DOI: https://doi.org/10.52973/rcfcv-luz312.art2

Recibido: 21/01/2021 Aceptado: 05/04/2021

Revista Cientica, FCV-LUZ / Vol. XXXI, N°2, 53 - 60, 2021

ABSTRACT

Ninety-nine uncastrated males were randomly distributed into four

grazing groups to examine variation in growth and carcass traits,

due to the implant regime [Implantation of 72 miligrams (mg) of

Ralgro® at day (d) 0 followed by its reimplantation at d 90 versus

implantation of Revalor® at d 0 followed by 72 mg of Ralgro® at

d 90)], and suplementation type [mineral supplementation (MS)

versus strategic supplementation (SS)]. With a 2 x 2 factorial

arrangement, the analysis of variance included the treatments

and their interaction (implant regimen x supplementation) as xed

eects, and the breed type as a random eect. The interaction

was not signicant; neither did the implant regimen on any growth

trait (P > 0.05). Compared to MS, the SS group had a greater daily

weight gain (779 vs. 541 grams; P < 0.001), required a shorter

(38.3 d lesser) time of fattening to reach the end point (198.3

versus 236.6 d; P < 0.001) with a heavier liveweight (498. 2 vs.

474. 4 kilograms; P = 0.02) at an earlier age (29.4 vs. 30. 8 months;

P < 0.001), with a higher carcass dressing percentage (59.13 vs

57.62 %; P = 0.03) and younger carcass bone maturity (P < 0.001).

With the exception of thoracic depth, carcass traits did not vary

with the implant regimen (P > 0.05). Both implant regimens are

comparable in their effects on the fattening performance and

commercially important carcass traits of grassfed bulls. SS is a

feasible practice to improve fattening performance of grazing bulls

but no benecial impact on their carcass quality was expected.

Key words: Strategic supplementation; implants; bull; beef

carcass; Brahman

RESUMEN

Noventa y nueve machos sin castrar se distribuyeron al azar en

cuatro grupos a pastoreo para examinar la variación en rasgos

de crecimiento y en canal, debida a régimen de implantes

[72 miligramos (mg) de Ralgro® el día (d) 0 seguido de su

reimplante el d 90 versus implantación de Revalor® el d 0

seguido de 72 mg de Ralgro® el d 90] y suplementación [mezcla

mineral (SM) versus suplemento estratégico (SE)]. El análisis

de varianza con arreglo factorial 2 x 2 incluyó, como efectos

jos, los tratamientos y su interaccion (régimen de implantes x

suplementación) y tipo racial como efecto aleatorio. En rasgos de

crecimiento, la interacción no fue signicativa (P > 0,05); tampoco

lo fué el régimen de implante (P > 0,05). El grupo con SE, con

respecto al que recibió SM, tuvo mayor ganancia diaria de peso

(779 vs. 541 gramos; P < 0,001) requirió 38,3 d menos de ceba

[(198,3 versus 236,6 d; (P < 0,001)] para alcanzar mayor peso

vivo nal (498,2 versus 474,4 kilogramos; P = 0,02) a una edad

más temprana (29,4 versus 30,8 meses; P < 0,001), con mayor

rendimiento en canal (59,13 versus 57,62 %; P = 0,03) y una

menor madurez ósea de la canal (P < 0,001). A excepción de

la profundidad torácica, los rasgos en canal no variaron con el

régimen de implantes (P > 0,05). Los dos regímenes agresivos

de implantes aquí evaluados son equiparables en sus efectos

sobre el desempeño en la ceba y caracteristicas comercialmente

importantes de la canal. La SE es una práctica factible para

mejorar el desempeño de toros en la ceba a pastoreo, pero no

puede esperarse benecio alguno en la calidad de sus canales.

Palabras clave: Suplementación estratégica; implantes; toros;

canales, Brahman

Fattening performance and carcass traits of implanted and

supplemented grassfed bulls

Desempeño en la ceba a pastoreo y rasgos de la canal de toros implantados y

suplementados

Nelson Huerta-Leidenz

1,2

* , Nancy Jerez-Timaure

1,3

, Susmira Godoy

, Carlos Rodríguez-Matos

y Omar Araujo-Febres

Facultad de Agronomía, Departamento de Zootecnia, Universidad del Zulia. Maracaibo, Venezuela.

Department of Animal and Food

Sciences, Texas Tech University. Texas, USA.

Instituto de Ciencia Animal, Facultad de Ciencias Veterinarias, Universidad Austral de

Chile. Valdivia, Chile.

Instituto Nacional de Investigaciones Agrícolas. Centro Nacional de Investigaciones Agropecuarias. Maracay,

Aragua, Venezuela.

Hato Santa Luisa C. A. Caracas, Venezuela. *Email: nelson.huerta@ttu.edu

Responses to implants and supplementation of grazing bulls / Huerta-Leidenz et al.__________________________________________

INTRODUCTION

With the construction of dikes (modules) to control oods and

to have water available during the dry season [32], the native

vegetation of the lower plains of Apure State (Venezuela) has

been replaced with better forage (e.g., Brachiaria spp.) resources

[21]. However, during the seasonal drought, the nutritional quality

of cultivated grasses can drop to levels that impair the biological

response of genetically improved cattle [27] even with mineral or

mineral-protein supplementation [9].

The unsuccessful attempts to improve the response of cattle with

greater genetic potential indicate the need for ad hoc application of

technological packages; particularly, when the ranchers in the area

intend to fatten cattle at the same breeding operation and harvest

them in packing houses authorized for carcass classification

and grading, hoping for a better return on investment [17, 29,

30]. Synthetic anabolic implants, based on steroidal compounds

such as trenbolone acetate + 17β-estradiol (ATB + E17) and

non-steroidal, estrogenic compounds, such as Zeranol (a lactone

of resorcylic acid, Ralgro®) constitute technological resources

widely used to improve the response in productive performance

and the lean: fat ratio in carcasses of castrated males (steers);

especially under intensive fattening in North America [1, 3, 33].

