera
5
*
1
Universidad Autónoma de Tamaulipas, Facultad de Medicina Veterinaria y Zootecnia. Ciudad Victoria, Tamaulipas, México.
2
Universidad Autónoma de Tamaulipas, Facultad de Ingenierías y Ciencias. Ciudad Victoria, Tamaulipas, México.
3
Universidad Autónoma Chapingo, Departamento de Zootecnia. Chapingo, Estado de México, México.
4
Grupo Papalotla S.A. de C.V. Ciudad de México, México.
5
Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Campo Experimental–General Terán, Nuevo León, México.
*Corresponding author: granados.danilo@inifap.gob.mx
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
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INTRODUCTION
Milk is a nutrient–rich food that constitutes a primary dietary
component, particularly for children [1
several essential nutrients, including vitamin D, calcium, protein,
cow’s milk (Bos taurus) [2].
3]. Conjugated linoleic acid
(CLA) is the end product of the ruminal biohydrogenation process of
linoleic and α–linolenic acids [4]. The cis–9, trans–11 CLA isomer
is generated endogenously or exogenously [5]. CLA has been
associated with enhanced health outcomes and may potentially
contribute to the prevention of obesity, arteriosclerosis, diabetes,
and certain types of cancer [6].
demand foods that are more natural, healthy, and functional,
with a concomitantly low environmental impact, has increased.
Spain have begun to commercially offer milk with a high content
method [3].
The content and chemical composition of conjugated linoleic
of factors, including the type of feed provided, the breed, age,
health status, and lactation stage of the cow. For example, the
primary factor influencing the fat and protein content of milk is
the composition of the diet [7
influenced by the type of feed consumed by the animal, including
grass, green fodder, silage, and supplements with fats or oilseeds
[8], as well as the use of vitamin–mineral supplements [9].
The scientific evidence suggests that the concentration of
conjugated linoleic acid (CLA) in milk derived from grazing cows
10]. This effect is
linoleic and α–linolenic acid, with the latter being the predominant
11]. The content of linoleic and α–linolenic fatty
acids in grasses can be increased through the implementation of
management techniques that promote rapid vegetative growth.
These techniques include the application of nitrogen fertilization,
which has been observed to cause an increase in the synthesis
and accumulation of lipids in forage plants [11, 12
α–linolenic fatty acids, respectively,
been reported in comparison to non–nitrogen–fertilized grasses
[11, 13
the present study’s hypothesis postulates that dairy cows fed a
nitrogen–fertilized pasture consumed at an early stage of regrowth
will produce milk with a higher concentration of CLA. Accordingly,
the objective of this study was to assess the impact of nitrogen
fertilization on the chemical composition and concentration of
fatty acids in milk from grazing cows.
MATERIALS Y METHODS
Location and area of study
The study was conducted on a farm with a dual–purpose
cattle production system located in the state of Tabasco, Mexico
(Longitude: -98.102778 and Latitude: 22.784167; 20 masl). The
region’s climate is tropical, with rain all year round, and the average
recorded precipitation is 2,452 mm·year
-1
[11]. Two plots of
2
each were used, which were planted with Cayman Blend
grass (Urochloa hybrid cv. GP0423 + GP4467; Grupo Papalotla).
Fertilization and pasture management
Fifty-six days (d) before the start of the experiment, a group
used in the study) was assigned to each of the plots to consume
the available grass and ensure that it had a uniform height at the
start of the experiment.
Twenty–eight and 10 d before the start of the experimental
phase, only one of the plots was fertilized with 150 kg·ha
-1
of
nitrogen (using urea), and the other remained as a control plot,
so there were two treatments: 1) fertilized Cayman Blend grass
and 2) unfertilized Cayman Blend grass.
Cow management and feeding
groups were randomly assigned to each plot using a randomized
complete block design.
Cows had a pre–experimental period of 7 d to adapt to the
management and an experimental period of 21 d for sampling.
The type of grazing used was intensive rotational grazing, where
each plot was divided into 29 sections (approximately 60 m × 4
m) and the occupancy time per section was 24 hours (h). This
ensured that the pasture of section 1 had 28 d of rest before
starting a new grazing cycle. The cows’ diet was supplemented
with commercial feed (2 kg DM·cow
-1
·d
-1
), which was offered daily
at machine milking (6:00).
