Pharmacological Control of Estrus in Tropical Cattle, an Economical Assessment of Different Synchronization Protocols

doi:10.4236/ojvm.2012.23024

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Open Journal of Veterinary Medicine, 2012, 2, 151-157

http://dx.doi.org/10.4236/ojvm.2012.23024 Published Online September 2012 (http://www.SciRP.org/journal/ojvm)

Pharmacological Control of Estrus in Tropical Cattle, an

Economical Assessment of Different Synchronization

Protocols

——Economics of Estrus Control in Tropical Cows

Juan J. Molina1, Iván Molina2, Alejandro Jiménez3, Carlos S. Galina3, Juan J. Romero4,5*

1Asesor Laboratorios Intervet Schering Plough, Bogotá, Colombia

2Director Técnico Agropecuaria Las Tinajas S. A., Bogotá, Colombia

3Departamento de Reproducción, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México,

Mexico City, México

4Programa de Investigación en Medicina Poblacional, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica

5Campus Benjamín Núñez, Heredia, Costa Rica

Email: *[email protected]

Received July 12, 2012; revised August 3, 2012; accepted August 9, 2012

ABSTRACT

To compare the fertility results and to assess the cost-effectiveness of several synchronization protocols applied under

the conditions of beef cattle enterprises in Colombia, 1658 multiparous zebu crossbred cows mostly Brahman and

Nelore ranging between 2 - 6 parities were used. Five protocols of pharmacological treatments varying in hormones

used, dosage and the time of application were tested. All cows were inseminated at 52 h by appointment. Pregnancy

diagnosis was undertaken over 45 d after insemination by rectal palpation. The total cost per cow and the total cost per

gestation, for each protocol, were calculated. Taking a herd of one-hundred cows as baseline for calculations, it was

estimated the cost of the total amount of pregnancies possibly obtained in each protocol; then, the excess between the

costs of a pregnant cow and the cost of a treated cow was estimated. Additionally, the costs due to cows empty after

four services were calculated. A total of 874 pregnancies were registered (52.7%), with pregnancies per protocol vary-

ing between 46.9% and 66 .2% (p < 005). The cost per treated cow, varied betw een $64.08 and $97.47 and the co st per

gestation from $126.01 to $177.26, without association between the cost of the treatment and the pregnancy rate. Pro-

tocol A was the best cost-effective with the lowest additional costs, the lowest amount of open days (2107.7 to 2231.7 d)

and IA straws (average = 134), with an additional costs of $6940.00. Synchronization of estrus using pharmacological

products seems to have a place in the management of cattle; however, caution should be called upon a careful assess-

ment both from the part of the farm and the professional in charge of the enterprise to avoid using the technique indis-

criminatively thus propitiating the use of a method that might not be cost efficient.

Keywords: Tropics; Bos Indicus; Cost-Benefit; Estru; Synchronization

1. Introduction

The use of Artificial Insemination in the trop ics has been

hampered by the difficulties in accurate detection of

signs of estrus in Zebu type cattle, the most popular

crossbred animal in the beef industry of the area. One

possible solution to implement the technique is to ma-

nipulate pharmacologically the estrous cycle and cou-

pling this procedure with fixed-time artificial insemina-

tion (F-TAI) regardless the signs of estrus, so called in-

semination by appointment. In relation to animals kept at

pasture under tropical conditions, the rate for detecting

animals in estrus does not go beyond 40% [1,2]. The

reasons for this low detection rate is multifactorial

mainly related to social behavior in the herd [3], age,

breed of the animals and the presence of the male [4,5].

Because of these limitations, the number of protocols to

synchronize estrus is abundant [5,6], the same can be

noted as to the hour(s) where F-TAI is app lied following

removal of the treatment [7,8]. However, few studies are

published whilst comparing protocols under the same

conditions and with the same clinicians applying the

procedure, particularly under beef cattle enterprises in the

tropics.

*Corresponding author. Interventions in the beef cattle in dustry have to be cost

J. J. MOLINA ET AL.

152

effective and render economic dividends to the producer

otherwise they will become an academic exercise. For

example Tenhagen et al. [9] showed that synchronization

of estrus in dairy cows in the USA was more cost-effec-

tive than inseminating animals displaying overt signs of

estrus and this was mainly due to more cows that were

culled and more open days among cows not culled.