On the contrary, few studies have evaluated the response of entire

males (bulls or bullocks) to anabolics, yielding null or inconsistent

results [12, 23 – 25]. Potent implants (e.g., ATB + E17), as well as

more aggressive anabolic combinations or strategies, administered

to predominantly Bos taurus steers during intensive fattening, have

negatively aected marbling level and the U.S.carcass quality

grade [33].

These ndings suggest that aggressive implant regimes used

to improve fattening performance in grazing bulls with Bos indicus

genetics, may have a more detrimental impact on carcass quality.

In the low (“modulated’) plains of Apure, improvements have

been observed in the growth rate of steers and bulls, fattened to

grazing with a strategic (catalytic) supplement [6] and in the same

ranch an additive supplementation brought about improvements in

quality traits of bull carcasses [17]. As the vast majority of cattle in

Venezuela are fattened on pasture, there is interest in evaluating

the eect of more aggressive implant regimes on the performance

of bulls under grazing conditions with a strategic supplementation.

Therefore, the objective of this trial was to examine the responses

to aggressive implant regimes and strategic supplementation in

growth and carcass traits of bulls, fattened to pastures of cultivated

grasses in the lower plains of Apure State.

MATERIALS AND METHODS

Trial location

The trial was carried out in a commercial ranch located in the low

ood plains of the Apure State (Venezuela). The ecological and soil

conditions of the area have been widely described [16, 17, 30, 31,

33]. The ranch has an infrastructure of dikes (modules) for ood

control. The grazing module (485 hectares – ha-) consists of 61

paddocks of 7.4 ha each with cultivated pastures and equipped

with electric fences (Gallaguer® model-6 wire electric fences,

Australia).

Animal handling

The animals were grown on the same ranch, so that their

management before the grazing trial was very similar. Cattle were

dewormed against ecto – and endo-parasites and vaccinated

against rabies and foot-and-mouth disease before entering the

fattening module on November 14, 1995 when the treatments

began. Trained technicians followed the criteria for animal care

and welfare described in the Bioethics and Biosafety guide of

the Venezuelan Fund for Scientic and Technological Research

(FONACIT) [13].

The trial included a total of 99 contemporary intact males (bulls).

At the beginning of the trial, the age was 23.0 ± 0.85 months (mo.),

and the average live weight (LW) was 347.1 ± 27.9 kilograms (kg) as

determined by a Fairbank-Morse ® Livestock, single-animal Scale,

LSA series model (USA). According to the feeder cattle grading

standards [28] the average frame size was 2.18 ± 0.6 (medium) with

a muscle thickness of 2.05 ± 0.6 (medium). The bulls were randomly

assigned to the four treatment groups, optimizing the balance of

observations by breed type, initial LW and treatment (TABLE I).

To avoid the paddock’s eect, the experimental groups were kept

under rotational grazing with seven (days) d of occupation and

21 d rest intervals, in modules of cultivated grasses [Brachiaria

arrecta (Tanner grass) and lesser proportion Cynodon nlemuensis

(Star grass), Brachiaria mutica (Pará grass) and Echinochloa

polystachya (German grass)].

Breed type

Treatment

1,2

Total

Ralgro-Ralgro Revalor-Ralgro

SS (n) MS (n) SS (n) MS (n)

Brahman 3 3 3 3 12

F1-Angus 3 4 3 6 16

F1-Romosinuano 3 5 3 5 16

F1-Senepol 4 5 2 5 16

F1-Simmental 4 5 3 5 17

Brahman cross 2 3 4 3 12

¾ Bos taurus 3 3 2 2 10

Total 22 28 20 29 99

TABLE I

Experimental design indicating distribution of

observations by breed type, supplementation treatment

and implant regime

Implant regime: Ralgro-Ralgro corresponds to double-dosis (72 mg)

of Ralgro

at day 0 followed by a second dosis of 72 mg of Ralgro

day 90; Revalor-Ralgro corresponds to a rst dosis of Revalor

at day 0,

followed by a second dosis (72 mg) of Ralgro

at day 90.

Supplementation

treatment: mineral supplementation as a positive control (MS) vs.

strategic supplementation (SS).

Breed types described as: F1-Angus,

F1-Romosinuano, F1-Senepol, and F1-Simmental were obtained by

artical insemination of purebred Brahman cows with semen from bulls

of Angus, Romosinuano, Senepol and Simmental breeds, respectively;

Brahman cross derived from a herd of Brahman cross cows bred with

purebred Brahman bulls; the ¾ Bos taurus were obtained by natural

mating of purebred Romosinuano bulls with F1-Romosinuano x Brahman

cows; n = number of observations.

_____________________________________________________________Revista Cientica, FCV-LUZ / Vol. XXXI, N°2, 53 - 60, 2021

Implant regimens

Two implant regimens were considered: (I) implantation of zeranol

(Ralgro®) at double dose [72 miligrams (mg); (2x-Ralgro®)] on d 0,

with reimplantation (2x-Ralgro®) at 90 d (Ralgro – Ralgro) and (II)

implantation of Revalor® (20 mg of 17 β – estradiol + 140 mg of

Trenbolone acetate) on d 0, with reimplantation of 2x-Ralgro® at

90 d (Revalor-Ralgro). The implants were subcutaneously placed

at the base of the ear of each animal following the manufacturer’s

instructions. The two implant regimens were randomly assigned to

the groups subjected to the supplementation treatments.

