Advances in Animal and Veterinary Sciences

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AAVS_7_5_412-416

 

 

Research Article

 

Nutrient Utilization and Milk Yield of Dairy Cows Fed a Diet Containing Monensin, Garlic Peel and Organic Minerals During the Lactation Period

 

Caribu Hadi Prayitno1*, Yusuf Subagyo1, Anuraga Jayanegara2

1Faculty of Animal Science, Jenderal Soedirman University, Jl. Dr. Soeparno, Karangwangkal, Purwokerto 53123, Indonesia; 2Department of Nutrition and Feed Technology, Faculty of Animal Science,Bogor Agricultural University, Jl. Agatis Kampus IPB Dramaga Bogor 16680, Indonesia.

 

Abstract | The objective of this research was to determine nutrient intake, nutrient digestibility, milk yield, and milk quality of dairy cows that consumed feed supplemented with monensin, garlic peel (Allium sativum), and organic minerals. Twenty-one Friesian Holstein dairy cows with 644±72 kg body weight received dietary treatments consisting of: T0: basal feed + 0.3 g/d monensin;T1: basal feed + 30 ppm garlic-peel powder; and T2: basal feed + 30 ppm garlic peel powder + organic minerals (1.5 ppm Cr, 0.3 ppm Se, and 40 ppm Zn-lysinate). Allocation of dietary treatments followed a completely randomized design with seven replicates per treatment. Results showed that supplementation with monensin, garlic peel, and organic mineral did not significantly affect nutrient intake (DM, OM, CF, CP, NDF, ADF, TDN), nutrient digestibility (DM, OM, CF, NDF, ADF, TDN), milk yield, or milk quality. However, treatment significantly decreased crude protein digestibility (P<0.01). The conclusion was that supplementation with garlic peel can replace monensin in feed for dairy cattle.

 

Keywords | Monensin, Garlic peel, Organic minerals, Nutrients, Dairy cattle

 

Editor | Kuldeep Dhama, Indian Veterinary Research Institute, Uttar Pradesh, India.

Received | December 25, 2018; Accepted | January 23, 2019; Published | March 25, 2019

*Correspondence | Caribu Hadi Prayitno, Faculty of Animal Science, Jenderal Soedirman University, Jl. Dr. Soeparno, Karangwangkal, Purwokerto 53123, Indonesia; Email: caribu_prayitno@yahoo.co.id

Citation | Praytitmo CH, Subagyo Y, Jayanegara A (2019). Nutrient utilization and milk yield of dairy cows fed a diet containing monensin, garlic peel and organic minerals during the lactation period Adv. Anim. Vet. Sci. 7(5): 412-416.

DOI | http://dx.doi.org/10.17582/journal.aavs/2019/7.5.412.416

ISSN (Online) | 2307-8316; ISSN (Print) | 2309-3331

Copyright © 2019 Prayitno et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

 

INTRODUCTION

 

Increasing the efficiency of ruminal fermentation is one of the goals of ruminant nutrition. Energy loss during ruminal fermentation accounts for 6–10% of gross energy intake due to the formation of methane from hydrogen and CO2 by methanogens (Cottle et al., 2011). Such energy loss should be minimized in order to enhance rumen fermentation efficiency. For decades, monensin (an ionophore antibiotic) has been used for ketosis prevention and for increasing production in dairy cows. Monensin improves feed digestibility, shifts the volatile fatty acid (VFA) profile toward propionate at the expense of acetate, decreases methanogenesis, decreases amino-acid fermentation and ruminal ammonia concentration, increases hepatic gluconeogenesis, and increases energy supply to the animal (Azzaz et al., 2015). However, since monensin use may leave residues in meat and dairy products, some researchers have suggested the use of herbal supplements, one of which is garlic, as alternatives to enhance ruminal fermentation efficiency (Jayanegara and Palupi, 2010; Wanapat et al., 2013). Garlic had been shown to modify microbial population structure in the rumen by reducing the population of gram-positive Prevotella sp., a bacteria species that plays a role in protein degradation and amino-acid deamination (Wang et al., 2016).

