Effects of Oregano Essential Oil on Reduction of Weaning Age and Increasing Economic Efficiency in Holstein Friesian Calves

Ibrahim Tapki1*, Huseyin Bahadir Ozalpaydin2, Nuran Tapki3, Mehmet Aslan4 and Muhammet Hanifi Selvi1

1Animal Science Department, Agriculture Faculty, Mustafa Kemal University, 31060, Hatay, Turkey

2Kilis Provincial Directorate, The Minister of Food, Agriculture and Animal, 79000, Kilis, Turkey

3Agriculture Economy Department, Agriculture Faculty, Mustafa Kemal University, 31060, Antakya, Turkey

4Agricultural Biotechnology Department, Agriculture Faculty, Erciyes University, 38030, Kayseri, Turkey

ABSTRACT

This study examined the potential use of oregano essentail oil as a milk additive for purposes of reducing weaning age; increasing economic efficiency; promoting calf growth as well as for improving blood parameters and general health status of Holstein Friesian calves. Twenty-eight Holstein Friesian calves were allocated into three groups: (a) Control calves were fed with whole milk (n=10), (b) OreganoLow (n=9), and (c) OreganoHigh (n=9) calves were fed with whole milk, plus 100 and 150 mg/l oregano essential oil per kg milk respectively. The amount of the milk offered on daily basis was calculated as 10% of each calf live weight and was given in two meal times. All calves were kept in individual pens during experimental period. Calves got weaned following the consumption of daily 900 g of concentrate feed over three consecutive days. Results demonstrated that OreganoLow calves marked improved growth performance, earlier weaning age and lower farm costs (P < 0.05) compared to Control and OreganoHigh calves. To conclude, dietary oregano essential oil seems to be a potential liquid feed additive that improves feed efficiency, health status, growth performance, and that reduces diarrhea incidents, hastens weaning age and minimizes dairy farm costs when used at the level of 100 mg/l.

Article Information

Received 06 June 2018

Revised 30 July 2018

Accepted 04 September 2018

Available online 31 January 2020

Authors’ Contribution

IT designed the study and carried out statistically analysis, HBO and MHS performed experimental work and laboratory analysis. NT analyzed the economical data. MA edited the paper.

Key words

Dairy calf, Thyme oil, Economic efficiency, Growth, Weaning

DOI: https://dx.doi.org/10.17582/journal.pjz/20180606130639

* Corresponding author: ibtapki@mku.edu.tr

0030-9923/2020/0002-0745 $ 9.00/0

Copyright 2020 Zoological Society of Pakistan

INTRODUCTION

Information on calf growth and the cost of calf rearing is important for cattle production. The sustainability of any cattle enterprise is directly correlated with the successful raising of calves for replacement stock. Replacement dairy calves are susceptible to many pathogens that cause preweaning diseases during the milk drinking period. Acute scours usually occur in newborn calves aged 15 days and earlier and are clinically characterized by watery diarrhea, progressive dehydration, and death within a few days of its onset (Blood et al., 1992; Izzaddeen and Kaygısız, 2018). Hastening weaning age, with the intention of reducing feed and labor costs, has attracted special attention among researchers during the last decades (Owen and Larson, 1982; Kehoe et al., 2007; Ozkaya et al., 2015). Antibiotics were used as feed additives to shorten the period of milk drinking. However, these substances have been completely prohibited as feed additive in the European Union and Turkey since 2006 as they are suspected of contributing substantially to the increasing resistance among animal and human pathogens (regulation 1831/2003/EC and 26056/2006 TR). Due to these restrictions, companies have resorted to essential oils (EOs) as feed additives in order to increase the palatability of feed; stimulate appetite, saliva production and secretion of digestive enzymes as well as to promote longer villi lengths. EOs dietary supplementation also appears as a natural and eco-friendly alternative (Jouany and Morgavi, 2007). The improved appetite, digestion and absorption of nutrients can result in maximum growth potential in a shorter period of milk drinking period with reduced costs (Jouany and Morgavi, 2007; Mohammed et al., 2013). During last two decades a substantial increase in the use of aromatic herbs and essential oils as feed additives in animal nutrition was recorded. Essential oils are extracted from various aromatic plants generally grown in warm areas such as the Mediterranean, and tropical countries. They are liquid, volatile, rarely coloured and dissolvable in organic solvents with a generally lower density than that of water (Bakkali et al., 2008). Essential oils, known for their antimicrobial effects, have been proposed as modulators of rumen fermentation. One of the most important essential oils is that of oregano. Oregano essential oil has antifungal and antibacterial effects on numerous microrganisms such as Erwinia amylovar, Bacillus subtilis, Escherichia coli, Hafnia alvei, Micrococcus luteus, Proteus vulgaris, Staphylococcus aureus and Streptococcus faecalis mainly due to its basic components involving carvacrol, thymol, α-terpinene and p-cymene (Azzouz and Bullerman, 1982; Lawrence and Reynolds, 1984; Deans and Svoboda, 1990; Ezzeddine et al., 2001; Marino et al., 2001; Burt et al., 2007). During the neonatal life of calves, some pathogens such as Escherichia coli and Salmonella spp. can be found in their digestive tracts from first day of their lives. These bacteria can cause enteritis, enterotoxemia or much more severe septicemia in the small intestine of calves (Scrag, 1982; Webster, 1986; Thickett et al., 1990). However, limited information regarding the effects of oregano essential oil doses on reducing the weaning age and farm costs of dairy calves is available.

