Abstract
It is well documented that choline is known as one of the essential ingredients of phospholipids. Choline acts as a determinative element for appropriate cell membrane functions. On the other hand α-tocopherol (Vit E) is a fat-soluble vitamin. This vitamin acts as a strong antioxidant in the living body's defense system against oxidative stress. Lipid peroxidation in peripartum and early lactating cows is significantly increased while the level of serum Vit E is decreases dramatically. These concomitant physiological changes demonstrate a higher level of oxidative stress subsequently leads to serious health issues in dairy cows. Therefore, the present research was designed to investigate the following items in dairy cattle: 1) evaluation of the possible changes in serum protein fractions, and 2) comparing the oxidative status of orally RPC and vitamin E supplementation in dairy cows in early lactation period. In the current study 30 early lactating primiparous and multiparous Holstein cows (body condition score (BCS)=2.51 ± 0.10) were used beginning five weeks postpartum. All the animals were randomly divided in to three groups (n=10) (number of lactation=2.61). The animals were randomly assigned to receive one of the following treatments. Group 1 served as control group were not received any supplement. The second group was supplemented with 90 g/d of RPC (Reashre Choline, Balchem, USA). The third group was administrated 4400 IU/d vitamin E (Roche, Vitamins Ltd; Switzerland). In the current study, serum protein electrophoresis showed four main fractions as follows: albumin, α-globulin, β-globulin, and γ-globulin. The recorded data showed that the percentages of albumin and γ-globulin fractions were higher in treated groups compared to the control group. In the animals supplementing with RPC and vitamin E the percentages of serum albumin increased to the value of 37. 70±1.63 and 38.21±1.28 respectively compare to the control group (34.69±1.21), which were significant (P<0.05).
Keywords: electrophoresis, serum proteins, RPC, vitamin E
1. Introduction
It is well documented that the blood proteins, excluding the γ-globulin fraction, are mainly synthesized in the liver ( 1 ). Electrophoresis of the protein content of a normal plasma or serum consequently leads to identifying two important protein fractions called albumin and globulin. The relative amount of these proteins is significantly linked to the animal species, for instance in laboratory animals (guinea pigs, rats, rabbits), humans, sheep, and goats the albumin level is higher than globulin. While in cows the ratio of albumin/globulin is almost equal ( 2 ). As well as animal species some other physiological and environmental factors such as animal age, gender, body mass index (BMI), endocrine status, lactation, pregnancy, ambient temperature, photoperiod, nutritional state, and estrus condition have significant effects on the level of serum protein ( 3 , 4 ). Different disease and health complication conditions lead to a significant reduction in the level of serum albumin. On the other hand, the level of α-globulin in serum samples obtained from the injured animals with traumas significantly increased, also the metabolism alterations in the case of lipoprotein metabolism lead to the changes in the level of serum β-globulin fraction.
However, since there have been several factors that can be responsible for the changes in the levels of serum proteins, it seems impossible to recognize all these responsible effectors ( 5 , 6 ). The lactation period has been known as one of the most anabolic and challenging conditions in the life cycle of female animals. During this important period, protein plays a pivotal role as an essential ingredient for milk production.
The classical and conventional assays based on the electrophoretic methods for serum protein fraction measurements are as follows: protein separation on agarose gel, and cellulose acetate membrane. By the way, capillary zone electrophoresis (CZE) has been proposed as the preferred technique for separation and quantification of serum proteins ( 7 ). In this method, the segregation of proteins and other charged molecules is performed in a capillary tube filled with a special buffer solution with the aid of high voltage electrical power ( 8 ).
Thiols have been known as one of the most potent reducing authoritative factors acting as antioxidants ( 9 ). Antioxidant status, especially the thiol status, is considered one of the most prominent factors for normal body function and physiology. It has been well documented that the possible changes in thiol status lead to induction of programmed cell death (Apoptosis) ( 10 ), this situation has been apperceived in some diseases such as renal failure and vascular disease ( 9 ).
During the respiratory oxidation procedure free radicals, oxidant agents, are produced. These oxidative elements can harm different macromolecules such as nucleic acids, fat, and proteins which can consequently lead to serious health problems ( 11 ). The natural body defense system which hampers the lesion of free radicals and neutralizes them have been known as total antioxidant capacity (TAC) ( 12 ).