 

Other inputs that may be used to enhance the efficiency of ruminal fermentation are minerals, particularly trace elements. Some trace elements are able to modify VFA and ammonia concentrations in the rumen by serving as activators for enzymes related to carbohydrate and protein degradation and fermentation (Prayitno et al., 2013). For example, selenium has been reported to positively affect the ruminal environment, increase total VFA production, and stimulate the growth of rumen microbes (Kišidayová et al., 2014). Trace elements also influence the metabolic efficiency of ruminants. Despite these findings, there have been limited studies of the combining of garlic and trace-element supplementation. The objective of this study, therefore, was to evaluate the effects of combined garlic peel and organic mineral supplements on nutrient intake, nutrient digestibility, milk production, and milk quality in lactating dairy cows. Monensin was used as an additive in the control diet since the combination of garlic peel and organic minerals was intended to replace an ionophore of this type.

 

MATERIALS AND METHODS

 

Experimental Procedure

This experiment was approved by the Faculty of Animal Science, Jenderal Soedirman University, Indonesia. The study used 21 Friesian Holstein dairy cows with 644±72 kg body weight. The cows were kept in individual cages and fed with total mixed rations that consisted of grass and concentrate with a 70:30 ratio as the basal feed (containing 63.9% total digestible nutrient and 12.85% crude protein). The study treatments consisted of T0: basal feed + 0.3 g/d monensin; T1: basal feed + 30 ppm garlic-peel powder; and T2: basal feed + 30 ppm garlic-peel powder + organic minerals (1.5 ppm Cr, 0.3 ppm Se, and 40 ppm Zn-lysinate). Treatments started at 30days pre-partum. Feed was offered twice a day, at 6 a.m. and 1p.m. Feed and feces were collected using a total collection method for five days, oven-dried at 60°C for 48h, then composited and ground for further analysis. Milk yield was collected at 5 a.m.and3p.m. and was recorded daily during the six-week post-partum period. Milk was weighed, sampled, and composited for composition analysis, using Lactoscan type Z435,to obtain milk fat, protein, lactose, solid non-fat, and density data.

 

Data Analysis

Data were analyzed using analysis of variance (ANOVA) for the three dietary treatments and seven replicates, according to a completely randomized design. When a parameter showed a significance effect at P<0.05, a post-hoc test, namely Duncan’s multiple range test, was applied to the data in order to compare the means for the different treatments.

 

RESULTS AND DISCUSSION

 

Feed Intake

The dietary treatments did not affect intake of DM, OM, crude fat, CP, CF, energy, NDF, or ADF) (Table 1). This may indicate that supplementation with monensin, garlic peel, orgarlic peel plus organic minerals did not affect the ruminal ecosystem. A similar finding is reported by Wanapat et al. (2013), who found that herbal supplementation did not affect DM intake or nutrient digestibility, except for crude protein. Yang et al. (2007) state that dairy cattle fed with essential oil or garlic oil did not demonstrate different dry matter intake. Odongo et al. (2007) also mention that there was no difference in intake between feed supplemented with monensin and a control, because the nutrient composition did not change.

 

Table 1: Nutrient intake (kg/d) of dairy cows across dietary treatments

 

Intake T0 T1 T2
Dry matter 10.13±1.77 9.76±1.84 9.34±0.44
Organic matter 8.15±1.4 7.88±1.46 7.50±0.37
Crude fat 0.20±0.04 0.19±0.04 0.19±0.01
Crude protein 1.35±0.22 1.42±0.31 1.29±0.02
Crude fiber 2.37±0.47 2.35±0.35 2.13±0.17
Energy (Mcal/kg DM) 32.7±5.81 29.6±4.33 28.7±4.24
NDF 6.73±1.21 6.75±0.72 6.07±0.44
ADF 2.98±0.60 2.96±0.47

2.67±0.23

 

T0: basal feed + 0.3 g/d monensin;T1: basal feed + 30 ppm garlic-peel powder;and T2: basal feed + 30 ppm garlic-peel powder + organic minerals (1.5 ppm Cr, 0.3 ppm Se, and 40 ppm Zn-lysinate).

 

Feed intake in dairy cattle is correlated with NDF and the digestibility of forage (Laconi and Jayanegara, 2015). Riaz et al. (2014) state that NDF was negatively correlated with feed intake. Osborne et al. (2004) state that monensin supplementation increased NDF intake or digestibility. However, some studies report non-significant effects or even a decrease from monensin supplementation, assumed tobe due to different supplementation levels (Broderick and Radloff, 2004) and forage: concentrate ratios or different lactation period (Plaizier et al., 2000). Plaizier et al. (2000) report that ionophores such as Rumensin or monensin increased NDF and ADF digestibility in forage-rich feed but did not significantly affect it in concentrate-rich feed, because NDF and ADF level in the forage was higher.