Supplementation treatments

The supplementation eect was measured by comparing the

traditional practice of mineral supplementation (MS) against

a strategic supplementation (SS). The MS group received the

complete mineral mixture at a rate of 80 grams (g)·animal

-1

·d

-1

oered continuously, at will. This MS contained P and Ca, and other

macro and micro elements to complement the mineral contribution

of the forage (TABLE II). The SS group was manually fed with

a supplement (1 kg·d

-1

) with a low ruminal load (catalytic) that

contained hydrolyzed feather meal, cane molasses, rice polish, a

mineral premix with P and Ca and an ionophore (Salocin® ) during

d 0-d 60 of the trial (Strategic Supplement-Phase 1; TABLE II). From

d 61 to d 182, they received a concentrate (Strategic Supplement-

Phase 2; TABLE II), which contained the same ingredients of the

Strategic Supplement-Phase 1, but in dierent proportions when

adding whole cottonseed, encapsulated bypass fat: ether extract

(EE): 22.4 %, as an additional source of bypass protein with low

ruminal degradability. Protein sources contributed 87.2 % of the

total crude protein (CP) of the supplement (54.7 % cottonseed

and 32.5 % feather meal), with a high proportion (50-70 %) of

bypass protein. The supply of the Strategic Supplement-Phase 2

was maintained for ca. 122 d (until the beginning of August, the

rainy season).

Growth performance and endpoint criteria

The average daily gain (ADG), was determined for the total

period of permanence in the module. The average LW at the end

of the fattening period was 484.52 ± 34.70 kg. Bulls were sent to

harvest when reaching a satisfactory conformation, as determined

by the visual evaluation of three judges, and/or the stability of the

daily gain/loss, once a LW of 475 kg of weight was exceeded. The

average shipping LW for transportation to the harvest plant was

509.51 ± 31.70 kg. The distribution of harvest lots with dierent

fattening d, by treatment, is presented in TABLE III.

Harvest and carcass evaluation

Dressing procedures and post-mortem inspection in the harvest

facility (Matadero Industrial Centro Occidental de Barquisimeto)

were carried out in accordance with Venezuelan standards [7].

The hot carcass was weighted and ve linear measurements were

taken before chilling (width and circumference of the thigh, length

of the pelvic limb, carcass length, and thorax depth), according to

Huerta-Leidenz et al. [15]. After refrigeration for 48 hours (h) at

4 °C (using a Vilter ® Cooler Ammonia Diusers, Model UF-42-41-

1/2-RA-HGP, USA), the chilled left sides were quartered between

the 12

and 13

rib. Two experienced judges assigned scores for

conformation and exterior fat nish, marbling level, physiological

bone and lean maturities, rib eye area (REA), and back fat

thickness over the REA (adjusted with the exterior fat finish)

following the stipulated procedures [28, 35]. The adipose maturity

was evaluated by the fat color, according to Decree 1896 [28]. The

Venezuelan category and the U.S. quality grade were respectively

estimated for each carcass [28, 35]. As the kidney, pelvic and

peri-cardiac fat depots (KPH) had been removed prior to carcass

chilling, its weight, or proportion of the carcass weight could not

be assessed. The US yield grade [35] of each bull carcass was

estimated assuming a constant KPH percentage value of 1.88 %

according to previous data [6, 17].

Composition

Supplement

Ingredient,%

Strategic-

Phase 1

Strategic-

Phase 2

Mineral

Feather meal 10.0 10.0 -

Whole cottonseed 0.0 49.9 -

Rice polish 77.0 27.1 -

Cane molasses 5.0 5.0 -

Mineral premix 7.0 7.0 -

Ionophore

1.0 1.0 -

Nutrient

EME, kcal/kg 2.514 2.809 -

PC, % 17.78 25.82 -

P, % 1.07 0.79 12.0

Ca, % 0.12 0.17 24.0

Mg, % - - 1.5

S, % - - 1.0

Mn, % - - 0.50

Zn,% - - 0.75

Fe, % - - 0.50

Cu, % - - 0.20

Co, % - - 0.004

I, % - - 0.02

Se, % - - 0.004

Strategic supplement-Phase 1 was supplied in the rst 60 days of the

trial; Strategic supplement-Phase 2 was administered manually from

day 60 to day 182 (122 days in total) at a rate of 1 kg·animal

-1

·day

-1

. The

mineral supplement was oered to the control (MS) group throughout

the test with free access (80 g·animal

-1

·day

-1

Salocin® was used as

the ionophore.

TABLE II

Composition of the forage supplements used in the trial

Responses to implants and supplementation of grazing bulls / Huerta-Leidenz et al.__________________________________________

Statistical analyses

The R software [11] was used for statistical analyses. Once

the fulllment of the assumptions of normality, independence and

sphericity of the variables was veried, the analysis of variance

(ANOVA) was performed with a mixed linear model, following a

completely randomized design with a 2 × 2 factorial arrangement

that included, as xed eects, type of supplementation, implant

regimen and their interaction. The breed type was included

in the model as a random effect. The multiple comparison of

means was made with the Tukey test (∝= 0.05). The type of

supplementation x implant regimen interaction was not signicant;

neither was the eect of implant regime on growth traits (P > 0.05).

RESULTS AND DISCUSSION

Pasture nutrient content

The nutritional contribution of the pasture during the entire trial,

with respect to its dry matter (DM) was estimated, on average:

total digestible nutrients (TDN), 63 %; CP, 6 %; nitrogen free

extract (NFE), 47 %; EE, 1 %; crude ber (CF), 34 %; ashes;

11 %; calcium (Ca), 1.1 %; phosphorus (P), 0.32 %. In general,

the average chemical composition of the pastures during the dry

season, coincides with that reported by Tejos et al. [34] for the

same paddocks, indicating a medium – to low-quality cultivated

grasses [Tanner (Brachiaria arrecta), Star (Cynodon nlemfuensis),

Pará (Brachiaria mutica) and German (Echinochloa polystachya)].