Sampling
After the pre–experimental period, grass and milk samples were
taken every 7 days, i.e. on d 14, 21 and 28 of the grazing cycle. Three
sampling points were randomly chosen within the corresponding
division of that days to obtain the grass samples using a 0.25 m
2
square. The grass was cut 10 cm from the ground, simulating the
paper bags to be dried and analysed. This process was carried out
on the three sampling days in both treatments. The milk samples
were weighed using an automatic milk weigher (Waikato MK New
from each cow. These samples were stored in sterilized jars and
the end of the experiment, 9 grass samples and 15 milk samples
were collected for each treatment.
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
_________________________________________________________________________________________________Revista Cientica, FCV-LUZ / Vol.XXXV
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Laboratory analysis
The chemical composition of the grass was determined using
the procedures described in the following methodologies: AOAC
[13] for PC, Van Soest et al. [14] for ADF and NDF, Mabjeesh et al.
[15
the milk was determined using a LactiCheck™–01 RapiRead brand
using gas chromatography, which had three phases: extraction,
Rivera et al. [4]. A Hewlett Packard 6890 chromatograph with an
automatic injector and a silica capillary column (100 m × 0.25 mm
× 0.20 μm thick, Sp–2560, Supelco) was used to quantify FA methyl
times of each peak obtained from the chromatogram, with a standard
of 37 FA methyl ester components (Supelco 37 Component FAME)
cis–9, trans–11 and trans–10, cis–12 (Nu–Check–Prep.).
Measured response variables
On pasture
Total forage production (kg·ha
-1
), leaf production (kg·ha
-1
), stem
production (kg·ha
-1
), bromatological composition (crude protein
States), in vitro
by gas chromatography (g·100 g
-1
of FA) (Hewlett Packard, 6890,
In milk
Daily milk production per cow (kg·d
-1
), energy–corrected milk
production (ECMP; kg·d
-1
and yield (g·d
-1
(g·100 g
-1
of FA).
Energy–corrected milk production was determined with the
following equation:
ECMP = (0.327×milk yield –kg·d
-1
–) + (12.95×fat yield –kg·d
-1
–)
+ (7.65×protein yield –kg·d
-1
–) [16].
Statistical analysis
a repeated measures model. For this, the Bayesian information
criteria of Schwarz and Akaike were obtained and used to determine
the most appropriate covariance structure for each variable. The
comparison of means was performed through the Tukey test
(P
the concentration of linoleic and α–linolenic acid in the grass and
the concentration of conjugated linoleic acid in milk.
RESULTS AND DISCUSSION
Forage production
Total forage production, leaf production, and stem production
of the grass increased (P
leaf production, and stem production increased (P
sampling days increased, where the maximum production of total
forage and its components was obtained on d 21 of sampling.
TABLE I
Forage production (total, per leaf and stem) and bromatological composition of Cayman Blend
grass (Urochloa hybrid cv. GP0423 + GP4467) with and without nitrogen fertilization
Variables
Treatments Sampling days P–Value
F
1
NF
1
14 21 28 Treatment Days T*D
Forage production (kg·ha
-1
)
Total 16.806.1
a
7.866.4
b
6.633.4
c
16.732.1
a
13.553.1
b
** * NS
Byleaf 9.075.3
a
4.090.5
b
3.449.3
c
9.035.3
a
7.047.6
b
** * NS
By steam 7.730.8
a
3.775.9
b
3.184.0
c
7.696.7
a
6.505.5
b
** * NS
Bromatological composition (DM %)
CP
1
17.0
a
14.3
b
15.6 14.6 16.8 ** NS NS
ADF
1
34.7
b
36.2
a
36.6
a
36.5
ab
33.1
b
* * NS
NDF
1
55.2
b
56.6
a
56.0 57.2 54.5 * NS NS
IVDMD
1
74.4 74.9 74.6 73.1 76.3 NS NS NS
EE
1
2.6
b
3.6
a
2.9
b
2.9
b
3.4
a
* * NS
1
F:fertilized,NF:unfertilized,T*Dtreatment*day,DM:drymatter,CP:crudeprotein,ADF:aciddetergentber,NDF:neutraldetergent
ber,IVDMD:
in vitrodrymatterdigestibility,EE:etherextract.