 

Nutrient Digestibility

Supplementation with monensin, garlic peel, and garlic plus minerals (Cr, Se, and Zn-lysinate) did not significantly affect nutrient digestibility except for crude protein digestibility (Table 2). This may indicate that monensin, garlic peel and garlic plus minerals played equivalent roles in ruminal ecosystems, although via different mechanisms. Moumen et al. (2016) state that ionophores such as monensin lowered acetate proportion and increased propionate in the rumen, thereby decreasing methane emission. The decreased acetate indicated a decrease in fibrolytic bacteria that impacted on fiber digestibility in the rumen (Rira et al., 2016). The function of monensin is to minimize ion transfer through the cell membrane. Gram-negative bacteria (starch-fermenting bacteria) are more resistant to monensin than gram-positive bacteria (fiber-degrading bacteria) (Azzaz et al., 2015). Decrease in fiber digestibility will decrease hydrogen production, which in turn will suppress rumen degradability (Jayanegara et al., 2016). This finding is in line with another study which suggests that hydrogen accumulation obstructs degradability in the rumen (Olijhoek et al., 2016). Apparently, monensin increases the ability of lactate-utilizing bacteria to convert hydrogen into propionate as well as the bioactive compounds present in garlic.

 

Table 2: Nutrient digestibility (%) of dairy cows across dietary treatments

 

Digestibility T0 T1 T2
Dry matter 73.6±4.26 73.6±9.05 71.2±7.30
Organic matter 76.1±2.87 76.8±8.37 73.1±7.01
Crude fat 77.3±10.3 73.0±22.2 74.5±11.6
Crude protein

92.7±2.68c

79.5±6.7a

81.7±6.63ab

Crude fiber 69.7±4.80 68.5±9.01 64.8±10.4
NDF 77.7±2.89 76.1±8.01 73.5±7.13
ADF 63.3±5.10 64.4±8.56 61.3±7.70
Energy 72.5±5.99 65.3±5.38

69.2±4.57

 

Different superscripts within the same row are significantly different at P<0.05.

T0: basal feed + 0.3 g/d monensin; T1: basal feed + 30 ppm garlic-peel powder; and T2: basal feed + 30 ppm garlic-peel powder + organic minerals (1.5 ppm Cr, 0.3 ppm Se, and 40 ppm Zn-lysinate).

 

Garlic modifies the microbial population profile in the rumen and reduces the contribution of gram-positive Prevotella sp. (P. ruminantium and P. bryantii in particular) while maintaining normal conditions. Prevotella sp. is a bacteria species that plays a role in protein degradation and amino-acid deamination. The deamination process might correlate with the limited supply of hydrogen, and since hydrogen is a prominent substance in methane formation, decreasing methane production will likely decrease dry matter intake and nutrient digestibility (Mills et al., 2003). The decreasing protein degradation resulting from garlic or garlic plus organic mineral supplementation indicates that protein is mostly absorbed in the small intestine. This is in accordance with the findings of Wanapat et al. (2013) and Prayitno et al. (2013), which suggest that garlic supplementation lowers crude protein digestibility. On the other hand, Selenomonas ruminantium is a gram-negative bacteria that can harness lactate as a source of energy. This bacteria is also part of the key pathway to succinate-propionate production for stimulating increasing concentration of propionate (McAllister et al., 2011; Meissner et al., 2010).

 

Table 3: Milk yield and milk composition across dietary treatments

 

Parameter T0 T1 T2

Milk yield

(kg, 4% FCM)

20.7±4.48 21.4±11.9 16.1±3.37
Milk component (%)      
- Fat 4.81±0.80 4.90±0.32 4.96±0.56
- Protein 3.34±0.11 3.20±0.10 3.46±0.17
- Lactose 5.02±0.17 5.13±0.15 5.19±0.26
- Solid non-fat 9.13±0.31 9.36±3.61 9.17±0.14
Total solid 13.9±1.02 14.3±0.46 14.1±0.76
Production (g/d)      
- Fat 1,015±331 1,073±676 814±272
- Protein 1,893±438 2,227±1,185 1,447±127
-Lactose 1,041±241 1,093±597 831±134
-Solid non-fat 1,893±438 2,000±1,185 1,447±127
Total solid 2,884±211 3,047±98

2,278±123

 

T0: basal feed + 0.3 g/d monensin;T1: basal feed + 30 ppm garlic-peel powder;and T2: basal feed + 30 ppm garlic-peel powder + organic minerals (1.5 ppm Cr, 0.3 ppm Se, and 40 ppm Zn-lysinate).