The content (% DM) of average crude protein (CP) according to

Tejos et al. [34] was one percentage point lower (ca. 5.0 %) than

the value of this work’s estimates. Assuming the bromatological

values reported by Tejos et al. [34], the CP content of the pasture

during the dry season could be lower than the cattle requirement

(CP: 7 %) [26], while the content of macro – and micro-elements

would present adequate values, with the only exception of copper,

slightly lower than the required content (Cu: 10 parts per million

(ppm) [26].

Eects of supplementation on fattening performance

The mean values and standard error for growth traits and other

performance indicators, according to the type of supplementation

are given in TABLE IV. The SS group, outperformed the MS

counterpart in ADG with an advantage of 227.7 g (P < 0.001). With

this faster growth rate, the SS group reached the end point more

rapidly (a 38.3 d shorter fattening period; P < 0.001), 1.44 mo

younger (P < 0.001) and 23.81 kg heavier in nal LW (P = 0.02).

ADG mean values in three consecutive, annual trials in the same

ranch [34] were 587, 532 and 531 g; all lower than the value found

herein for the SS group (ca. 769 g). A preliminary report from the

present trial [5] indicated that the SS group had a faster growth rate

during the rst supplementation phase (0 - 60 d), and this increase

in ADG was maintained for 150 d; thereafter, the response was

attenuated in relation to the MS group [5]. Also, Byers et al. [5]

reported the total consumption of DM by the MS group vs. SS

was 15.3 vs. 17.2 kg·head

-1

or 84 vs. 945 g·d

-1

until d 182 [5]. The

accelerated growth rate allowed SS cattle to be nished before

the start of the rainy season and its commercialization had a price

advantage, producing a 2 : 1 return on the SS investment [5].

The mean value for the SS nal LW exceeds between 17 to

27 kg to those reported for bulls of similar age (29 to 30 mo in the

same ranch [34] with nal LW of 471 kg (born in 2000), 481 kg

(born in 2001) and 477 kg (born in 2002). The final LW of SS

bulls also tends to be higher than those reported by Plasse et

al. [27] for Brahman bulls and four groups of crosses 1/4 Bos

taurus 3/4 Bos indicus (462 kg at 30.6 mo) and for most of the

breed types considered by Riera et al. [29]. The best indices of

productive performance achieved with SS could be due to its

protein sources of low ruminal degradability, such as hydrolyzed

feather meal and cottonseed, which have been shown to favor a

slow release of nitrogen (N) in the rumen, increasing the eciency

of the microbiota to synthesize proteins [4]. Furthermore, it is

known that a large part of the bypass protein fraction is degraded

in the intestine to peptides and amino acids that promote muscle

protein synthesis [14].

The literature supports the provision of a high-protein supplement

in small amounts (catalytic) to stimulate the consumption and

digestion of poor-quality forages [8], and several studies have

found that Nitrogen supplementation improves the utilization of

tropical grasses [4, 20], by achieving a greater extraction of energy

from the forage [10]. The bypass fat derived from the cottonseed

included in the strategic supplement-phase 2 could also improve

the digestible protein/digestible energy ratio and consequently,

the eciency and quantity of microbial protein [38]. On the other

hand, the addition of ionophores to the diet is known to increase

the ruminal synthesis of propionic acid, while reducing that of

butyric and acetic acids, as well as the production of methane

and ammonium; increasing the digestibility of DM, CP and ber

which optimizes the use of forages [2, 37, 39]. In sum, the change

in the ruminal fermentation pattern induced by the ionophore could

also favor the ADG in the SS group.

Fattening

days

Type of Supplementation

SS MS

RAL-RAL REV-RAL RAL-RAL REV-RAL

181 5 7 0 1 13

195 7 6 0 0 13

209 7 5 3 2 17

223 3 2 4 9 18

237 0 0 12 9 21

258 0 0 9 8 17

n 22 20 28 19 99

TABLE III.

Frequency distribution of harvest cattle lots by days

of fattening required to reach end point by type of

supplementation and implant regimen

Supplementation treaments: whole mineral supplementation (MS);

Experimental strategic supplementation (SS).

Implant regimens:

RAL-RAL corresponds to double-dosis implant (72 mg) of Ralgro®

at day 0 followed by a second dosis of 72 mg of Ralgro® at day 90;

REV-RAL corresponds to a rst dosis of Revalor® at day 0, followed by

a second dosis (72 mg) of Ralgro® at day 90

_____________________________________________________________Revista Cientica, FCV-LUZ / Vol. XXXI, N°2, 53 - 60, 2021

Eects of supplementation on carcass traits

SS only favored (P < 0.05) carcass dressing percentage and

physiological bone maturity (P < 0.001) (TABLE V). Carcasses

from the SS group signicantly dressed 1.5 percentage points more

than their MS counterparts. Also, SS carcasses exhibited a greater

youth of the skeleton (bone maturity) than those from the MS group

(P < 0.001), which corresponds to their younger chronological age

at harvest (TABLE IV). Without reaching statistical signicance,

carcasses from bulls with SS tended to have a more abundant

fat cover (P = 0.07), thicker back fat (P = 0.08) and a larger REA

(P = 0.09). The tendency to a more desirable fat cover in carcasses

from the group SS could be due to the surpassing fat provided

by the cottonseed, which is hydrolyzed in the small intestine and

absorbed for the synthesis of body fat [19].