However, Hoff-Sousa and Ferrugem-Moraes [10] in beef

cattle raised in southern Brazil, showed that whilst the

total cost for a pregnancy using natural mating was 5

dollars, this cost increased to 20 dollars if AI was to be

applied and 24 if AI was accompanied with an estrous

synchronization protocol. Oltenacu et al. [11] in the USA

working with dairy cows undertook an economic evalua-

tion of several factors that affect pregnancy. Accurate

estrus detection was among the most profitable manage-

rial decisions. Thus, economic calculations will certainly

differ according to the type of enterprise and production

item to be evaluated .

The objective of the present study is to compare the

fertility results and to assess the cost-effectiveness of

several protocols applied under the conditions of beef

cattle enterprises in Colombia.

2. Material and Methods

2.1. Animals

A total of 1658 multiparous zebu cros sbred cows, mostly

Brahman and Nelore, were chosen from 4 farms located

in the Department of Antioquia-Medellin, Puerto Berrío,

Colombia. The site is located at 125 m above sea level, at

06˚29'40" latitude north and 74˚24'24" longitude west.

Average temperature is around 29˚C and pluvial precipi-

tation around 2300 mm. Animals ranged from 4 to 12

years old, with 2 to 6 parities. The selection was done by

the same two practitioners ba sed on: 1 ) having at least 40

days since calving when the synchronization procedure

was implemented; 2) the body condition score of the

cows, including only those with a minimum of 2.5 in a

scale 1 to 5; and 3) presence of a corpus luteum, or traces

of follicular activity, detected by rectal palpation.

2.2. Treatments

Five protocols of pharmacological treatments were ob-

served on field conditions. All used a synthetic pro-

gestagen (Crestar, Intervet Schering Plough Animal

Health) as base at day 0, with several variations between

them like the hormones used, dosage and the time of ap-

plication (Table 1). Not all protocols were used in each

farm because that depended of the willingness of the

farmers; however, all of them were applied under the

supervision of the same two veterinarians. Moreover, in

order to distribute similarly the experimental error, all

cows were inseminated by the same veterinarians fol-

lowing the FTAI at 52 h. In farms where two or more

protocols were applied, cows were randomly allocated in

each treatment.

No experimentation was performed during this study,

this was an observational study of the estrus synchroni-

zation on field conditions. The approval of the Animal

Welfare and Bioethics Committee of the Veterinary

School of the National University in Costa Rica was ob-

tained.

2.2.1. Pregnancy Di agnosis

In all protocols the pregnancy diagnosis was done over

45 d after insemination by rectal palpation by the same

veterinarians that selected and treated the cows. They

have at least ten years of experience in this kind of re-

productive procedures.

2.2.2. Cost Analyses

To assess the monetary cost of each protocol, it was cal-

culated the cost of the pharmaceutical treatments, ad-

ding the costs for the professional labor of the veter-

inarians. The rate of each hormone was estimated using

the current price in Mexico quoted in US dollars as cur-

rency. So, the price for each dose of drug was the fol-

lowing: Norgestomet (Crestar® implant) + estradiol va-

lerate (Crestar® injection), $15.87; equine chorionic go-

nadotropin (Folligon®), $16.27; estradiol benzoate (Me-

salin®), $4.65; gonadorelin (Fertagyl®), $18.30; clopros-

tenol (Estrumate®), $14.48; estradiol ciprionate, $9.58.

All these products are manufactured by Intervet Schering

Plough Animal Health. Additionally, the cost for the

professional labor of the veterinarian was estimated in a

total of $20.00 per cow for the whole treatment. At last,

the mean price fo r the semen was fit o n $10.00. The total

cost for veterinary services during the complete protocol,

including all the visits, was estimated on $20.00 per cow.

With these data, the total cost per cow (TCPC) for

each protocol (TCPP), was calculated. Once the preg-

nancy rate (PR) of each protocol was obtained, a calcula-

tion of the cost of each gestation (TCG) was done as fol-

lows: .

TCG TCPCPR



Taking a herd of one-hundred cows as baseline for

calculations, it was estimated the co st of the total amo u n t

of pregnancies possibly obtained in each protocol (CTPP)

using the formula: CTPP = (100*PR)*TCG. Finally, in

order to have a relative estimation of the cost of a ges-

tation per protocol, the excess between the cost of a preg-

nant cow in relation to the cost a treated cow (EPP) was

calculated using the formulae EPP = (TCG/TCPC)*100.

The estimation of both costs for a treated cow and for

a pregnant animal, at 95% of confidence was carried out

using @RISK 5.7 software (Palisade), using the mod-

J. J. MOLINA ET AL.

153

Table 1. Description of protocols used for heat synchronization in zebu cows on field conditions in the humid tropic of Co-

lombia. The name of the product in bolds indicates the hormone that makes the treatment different.

