Received: 23/11/2024 Accepted: 02/01/2025 Published: 04/03/2025 1 of 8

https://doi.org/10.52973/rcfcv-e35577 RevistaCientíca,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 prole

in milk from grazing cows

Fertilización nitrogenada del pasto Cayman Blend (Urochloa híbrida cv. GP0423 + GP4467)

sobre la composición química y el perl de ácidos grasos en leche de vacas en pastoreo

Isabel Cristina Acosta–Balcazar

, Yuridia Bautista–Martínez

, Benigno Estrada–Drouaillet

, José Felipe Orzuna–Orzuna

Miguel Ruíz–Albarran

, Jorge David Guiot–García

, Lorenzo Danilo Granados–Rivera

Universidad Autónoma de Tamaulipas, Facultad de Medicina Veterinaria y Zootecnia. Ciudad Victoria, Tamaulipas, México.

Universidad Autónoma de Tamaulipas, Facultad de Ingenierías y Ciencias. Ciudad Victoria, Tamaulipas, México.

Universidad Autónoma Chapingo, Departamento de Zootecnia. Chapingo, Estado de México, México.

Grupo Papalotla S.A. de C.V. Ciudad de México, México.

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 prole in milk / Acosta–Balcazar et al.________________________________

2 of 8 3 of 8

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



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

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

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 prole in milk / Acosta–Balcazar et al.________________________________

_________________________________________________________________________________________________Revista Cientica, FCV-LUZ / Vol.XXXV

3 of 8

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

14 21 28 Treatment Days T*D

Forage production (kg·ha

-1

)

Total 16.806.1

7.866.4

6.633.4

16.732.1

13.553.1

** * NS

Byleaf 9.075.3

4.090.5

3.449.3

9.035.3

7.047.6

** * NS

By steam 7.730.8

3.775.9

3.184.0

7.696.7

6.505.5

** * NS

Bromatological composition (DM %)

17.0

14.3

15.6 14.6 16.8 ** NS NS

ADF

34.7

36.2

36.6

36.5

33.1

* * NS

NDF

55.2

56.6

56.0 57.2 54.5 * NS NS

IVDMD

74.4 74.9 74.6 73.1 76.3 NS NS NS

2.6

3.6

2.9

3.4

* * NS

F:fertilized,NF:unfertilized,T*Dtreatment*day,DM:drymatter,CP:crudeprotein,ADF:aciddetergentber,NDF:neutraldetergent

ber,IVDMD:

in vitrodrymatterdigestibility,EE:etherextract.

a,b

: Dierentsuperscriptsinthesamerowandwithineachfactor

(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,

P≤0.05).*P≤0.05,**P≤0.01,NS:non–signicantdierence,P>0.05

Nitrogen fertilization of Cayman Blend grass and fatty acid prole 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 prole 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

(Urochloa12], 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 [12et 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 prole (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

0.020 0.08

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

0.032 0.47

0.023 **

Lignoceric 1.30 0.365 1.30 0.375 NS

Unidentied 11.10 0.6040 10.14 0.451 NS

SEM:standarderrorofthemean.

a,b

Dierentlettersbetweentreatmentsindicatea

signicantdierence(Tukey,

P≤0.05).**P≤0.01.NS:non–signicantdierence,P>0.05

Nitrogen fertilization of Cayman Blend grass and fatty acid prole in milk / Acosta–Balcazar et al.________________________________

_________________________________________________________________________________________________Revista Cientica, 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 prole 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

6.10

6.50

NS * NS

ECMP(kg·d

-1

) 6.11 6.72 6.96

5.92

6.37

NS * NS

Percentage (%)

Fat 3.99

3.03

3.35

3.50

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

193.38

218.08

NS * NS

Protein 227.71 214.32 244.18

204.44

214.43

NS * NS

Lactose 332.01 305.54 352.58

294.98

308.77

NS * NS

F:fertilized,NF:unfertilized,T*Dtreatment*day,ECMP:energy–correctedmilkproduction

a,b:

Dierentsuperscriptsinthesamerow

andwithineachfactor(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,

P≤0.05).*P≤0.05,NS:non–signicant

dierence,

P>0.05

Nitrogen fertilization of Cayman Blend grass and fatty acid prole 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 prole (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

1.32

1.53

NS * NS

Lauric 2.61 2.59 2.76

2.22

2.82

NS * NS

Myristic 10.52 10.55 11.00

9.39

11.20

NS * NS

Myristoleic 0.83 0.80 0.89

0.72

0.83

NS * NS

Pentadecanoic 1.30 1.21 1.24 1.22 1.30 NS NS **

Palmitic 32.08 32.70 32.15

29.64

35.39

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

3.40

2.66

NS * NS

Oleic 27.12 24.49 25.23

29.77

22.41

NS * NS

Linoleic 0.93 0.92 0.94

1.00

0.84

NS * NS

Arachidic 0.16 0.16 0.17 0.14 0.18 NS NS NS

α–Linolenic 0.25 0.23 0.26

0.26

0.20

NS * NS

CLA 0.66 0.67 0.73

0.75

0.50

NS * **

Unidentied

2.21 2.10 2.23 2.17 2.07 NS NS **

F:fertilized,NF:unfertilized,T*Dtreatment*day,CLA:conjugatedlinoleicacid.

a,b:

Dierentsuperscriptsinthesamerowandwithineachfactor

(treatmentsorsamplingdays)indicateasignicantdierence(Tukey,

P≤0.05).*P≤0.05,**P≤0.01,NS:non–signicantdierence,P>0.05

TABLE V

Comparison of means of fatty acids in milk (g·100 g

-1

of FA) that had

signicant 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

0.27

0.25

0.17

0.72

Pentadecanoic 1.34

1.16

1.40

1.14

1.28

1.20

Heptadedcanoic 0.92

0.75

0.81

0.80

0.93

0.87

Cis–10–Heptadecanoic 0.27

0.28

abc

0.19

0.20

0.28

0.35

CLA 0.78

0.66

0.54

0.68

0.85

0.47

Unidentied 2.36

2.02

2.26

2.10

2.32

1.89

F:fertilized,NF:unfertilized,CLA:conjugatedlinoleicacid.

a,b,c

: Dierentlettersinthe

samerowindicatesignicantdierence(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 prole in milk / Acosta–Balcazar et al.________________________________

_________________________________________________________________________________________________Revista Cientica, 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

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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