Phospholipids are known as the main components of living cells. Choline is known as one of the essential ingredients of phospholipids. This acts as a determinative element for appropriate cell membrane functions. Also, choline plays a pivotal role in lipids transport in the blood. The proper blood lipid transport is considered an essential element in the prevention of fatty liver and ketosis in the lactating dairy cow. Therefore, fortifying diets with the choline supplement may ameliorate the lipids metabolism and transport in the blood and consequently reduce the peril of ketosis and fatty liver disorders. Unfortunately, one of the difficulties in providing dietary choline is the rumen microbial degradation of choline ( 13 ). Therefore, the rumen-protected form of choline (RPC) must be used in the diet formulation. It is well documented that choline is essential for tissue metabolism ( 14 ). In a study on dairy cattle, conducted by Cooke (25) it is established that the RPC consumption could hinder fatty liver disorder induced by feed restriction
. Therefore, Vit E can ameliorate the oxidative stress and improve the health of dairy cows ( 17 ). In the same way as absorption and metabolisms of lipids, Vit E is absorbed from the intestine and transported to the liver. In the liver, α-tocopherol is wrapped in lipoproteins and via blood plasma, spread out from the liver to the other tissues of the living body ( 18 ). The consumption of diet formulation which is fortified with Vit E seriously leads to the dairy cows' health betterment ( 19 , 20 ). Lipid peroxidation in peripartum and early lactating cows is increased significantly ( 21 , 22 ) while the level of blood serum Vit E is decreases dramatically ( 23 ). These concomitant physiological and metabolic changes demonstrate a higher level of oxidative stress which subsequently leads to serious health issues in dairy cows ( 24 ). Previously published works in cattle, mice, and rats (35, 36) showed that Vit E plays a key role in recovering from postpartum-related oxidative stress and alleviating the lipid peroxidation which occurred in liver ( 25 , 26 ). In a study conducted by Soltys ( 27 ), it was shown that Vit E supplementation could improve the liver antioxidant capacity and the TAC in fatty liver induced mice. There have been a few published works investigating the role of Vit E supplementation on liver metabolism and the incidence of metabolic disorders in dairy cattle.
Therefore, the present research was designed to investigate the following items in dairy cattle: 1) evaluation of the possible changes in serum protein fractions, and 2) comparing the oxidative status of orally RPC and vitamin E supplementation in dairy cows in early lactation period. The expected results may demonstrate a contribution to a better comprehension of biochemical processes in early lactating cows.
2. Materials and Methods
2.1. Animals
In the current study 24 early lactating primiparous and multiparous Holstein cows (body condition score (BCS)=2.51 ± 0.10) were used beginning five weeks postpartum. The animals were healthy, with a normal appearance, and housed in individual tie stalls. The animals' selection criteria were based on parity, previous lactation milk yield, and BCS.
2.2. Study Design
All the 24 animals were randomly divided in to three groups (n=8) (number of lactation = 2.61). The animals were randomly assigned to receive one of the following treatments. Group 1 served as control group were not received any supplement. The second group was supplemented with 90 g/d of RPC (Reashre Choline, Balchem, USA). The third group was administrated 4400 IU/d vitamin E (Roche, Vitamins Ltd; Switzerland). The animals were fed total mixed rations (TMR) ad libitum. The diet formulation was based on the nutrient requirements of dairy cattle using the National Research Council (NRC) recommendation as shown in table 1 ( 28 ). The RPC and Vit E were top-dressed onto the TMR.
Table 1.
Ingredients and nutrient composition of the diet
| Ingredient (g/kg of DM) | Composition | ||
|---|---|---|---|
| Alfalfa hay (medium chopped) | 204.7 | DM (g/kg) | 590 |
| Corn silage | 175.8 | CP (g/kg) | 171.7 |
| Beet pulp | 41.3 | Ash (g/kg) | 57.6 |
| Ground barley grain | 198.8 | Total fat (g/kg) | 43.8 |
| Ground corn grain | 58.7 | NDF (g/kg) | 304.8 |
| Ground wheat grain | 28.5 | ADF (g/kg) | 183.8 |
| Solvent extracted soybean meal | 79.9 | NFC c (g/kg) | 382.1 |
| Wheat bran | 7.1 | Ca (g/kg) | 8.1 |
| High lint whole cottonseed | 29.5 | P (g/kg) | 5.0 |
| Canola meal | 100.2 | NEL (Mcal/kg) | 1.66 |
| Corn gluten meal | 11.5 | RUP (g/kg of CP) | 314.5 |
| Fat supplement (energy booster) | 15.9 | RDP (g/kg of CP) | 685.5 |
| Minerals and vitamins supplement | 6.3 | Met (g/kg MP) | 22.1 |
| Salt | 2.5 | Lys (g/kg MP) | 76.9 |
| Calcium carbonate | 3.2 | ||
| Sodium bicarbonate | 10.2 | ||
| Di calcium phosphate | 3.7 | ||
| Magnesium oxide | 1.9 | ||
| Mycosorb | 0.6 | ||
| Biotin premix | 0.7 | ||
| Zeolit | 19.0 | ||
2.3. Blood Sampling
Before the morning meal on the last day of the experiment, the blood samples were obtained from the coccygeal vein (tail vein) in heparinized and non-heparinized Vacutainers (Becton Dickinson, Franklin Lakes, NJ) tubes. Following the blood sampling, all the samples were placed on ice immediately.