a,b
: Dierentsuperscriptsinthesamerowandwithineachfactor
(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,
P≤0.05).*P≤0.05,**P≤0.01,NS:non–signicantdierence,P>0.05
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
4 of 8 5 of 8
As posited by Acosta–Balcazar et al. [3], the forage production
and nutritional quality of grasses are subject to the influence of both
abiotic and biotic factors. The former encompasses temperature,
humidity, solar radiation, soil fertility, and mineral fertilization, while
the latter pertains to grass species and crop management. Among
the primary elements utilized in mineral fertilization is nitrogen,
which plays a pivotal role in the synthesis of the cytokinin hormone,
a vital regulator of plant growth. This hormone also initiates the
process of cell division and differentiation. Similarly, nitrogen has
been observed to elevate foliar nitrogen concentrations, stimulate
photosynthesis and internode elongation, and augment the size
grasses [17, 18]. These effects of nitrogen may be responsible for
the higher forage production observed in the fertilized Cayman Blend
grass in the current study. Benalcázar–Carranza et al. [19] asserts
that nitrogen is the most crucial nutrient for forage production, as
it can facilitate the optimization of biomass production in grasses
when administered in appropriate quantities.
Bromatological composition in grass
The CP content of the grass increased (P
EE contents in the nitrogen–fertilized grass decreased (P
affected (P>0.05) by nitrogen fertilization.
The nitrogen plays a pivotal role in the synthesis of metabolic
compounds in grass, particularly in leaves [11]. The elevated CP
content observed in nitrogen–fertilized grass is consistent with
expectations, given that nitrogen is the primary component of proteins.
The application of nitrogen fertilizers has been demonstrated to
enhance CP content in tropical grasses by up to 19].
Likewise, the present study revealed that the contents of ADF
Cayman Blend grass than in unfertilized grass. The ADF content is
useful for evaluating digestibility in grasses, while NDF is associated
with the proportion of structural carbohydrates (lignin, cellulose, and
hemicellulose), which can influence the availability of metabolizable
energy and limit ingestive capacity in ruminants [20]. A high lignin
content in the cell wall of pastures reduces the contact area between
ruminal bacteria and forage particles, which has a detrimental impact
on the ruminal degradability of the feed and the equilibrium between
energy and protein at the ruminal level.
As vegetative development progresses, the cell content
declines at an accelerated rate, and the leaves age and lose
their photosynthetic capacity. This physiological effect may be
associated with the reduced levels of ADF and EE observed on
et al. [20].
Fatty acid prole in grass
ten belong to the group of saturated FA (SFA; lauric, myristic,
pentadecanoic, palmitic, heptadecanoic, stearic, arachidic,
behenic, tricosanoic, and lignoceric), two are monounsaturated
γ–linolenic and α–linolenic) (
With the exception of linoleic and tricosanoic acids, the other
fatty acids found were similar in both treatments. Fertilisation
increased the content of linoleic acid (LFA) and decreased that of
to make a difference between treatments.
Despite this, the linoleic and α–linolenic contents of Cayman
Blend grass with and without fertilization were higher than the FA
values reported by Mojica et al. [12] in grasses of the same genus
(Urochloa12], the linoleic acid
values ranged between 0.32 and 0.99 g.·100 g
-1
of FA, while the
α–linolenic acid values ranged from 0.12 to 1.08 g.·100 g
-1
of FA
in the Toledo, Mulato, and Humidicola grasses.
Morales–Almaráz et al. [10] mention that the fat portion of
linoleic and α
linoleic and α
the total FA in fertilized and unfertilized grass. This variation in
the percentages of linoleic and α–linolenic FA could be mainly
explained by the difference in the forage grasses used, the
treatments applied, and the environmental conditions of each
experiment [12et al. [8] pointed
out that the content and composition of FA in forage grasses are
affected by several factors, such as the species and variety of
plants, climate, light intensity, rainfall, fertilization, growth stage,
soil fertility, among others.