Riera [30] evaluated the response to fattening of grazing bulls in

the same ranch, with a supplement based on 30 % corn our, 20 %

chicken litter, 15 % rice polish, 10 % soybean (Glycine max), 10 % corn

cob, 10 % molasses and 5 % of meat and bone meal. This author [30]

indicated that bull carcasses derived from the supplemented group

had a more desirable conformation and fat cover scores, as well as

a slightly more abundant marbling (P < 0.05). Also, Jerez-Timaure

and Huerta-Leidenz [17] reported a signicant increase in carcass

weight, younger bone maturity, better conformation scores, thicker

backfat and lesser yellowish fat color in the supplemented group of

bulls with respect to the control when testing a supplement based

on 41 % chicken manure, 50 % rice polish, 6 % molasses, 1.5 %

salt, 1.5 % mineral mixture and 0.83 % Rumensin ®) [17]. The

signicant improvements in quality traits related to carcass nish

observed with other types of supplementation in the same ranch

[17, 29, 30, ] may also be due to the fact that in these previous

trials, the experimental groups of bulls were not implanted.

Eects of implant regimens on fattening performance

The variables indicating productive performance did not vary

with the implant regimen (P > 0.05). Regrettably, the lack of a

control (non-implanted) group of bulls in the present investigation

does not allow to further infer about the growth promoting eects

of these implant regimens. When experiments include a control

(non-implanted) group, even under intensive fattening conditions no

signicant responses of bulls to the use of implants have been found

[24, 25]. Perhaps it is due to the interference of the endogenous

production of androgens. In fact, grass-fed bulls implanted with

zeranol before puberty have grown 4.8 % faster than non-implanted

bulls [22]; but after puberty, the response to this nonsteroidal implant

Variable

Suplementation

Type

SEM

P value

(n = 57)

(n = 42)

Hip height, cm 134.29 134.60 0.96 0.50

Fattening days 236.63 198.33 3.10 < 0.001

Chronological

age (mo.)

30.83 29.39 0.32 < 0.001

Final liveweight

on test, kg

474.42 498.23 8.16 0.02

Shipping

liveweight, kg

510.73 507.86 7.68 0.46

ADG, g 541.32 769.01 33.14 < 0.001

MS: Mineral supplementation; SS: Strategic supplementation. ADG:

Average daily gain.

Standard Error of Mean.

TABLE IV

Eects of type of suplementation on growth

performance traits of bulls during fattening on grass

Variable

Suplementation

type

SEM P value

(n = 57)

(n = 42)

Hot carcass weight, kg 294.16 300.21 4.76 0.71

Dressing, % 57.62 59.13 0.46 0.03

Conformation score

3.57 3.62 0.18 0.24

Finish score

3.63 3.05 0.16 0.42

Skeletal maturity

204.03 186.42 6.55 < 0.001

Lean maturiry

205.09 217.14 13.68 0.32

Overall maturity

205.44 201.90 9.25 0.47

Adipose maturity

2.93 2.92 0.07 0.77

Ribeye area, cm

81.75 83.64 2.66 0.09

Back fat thickness, mm 1.37 1.76 0.29 0.07

Marbling score

5.85 5.86 0.09 0.71

Thigh width, cm 61.30 62.37 0.88 0.41

Leg perimeter, cm 120.87 120.86 1.24 0.79

Length of pelvic limb, cm 57.18 56.50 1.04 0.84

Carcass length, cm 131.95 131.52 0.95 0.70

Thoracic depth, cm 37.75 37.76 0.80 0.42

TABLE V

Eects of type of suplementation on carcass traits

MS: Mineral supplementation; SS, Strategic supplementation. SEM:

Standard error of mean.

Conformation score: 1 = Very convex, 2 = Convex,

3 = Rectilinear, 4 = Concave, 5 = Very concave;

Finish score: 1 = Extremely

abundant, 2 = Abundant, 3 = Medium, 4 = Slight, 5 = Scarce;

Maturity:

carcass within the 100–199 maturity range score represents the

youngest group (100 is equal to A00 and 199 is equal to A99); 200–299:

represent carcasses with intermediate, more advanced maturity (200 is

equal to B00 and 299 is equal to B99);

Adipose maturity based on fat

color: 1 = Ivory white, 2 = Creamy white, 3 = Light yellow, 4 = Intense

yellow, 5 = Orange;

Marbling score: 1 = Abundant, 2 = Moderate,

3 = Small, 4 = Slight, 5 = Traces, 6 = Practically devoid.

Responses to implants and supplementation of grazing bulls / Huerta-Leidenz et al.__________________________________________

was inconsistent, presumably because the production of natural

hormones would already be sucient to promote growth [22].

However, this explanation is not conclusive because bulls

implanted with ATB or zeranol have presented lower levels of

testosterone, reaching puberty 12 weeks later than not implanted

counterparts [18]. Concentration and/or administration modes

have shown to affect the bulls’ response to the anabolic. The

eectiveness of boldenone undecylenate on the nal LW and ADG

of fattened bulls has been reported [12] to be dose-dependent

resulting signicantly dierent from the control when the compound

was injected at the highest dose [1 mililiter (mL)·45 kg of LW

-1

Comparison of implant regimens for carcass traits

Except for the thoracic depth, carcass traits did not vary signicantly

with the implant regimen. Carcasses of bulls implanted with Revalor-

Ralgro exhibited deeper thoracic cavities (P < 0.01) [38.4 centimeters

(cm)], 4 cm more than those from the Ralgro-Ralgro group (37.08 cm)

with a standard error of the mean of 0.75 cm (values not presented in

tabular form). The signicance of this single nding is imponderable

because no precedent was found in this regard; but it could suggest

dierences in muscle distribution in the forequarters.