The main objective of this study was hence to investigate the possible use of oregano essential oil as a milk additive to reduce weaning age, increase economic efficiency, promote calf growth, improve blood parameters and minimize production costs of Holstein Friesian calves.

 

MATERIALS AND METHODS

Calves, diets and handling

The study was conducted on a private dairy farm in Hatay, Turkey. Twenty-eight Holstein Friesian calves were divided into 3 equal groups based on their birth weight and sex: (a) Control group calves fed with whole milk (n= 10), (b) OreganoLow calves (n= 9) and OreganoHigh calves (n= 9) fed with whole milk plus 100 and 150 mg oregano oil per kg milk respectively. Calves were weighed right after birth; taken away from their mothers within three hours; placed into individual pens and allowed to drink colostrum for three days. The calves started to be fed with whole milk or whole milk plus oregano oil on day 4 postpartum. The amount of the milk offered daily was calculated as 10% of each calf live weight and was given in two meal times. Calf starter feed, alfalfa hay and fresh water were available ad libitum. Calves were weaned after consuming 900 g of concentrate feed daily over three consecutive days. The commercial calf starter comprised of dry matter, 900g/kg; metabolic energy, 2800 Kcal/kg; crude protein, 198 g/kg; crude fiber, 55, g/kg; vitamin A, 12.000 IU/kg; vitamin D3, 3600 IU/kg; vitamin E, 25mg/kg; calcium, 1.5%; phosphorus, 0.5%. The calf starter ingredients were barley, 30; maize, 18; wheat bran, 10; soybean meal, 25; cotton seed meal, 5; sunflower meal, 5; molasses, 5; mineral and vitamin mixture, 2 in % and alfalfa hay nutrient content were dry matter, 850 g/kg; metabolic energy, 1530 Kcal/kg; crude protein, 150 g/kg; crude fiber, 290 g/kg.

The oregano (Origanum onites L.) plants were collected from the the farm of Mustafa Kemal University, Turkey in 2012 growing season. The stems, leaves and flowers of oregano plants were air-dried in the shade. Essential oil was isolated by hydrodistillation in a clevenger type apparatus for 3 h. Analysis of the essential oil was carried out using a Thermo Scientific Focus gas choromatograph equipped with mass spectrometry (GC-MS) using DB-5MS fused silica column. Helium was used as the carrier gas at a flow rate of 1 ml/min. Mass range m/z 50–650 amu. Mass spectrometry transfer line temperature 250 °C. MS ionization source temperature and injection port temperature were 220 °C. The samples were injected with a 250 split ratio. The injection volume was 1 µL. Oven temperature was programmed from 50 °C to 220 °C at 3 °C /min. The structure of each compound was identified by comparison of their mass spectrum with the Wiley Registry, 9th edition.

The data got gathered Xcalibur software program. The retention indices (RIs) were calculated for all volatile compontents using a homologous series of n-alkane standard solutions C8–C20 (Fluka, product No. 04070) and C21–C40 (Fluka, product No. 04071). The chemical composition of the oregano essential oil is shown in Table I.

Calf performance characteristics such as weaning body weight, total body weight gain, daily live weight gain, weaning age, initial hay and concentrate feed consumption ages, fecal scores, total milk, hay, concentrate, oregano essential oil consumption, dry matter intake, feed conversion ratio, daily milk, hay and concentarate feed consumption were recorded during the experimental period. The number of calves with diarrhea and the severity of the diarrhea were determined daily. Faeces scores and health status were recorded each morning at feeding time.