TABLE II
Fatty acid prole (g·100 g
-1
of FA) of Cayman Blend grass (Urochloa
hybrid cv. GP0423 + GP4467) with and without nitrogen fertilization
Fatty acids
Treatments
P–Value
Fertilized SEM Unfertilized SEM
g.100 g
-1
of fatty acids
Lauric 0.93 0.045 0.64 0.250 NS
Myristic 0.43 0.037 0.43 0.108 NS
Pentadecanoic 0.18 0.022 0.13 0.039 NS
Palmitic 24.35 3.408 24.10 1.980 NS
Palmitoleic 0.45 0.178 0.41 0.152 NS
Heptadecanoic 0.30 0.009 0.25 0.034 NS
Stearic 2.66 0.248 2.49 0.044 NS
Oleic 2.59 0.316 1.94 0.591 NS
Linoleadic 0.12
a
0.020 0.08
b
0.020 **
Linoleic 17.74 2.184 17.04 1.389 NS
Arachidic 0.53 0.080 0.46 0.051 NS
γ–Linolenic 0.23 0.017 0.18 0.017 NS
α–Linolenic 37.66 2.232 36.88 0.526 NS
Behenic 0.94 0.277 0.84 0.219 NS
Tricosanoic 0.37
b
0.032 0.47
a
0.023 **
Lignoceric 1.30 0.365 1.30 0.375 NS
Unidentied 11.10 0.6040 10.14 0.451 NS
SEM:standarderrorofthemean.
a,b
Dierentlettersbetweentreatmentsindicatea
signicantdierence(Tukey,
P≤0.05).**P≤0.01.NS:non–signicantdierence,P>0.05
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
_________________________________________________________________________________________________Revista Cientica, FCV-LUZ / Vol.XXXV
5 of 8
Chemical composition of milk
Milk production was similar across treatments (P>0.05) but was
P
content (P>0.05). However, cows consuming fertilized Cayman
P
sampling days, milk fat increased (P
compared to d 14 of sampling. Fat, protein, and lactose yields
were not affected (P>0.05) by the treatments (
The differences found in fat, protein and lactose yields per sampling
day were due to the amount of milk produced on those days.
The milk production observed among the experimental groups was
comparable, with the mean values recorded (6.3 and 6.9 kg·cow
-1
·d
-1
)
falling within the typical range (3 to 9 kg·cow
-1
·d
-1
) for cows under
grazing conditions with tropical grasses [21]. However, the results
were lower than those reported by Plata et al. [22], who observed
milk yields of between 14 and 16 kg·d
-1
the results of the present study were higher than those reported
by Mojica et al. [12], who observed a daily milk yield of 4.8 kg in
lactating cows consuming different grasses. The discrepancy in the
observed daily milk production between studies may be attributed
cows under evaluation.
Conversely, milk production in both treatments demonstrated
a decline as the experimental period increased. Acosta–Balcazar
et al. [8] cite the observation that following the peak of milk
production, milk–secreting cells in the mammary gland undergo
a decline as the lactation period increases. This results in a
This natural physiological mechanism of the mammary gland
provides an explanation for the reduction in milk production at
the conclusion of the experimental period.
Fatty acid prole in milk
lauric, myristic, pentadecanoic, palmitic, heptadecanoic, stearic,
α–
linolenic, and the cis–9 trans–11 isomer of conjugated linoleic
than 0.1 g·100 g
-1
of FA). Of the FA detected in milk, those with the
highest concentration were myristic, palmitic, stearic, and oleic,
representing between 10 and 33 g·100 g
-1
of total FA.
P
and sampling days were caproic, pentadecanoic, heptadecanoic,
concentration of caproic and cis–10–heptadecanoic FA was
obtained with the NF/28 interaction. Likewise, heptadecanoic and
CLA FA showed higher concentrations with the NF/21 interaction
than with other interactions. The highest concentration of FA from
NF/21 interactions.
(0.053 g·100 g
-1
)(P
CLA in milk, in which when the linoleic content in grass increased
by one percentage unit, the CLA content in milk increased by
0.053 g·100 g
-1
of FA.
The percentage of milk fat was found to be higher in cows that
consumed nitrogen–fertilized grass. This effect may be attributed
fertilized plot, resulting from the enhanced total forage production.