Carcass classication/grading of the experimental groups

The chi square test did not detect significant differences

(P > 0.05) between the category / grade frequencies for the

different treatments. The TABLE VI shows the distribution of

these frequencies. In general, the carcass sample had a poor

grading performance in quality, indicated by: (a) predominance of

category B, the second in quality for bull carcasses by Venezuelan

standards; (b) 52 % were “Bullocks” (bulls under 30 mo of age)

that did not exceed the fourth USDA quality (Standard) grade;

and (c) 48 % were carcasses with B or more advanced maturity

(‘Bulls”), which are not eligible to be quality-graded in the USA.

[35]. In compensation, the sample performed outstandingly in the

U.S. Department of Agriculture (USDA) yield grade (USDA-YG),

reaching the top two yield grades (USDA-YG 1 and USDA-YG 2)

with superior yield capabilities in boneless lean cuts.

The results of the present trial agree with other reports reporting

carcass grades for fed entire males where the “Bulls” of “Bullocks”

with Bos indicus inuence, hardly exceeded the USDA-Standard

grade, but exhibited the top USDA yield grades [16, 36].

Carcass category/

grade

Supplementation

Implant regimen

MS n (%) SS n (%) RAL-RAL n (%) REV-RAL n (%)

Venezuelan carcass category

A 4 (7.0) 3 (7.1) 3 (6.0) 4 (8.2)

B 33 (57.9) 30 (71.4) 30 (60.0) 33 (67.3)

C 20 (35.1) 9 (21.4) 17 (34.0) 12 (24.5)

= 2.23; P = 0.32 χ

= 1.13; P = 0.56

USDA carcass quality grades

High Standard 4 (7.0) 4 (9.5) 4 (8.0) 4 (8.2)

Low Standard 21 (36.8) 22 (52.4) 18 (36.0) 25 (51.0)

Bull 32 (56.1) 16 (38.0) 28 (56.0) 20 (40.8)

= 3.15; P = 0.20 χ

= 2.46; P = 0.29

USDA carcass yield grades

1 32 (56.1) 21 (50.0) 29 (58.0) 24 (49.0)

2 25 (43.9) 20 (47.6) 21 (42.0) 24 (49.0)

3 0 (0.0) 1 (2.4) 0 (0.0) 1 (2.0)

= 1.66; P = 0.43 χ

= 1.60; P = 0.45

Total 57 42 50 49

MS: Mineral supplementation; SS: Strategic supplementation;

RAL-RAL: corresponds to double-dosis implant (72 mg) of Ralgro

day 0 followed by a second dosis of 72 mg of Ralgro

at day 90. REV-RAL: corresponds to a rst dosis of Revalor

at day 0, followed

by a second dosis (72 mg) of Ralgro

at day 90;

A and B Venezuelan carcass categories correspond to the second – and third-quality,

respectively;

Carcasses of bulls younger than 30 mo. of age and (or) exhibiting an A physiological maturity are designated in the

“Bullock” class, USDA Standard quality grade corresponds to the fourth quality, for bullock carcasses;

USDA yield grades (YG) are rated

numerically, namely 1, 2, 3, 4, and 5; a YG 1 carcass is expected to have the highest proportion (> 53.5 %) of boneless, closely-trimmed

retail cuts, while a YG 5 carcass is expected to have the lowest proportion (< 44.3 %) of boneless, closely-trimmed retail cuts.

TABLE VI

Frequency distribution of carcass categories / grades according to supplementation type and

implant regimen

_____________________________________________________________Revista Cientica, FCV-LUZ / Vol. XXXI, N°2, 53 - 60, 2021

CONCLUSIONS AND IMPLICATIONS

Both implant regimens are comparable in their eects on the

fattening performance and commercially important carcass traits

of grassfed bulls. The main limitation of the present study was the

absence of a control (non-implanted) group to quantify the eects

of the two implant regimes on the response variables under study.

Strategic supplementation proves to be a feasible practice to adopt

in low-plains pastures to improve the fattening performance of

bulls, but its impact on the overall quality of the carcass is expected

to be marginal. From bulls thus implanted and supplemented, one

can only expect very lean carcasses with high potential for cutout

performance, but value adding will be extremely dicult if a yield

grading system is not in place.

FUNDING

This research was funded by the Fondo Nacional de Ciencia,

Innovación y Tecnología (FONACIT) de Venezuela and the Consejo

de Desarrollo Cientíco y Humanístico de la Universidad del Zulia

(CONDES-LUZ).

ACKNOWLEDGMENTS

The authors thank the sta of Hato Santa Luisa Co. for their

support during the experimental trial and Matadero Centro-

Occidental (MINCO) for their valuable assistance during cattle

harvesting and carcass evaluation.

CONFLICT OF INTEREST

The authors declare no conict of interest.

BIBLIOGRAPHIC REFERENCES

[1] ARAUJO-FEBRES, O. Los promotores de crecimiento

(implantes) en el ganado bovino. En: O. Araujo-Febres (Ed.).

Tópicos especiales en la nutrición de rumiantes. Editorial

Astro Data. Maracaibo. Pp. 167-193. 2014.

[2] ARAUJO-FEBRES, O.; FERNÁNDEZ, M. C. Efecto en

novillos del Monensin y el nivel de bra de la dieta sobre el

consumo y la digestibilidad de la materia seca. Rev. Fac.

Agron. (LUZ): 8: 143-153. 1991.

[3] ARIAS, R.; SANTA-CRUZ, C.; VELÁSQUEZ, A. Eect of High

Potency Growth Implants on Average Daily Gain of Grass-

Fattened Steers. Animals. 9: 587. 2019.