Day Protocol A

Estradiol Benzoate Protocol B

Gonadorelin Protocol C

Equine Chorionic Gonado t ropin

With Without With Without With Without

0 Crestar® implant

Crestar® injection Crestar® implant

Crestar® injection

9 Remove Implant

Folligon® 400 UI Remove Implant

Folligon® 400 UI

11 FTAI 52 h. FTAI 52 h. FTAI 52 h.

Fertagyl 1ml FTAI 52 h. FTAI 52 h. FTAI 52 h.

24 Crstar® Reimpla nt

Mesalin 1 mg Crestar® Reimplant Crestar® Reimplant Crestar® Reimplant

30 Remove Implant

Folligon® 150 UI Remove Implant

31 - 33 FTAI 52 h. FTAI 52 h.

32 Remove Implant Remove Implant

33 - 35 FTAI 52 h. FTAI 52 h.

40 - 45 Pregnancy

diagnosis Pregnancy

diagnosis

Day Protocolo D

Crestar new/used Protocolo E

Estradiol Ciprionate (ECP)

New Used With Without

0 Crestar® implant Crestar® implantEstradiol

Benzoate 2.5 mg Crestar® implant Crestar® implant

Remove Implant Estrumate®

2 ml Folligon® 330 UI

9 Remove Implant

Folligon® 400 UI Remove Implant

Folligon® 400 UI ECP

0.5 ml (1 mg)

Remove Implant

Folligon® 400 UI

11 FTAI 52 h. FTAI 52 h. IATF 52 h. IATF 52 h.

31 - 33 Heat detection Heat detection

36 - 47

40 - 45 Pregnancy diagnos is Pregnancy diagnosis Pregnancy diagnosis Pregnancy diagnosis

FTAI 52 h = Fixed time artificial insemination, Crestar: Implant (Norgestomet 3 mg) + Injection (Norgestomet 3 mg, Estradiol Valerate 5 mg), Folligon:

eCG (equine Chorionic Gonadotropin), Fertagyl: GnRH(Gonadotropin R elease Hormone), Mesalin: Estradiol beanzoate.

cost estimation assuming a variation of 10% from the

base price for each component of the treatment. The

variation from demean was obtained after a run with

10,000 iterations. Additionally, an approach of the costs

for the owner due to cows empty after four services, for

each protocol was estimated by means of a deterministic

model carried out in Microsoft Excel. For this purpose, it

was assumed a constant pregnancy rate (the observed one

in the protocol i.e. fertility at first insemination) for each

time of AI and a heat interval of 21 d. This calculation

included the total amount of days empty, AI straws pro-

jected to use and their associated costs assuming a cost of

$3.00 US dollars per day empty and a cost of $10.00 US

dollars per AI straw.

The costs for the remaining days empty and AI straws

after four services were not estimated. Cost for manage-

ment, feed, and others related to the maintenance of the

herds was not taken into consideration due to the vari-

J. J. MOLINA ET AL.

154

ability in the sample.

3. Results

3.1. Reproductive Efficacy of the Protocols

A total of 874 pregnancies were registered from the 1658

cows studied (52.7%). The general percentage of preg-

nancies per protocol varied between 66.2% (protocol A)

and 46.9% (protocol D). There were not differences be-

tween protocols B, C, D and E, but all of them were dif-

ferent to protocol A (Table 2).When segregating the re-

sults per treatment within each protocol, these percent-

ages vary to 66.9% for protocol A with estradiol benzo-

ate, and 43.7% for protocol D with the re-used implant of

Norgestomet (p < 0.05) (Table 2).

3.2. Costs per Treated Cow (Gross Cost)

Regarding the cost per treated cow, in average, protocol

D was the cheaper whilst protocol C was the most ex-

pensive. Even within each protocol, the total cost varied

between 64.08 US dollars for protocols B and D; spe-

cifically without Gonadorelin and with the new Crestar,

respectively, while it was $97.47 for protocol C when

using eCG (Table 3).

3.3. Costs per Pregnant Cow (Net Cost per

Pregnancy)

When the pregnancy rate was taken into account, the cost

for each gestation varied from $126.01 in protocol A

without estradiol benzoate, to $177.26 in protocol C with

eCG (P < 0.05). No statistical differences were found in

the net cost per pregnancy within each protocol; however,

the absolute difference in some protocols was quite im-

portant. For instance, in protocol B, there was an abso-

lute difference of $29.97 while in protocol D it was

$26.57 (Table 3). So, at the end, although protocol B

without Gonadorelin was the cheaper regarding th e gross

cost of treatment ($64.08), it was, the second one with

the higher excess cost between treated and pregnant cows

($121.27). Besides, the protocol D had excess costs of

$99.10 and $128.86 when using new and re-used Cre-

star (Table 3). These results indicate that there is not a

direct association between the cost of the treatmen t and its

efficacy measured as pregnancy rate.