Consistency of faeces was scored on a four-point scale. Score 1: Faeces were normal (soft solid consistency, no fluid); Score 2: Faeces were soft (semisolid consistency); Score 3: Faeces were loose (mostly solid, runny, but stays on top of bedding, and Score 4: Faeces were watery diarrhea (fluid, no solid materials which sifts through bedding (Larson et al., 1977).

Economic efficiency measurements

Cost parameters were classified according to the methods implied by Debertin (1986). Total fixed costs (TFC) were considered the same for each group, e.g. labor, vaccination etc.

Total variable costs (TVC) during the weaning period included the cost of hay, concentrate feed, milk, oregano essential oil and veterinary services.

Total cost (TC) was calculated as the sum of the total fixed and variable costs.

Partial measures of efficiency were calculated according to Debertin (1986) as essential oil cost/total cost (EOC/TC), essential oil cost/total variable cost (EOC/TVC) and essential oil cost/feed cost (EOC/FC)

 

Table I. Chemical composition of oregano essential oil.

No	Compound name	RT	KI	Area (%)
1	Carvacrol	44.46	2237	65.2
2	Terpinen-4-ol	21.78	1588	6.12
3	β-Terpinene	8.86	1275	5.49
4	p-Cymene	9.68	1285	4.89
5	trans-Sabinene hydrate	19.72	1546	4.54
6	α-Terpinene	6.91	1183	2.17
7	Isoborneol	25.35	1597	2.12
8	α-Myrcene	6.51	1169	1.22
9	trans-Sabinene hydrate	16.58	1508	1.00
10	α-Bisabolene	26.36	1604	0.87
11	Caryophyllene	21.38	1575	0.73
12	1-Terpıneol	20.28	1560	0.55
13	α-Terpınolene	10.05	1453	0.50
14	Sum of the other 21 compounds	------	------	4.60
	Total			100,00

 

Components with levels equal or over 0.5% are shown. RT, Retention time; KI, Kovats index.

 

Statistical analysis

The data got tested via one-way ANOVA procedure of SPSS (Windows version of SPSS, release 16.00) and means were compared by using Duncan Multiple Range Test of the same software. Birth weight of calves was used as a covariant factor in the analysis of the live weight, daily weight gain and weaning weight. The data were presented as mean ± SE and significance was declared at (P < 0.05).

 

RESULTS

Chemical composition of oregano oil

According to the gas chromatography (GC-MS) analysis, oregano essential oil involved 34 components (Table I). The seven main ingredients, representing more than 2% of the total oil content, were carvacrol (65.2%), terpinen-4-ol (6.12%), β-terpinene (5.49%), p-cymene (4.89%), trans-sabinene hydrate (4.54%), α-terpinene (2.17%) and isoborneol (2.12%). According to these reports, carvacrol and β-terpinene are the main compounds of oregano essential oil. From this point of view, our results obtained from the GC-MS analysis are highly consistent with the previous studies.

Growth performance

Means ± standard error, and results of variance analysis for growth performance traits are shown in Table II and an economic analysis is provided in Table III. Birth weight differences were not significant among the calf groups (P > 0.05). The calves were assigned to treatments based on their birth weight. Thus, there should not be a significant difference in birth weight among different groups. Although the tracked weaning weight differences among the calves were not significant (P > 0.05), the weaning weights of the OreganoLow calves were 2.2 and 1.3 kg heavier than that of the Control and the OreganoHigh calves, respectively. The non-significant weaning weight differences among three groups could be attributed to earlier weaning age of the OreganoLow calves (Table II).

The tracked differences for the total body weight and daily live weight gains among calves were significant (P < 0.05). The OreganoLow calves had 3.3 and 2.7 kg higher total body weight and 0.108 and 0.063 kg greater daily live weight gain compared with that of the Control and the OreganoHigh calves respectively (Table II). Faecal scores (Table II) among three groups were significantly different (P < 0.05) since the OreganoLow calves had lower faecal scores than the Control and OreganoHigh calves by 1.77 and 1.07 point respectively. As indicated, the OreganoLow calves had less frequent diarrhea which could be attributed to the diarrhea prevention characteristic of oregano oil.

The differences tracked for weaning age among calf groups were significant (P < 0.05). OreganoLow and OreganoHigh calves fed with whole milk supplemented with oregano essential oil at the level of 100 and 150 mg/l respectively had earlier weaning ages than that of the Control group calves, and weaning ages for the OreganoLow calves were 7.2 and 1.7 days earlier than that of the Control and the OreganoHigh calves respectively (Table II).