2.4. Measurement of Total Antioxidant Capacity and Plasma Total Thiol Molecules (TTM)
The FRAP test (ferric reducing antioxidant power) was used for plasma TAC evaluation according to the previously described method by Benzie ( 29 ).
As previously described by Hu and Dillared ( 30 ) total sulfhydryl content was determined in plasma.
2.5. Capillary Zone Electrophoresis
The Capillary system (Sebia, Issy-les-Moulineaux, France) was operated according to the manufacturer’s instructions under software version 1.4.1.
2.6. Statistical Analyses
Statistical analyses were performed using SAS. All dependent variables and their residuals were evaluated for normality using Proc GLM procedure by inspection of standardized residuals plotted against the predicted residuals. Significant level were declared at P<0.05.
3. Results
In the current study, serum protein electrophoresis showed four main fractions as follows: albumin, α-globulin, β-globulin, and γ-globulin. The percentages of the measured serum albumin and globulins fractions of the animals are presented in table 2. The recorded data showed that the percentages of albumin and γ-globulin fractions were higher in treated groups compared to the control group. In the animals supplementing with RPC and vitamin E the percentages of serum albumin increased to the value of 37. 70±1.63 and 38.21±1.28 respectively compare to the control group (34.69±1.21), which were significant (P<0.05). Whereas the treatments did not affect different fractions of globulin significantly, but there were numerical increases in the percentages of γ-globulin in both treated groups (Table 2).
Table 2.
Serum protein fractions
| Protein Fraction | Control | RPC | Vit E |
|---|---|---|---|
| Albumin | 34.69±1.21b | 37. 70±1.63a | 38.21±1.28a |
| α-globulin | 14.21±1.11a | 13.34±1.01a | 12.60±1.18a |
| β-globulin | 9.31±1.43a | 7.11±1.00a | 6.52±0.98a |
| γ-globulin | 33.65±1.87a | 33.86±1.21a | 34.64±1.32a |
ab different superscripts are indicating significant differences (P<0.05)
The recorded data in the current study showed that the amounts of TTM in treated groups, RPC (1.45±0.67) and Vit E (1.52±0.98) were affected significantly compared to the control group (1.24±0.76) (P<0.05) (Table 3). While the results revealed that RPC and Vit E did not affect TAC significantly (P>0.05). The recorded data for TTM and TAC are tabulated in table 3.
Table 3.
The amount of TTM and TAC in early lactating cows supplementing with RPC and vitamin E
| Control | RPC | Vit E | |
|---|---|---|---|
| TTM | 1.24±0.76b | 1.45±0.67a | 1.52±0.98a |
| TAC | 0.115±0.01a | 0.126±0.08a | 0.130±0.06a |
ab different superscripts are indicating significant differences (P<0.05)
4. Discussion
During the lactation period, dairy cattle tolerate several physiological alterations. All these changes take place in relation to the animals' blood composition in case of alteration in metabolites levels and transport. In reality, lactating animals adapt their body metabolism and physiology to furnish sufficient sources of nutrients for milk production ( 31 ).
The recorded data in the current study revealed that the serum proteins in the treated animals were separated into 4 major fractions such as albumin, α, β, and γ globulin. The results of a study conducted by Saun indicated that the albumin is associated with postpartum diseases, they mentioned that the level of albumin in the serum of the early lactating animal could be used for prediction of disease ( 32 ). Despite the concerns regarding variables befuddle albumin altered level interpretation, it acts as a proper indicator for some metabolic diseases in early lactating cattle with an ability to reflect the availability of amino acids from the labile protein reservoirs. The results of the current study revealed that supplementation of RPC and Vit E had significant effects on level of albumin in the serum samples of the treated animals. Some beneficial effects of RPC and Vit E were related to the betterment of the liver function, on the other hand, it might be a consequence of the induction of insulin secretion, which lowers plasma NEFA concentration via the reduced lipolysis. The insulin secretion is induced by the increased level of glucose. Consequently, the fat metabolization from adipose tissue was suppressed and the amount of NEFA was significantly reduced. Hence the liver load for NEFA oxidation is reduced, and the fat accumulation decreased in the liver. Commonly, in the early lactating cows, the blood NEFA content originating from adipose tissues increased significantly due to negative energy balance ( 33 ).
