Animals, Diets, and Experimental Design
A total of 24 growing Sahiwal heifers were selected from Livestock Farm Complex (LFC), DUVASU, Mathura and randomly assigned into four dietary treatments on body weight (100.20±4.84 kg) and age (12-15 months) basis. Heifers either received a basal diet devoid of supplemental Cu (control) or were supplemented with 10 ppm of inorganic Cu as copper sulphate pentahydrate (CuSO4.5H2O, molecular weight 249.68, minimum assay purity 99%, Central Drug House Pvt. Ltd. New Delhi), 5 ppm and 10 ppm of nano Cu as cupric oxide nanopowder (CuO, molecular weight 79.54, APS: 40 nm, SSA: 80 m2/g, minimum assay purity 99%, Sisco Research Laboratories Pvt. Ltd. Maharashtra, India). The dietary requirements of experimental animals were met by offering total mixed ration (TMR) consisted of concentrate: green berseem fodder: wheat straw in the proportion of 50:35:15 following NRC [15] guidelines.
To ensure that each animal consumed the calculated amount of Cu, the calculated amount of CuSO4.5H2O and CuO nanopowder was mixed with barley flour and prepared the premix (@ 2 ppm Cu/g of barley flour) and offered prior to providing the ration. TMR was prepared daily by hand mixing and was offered at 09:00 h and 18:00 h. The animals were provided with fresh and clean drinking water free of choice daily. Experimental animals were housed in a proper ventilated shed having the good arrangement for individual feeding and watering without having access to the other animal’s diet. Deworming of all the experimental animals was done before the start of the experiment.
Table 1 Ingredients and chemical composition of total mixed ration
Ingredients composition
|
Content (g/kg DM or as depicted)
|
Berseem fodder
|
350
|
Wheat straw
|
150
|
Barley grains
|
130
|
Wheat bran
|
100
|
Gram chunni
|
100
|
Mustard oil cake
|
160
|
Mineral mixture and vitamin premixα
|
10
|
Copper supplementβ
|
Variable
|
Chemical composition
|
Dry matter, g/kg of diet
|
620.9
|
Crude protein
|
161.6
|
Ether extract
|
33
|
Neutral detergent fiber
|
534.5
|
Acid detergent fiber
|
274.3
|
Calcium
|
11.6
|
Phosphorus
|
6.4
|
Copper, mg/kg DM
|
8.75
|
Zinc, mg/kg DM
|
39.40
|
Iron, mg/kg DM
|
296.49
|
αMineral and vitamin premix contained (per kg): vitamin A, 700000 IU; vitamin D3, 70,000 IU; vitamin E, 250 mg; nicotinamide, 3.0 g; Ca, 190 g; P, 90 g; Na, 50 g; Zn, 9.6 g; Fe, 1.5 g; Mn, 6.0 g; I, 325 mg; Co, 150 mg; Se, 10 mg; Mg, 19.0 g. βIn inCu10 group - 10.0 mg/kg Cu as CuSO4.5H2O, nanoCu5 and nanoCu10 group -5 and 10.0 mg/kg Cu as nano copper oxide, respectively.
Observation Recorded and Analytical Procedures
Feeds and fodders intake was observed daily by weighing feedstuffs offered and leftover residue, and dry matter intake (DMI) was enumerated daily according to the DM content of the diet. Body weight (BW) of the experimental heifers was recorded at the starting of experiment and then at 15, 30, 45, 60, 75, 90, 105 and 120 days of experiment by using computerized weighing machine (Leotronic Scales Pvt. Ltd., India). Heifers were weighed for 2 consecutive days in the morning at 06:00 h before offering feeds, fodders, and water. The average of consecutive two days was considered as BW for that fortnight and considered for average daily gain (ADG), feed conversion ratio (FCR), and feed conversion efficiency (FCE). Samples of feeds and fodders offered and leftover residue were dried in a hot air oven at 60 °C upto a constant weight was achieved and then ground to pass a 1-mm sieve in a Wiley mill. The samples were analyzed for DM (Method 973.18c), CP (Method 4.2.08), ether extract (EE; Method 920.85), and total ash (TA; Method 923.03) [16]. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined according to the procedures described by Van Soest et al. [17]. Calcium (Ca) and Phosphorus (P) in feeds, fodders, leftover residue, and fecal samples were evaluated by Talapatra et al. [18] and volumetric method, respectively. The concentration of trace minerals like Cu, Zn and Fe in different samples of feeds and fodders and orts left were evaluated by Atomic Absorption Spectrophotometer (AAS; Perkins, USA). Ingredients and chemical composition of the basal diet fed during the experimental period is depicted in Table 1.