Initial hay and concentrate feed consumption ages were significantly different among three groups (P < 0.05). The OreganoLow calves had 2.9 and 1.3 days

 

Table II. The effects of dietary oregano oil on calf growth performance (mean ± SE).

Growth parameters	Control (n=10)	Oregano low (n=9)	Oregano high (n=9)	p values
Initial BW (kg)	38.8 ± 3.16	37.7 ± 2.82	39.1 ± 2.95	0.910
Weaning BW (kg)	59.4 ± 8.51	61.6 ± 9.28	60.3 ± 7.63	0.165
Total BW gain (kg)	20.6 ± 2.48a	23.9 ± 3.01b	21.2 ± 2.89ab	0.021
Daily live weight gain (kg)	0.34 ± 0.01a	0.44 ± 0.01b	0.38 ± 0.01c	0.002
Weaning age (d)	60.6 ± 2.8a	53.4 ± 2.2b	55.1 ± 2.5c	0.004
Initial hay consumption age (d)	13.6 ± 1.1a	10.7 ± 1.5b	12.0 ± 1.2c	0.038
Initial concentrate consumption age (d)	11.0 ± 1.4a	9.1 ± 2.0b	10.3 ± 1.2c	0.042
Average fecal score (p)	2.85 ± 0.079a	1.08 ± 0.031b	2.15 ± 0.053c	0.002
Total milk consumption (kg)	252.5 ± 10.1a	225.5 ± 9.1b	232.3 ± 8.2c	0.001
Total hay consumption (kg)	6.16 ± 0.30	6.23 ± 0.32	6.14 ± 0.37	0.074
Total concentrate consumption (kg)	30.94 ± 2.73a5a	28.91 ± 2.53b	28.70 ± 2.47b	0.001
Total dry matter intake (kg)	64.7 ± 5.23b	59.5 ± 3.98a	60.1 ± 4.09ab	0.047
Feed conversion ratio	3.14 ± 0.05a	2.49 ± 0.08b	2.83 ± 0.04c	0.032
Daily milk consumption (kg)	4.17 ± 0.07	4.23 ± 0.04	4.22 ± 0.05	0.072
Daily hay consumption (kg)	0.102 ± 0.018a	0.117 ± 0.019b	0.112 ± 0.011c	0.023
Daily concentrate consumption (kg)	0.51 ± 0.06a	0.54 ± 0.07b	0.52 ± 0.09c	0.024

 

Mean values within a row having different superscripts are different (P < 0.05); Control calves, fed whole milk; OreganoLow Calves, whole milk plus 100 mg oregano oil per kg milk; OreganoHigh Calves, whole milk plus 150 mg oregano oil per kg milk.

 

Table III. The economy of dietary oregano oil in calf feeding (mean ± SE).

Economical parameters	Control (n=10)	Oregano low (n=9)	Oregano high (n=9)	p values
Total fixed cost per calf (USD)	273.4±14.21	273.4±14.21	273.4±14.21	-
Total variable cost per calf (USD)	263.8±20.1c	167.5±17.4a	185.7±19.5b	<0.001
Milk cost (USD)	123.4±14.2c	110.2±12.9a	113.6±13.0b	0.020
Hay cost (USD)	1.64±0.09c	1.52±0.01b	1.50±0.05a	0.013
Concentrate feed (USD)	16.5±2.5b	15.42±3.5a	15.31±2.7a	0.015
Essential oil (USD)	0	2.5±0.06	4.2±0.08	0.003
Veterinary drugs and services (USD)	122.2±7.1c	37.8±6.8a	51.1±9.5b	0.002
Total costs per calf (USD)	537. 2±19.5c	440.9±15.6a	459.1±19.1b	0.024
Total cost per kg live weight gain (USD)	26.1±3.8c	18.4±2.2a	21.7±3.0b	0.013
Total cost per kg DM (USD)	8.3±1.1b	7.4±0.9a	7.6±1.2a	0.044
Essential oil cost/total cost (%)	0	0.57±0.01	0.91±0.07	<0.001
Essential oil cost/total variable cost (%)	0	1.49±0.04	2.26±0.09	0.003
Essential oil cost/feed cost (%)	0	14.76±1.8	24.99±2.4	<0.001

 

Mean values within a row having different superscripts are different (P < 0.05); Control Calves: fed whole milk, OreganoLow Calves: whole milk plus 100 mg oregano oil per kg milk; OreganoHigh Calves: whole milk plus 150 mg oregano oil per kg milk.