TABLE III
Chemical composition of milk from cows that consumed Cayman Blend grass (Urochloa
hybrid cv. CIAT BR02/1752 + GP0423) with and without nitrogen fertilization
Variables
Treatments Sampling days P–Value
F NF 14 21 28 Treatment Days T*D
Production(kg·d
-1
) 6.30 6.90 7.21
a
6.10
b
6.50
ab
NS * NS
ECMP(kg·d
-1
) 6.11 6.72 6.96
a
5.92
b
6.37
ab
NS * NS
Percentage (%)
Fat 3.99
a
3.03
b
3.35
b
3.50
ab
3.68ª * NS NS
Protein 3.37 3.41 3.42 3.42 3.33 NS * NS
Lactose 4.85 4.92 4.94 4.93 4.79 NS * NS
Yield (g·d
-1
)
Fat 197.96 224.67 222.49
a
193.38
b
218.08
ab
NS * NS
Protein 227.71 214.32 244.18
a
204.44
ab
214.43
b
NS * NS
Lactose 332.01 305.54 352.58
a
294.98
b
308.77
ab
NS * NS
F:fertilized,NF:unfertilized,T*Dtreatment*day,ECMP:energy–correctedmilkproduction
a,b:
Dierentsuperscriptsinthesamerow
andwithineachfactor(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,
P≤0.05).*P≤0.05,NS:non–signicant
dierence,
P>0.05
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
6 of 8 7 of 8
the ruminal production of acetic and butyric acid, which serve as the
primary substrates for synthesizing milk fat in the mammary gland [8].
Bovine milk contains approximately 400 FA, among which the
majority are at trace levels, and only 15 are greater than or equal
4]. However, in the current study, in both treatments,
pentadecanoic, palmitic, palmitoleic, stearic, elaidic, and oleic).
the concentration of the four most abundant FAs differed from the
FA in milk from grazing cows was found to be lower than the values
reported in previous studies [23, 24]. However, the range (27.27 to
29.51 g·100 g
-1
FA) of oleic FA in milk from grazing cows reported by
Lahlou et al. [23] and Ortega et al. [24] was higher than the values
of oleic FA observed in the present study. Acosta–Balcazar et al. [3]
state that the content of unsaturated FA (oleic) in the milk of grazing
ruminants typically increases, while the content of saturated FA
(e.g., palmitic, stearic, and myristic) typically decreases.
TABLE IV
Fatty acid prole (g·100 g
-1
of FA) in milk from cows that consumed Cayman Blend grass (Urochloa
hybrid cv. CIAT BR02/1752 + GP0423) with and without nitrogen fertilization
Variables
Treatments Sampling days P–Value
F NF 14 21 28 Treatment Days T*D
Butyric 0.84 0.82 0.84 0.64 1.01 NS NS NS
Caproic 0.23 0.38 0.20 0.22 0.50 NS NS *
Capric 1.39 1.59 1.61
a
1.32
b
1.53
ab
NS * NS
Lauric 2.61 2.59 2.76
ab
2.22
b
2.82
a
NS * NS
Myristic 10.52 10.55 11.00
ab
9.39
b
11.20
a
NS * NS
Myristoleic 0.83 0.80 0.89
a
0.72
b
0.83
ab
NS * NS
Pentadecanoic 1.30 1.21 1.24 1.22 1.30 NS NS **
Palmitic 32.08 32.70 32.15
ab
29.64
b
35.39
a
NS * NS
Palmitoleic 1.52 1.37 1.49 1.59 1.25 NS NS NS
Heptadecanoic 0.83 0.87 0.86 0.84 0.84 NS NS **
Cis–10–Heptadecanoic 0.83 0.87 0.86 0.84 0.84 NS NS **
Stearic 13.27 15.00 13.71 14.31 14.39 NS NS NS
Elaidic 3.02 3.28 3.39
ab
3.40
a
2.66
b
NS * NS
Oleic 27.12 24.49 25.23
ab
29.77
a
22.41
b
NS * NS
Linoleic 0.93 0.92 0.94
ab
1.00
a
0.84
b
NS * NS
Arachidic 0.16 0.16 0.17 0.14 0.18 NS NS NS
α–Linolenic 0.25 0.23 0.26
a
0.26
ab
0.20
b
NS * NS
CLA 0.66 0.67 0.73
ab
0.75
a
0.50
b
NS * **
Unidentied
2.21 2.10 2.23 2.17 2.07 NS NS **
F:fertilized,NF:unfertilized,T*Dtreatment*day,CLA:conjugatedlinoleicacid.