Peripheral blood samples were collected before feeding and watering of heifers at 07:00 h in heparinised vacuutainer tubes (BD Franklin, USA) at 0, 30, 60, 90 and 120 days post-Cu supplementation. Collected blood samples were centrifuged at 3000 rpm for 30 min to remove the plasma from packed erythrocytes. Samples of blood plasma were kept at -20 °C until further analysis of SOD, CAT, GSHPx, MDA, LPO, Cp, TAS, total Ig, IgG and IL-6 content. SOD, CAT, GSH-Px, MDA, LPO, Cp, IgG and IL-6 were estimated in blood plasma by using ELISA Test Kits (Catalog No. E0003Bo; E0025Bo; E0006Bo; E0198Bo; E0561Bo; E0395Bo; E0010Bo; E0001Bo, respectively) from Bioassay Technologies, China. TAS measured as ferric reducing antioxidant power (FRAP) assay procedure described by Benzie and Strain [19]. The total Ig was estimated by zinc turbidity method [20].
mRNA Expression Study
The immunity and antioxidant status related genes (namely IL-6, IL-10, SOD and CAT) were estimated in peripheral blood mononuclear cells (PBMCs) isolated from fresh blood samples.
Blood samples were collected from jugular vein using sodium heparinized vacutainer under sterile conditions. About 4 ml of blood was collected in the sterile fresh tube. Peripheral blood mononuclear cells (PBMCs) were separated from blood samples with use of histopaque-1077 (Sigma). RNA was isolated from PBMCs by Trizol method. The purity and concentration of total RNA was examined with use of the Biophotometer (Eppendorf, Germany). RNA samples of A260/A280 value more than 1.8 were used for cDNA synthesis. cDNA synthesis was carried out from the mRNA found in the total RNA using Revertaid® First strand cDNA synthesis kit (Thermo Scientific, USA) with use of moloney murine leukemia viral reverse transcriptase enzyme by using the manufacturer’s guidelines. Real time RT-PCR (qRT-PCR) was carried out after checking each primer for its specificity. The cDNA was checked for quality by performing RT-PCR with standard GAPDH primers. After that amplified DNA was exposed to agarose gel electrophoresis as per guidelines given by Sambrook and Russel [21]. The size of the PCR products amplified was calculated from the standard 50 bp or 100 bp DNA ladder (Invitrogen, USA).
Table 2 Description of primers used for real-time qRT-PCR
Gene
|
Primer sequences
|
Product size (bp)
|
References
|
IL-6
|
F5’-ATCAGAACACTGATCCAGATCC-3’
R5’-CAAGGTTTCTCAGGATGAGG-3’
|
145
|
[22]
|
IL-10
|
F5’-AAGGTGAAGAGAGTCTTCAGTGAGC-3’
R5’-TGCATCTTCGTTGTCATGTAGG-3’
|
110
|
[22]
|
SOD
|
F5’-GAAGAGAGGCATGTTGGAGA-3’
R5’-CCAATTACACCACGAGCCAA-3’
|
220
|
[23]
|
CAT
|
F5’-GCAGATACCTGTGAACTGTC-3’
R5’-GTAGAATGTCCGCACCTGAG-3’
|
229
|
[24]
|
GAPDH
|
F5’-TTCTACTGGCGCTGCCAAGG -3’
R5’-GATCCACAACAGACACGTTGGG-3’
|
107
|
[22]
|
IL-6, interleukin-6; IL-10, interleukin-10; SOD, superoxide dismutase; CAT, catalase; GAPDH, glyceraldehydes-3-phosphate dehydrogenase
Real-Time RT-PCR was performed using SYBR Green master mix (PowerUpTM SYBRTM Green master mix [2X]; Thermo Fischer Scientific, USA). The results were expressed as threshold cycle values (CT). To study the relative change in gene expression, the 2-∆∆CT method was used as described previously by Livak and Schmittgen [25]. The formula used to calculate the fold change in gene expression was “fold change = 2-∆∆CT,” [where ∆∆CT = (CT,target gene - CT, GAPDH) treatment - (CT,target gene -CT,GAPDH) control]. The results were analyzed in comparison with the CT value of the target gene and the reference gene.
Statistical Analyses
The data for measured variables were subjected to analysis of variance using the mixed model repeated measure procedure of the Statistical Software Package (SPSS for windows, V21.0; Inc., Chicago, IL, USA). The effect of treatments, days in trial and their interaction on variables like antioxidants and immune response were analyzed by using following model:
Yijk = µ + Ti + Dj + (T × D)ij + eijk
where Yijk is the dependent variable, µ is the overall mean of the population, Ti is the mean effect of the Cu, Dj is the mean effect of days of sampling (j = 0, 30, 60, 90 and 120 days of dietary treatment), (T × D)ij is the effect of the interaction between treatment and days of trial and eijk is unexplained residual element assumed to be independent and normally distributed. Individual animal was used as the experimental unit for all data. The statistical difference between the means was determined by using ‘‘Tukey’s honest significant difference (HSD) test.’’