[4] BENTO, C. B. P.; AZEVEDO, A. C.; GOMES, D. I.; BATISTA,

E. D.; RUFINO, L. M. A.; DETMANN, E.; MANTOVANI, H. C.

Eect of protein supplementation on ruminal parameters and

microbial community ngerprint of Nellore steers fed tropical

forages. Animals. 10(1): 44-54. 2016.

[5] BYERS, F.M.; HUERTA-LEIDENZ, N.O.; RODRGUEZ-MATOS,

C.; ORDOEZ, J.; AVELLANEDA, J.F.; STONE JR., G. Strategic

nutritional management technologies for enhancing forage beef

production in the tropical Venezuelan llanos. Arch. Latinoam.

Prod. Anim. 5 (Suppl. 1): 177-179. 1997.

[6] CONNELL, J.; HUERTA-LEIDENZ, N.; RODAS-GONZALEZ,

A. Respuesta a la tipificación en pie, suplementación y

anabolizantes de becerros en crecimiento a sabana. Arch.

Latinoam. Prod. Anim. 10(3): 156-163. 2002.

[7] COMISIÓN VENEZOLANA DE NORMAS INDUSTRIALES

(COVENIN). Carne de Bovino. Definiciones generales.

Norma venezolana COVENIN 435-82.C.D.U. 636.2:337.5.

Caracas, Venezuela. 1982.

[8] DELCURTO, T; HESS, B; HUSTON, J; OLSON, K. Optimum

supplementation strategies for beef cattle consuming

low-quality roughages in the western United States. J Anim.

Sci. 77 (Suppl E):1-16. 2000.

[9] DEPABLOS, L.; ORDÓEZ, J.; GODOY, S.; CHICCO, C.D.

Suplementación mineral proteica de novillas a pastoreo

en los Llanos Centrales de Venezuela. Zoot. Trop. 27(3):

249-262. 2009.

[10] DETMANN, E.; VALENTE, É. E. L.; BATISTA, E. D.; HUHTANEN,

P. An evaluation of the performance and efficiency of

nitrogen utilization in cattle fed tropical grass pastures with

supplementation. Livest. Sci. 162: 141-153. 2014.

[11] DEVELOPMENT CORE TEAM R: A Language and Environment

for Statistical Computing. Vienna, Austria: R Foundation for

Statistical Computing. Version 3.6. https://bit.ly/3wFcoJK. 2020.

[12] ELSHARAWY, N.T.; AHMED, A.E.; HARIDY, M.; KASSAB,

A.Y.; HAMDON, H.A. Safety range of Boldenone Undecylenate

injection in beef bulls. Biosci. Res. 16(2): 1556-1564. 2019.

[13] FONDO NACIONAL DE CIENCIA, INNOVACIÓN Y

TECNOLOGA (FONACIT). Código de Bioética y Bioseguridad.

Ministerio del Poder Popular para Ciencia y Tecnología. 3ra.

Ed. 63 pp. 2008.

[14] GARG, M.R. Role of bypass protein in feeding ruminants on crop

residues based diets Review A.J.A.S. 11 (2):107-116. 1998.

[15] HUERTA-LEIDENZ, N.; ALVARADO, E.; MARTNEZ, L.;

RINCÓN, E. Conformación, acabado y características biométricas

de la canal de diferentes clases de bovinos sacricados en el

Estado Zulia. Rev. Fac. Agron. (LUZ). 5: 522-536. 1979.

[16] HUERTA-LEIDENZ, N.; RUIZ-FLORES, A.; VALERIO-

HERNANDEZ, J.; JEREZ-TIMAURE, N.; RODAS-GONZALEZ,

A. Bullock carcass performance trends in Brahman and F1

crosses fattened on tropical pastures. NACAMEH. 14 (1):16-

30. 2020.

[17] JEREZ-TIMAURE, N.; HUERTA-LEIDENZ, N. Eects of breed

type and supplementation during grazing on carcass traits

and meat quality of bulls fattened on improved savannah.

Livest. Sci. 121, 219–226. 2009.

[18] JONES, S. J.; JOHNSON, R. D.; CALKINS, C. R.; DIKEMAN,

M. Eects of trenbolone acetate on carcass characteristics

and serum testosterone and cortisol concentrations in bulls

and steers on dierent management and implant schemes.

J Anim. Sci. 69:1363 – 1369. 1991.

[19] LABRUNE, H. J.; REINHARDT,C. D.; DIKEMAN, M,. E.;

DROUILLARD, J.S. Eects of grain processing and dietary

lipid source on performance, carcass characteristics, plasma

fatty acids, and sensory properties of steaks from nishing

cattle. J. Anim. Sci. 86:167-172. 2008.

Responses to implants and supplementation of grazing bulls / Huerta-Leidenz et al.__________________________________________

[20] LACHMANN, M.; BORTOLIN, E.; LOSADA, F.; ROMERO,

M.; ARAUJO-FEBRES, O. Inuencia del nivel de nitrógeno

suplementado sobre el consumo, la digestibilidad y la ganancia

de peso en novillos alimentados con heno de sorgo y alimento

concentrado. Rev. Fac. Agron. (LUZ). 14: 665-671. 1997.

[21] LASCANO, C.E. Harry Stobbs Memorial Lecture: Managing

the grazing resource for animal production in tropical America.

Trop. Grassl. 25: 66-72. 1991.

[22] MACKENZIE, J.R. Eects of zeranol implant on behavior,

growth rate, and carcass characteristics of Friesian bulls.

New Zealand J. Exp. Agricul. 11: 225-229. 1983.