a,b:
Dierentsuperscriptsinthesamerowandwithineachfactor
(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,
P≤0.05).*P≤0.05,**P≤0.01,NS:non–signicantdierence,P>0.05
TABLE V
Comparison of means of fatty acids in milk (g·100 g
-1
of FA) that had
signicant interaction (P≤0.01) between treatments and sampling days
Fatty acids
Interactions (treatments*days)
F/14 F/21 F/28 NF/14 NF/21 NF/28
Caproic 0.15
c
0.27
b
0.27
b
0.25
bc
0.17
bc
0.72
a
Pentadecanoic 1.34
ab
1.16
b
1.40
a
1.14
b
1.28
ab
1.20
ab
Heptadedcanoic 0.92
ab
0.75
b
0.81
ab
0.80
ab
0.93
a
0.87
ab
Cis–10–Heptadecanoic 0.27
bc
0.28
abc
0.19
c
0.20
c
0.28
ab
0.35
a
CLA 0.78
ab
0.66
ab
0.54
ab
0.68
ab
0.85
a
0.47
b
Unidentied 2.36
a
2.02
ab
2.26
ab
2.10
ab
2.32
a
1.89
b
F:fertilized,NF:unfertilized,CLA:conjugatedlinoleicacid.
a,b,c
: Dierentlettersinthe
samerowindicatesignicantdierence(Tukey,
P≤0.05)
TABLE VI
Estimators of the linear regression model between the linoleic and
α–linolenic acid contents of Cayman Blend grass (Urochloa hybrid cv.
CIAT BR02/1752 + GP0423) with and without nitrogen fertilization
and the concentration of conjugated linoleic acid in milk
Estimator
Intercept/F 0.430
Intercept/NF 0.388
Linoleic 0.053*
α–Linolenic -0.017
F:fertilized,NF:unfertilized,*
P≤0.05
Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________
_________________________________________________________________________________________________Revista Cientica, FCV-LUZ / Vol.XXXV
7 of 8
α–linolenic
FA in milk was found to exceed the ranges of linoleic (1.40 to
2.37 g·100 g
-1
of FA) and α–linolenic (0.34 to 0.44 g·100 g
-1
of
FA) reported in milk from cows raised in production systems
similar to the one evaluated in the current study [25, 26]. These
discrepancies may be attributed to factors such as grazing duration
or the administration of concentrated feed supplements. A study
with dairy cows [26
in milk increased by 9.1 g·kg
-1
and 11.5 g·kg
-1
, respectively, when
the animals grazed for half a day and a full day.
As indicated by Prieto et al. [26], the concentration of CLA in milk
of lactating ruminants increases in correlation with the duration
effect of the treatments on the concentration of CLA in milk, which
instead decreased at the end of the experimental period. This effect
may be attributed to alterations in lipid metabolism in dairy cows,
27], who
reserves during the initial stages of lactation, which subsequently
diminished with the progression of the lactation period.
Morales–Almaráz et al. [10] indicate that the concentration
of conjugated linoleic acid (CLA) in milk from ruminants that
are fed only grass is higher than in milk from ruminants that
are supplemented with concentrate or fed total mixed rations.
This effect is anticipated, as grasses are known to contain
higher concentrations of linoleic and α–linolenic FA, which
serve as precursors in the formation of CLA through ruminal
biohydrogenation [8]. Similarly, Morales–Almaráz et al. [10] indicate
that the concentration of α–linolenic FA is higher in grasses than in
legumes, due to the fact that lipids are found in leaf chloroplasts,
and grasses contain a greater proportion of vegetative material
comprising a considerable proportion of foliage may result in an
augmented intake of α–linolenic FA, consequently leading to an
elevated concentration of CLA in milk.
Although α
of total FA), the current study found that only the concentration of
be concluded that management strategies designed to increase
the concentration of linoleic acid in pasture may result in a higher
concentration of CLA in the milk of dairy cows.
CONCLUSION
The application of nitrogen fertilizers has been demonstrated
to enhance the production of leaves, stems, and total forage of
Cayman Blend grass. Similarly, nitrogen fertilization enhances the
bromatological composition of the grass by elevating the protein
concentration and reducing the concentration of neutral detergent
fertilized Cayman Blend grass has been demonstrated to enhance
the milk. Nevertheless, a positive linear relationship exists between
the concentration of linoleic acid in grass and the proportion of
conjugated linoleic acid in milk.
ACKNOWLEDGMENTS
To the National Council of Science and Technology (CONACYT)
Conflict of interest
the author(s).
Funding
This research was partial supported by the Grupo Papalotla.
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