 

Milk Production and Quality

Dietary treatments did not significantly affect milk production and quality (Table 3). Mineral supplements along with garlic peel did not increase milk yield, and this is assumed to be the result of antagonistic effects of the combined ingredients. This result was in contrast to our previous study, which found that garlic plus organic minerals increased milk yield by up to 30% (Prayitno et al., 2013). Furthermore, monensin supplementation did not improve milk yield as mentioned by Odongo et al. (2007), in that the milk yield of dairy cattle fed with 24 mg/kg DM monensin was similar to that of the control (19.7 vs 19.1 kg/d).

 

Milk production and quality are affected by the nutrient content of feed. However, dietary treatments did not significantly affect milk production and quality in this study, because of the equal performance of monensin and garlic peel in reducing acetate and increasing propionate. Busquet et al. (2006) report that 300 mg/l of garlic oil in ruminal fluid: buffer mixture was effective in lowering acetate and increasing propionate as compared to yucca extract, tea tree oil, and cinnamaldehyde. Ionophores such as monensin may lower acetate proportion and increase propionate in the same way as garlic, leading to methane decrease (Azzaz et al., 2015). Acetate decrease may lower milk fat but increase milk lactose and therefore milk quality remains the same. Duplessis et al. (2017) report that the milk yield of dairy cattle was significantly affected by the amount of glucose which can be produced from propionate in the rumen. Acetate and β-hydroxybutyrate are harnessed in the formation of fatty acids attached to glycerol to form milk fat. Acetate is crucial for dairy cattle because it is used in the rumen as an energy source (Urrutia and Harvatine, 2017). Acetate which is synthesized into oxaloacetic acid enters the lipid cycle along with triglycerides and fatty acids. Glycerol is used as an energy source (Syahniar et al., 2016) while acetate becomes a short chain fatty acid and undergoes glycolysis into ATP with glucose.

 

The mechanism of propionate conversion into lactose is affected by minerals, particularly Cr and Se. Cris a trace mineral that performs physiologically in glucose metabolism by increasing the insulin activity potential (Leiva et al., 2015).The optimum performance of secretory cells for normal function needs to be maintained by supplementing with selenium. As the physiological form of selenium, glutathione protects membrane cells and sub-cells against oxidative damage, including in the secretory cells of mammary glands (Miranda et al., 2011). Propionic acid undergoes gluconeogenes is in the liver, and this produces glucose that is carried by the blood to the secretory cells of udder glands to be used for milk lactose synthesis (Udén and Danfaer, 2008). A high ratio of propionate to acetate will increase lactose production. Lactose synthesis commences with one glucose molecule ina pair of glucose molecules entering the udder being converted into galactose. Galactose is then condensed with glucose to form lactose by the action of lactose synthetase enzyme (Udén and Danfaer, 2008).


CONCLUSION

 

Supplementation with monensin, garlic peel, and organic minerals did not affect nutrient intake (DM,OM,CP,CF, energy, NDF, and ADF), nutrient digestibility (DM,OM,CF, energy, NDF, and ADF), milk production, or milk quality of lactating dairy cows. However, supplementation with garlic peel and garlic peel plus organic minerals decreased the digestibility of crude protein. Supplementation of garlic peel can therefore replace monensin in the feed of dairy cattle.

 

acknowledgements

 

The authors are grateful to Indonesian Ministry of Research, Technology and Higher Education for providing a financial support for this study.

 

Conflict of interest

 

All authors declare that there is no conflict of interest.

 

authors contribution

 

CHP designed and performed the experiment, and wrote the first draft of the manuscript; YS conducted data and statistical analyses, and revised the manuscript; AJ reviewed data analysis and revised the manuscript.