Reduction in the amount of NEFA and triglycerides in the blood serum due to choline administration leads to the betterment in the liver health condition. It is well documented that choline act as a donor of the methyl group and exerts its beneficial effects through the betterment of lipid metabolism.
A study conducted by El-Shahat in ewes showed that supplementation of Vit E leads to the increment in the levels of albumin, globulin, and total serum protein ( 34 ). Similarly, Helal showed that Vit E administration in buffaloes leads to the increment in the levels of albumin, globulin, and total serum protein ( 35 ).
The results of a study conducted by Deihl showed that Vit E deficiency in rabbits leads to a reduction in the levels of serum albumin and a dramatic increase in the globulin levels, while the total protein concentration remains constant ( 1 ). Some previously published research showed that the blood metabolites such as albumin and globulin in cows and goats were not affected by choline supplementation ( 36 - 40 ).
Conclusion
Authors' Contribution
Study concept and design: Y. S. K. and A. D. H.
Acquisition of data: S. K. H. and I. S. H.
Analysis and interpretation of data: A. A. A. and Z. H. A.
Drafting of the manuscript: A. A. B. and H. A. L.
Critical revision of the manuscript for important intellectual content: M. A. Y. and H. A. K.
Statistical analysis: S. K. H.
Administrative, technical, and material support: Y. S. K.
Ethics
All the steps of this study were performed in accordance with the guidelines for the use and care of animals and approved by the animal ethical committee of Department of pharmacy, Al-Manara College For Medical Sciences, (Maysan), Iraq.
Conflict of Interest
The authors declare that they have no conflict of interest.
References
- 1.Diehl JF, Delincee H. Vitamin E deficiency in rabbits receiving a high PUFA diet with and without a non-absorbable antioxidant II. Incorporation of 14C-labelled glycine and L-leucine into liver and plasma proteins. Z Ernahrungswiss. 1986;25:180–8. doi: 10.1007/BF02021250. [DOI] [PubMed] [Google Scholar]
- 2.Swenson MJ. Dukes physiology of domestic animals. 11th ed. Ithaca, NY : Cornell University Press; 1993. pp. 41–3. [Google Scholar]
- 3.Doxey DL. Clinical pathology and diagnostic procedures. 2nd ed. London, UK: Bailliere; 1986. [Google Scholar]
- 4.Coles EH. Veterinary clinical pathology. 4 ed. Saunders, Philadelphia: 1986. [Google Scholar]
- 5.Karagül H, Altintaş A, Fidanci UR, Sel T. Klinik Biyokimya. Ankara: Medisan Yayınevi; 2000. [Google Scholar]
- 6.Murray RK. Plasma proteins and immunoglobulins. 26th ed. Mc Graw Hill Co: 2003. [Google Scholar]
- 7.Henskens Y, De-Winter J, Pekelharing M, Ponjee G. Detection and identification of monoclonal gammopathies by capillary electrophoresis. Clin Chem. 1998;44:1184–90. [PubMed] [Google Scholar]
- 8.Henskens Y, Van Dieijen-Visser MP. Capillary zone electrophoresis as a tool to detect proteins in body fluids: reproducibility, comparison with conventional methods and a review of the literature. Ned Tijdschr Klin Chem. 2000;25:219–29. [Google Scholar]
- 9.Ueland PM, Mansoor MA, Guttormsen AB, Mullerm F, Aukrust P, Refsum H, et al. Reduced, oxidized and protein-bound forms of homo-cysteine and other aminothiols in plasma comprise the redox thiol status - a possible element of the extracellular antioxidant defense system. J Nutr. 1996;126:1281–4. doi: 10.1093/jn/126.suppl_4.1281S. [DOI] [PubMed] [Google Scholar]