earlier initial hay consumption age and 1.9 and 1.2 days earlier initial concentrate feed consumption age compared with the Control and the OreganoHigh calves respectively. The lower initial hay and concenrate feed consumption ages of the Oregano Low calves resulted from the increased saliva secretion, increased appetite and the promotion of rumen development. Apart from total hay consumption, there were significant differences in total milk and concentrate feed consumption among three goups (P < 0.05). The Oregano Low calves consumed 27 and 6.8 kg less milk compared with the Control and the OreganoHigh calves respectively. Although there was no total hay consumption difference among calf groups, the OreganoLow calves consumed 0.076 and 0.087 kg more hay compared with the Control and the OreganoHigh calves. Compared with the Control group, the OreganoLow and the OreganoHigh calves consumed 2.032 and 2.242 kg less concentrate feed respectively (Table II). Total dry matter intake differences were significant among three groups (P < 0.05). There were also significant (P < 0.05) differences among the calves in terms of feed conversion ratio. The OreganoLow calves had 0.65 and 0.34 greater feed conversion compared with the Control and OreganoHigh calves respectively. Also, the OreganoLow calves consumed more daily hay (0.015 and 0.005 kg) and concentrate (0.031 and 0.021 kg) compared with the Control and OreganoHigh calves respectively. This fact resulted in the earlier weaning age of the OreganoLow calves. Although there was no difference in daily milk consumption among calf groups, total milk consumption was significantly different (P < 0.05) among all groups (Table II).

Economical analysis

Total variable cost per calf was significantly different (P < 0.05) among calf groups in terms of milk, hay, concentrate feed, oregano oil, veterinary drugs as well as service costs. The OreganoLow calves had 96.3 and 18.2 USD lower total variable cost per calf than that of the Control and the OreganoHigh calves respectively. There was a significant (P < 0.05) difference among three groups with respect to total cost per kg live weight gain. The OreganoLow calves had 7.7 and 3.3 USD lower total cost per kg live weight gain compared with the Control and the OreganoHigh calves respectively. Total cost per kg dry matter varied significantly among groups (P < 0.05). The OreganoLow calves had 0.9 and 0.2 USD lower total costs per kg dry matter compared with Control and OreganoHigh calves. The ratio of oregano oil cost within the total costs, total variable costs, and total feed costs were significantly different between the OreganoLow and the OreganoHigh calves. The OreganoLow calves had 0.34%, 0.77% and 10.23% better cost ratio compared with the OreganoHigh calves (P < 0.05) (Table III).

The milk cost had the highest ratio in the total variable costs followed by the veterinary drugs and services costs. Total cost per kg live weight gain and total cost per dry matter intake were, also, the lowest in the OreganoLow calves. The OreganoLow treatment had better esential oil cost/total cost (%), essential oil cost/total variable cost (%) and essential oil cost/feed cost (%) than the Oregano High calves (P < 0.05) (Table III).

 

DISCUSSION

Oregano essential oil has been known to possess antifungal and antibacterial activities against many different types of microorganisms, including milk-born pathogens (Bampidis et al., 2006; Benchaar et al., 2008; Arslan and Dervis, 2010; Shafaghat, 2011; Rahbar et al., 2012). The antifungal and antibacterial activities of essential oils are mainly due to the oxygenated terpenoids in essential oils while some hydrocarbons also display antifungal and antibacterial effects.

Feeding efficiency, diarrhea reduction, weaning age, growth performance, and general health profiles of Holstein Friesian calves were improved by the use of oregano essentail oil as a milk additive. Similar results were reported by Bampidis et al. (2006), Castillejos et al. (2008), Simitzis et al. (2008), Hernandez et al. (2009), Unlu and Erkek (2013), Vakili et al. (2013), Van der Vliet and Cardozo (2013), Ozkaya et al. (2015) and Seifzadeh et al. (2017). Bampidis et al. (2006) reported that dried oregano leaves administered as an oral solution to calves with diarrhoea may be as effective in the treatment of colibacillosis. In contrast, Chaves et al. (2008) reported that oregano essential oil did not improve growth or feed efficiency of lambs. In addition, Santos et al. (2015) reported that oregano essential oil reduces amount of milk replacer consumption and did not improve growth of calves. It can be claimed that these differences were derived from the different animals species used and/or oregano oil forms. Experimental design was different in that some animals were fed with oregano oil sprayed onto the diet, some were fed with dried oregano, and some swallowed capsulated oregano oil. The results of the current study demostrated that the OreganoLow group of calves was weaned earlier than that of the Control or OreganoHigh groups. In addition to this, oregano essential oil improved calves’ appetite and accelerated the stimulation of the digestive tract for food consumption and prolongs the due to antibacterial activities against many different types of bacteria. Wenk (2000), Simitzis et al. (2008) and Hernandez et al. (2009) indicated similar results, whereas contrasting results were published by Chaves et al. (2008). These discrepancies were derived from different doses and forms of essential oil. Therefore, the smell and/or overdose of essential oil can have a negative effect on rumen microflora and fermentation. A threshold profile, characterized by a virtual stop of fermentation when doses are higher than the threshold level, occurs for thymol/carvacrol based essential oil. Effective dose could help determine which compound would be the most appropriate for a particular production objective, such as decreasing protein degradation. This also, highlights the toxic nature of oregano essential oil on rumen microbes, and that there is a narrow dose window for the successful adoption (Macheboeuf et al., 2008). Essential oils at high doses reduced the number of rumen proteolytic bacteria, decreased rumen deamination rate and decreased hay consumption (Garcia et al., 2007). Effects among essential oil components lead to antagonistic and synergistic interactions which are considered crucial for microorganisms. Some studies have demonstrated that whole or partially purified essential oil components are considered to have more intense antibacterial activity than single isolated components (Lachowicz et al., 1998; Hammer et al., 1999; D’Antuono et al., 2000; Ezzeddine et al., 2001; Mourey and Canillac, 2002).