Table 2. Percentage of gestations, by protocols used for heat synchronization, in zebu cows on field conditions in the humid

tropic of Colombia.

95% CI Diff.*

Protocol Treatment Total Gestations%

IL SL

A Total 394 261 66.2 61.6 70.9 a

Estradiol benzonate With 305 204 66.9 61.6 72.2

Without 89 57 64.0 54.1 74.0 0.70

B Total 280 131 46.8 40.9 52.6 b

Gonadorelin With 145 70 48.3 40.1 56.4

Without 135 61 45.2 36.8 53.6 0.63

C Total 82 44 53.7 43.9 64.5 a,b

Equine chorionic gonadotr opin With 40 22 55.0 39.6 70.4

Without 42 22 52.4 37.3 67.5 0.82

D Total 601 282 46.9 42.9 50.9 b

Implant of norgestomet New 301 151 50.2 44.5 55.8

(new/used) Used 300 131 43.7 38.1 49.3 0.12

E Total 301 156 51.8 46.2 57.5 b

Estradiol ciprionate With 198 104 52.5 45.6 59.5

Without 103 52 50.5 40.8 60.1 0.81

*Different letters indicate difference in the global percentage of gestations between protocols. The numbers indicate the exact P-value of the

comparison within each protocol; both calculations at 95% of confidence.

J. J. MOLINA ET AL. 155

Table 3. Costs analyses for each protocol of synchronization used for heat synchr onization in zebu cows on field conditions in

the humid tropic of Colombia.

Protocol A Protocol B Protocol C Protocol D Protocol E

Estradiol benzoate Gonadorelin eCG Norgestomet new/used ECP

Parameter

With Without With WithoutWith WithoutNew Used With Without

% of gestation 66.9 64.0 48.3 45.2 55 52.4 50.2 43.7 52.5 50.5

Total cost per treated cow* 85.33 80.59 82.70 64.08 97.47 80.62 64.12 67.39 73.94 64.21

Cost per gestation



127.66 126.01 171.76 141.79 177.26 153.63 127.66 154.23 140.78 127.00

Excess cost pregnant/treated

cow (%) 49.61 56.36 107.69 121.27 81.86 90.56 99.10 128.86 90.40 97.79

Cows pregnant after 4

services** 83 82 73 72 77 75 74 71 75 74

Total of AI straws until 4

services** 133 135 151 154 144 147 149 156 147 149

Total of days empty until 4

services*** 2107.7 2231.7 3223.6 3409.6 2789.6 2975.6 3099.6 3533.5 2975.6 3099.6

Total cost due to days empty 6155.8 6695.1 9615 10191.58368.9 8852. 5 9261.6 10470.4 8833.9 9205.8

Additional costs due to IA +

days empty**** 6648.3 7230.8 10384.311006.99038.5 9560.7 10002.6 11308.2 9540.7 9942.4

*In US Dollars. Based on a stochastic model using the cost estimation module in @Risk. **On a base of 100 cows treated per protocol. ***This does not include

the days before treatment. ****This is the sum of the cost due to days open + the extra cost due to AI straws used, assuming a cost of $10.00 US Dollars per

straw.

3.4. Estimated Economic Losses Associated to

Reproductive Failure per Protocol

The failure of getting the cows pregnant at first service

adds to the costs for days open and additional AI straws

used until the pregnancy of the cows in a hypothetical

fourth service. Protocol A was the best cost-effective

because its additional costs were the lowest among all

protocols and had the lowest amount of open days

(2107.7 to 2231.7 d) and IA stra ws ( aver age = 134), then,

the additiona l costs reached almost $6940.00 on average.

Protocols B and D were less efficient, with more than

3200 d of additional open days due to reproductive fail-

ure, reaching, on average, more than $10500.00 in addi-

tional costs after four simulated rounds of AI keeping

constant the pregnancy rate observed in each protocol.

On the other hand, the protocols C and E occupied an

intermediate position; however, both had estimated addi-

tional costs over $9300.00 (Tab le 3 ). The sensitivity an a l y -

sis indicated that the most important source of variation

in the model assessing the eco nomic losses was the preg-

nancy rate of the protoco l s.