 

REFERENCES

 

  • Azzaz HH, Murad HA, Morsy TA (2015). Utility of ionophores for ruminant animals: a review. Asian J. Anim. Sci. 9: 254–265. https://doi.org/10.3923/ajas.2015.254.265
  • Broderick GA, Radloff WJ (2004). Effect of molasses supplementation on the production of lactating dairy cows fed diets based on alfalfa and corn silage. J. Dairy Sci. 87: 2997–3009. https://doi.org/10.3168/jds.S0022-0302(04)73431-1
  • Busquet M, Calsamiglia S, Ferret A, Kamel C (2006). Plant extracts affect in vitro rumen microbial fermentation. J. Dairy Sci. 89: 761–771. https://doi.org/10.3168/jds.S0022-0302(06)72137-3
  • Cottle DJ, Nolan JV, Wiedemann SG (2011). Ruminant enteric methane mitigation: a review. Anim. Prod. Sci. 51: 491. https://doi.org/10.1071/AN10163
  • Duplessis M, Lapierre H, Ouattara B, Bissonnette N, Pellerin D, Laforest JP, Girard CL (2017). Whole-body propionate and glucose metabolism of multiparous dairy cows receiving folic acid and vitamin B 12 supplements. J. Dairy Sci. 100: 8578–8589. https://doi.org/10.3168/jds.2017-13056
  • Jayanegara A, Palupi E (2010). Condensed tannin effects on nitrogen digestion in ruminants: a meta-analysis from in vitro and in vivo studies. Media Peternak. 33: 176–181. https://doi.org/10.5398/medpet.2010.33.3.176
  • Jayanegara A, Dewi SP, Laylli N, Laconi EB, Nahrowi, Ridla M (2016). Determination of cell wall protein from selected feedstuffs and its relationship with ruminal protein digestibility in vitro. Media Peternak. 39: 134-140. http://dx.doi.org/10.5398/medpet.2016.39.2.134
  • Kišidayová S, Mihaliková K, Siroka P, Čobanová K, Váradyová Z (2014). Effects of inorganic and organic selenium on the fatty acid composition of rumen contents of sheep and the rumen bacteria and ciliated protozoa. Anim. Feed Sci. Technol. 193: 51–57. https://doi.org/10.1016/j.anifeedsci.2014.04.008
  • Laconi EB, Jayanegara A (2015). Improving nutritional quality of cocoa pod (theobroma cacao) through chemical and biological treatments for ruminant feeding: in vitro and in vivo evaluation. Asian-Australas. J. Anim. Sci. 28: 343–350. https://doi.org/10.5713/ajas.13.0798
  • Leiva T, Cooke RF, Brandão AP, Aboin AC, Ranches J, Vasconcelos JLM (2015). Effects of excessive energy intake and supplementation with chromium propionate on insulin resistance parameters, milk production, and reproductive outcomes of lactating dairy cows. Livest. Sci. 180: 121–128. https://doi.org/10.1016/j.livsci.2015.08.007
  • McAllister TA, Beauchemin KA, Alazzeh AY, Baah J, Teather RM, Stanford K (2011). Review: The use of direct fed microbials to mitigate pathogens and enhance production in cattle. Can. J. Anim. Sci. 91: 193–211. https://doi.org/10.4141/cjas10047
  • Meissner H, Henning P, Horn C, Leeuw KJ, Hagg F, Fouche G (2010). Ruminal acidosis: A review with detailed reference to the controlling agent Megasphaera elsdenii NCIMB 41125. South Afr. J. Anim. Sci. 40. https://doi.org/10.4314/sajas.v40i2.57275
  • Mills JAN, Kebreab E, Yates CM, Crompton LA, Cammell SB, Dhanoa MS, Agnew RE, France J (2003). Alternative approaches to predicting methane emissions from dairy cows. J. Anim. Sci. 81: 3141. https://doi.org/10.2527/2003.81123141x
  • Miranda SG, Purdie NG, Osborne VR, Coomber BL, Cant JP (2011). Selenomethionine increases proliferation and reduces apoptosis in bovine mammary epithelial cells under oxidative stress. J. Dairy Sci. 94: 165–173. https://doi.org/10.3168/jds.2010-3366