The use of oregano oil in dairy calves improves economic efficiency. Our results overlap with the findings of Mohammed et al. (2013).

 

CONCLUSION

Essential oils are becoming increasingly popular for a wide variety of purposes including flavouring substances for food products, food preservation, alcoholic beverages, complementary medicine as well as cosmetic industries due to its antimicrobial, antioxidant and other biological activities. The results showed that oregano essential oil seems to be an ideal liquid feed additive to improve feed efficiency, health status, and growth performance of calves and to reduce diarrhea incidents and hastened weaning age. It also decreases farm costs when used in effective doses. However, further studies should be performed in large scale dairy farms under semi-commercial and commercial farm conditions.

 

ACKNOWLEDGMENTS

To Foundation for Scientific Research Projects Coordination Unit of Mustafa Kemal University (Project number: 1103Y0119), for financial support.

 

Statement of conflict of interest

Authors have declared no conflict of interest.

 

REFERENCES

Arslan, M. and Dervis, S., 2010. Antifungal activity of essential oil against three vegetative compatibility groups of Verticillium dahlia. World J. Microbiol. Biotechnol., 26: 1813-1821. https://doi.org/10.1007/s11274-010-0362-2

Azzouz, M.A. and Bullerman, L.R., 1982. Comperative antimycotic effects of selected herbs, species, plant compenents and comercial anti-fungal agents. J. Fd. Protec., 45: 1298-1301. https://doi.org/10.4315/0362-028X-45.14.1298

Bakkali, F., Averbeck, S., Averbeck, D. and Idaomar, M., 2008. Biological effects of essential oils – A review. Fd. Chem. Toxicol., 46: 446–475. https://doi.org/10.1016/j.fct.2007.09.106

Bampidis, V.A., Christodoulou, V., Florou-Paneri, P. and Christaki, E., 2006. Effect of dried oregano leaves versus neomycin in treating newborn calves with colibacillosis. J. Vet. Med. Ser. A., 53: 154-156. https://doi.org/10.1111/j.1439-0442.2006.00806.x

Benchaar, C., Calsamiglia, S., Chaves, A.V., Fraser, G.R., Colombatto, D., McAllister, T.A. and Beauchemin, K.A., 2008. A review of plant-derived essential oils in ruminant nutrition and production. Anim. Feed Sci. Technol., 145: 209–228. https://doi.org/10.1016/j.anifeedsci.2007.04.014

Blood, D.C., Radostits, O.M., Arundel, J.H. and Gay, C.C., 1992. Veterinary medicine. A textbook of the diseases of cattle, sheep, pigs, goats and horses, 7th ed. Bailliere Tindall, London, UK, pp. 2065.