- 10.Marchetti P, Decaudin D, Macho A, Zamzami N, Hirsch T, Susin SA, et al. Redox regulation of apoptosis: Impact of thiol oxidation status on mitochondrial function. Eur J Immunol. 1997;27:289–96. doi: 10.1002/eji.1830270142. [DOI] [PubMed] [Google Scholar]
- 11.Jamro A, Beltwoski J. Cervastatin modulates plasma paraoxonase/arylesterase activity and oxidant/antioxidant balance in rat. Pharmacology. 2002;54:143–50. [PubMed] [Google Scholar]
- 12.Kankfer M, Lipko J. The relationship between lipid peroxidation in tensity and total antioxidant capacity in cases of spontanously released and retained bovine placenta. Vet Med. 2006;157:405–9. [Google Scholar]
- 13.Sharma BK, Erdman RA. Effects of dietary and abomasally infused choline on milk production responses of lactating dairy cows. J Nutr. 1989;119:248– 54. doi: 10.1093/jn/119.2.248. [DOI] [PubMed] [Google Scholar]
- 14.Erdman RA. Vitamins. In Large Dairy Herd Management (Eds H. H. Van Horn & C. J. Wilcox) Champaign, IL: American Dairy Science Association. 1992:297–308. [Google Scholar]
- 15.Cooke RF, Silva-Del RN, Caraviello DZ, Bertics SJ, Ramos MH, Grummer RR. Supplemental choline for prevention and alleviation of fatty liver in dairy cattle. J Dairy Sci. 2007;90:2413–8. doi: 10.3168/jds.2006-028. [DOI] [PubMed] [Google Scholar]
- 16.Ibrahim W, Lee US, Yeh CC, Szabo J, Bruckner G, Chow CK. Oxidative stress and antioxidant status in mouse liver: effects of dietary lipid, vitamin E and iron. J Nutr. 1997;127(7):1401–6. doi: 10.1093/jn/127.7.1401. [DOI] [PubMed] [Google Scholar]
- 17.Burton GW, Traber MG. Vitamin E: antioxidant activity, biokinetics, and bioavailability. Annu Rev Nutr. 1990;10:357–82. doi: 10.1146/annurev.nu.10.070190.002041. [DOI] [PubMed] [Google Scholar]
- 18.Herdt TH, Smith JC. Blood-lipid and lactation-stage factors affecting serum vitamin E concentrations and vitamin E cholesterol ratios in dairy cattle. J Vet Diagn Invest. 1996;8:228–32. doi: 10.1177/104063879600800213. [DOI] [PubMed] [Google Scholar]
- 19.LeBlanc S, Duffield T, Leslie K, Bateman K, TenHag J, Walton J, et al. The effect of prepartum injection of vitamin E on health in transition dairy cows. J Dairy Sci. 2002;5(6):1416–26. doi: 10.3168/jds.S0022-0302(02)74209-4. [DOI] [PubMed] [Google Scholar]
- 20.Politis I, Bizelis I, Tsiaras A, Baldi A. Effect of vitamin E supplementation on neutrophil function, milk composition and plasmin activity in dairy cows in a commercial herd. J Dairy Res. 2004;71(3):273–8. doi: 10.1017/s002202990400010x. [DOI] [PubMed] [Google Scholar]
- 21.Castillo C, Hemandez J, Bravo A, Lopez-Alonso M, Pereira V, Benedito JL. Oxidative status during late pregnancy and early lactation in dairy cows. Vet J. 2005;169(2):286–92. doi: 10.1016/j.tvjl.2004.02.001. [DOI] [PubMed] [Google Scholar]
- 22.Bernabucci U, Ronchi B, Lacetera N, Nardone A. Influence of body condition score on relationships between metabolic status and oxidative stress in periparturient dairy cows. J Dairy Sci. 2005;88(6):2017–26. doi: 10.3168/jds.S0022-0302(05)72878-2. [DOI] [PubMed] [Google Scholar]
- 23.LeBlanc SJ, Herdt TH, Seymour WM, Duffield TF, Leslie KE. Peripartum serum vitamin E, retinol, and beta-carotene in dairy cattle and their associations with disease. J Dairy Sci. 2004;87:609–19. doi: 10.3168/jds.S0022-0302(04)73203-8. [DOI] [PubMed] [Google Scholar]
- 24.Miller JK, Brzezinska-Slebodzinska E, Madsen FC. Oxidative stress, antioxidants, and animal function. J Dairy Sci. 1993;76(9):2812–23. doi: 10.3168/jds.S0022-0302(93)77620-1. [DOI] [PubMed] [Google Scholar]