[23] MORON – FUENMAYOR, O.; ARAUJO-FEBRES, O.; RINCON

– URDANETA, E. Efecto del implante, de la castración y

mestizaje en toretes mestizos comerciales a pastoreo con

suplementación. Rev. Fac. Agron. (LUZ). 9:49-62. 1992

[24] MORON-FUENMAYOR, O.; ARAUJO-FEBRES, O.;

BRILLEMBOURG, D. Efecto de la condición sexual y del implante

con ATB+l7b-estradiol sobre el crecimiento de animales mestizos

Santa Gertrudis. Rev. Fac. Agron. (LUZ). 11:81-87. 1994.

[25] MORÓN-FUENMAYOR, O.; ARAUJO-FEBRES, O.; HUERTA-

LEIDENZ, N.; RINCÓN, E. Efecto de los agentes anabólicos

sobre la ceba a corral y las caracteristicas de la canal de

toretes mestizos Santa Gertrudis. Rev. Fac. Agron. (LUZ).

10: 325–342. 1993.

[26] NATIONAL RESEARCH COUNCIL (NRC). Nutrient Requirements

of Beef Cattle,National Academies Press,Washington, D. C.

Pp. 40-46. 2000.

[27] PLASSE, D.; FOSSI, H.; HOOGESTEIJN, R.; VERDE,

O.; RODRGUEZ, M.C.; RODRGUEZ, R. Producción

de vacas F

Bos taurus x Brahman apareadas con toros

Brahman y de vacas Brahman con toros F

Bos taurus x

Brahman versus Brahman. 1. Pesos al nacer, destete, 18 meses

y peso nal. Livest. Res. Rural Develop. 12 (4): 14. 2000.

[28] REPÚBLICA DE VENEZUELA. Decreto Presidencial No. 1896.

Ministerio de Agricultura y Cría. Gaceta Ocial de la República

de Venezuela No 36.242. Caracas Venezuela. 4 pp. 1997.

[29] RIERA-SIGALA, T.J.; RODAS-GONZÁLEZ, A.; RODRGUEZ-

MATOS, C.; AVELLANEDA, J.F.; HUERTA-LEIDENZ, N.

Growth traits and carcass weights of purebred Brahman and

F1 Brahman x Bos taurus bulls raised and fattened semi-

intensively on improved savannah. Arch. Latinoam. Prod.

Anim. 12: 66-72. 2004.

[30] RIERA, S.T. Crecimiento y características de toros de cinco

tipos raciales y el efecto de tecnologías postmortem sobre la

calidad de la carne. Universidad Rafael Urdaneta. Maracaibo,

Venezuela. Tesis de Grado. 86 pp. 1994.

[31] RODAS-GONZÁLEZ, A.; HUERTA-LEIDENZ, N.; JEREZ-

TIMAURE, N. Benchmarking Venezuelan quality grades for

grass-fed cattle carcasses. Meat Muscle Biol. 1(1): 1-80. 2017.

[32] SMITH, J.K.; CHACÓN-MORENO, E.J.; JONGMAN, R.H.G.;

WENTING, P.H.; LOEDEMAN, J.H. Eect of dyke construction

on water dynamics in the ooding savannahs of Venezuela.

Earth Surf. Process. Landforms. 31: 81-96. 2006.

[33] SMITH, Z. K.; JOHNSON, B.J. Mechanisms of steroidal

implants to improve beef cattle growth: a review. J. Appl.

Anim. Res. 48(1): 133-141. 2020.

[34] TEJOS, M.R.; MEJAS, N.; PÉREZ, Y.; AVELLANEDA, J.F.

Manejo de pasturas y producción de carne en el llano bajo

de Venezuela. 2005. IX Seminario de pastos y forrajes.

Asociación Venezolana de Producción Animal. Pp. 171-181.

En Línea: https://bit.ly/3xmJFtl. 13/11/2020

[35] UNITED STATES DEPARTMENT OF AGRICULTURE (USDA).

Ocial United States standards for grades of carcass beef.

2017. Agricultural Marketing Service , Washington, D.C. On

Line: https://bit.ly/3wyFM4I. 30/03/2021.

[36] VAZQUEZ-MENDOZA, O.V.; ARANDA-OSORIO, G.; HUERTA-

BRAVO, M.; KHOLIF, A.E.; ELGHANDOUR, M.M.Y.; SALEM,

A.Z.M.; MALDONADO-SIMÁN, E. Carcass and meat properties

of six genotypes of young bulls nished under feedlot tropical

conditions of Mexico. Anim. Prod. Sci. 57: 1186-119. 2017.

[37] VEDOVATTO, M.; PEREIRA, C. S;, BELTRAME, J. A. M.;

NETO, I. M. C.; BENTO, A. L. L.; MARTHA, G. O. D.; MORAIS,

M. G.; FRANCO, G. L. Inclusion of concentrate and growth

promoters’ additives in sheep diets on intake, digestibility,

degradability, ruminal variables and nitrogen balance. Rev.

Mex. Cien. Pec. 11(1):132-152. 2020.

[38] WANAPAT, M; FOIKLANG, S.; ROWLINSON, P.; PILAJUN,

R. Eect of carbohydrate sources and cotton seed meal in

the concentrate: II. Feed intake, nutrient digestibility, rumen

fermentation and microbial protein synthesis in beef cattle.

Trop. Anim. Health Prod. 44: 35-42. 2012.

[39] WANG, L.M. Investigation of Alternatives to Ionophore/

Antibiotic Management Strategies in Finishing Cattle and the

Inherent Eect on Beef Quality and Shelf Life. University of

Guelph, Guelph, Ontario, Canada. Thesis of Grade. 149 pp.

2019.