Burt, S.A., Van Der Zee, R., Koets, A.P., De., Graaff, A.M.., Van Knapen, F., Gaastra, W., Haagsman, H.P. and Veldhuizen, E.J., 2007. Carvacrol induces heat shock protein 60 and inhibits synthesis of flagellin in Escherichia coli O157:H7. Appl. environ. Microbiol., 73: 4484-4490. https://doi.org/10.1128/AEM.00340-07

Castillejos, L., Calsamiglia, S., Martín-Tereso, J. and Ter Wijlen, H., 2008. In vitro evaluation of effects of ten essential oils at three doses on ruminal fermentation of high concentrate feed lot-type diets. Anim. Feed Sci. Technol., 145: 259–270. https://doi.org/10.1016/j.anifeedsci.2007.05.037

Chaves, A.V., Stanford, K., Gibson, L.L., McAllister, T.A. and Benchaar, C., 2008. Effects of carvacrol and cinnamaldehyde on intake, rumen fermentation, growth performance, and carcass characteristics of growing lambs. Anim. Feed Sci. Technol., 145: 396-408. https://doi.org/10.1016/j.anifeedsci.2007.04.016

D’antuono, L.F., Galleti, G.C. and Bocchini, P., 2000. Variability of essential oil content and composition of Origanum vulgare L. populations from a North Mediterranean area (Liguria Region, Northen Italy). Annls Bot., 86: 471-478. https://doi.org/10.1006/anbo.2000.1205

Debertin, D.L., 1986. Agricultural production economics, Macmillan, New York, USA, pp. 413.

Deans, S.G. and Svoboda, K.P., 1990. The antimicrobial proprieties of marjoram (Origanum majorana L.) volalite oil. Flav. Fragr. J., 5: 187-190. https://doi.org/10.1002/ffj.2730050311

Ezzeddine, N.B., Abdelkefi, M.M., Ben-Aissa, R. and Chaabouni, M.M., 2001. Antibacterial screening of Origanum majorana L. oil from Tunisia. J. Essent. Oil Res., 13: 295-297. https://doi.org/10.1080/10412905.2001.9699698

Garcia, V., Catala, P., Madrid, G.J., Hernandez, F., Megias, M.D. and Andrade-Montemayor, H.M., 2007. Potential of carvacrol to modify in vitro rumen fermentation as compared with monensin. Animal, 1: 675–680. https://doi.org/10.1017/S1751731107730781

Hammer, K.A., Carson, C.F. and Riley, T.V., 1999. Antimicrobial activity of essential oils and other plant extracts. J. appl. Microbiol., 86: 985-990. https://doi.org/10.1046/j.1365-2672.1999.00780.x

Hernández, J., Benedito, J.L., Vázquez, P., Pereira, V., Méndez, J., Sotillo, J. and Castillo, C., 2009. Supplementation with plant extracts (carvacrol, cinnamaldehyde and capsaicin): Its effects on acid-base status and productive performance in growing/finishing bull calves. Berliner Munchener tierarztl. Wochenschr., 122: 93-99.

Izzaddeen, S.I. and Kaygısız, A., 2018. Effect of essential oil of Laurel (Laurus nobilis L.) on performance, blood and fecal parameters of Holstein calves during suckling period. Pakistan J. Zool., 50: 1087-1096. https://doi.org/10.17582/journal.pjz/2018.50.3.108 7.1096

Jouany, J.P. and Morgavi, D.P., 2007. Use of ‘natural’ products as alternatives to antibiotic feedadditives in ruminant production. Animal, 1: 443-1466. https://doi.org/10.1017/S1751731107000742

Kehoe, S.I., Dechow, C.D. and Heinrichs, A.J., 2007. Effects of weaning age and milk feeding frequency on dairy calf growth, health and rumen parameters. Livest. Prod. Sci., 110: 267-272. https://doi.org/10.1016/j.livsci.2006.11.007

Lachowicz, K.J., Jones, G.P., Briggs, D.R., Bienvenu, F.E., Wan, J., Wilcock, A. and Coventry, M.J., 1998. The synergistic preservative effects of the essential oils of sweet basil (Ocimum basilicum L.) against acid-tolerant food microflora. Lett. appl. Microbiol., 26: 209-214. https://doi.org/10.1046/j.1472-765X.1998.00321.x

Larson, L.L., Owen, F., Albright, G.J.L., Appleman, R.D., Lamb, R.C. and Muller, L.D., 1977. Guidelines toward uniformity inmeasuring and reporting calf experimental data. J. Dairy Sci., 60: 989-991. https://doi.org/10.3168/jds.S0022-0302(77)83975-1

Lawrence, B.M. and Reynolds, R.J., 1984. Progress in essential oils. Perfum. Flavor., 9: 23-31.