- 25.Ferre N, Camps J, Paul A, Cabre M, Calleja L, Osada J, et al. Effects of high-fat, low-cholesterol diets on hepatic lipid peroxidation and antioxidants in apolipoprotein E-deficient mice. Mol Cell Biochem. 2001;218:165–9. doi: 10.1023/a:1007296919243. [DOI] [PubMed] [Google Scholar]
- 26.Bouwstra RJ, Goselink RM, Dobbelaar P, Nielen M, Newbold JR, van Werven T. The Relationship Between Oxidative Damage and Vitamin E Concentration in Blood, Milk, and Liver Tissue from Vitamin E Supplemented and Nonsupplemented Periparturient Heifers. J Dairy Sci. 2008;91:977–87. doi: 10.3168/jds.2007-0596. [DOI] [PubMed] [Google Scholar]
- 27.Soltys K, Dikdan G, Koneru B. Oxidative stress in fatty livers of obese Zucker rats: Rapid amelioration and improved tolerance to warm ischemia with tocopherol. J Hepatol. 2001;34:13–8. doi: 10.1053/jhep.2001.25452. [DOI] [PubMed] [Google Scholar]
- 28.NRC. National Research Council. Nutrient Requirements of Dairy Cattle. 2001 [Google Scholar]
- 29.Benzie IF, Strain JJ. Ferric reducing/antioxidant power assay: direct measure of total antioxidant activity of biological fluids and modified version for simultaneous measurement of total antioxidant power and ascorbic acid concentration. Meth Enzymol J. 1999;299:15–27. doi: 10.1016/s0076-6879(99)99005-5. [DOI] [PubMed] [Google Scholar]
- 30.Hu ML, Dillared CJ. Plasma SH and GSH measurement. Methods in Enzymology. 1994;233:385–7. [Google Scholar]
- 31.Drackley JK. Biology of dairy cows during the transition period: the final frontier? . J Dairy Sci. 1999;89:2259–73. doi: 10.3168/jds.s0022-0302(99)75474-3. [DOI] [PubMed] [Google Scholar]
- 32.Saun RJV. Metabolic profiling and health risk in transition cows. Proc Am Assoc Bov Pract. 2004;37:212–3. [Google Scholar]
- 33.Overton TR, Waldron MR. Nutritional management of transition dairy cows: strategies to optimize metabolic health. J Dairy Sci. 2004;87:105–19. [Google Scholar]
- 34.El-Shahat KH, Monem UMA. Effects of Dietary Supplementation with Vitamin E and /or Selenium on Metabolic and Reproductive Performance of Egyptian Baladi Ewes under Subtropical Conditions. World Appl Sci J. 2011;12(9):1492–9. [Google Scholar]
- 35.Helal TS, Ali FA, Ezzo O, El-Ashry MA. Effect of supplement ting some vitamins and selenium during the last stage of pregnancy on some reproductive aspects of Egyptian dairy buffaloes. J Agric Sci. 2009;19:4289–99. [Google Scholar]
- 36.Mohsen MK, Gaffar HMA, Khalafalla MM, Shitta AA, Yousif AM. Effect of Rumen Protected Choline Supplementation on Digestibility, Rumen Activity and Milk Yield in Lactating Friesian Cows. Slovak J Anim Sci. 2011;44:2011. [Google Scholar]
- 37.Ambrosio FD, Campagnoli A, Susca F, Fusi E, Rebucci R, Agazzi A, et al. Effects of rumen-protected choline supplementation in periparturient dairy goats. Vet Res Commun. 2007;31:393–6. doi: 10.1007/s11259-007-0064-x. [DOI] [PubMed] [Google Scholar]
- 38.Bindel DJ, Titgemeyer EC, Drouillard JS, Ives SE. Effects of choline on blood metabolites associated with lipid metabolism and digestion by steers fed corn-based diets. J Anim Sci. 2005;83:1625–32. doi: 10.2527/2005.8371625x. [DOI] [PubMed] [Google Scholar]
- 39.Zahra LC, Duffield TF, Leslie KE, Overton TR, Putnam D, Leblanc SJ. Effects of rumen-protected choline and monensin on milk production and metabolism of periparturient dairy cows. J Dairy Sci. 2006;89:4808–18. doi: 10.3168/jds.S0022-0302(06)72530-9. [DOI] [PubMed] [Google Scholar]
- 40.Toghdory A, Emanuele S, Choorchi T, Naerian A. Effect of choline and rumen protected choline on milk production, milkcomposition and blood metabolites of lactating dairy cows. J Dairy Sci. 2007;90:353–64. [Google Scholar]