  • Moumen A, Azizi G, Chekroun KB, Baghour M (2016). The effects of livestock methane emission on the global warming: a review. Int. J. Glob. Warm. 9: 229. https://doi.org/10.1504/IJGW.2016.074956
  • Odongo NE, Bagg R, Vessie G, Dick P, Or-Rashid MM, Hook SE, Gray JT, Kebreab E, France J, McBride BW (2007). Long-term effects of feeding monensin on methane production in lactating dairy cows. J. Dairy Sci. 90: 1781–1788. https://doi.org/10.3168/jds.2006-708
  • Olijhoek DW, Hellwing ALF, Weisbjerg MR, Dijkstra J, Hojberg O, Lund P (2016). Effect of short-term infusion of hydrogen on enteric gas production and rumen environment in dairy cows. Anim. Prod. Sci. 56: 466. https://doi.org/10.1071/AN15521
  • Osborne JK, Mutsvangwa T, Alzahal O, Duffield TF, Bagg R, Dick P, Vessie G, McBride BW (2004). Effects of monensin on ruminal forage degradability and total tract diet digestibility in lactating dairy cows during grain-induced subacute ruminal acidosis. J. Dairy Sci. 87: 1840–1847. https://doi.org/10.3168/jds.S0022-0302(04)73341-X
  • Plaizier JC, Martin A, Duffield T, Bagg R, Dick P, McBride BW (2000). Effect of a prepartum administration of monensin in a controlled-release capsule on apparent digestibilities and nitrogen utilization in transition dairy cows. J. Dairy Sci. 83: 2918–2925. https://doi.org/10.3168/jds.S0022-0302(00)75192-7
  • Prayitno CH, Subagyo Y, Suwarno S (2013). Supplementation of Sapindus rarak and garlic extract in feed containing adequate cr, se, and zn on rumen fermentation. Media Peternak. 36: 52–57. https://doi.org/10.5398/medpet.2013.36.1.52
  • Riaz MQ, Südekum KH, Clauss M, Jayanegara A (2014). Voluntary feed intake and digestibility of four domestic ruminant species as influenced by dietary constituents: A meta-analysis. Livest. Sci. 162: 76–85. https://doi.org/10.1016/j.livsci.2014.01.009
  • Rira M, Morgavi DP, Popova M, Marie-Magdeleine C, Silou-Etienne T, Archimède H, Doreau M (2016). Ruminal methanogens and bacteria populations in sheep are modified by a tropical environment. Anim. Feed Sci. Technol. 220: 226–236. https://doi.org/10.1016/j.anifeedsci.2016.08.010
  • Syahniar TM, Ridla M, Samsudin AA, Jayanegara A (2016). Glycerol as an energy source for ruminants: a meta-analysis of in vitro experiments. Media Peternak. 39: 189–194. https://doi.org/10.5398/medpet.2016.39.3.189
  • Udén P, Danfaer A (2008). Modeling glucose metabolism in the dairy cow—A comparison of two dynamic models. Anim. Feed Sci. Technol. 143: 59–69. https://doi.org/10.1016/j.anifeedsci.2007.05.004
  • Urrutia N, Harvatine KJ (2017). Effect of conjugated linoleic acid and acetate on milk fat synthesis and adipose lipogenesis in lactating dairy cows. J. Dairy Sci. 100: 5792–5804. https://doi.org/10.3168/jds.2016-12369
  • Wanapat M, Kang S, Khejornsart P, Wanapat S (2013). Effects of plant herb combination supplementation on rumen fermentation and nutrient digestibility in beef cattle. Asian-Australas. J. Anim. Sci. 26: 1127–1136. https://doi.org/10.5713/ajas.2013.13013
  • Wang M, Wang R, Xie TY, Janssen PH, Sun XZ, Beauchemin KA, Tan ZL, Gao M (2016). Shifts in rumen fermentation and microbiota are associated with dissolved ruminal hydrogen concentrations in lactating dairy cows fed different types of carbohydrates. J. Nutr. 146: 1714–1721. https://doi.org/10.3945/jn.116.232462
  • Yang WZ, Benchaar C, Ametaj BN, Chaves AV, He ML, McAllister TA (2007). Effects of garlic and juniper berry essential oils on ruminal fermentation and on the site and extent of digestion in lactating cows. J. Dairy Sci. 90: 5671–5681. https://doi.org/10.3168/jds.2007-0369
  •