Macheboeuf, D., Morgavi, D.P., Papon, Y., Mousset, J.L. and Arturo-Schaan, M., 2008. Dose–response effects of essential oils on in vitro fermentation activity of the rumen microbial population. Anim. Feed Sci. Technol., 145: 335-350. https://doi.org/10.1016/j.anifeedsci.2007.05.044

Marino, M., Bersani, C. and Corni, G., 2001. Impedance measurements to study the antimicrobial activity of essantial oils from Lamiceae and Compositae. Int. J. Fd. Microbiol., 67: 187-195. https://doi.org/10.1016/S0168-1605(01)00447-0

Mohammed, H.H., Badawi, M. and El-Sayed, M.A.A., 2013. Effects of commercial feed additives on performance, economic efficiency, blood metabolites and some maintenance behaviour in goats. J. Vet. Sci. Med. Diagn., 2: 1-7. https://doi.org/10.4172/2325-9590.1000112

Mourey, A. and Canillac, N., 2002. Anti-Listeria monocytogenes activity of essential oils components of conifers. Fd. Contr., 13: 289-292. https://doi.org/10.1016/S0956-7135(02)00026-9

Owen, F.G. and Larson, L.L., 1982. A simplified liquid feeding program for calves. J. Dairy Sci., 65: 1350-1356. https://doi.org/10.3168/jds.S0022-0302(82)82352-7

Ozkaya, S., Erbas, S., Ozkan, O., Baydar, H. and Aksu, T., 2015. The use of the aromatic waters of oregano (Origanum onites L.) as feed additives in calves diets. In: Int. Sci. Agric. Symp. (Agrosym 2015), 8: Jahorina, Saraybosna. Proceedings. Jahorina, Saraybosna: p. 699.

Rahbar, N., Shafaghat, A. and Salimi, F., 2012. Antimicrobial activity and constituents of the hexane extracts from leaf and stem of Origanum vulgare L. ssp. viride (Boiss.) Hayek. growing wild in Northwest Iran. J. med. Pl. Res., 6: 2681-2685. https://doi.org/10.5897/JMPR11.1768

Santos, F.H.R., De Paula, M.R., Lezier, D., Silva, J.T., Santos, G. and Bittar, C.M.M., 2015. Essential oils for dairy calves: effects on performance, scours, rumen fermentation and intestinal fauna. Animal, 9: 958-965. https://doi.org/10.1017/S175173111500018X

Scrag, L., 1982. Health problems in the cattle stable top agrar extra. 1. Edition Landwirtschaftsverlag Ltd., Münster-Hiltrup, pp. 15-18.

Seifzadeh, S., Mirzaei Aghjehgheshlagh, F., Abdibenemar, H., Seifdavati, J. and Navidshad, B., 2017. The effects of a medical plant mix and probiotic on performance and health status of suckling Holstein calves. Italian J. Anim. Sci., 16: 44-51. https://doi.org/10.1080/1828051X.2016.1249421

Shafaghat, A., 2011. Antibacterial activity and GC/MS analysis of the essential oils from flower, leaf and stem of Origanum vulgare ssp. viride growing wild in north-west Iran. Nat. Prod. Commun., 6: 1351-1352. https://doi.org/10.1177/1934578X1100600933

Simitzis, P.E., Deligeorgis, S.G., Bizelis, J.A., Dardamani, A., Theodosiou, I. and Fegeros, K., 2008. Effect of dietary oregano oil supplementation on lamb meat characteristics. Meat Sci., 79: 217-223. https://doi.org/10.1016/j.meatsci.2007.09.005

Thickett, B.; Mitchell, D. and Hallows, B., 1990. Calf rearing. 2nd (ed) Farming Pres Ltd, UK, p. 176.

Unlu, H.B. and Erkek, R., 2013. Effects of thyme and garlic essential oil on calf performance and some blood parameters. Ege J. agric. Res., 50: 299-310.

Vakili, A.R., Khorrami, B., Mesgaran, M.D. and Parand, E., 2013. The effects of thyme and cinnamon essential oils on performance, rumen fermentation and blood metabolites in Holstein calves consuming high concentrate diet. Asian-Austral. J. Anim. Sci., 26: 935-944. https://doi.org/10.5713/ajas.2012.12636

Webster, J., 1986. Calf husbandry: Health and welfare. Reprinted by Collins Professional and Technical Books. London, pp. 202.

Van Der Vliet, H. and Cardozo, P.W., 2013. Head-start strategies for optimal calf rearing. Int. Dairy Top., 7: 13-14.

Wenk, C., 2000. Herbs, spices and botanicals: ‘Old fashioned’ or the new feed additives for tomorrow’s feed formulations? Concepts for their successful use. In: Annual symposium of biotechnology in feed industry (BFI2000), 16. 2000. Nicholasville. Proceedings: Nicholasville: Alltech’s Annual Symposium, pp.79-96.