4. Discussion

The use of pharmacological agents to promote estrous

expression is a technique to ascertain a massive use of

Artificial Insemination in cattle raised under tropical

conditions. The value of this procedure has to be meas-

ured by the number of animals pregnant after an inter-

vention. It is however, a rather difficult task to compare

fertility results between different experiments for the

variability that exists in each field trial. The protocols

tested in the present study afforded an overall fertility of

52% which is rather similar to many of the studies re-

viewed; in effect, conception rates after treatment with

hormonal combinations in different studies vary between

40% and 70% [12-17]. Reviews of several studies have

been published by Bo et al. [5] and Barusselli et al. [18]

and earlier by Galina and Arthur [19]. The ranking of all

these studies established an average of around 40%

ranging from 20% to 60% after first insemination.

Nonetheless, the remaining non-pregnant animals had the

inherent cost of being inseminated, especially if fixed

time insemination is used, with negative results resulting

in lengthier periods of days open. Most of the studies

report the number of animals pregnant following an in-

tervention but hard ly any information if the no n-pregnant

animals were actually at the risk of becoming pregnant.

Diaz et al. [20] in a survey where cows were sampled for

progesterone following a protocol of synchronization

observed that 30% of the animals did not form a CL.

Moreover, in an old study Landivar et al. [21] compared

fertility in different herds, either following spontaneous

or synchronized estrus and using either natural mating or

artificial insemination, reported no differences in fertility

if AI or natural mating were used being the variation the

J. J. MOLINA ET AL.

156

animals utilized in the study rather than the technique to

make them pregnant. So, the relationship of cost-benefit

of synchronizing zebu cows with the goal of pregnancy

should be an exercise that practitioners should undertake

before embarking in costly protocols which are not cost-

effective. Two of the main challenges of zebu cattle un-

der tropical conditions are the long postpartum anestrus

and the low estrus detection rate [5,19]; so the protocols

for synchronization of ovulation can have large positive

impacts on the reproductive efficiency in the herds raised

under tropical conditions if adequately used [6].

Several protocols have been tested for estrus synchro-

nization, since the early days of utilizing only pros-

taglandins, to those more elaborate using progestins, es-

trogens and GnRH [12,13,17,22-25]. Diverse studies hav e

documented the success of several protocols applied in

diverse climatic conditions, different breeds, time post-

partum where the intervention was undertaken and feed-

ing strategies. However, studies comparing the results of

protocols used on the same field conditions applied rou-

tinely by practitioners in different management condi-

tions are less frequent. Besides, several progesterone or

progestins have been investigated for estrus synchroniza-

tion in zebu cows in controlled conditions, varying con-

siderably the success in synchronization and gestation

rates [12,13,17,18,24].

Whilst rates of gestation of the protocols tested in the

present report are similar to others, we are aware that the

absence of the characteristics for each cow included in

the study, did not allow us to carry out a mixed model

including fixed and random effects, which could assess

the effect of variables such as breed, number of parities,

body condition score and time postpartum among others

taking into consideration the random effect of the herd,

on the synchronization and pregnancy rates. What we can

assume is that there aren’t differences between the body

condition score, number of parities and time postpartum,

as well as the breeds between protocols. In this scenario

we can take for granted a global similarity of the groups

treated. A favorable argument is that all cows of the

study were selected by only two veterinarians who were

the same that applied the treatments and undertook the

pregnancy diagnosis hence the sources of error were

equally distributed in all protocols.

Some studies report the costs of hormonal treatments

for synchronization in beef cattle, most of them in Bos

taurus; however, the calculations are based on the costs

of hormonal treatment, without taking into consideration

fixed cost such as labor and the possibility of applying

various treatments in the case of cows having to be rein-

seminated. Also, fewer studies used mathematical mod-

els to simulate the effect of measures of management on

the net income of a beef farm [26] the modeling of the

cost-benefit of different protocols taking into account

other aspects such as the cost of the IA straws, the added

value of labor as well as the cost of the days open, are

exercises that should be taken to understand the economic

merit of hor monal treatments. Bolivar and M al do na do [ 27 ]

and Alarcón et al. [28] have attempted to analyze the

cost-benefit of using embryo transfer in cattle; their re-

sults indicate that the technique might be overvalued for

the average farmer for it has its place in stud farming.

In conclusion, synchronization of estrus using phar-

macological products seems to have a place in the ma-

nagement of cattle and its popularity h as expanded in the

last decade. However, caution should be called upon a

careful assessment both from the part of the farm and the

professional in charge of the enterprise to avoid using the

technique indiscrimin atively thus propitiating the use of a

method that might not be cost-efficient.

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