Effect of Different Energy Levels in Starter Ration Of Suckling Angus Calves on Blood Biochemical Parameters, Hormone Profile, Immune Response and Antioxidant Status

In ruminant’s production, feeding play an important role in growth both in preweaning and postweaning stage (Gayathri and Panda 2018). Preweaning claves receive nutrients from milk or milk replacer for growth in early days of life. However, solid feed like forages and concentrate are necessary for preweaning calves to develop rumen which ultimately enhance growth. Adequate amount of forage and starter diet fosters rumen volume and papillae development, favoring growth of pre-weaned calves. Sun et al., (2018) reported that starter feeding increased proliferation of rumen and enhanced rumen development in pre-weaned lambs. Composition of solid feed during preweaning stage could also affect rumen development, growth and behavior of animals (Suárez et al., 2006; Khan et al., 2008; Muhammad et al., 2016; Aziz ur Rahman et al., 2017; Rahman et al., 2019). Khan et al., (2008) reported that rumen development is affected in calves fed pelleted calf starter containing 25% starch and based on wheat, oats, barley and corn. Suárez et al., (2006) fed young veal calves calf starter containing neutral detergent fiber, pectin, starch, or combinations and reported that differences in diet composition resulted in differences in rumen size and morphological development of rumen.
       
Based on review, it could be seen that solid feed type and composition is closely related with rumen development of young pre-weaned calves. However, most of the studies focused on solid feed type and composition effects on intake, rumen development and growth of pre-weaned calves but scientific literature regarding the effects of energy contents in solid feed of pre-weaned Angus on blood metabolites, hormonal profile, antioxidant status and immune response is limited. Therefore, this study was conducted to evaluate the effects of energy level in starter ration on hormone, blood metabolite levels and immune index of pre-weaning angus calves.

The experiment was carried out in the Breeding Research Center of Hunan Tianhua Industrial Co., Ltd. (Loudi City, Hunan Province, China). Animal Welfare and use Committee of Hunan Agricultural University approved all experimental procedure of current study.
 
Experimental design, animal management and diet
 
In this study, eighteen Angus calves of twenty days old with initial BW = 43.4±4.25 kg were selected. Animals were divided into 3 different experimental groups in such a way that each experimental group contained three replicates and each replicate had two calves. Dietary treatments were: Low metabolizable energy (LME) that was 11.19 MJ/kg; Medium metabolizable energy (MME) that was 12.38 MJ/kg and High metabolizable energy (HME) that was 13.62 MJ/kg. Proximate analysis of feed, orts and fecal samples were determined by the following the procedure of Association of Official Analytical Chemists (AOAC, 1990). Ankom Fibre Analyser (Ankom Technology, Fairport, NY) was used to determine the fractions of NDF and ADF. Metabolizable energy we calculated by using nutrient composition of ingredient.  However, formula used was just contribution of specific ingredient percentage in the total ration and sum of all ingredients. The diets were not iso-nitrogenous and contained 23, 20 and 23 per cent CP respectively along with variation in energy level. The quality of fodder was determined as described in literature (Vasileva and Naydenova, 2017; Zulfiqar et al., 2017). The duration of the experiment was 90 days. The composition of pelleted starter rations is shown in Table 1. Besides, pelleted starter ration, calves were offered whole oat hay ad-libitum. Milk was provided to each calf from their dams by suckling method at 07:00 and 18:00 every day. After milk feeding calves were separated from their dams. The starters and oat hay were offered at 08:00 and 15:30 and refusal of feed was ensured at 10%.
 

 
Blood sample collection and chemical analysis
 
Blood was collected from the Jugular vein of the each calf at the end of the experiment. Collected blood was in a 0.5 ml heparin sodium centrifuge tube and analyzed for red blood cells, white blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red cell distribution width, platelets, mean platelet volume, platelet distribution width and thrombocytocrit as described in the previous studies (Rezende et al., 2014).
               
For blood plasma collection, blood samples were centrifuged at 3000 rpm/min for 10 min as described in previous studies (Xia et al., 2018). The collected serum was dispensed into a 2 ml centrifuge tube and store at -20° for testing. The plasma biochemical indicators were determined using an automated biochemistry analyser (Hitachi 7020; Hitachi Co., Tokyo, Japan). Blood metabolites were determined in this study by using commercial test kits (Andygene, Beijing, China) following the procedure as described in literature (Sheikh et al., 2019; Kumar et al., 2018). The levels of immune indices, hormone and antioxidant index (SOD, GSH-PX, MDA concentrations) in plasma were also determined by using commercial test kits (Andygene, Beijing, China).

Data processing and analysis
 
All collected data were analyzed by using SPSS 23.0 software. Mean values were compared using Tukey’s test.

Results of blood biochemical parameters are presented in Table 2. Result reveled that red blood cells, hemoglobin, hematocrit and thrombocytocrit was higher in HME diet (P<0.05). While, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean platelet volume and platelet distribution width was higher in MME diet as compared to HME diet (P<0.05).
 

       
Results of effect of different levels of energy in diet of suckling Angus calves on protein and fat metabolism are presented in Table 3. Highest HDL contents were observed in HME fed calves as compared to other dietary treatments (P<0.05). Lowest HDL contents were observed in LME fed calves as compared to other dietary treatments (P<0.05).
 

 
Results of effect of different levels of energy in diet of suckling Angus claves on immunity parameter are presented in Table 4. Result of current study revealed that IgA content were lowest in calves fed starter ration of LME as compared  to calves received calf starter with MME and HME diet (P<0.05). Calf received different energy level in the diet had no effect on IgG, IgM and C4 (P>0.05). The calves on LME starter diet represented higher compliment C3 contents as compared to calves on MME starter diet (P<0.05).
 

       
Effect of different energy level in starter ration of calves on hormone level and antioxidant index is presented in Table 5. Results of present study showed that hormone level and antioxidant index were similar in all calves received LME, MME and HME starter diet (P>0.05).
 

       
A close relationship exists between diet nutritional factors, hormones and blood metabolites in pre-weaned calves (Fernández et al., 2012). Klinkon and Ježek, (2012) studied the effect of milk feeding in calves without any solid feed on hemoglobin, red blood cells and hematocrit and reported that the veal calves fed predominantly with milk, the values hemoglobin, red blood cells and hematocrit decreased and calves become anemic. Based on findings of previous studies and current study, one could just guess that change in nutritional content of feed especially energy level in the feed of preweaning growing Angus calve influence the hemoglobin, red blood cells and hematocrit.
       
No effect of dietary treatments on white blood cells indicate that all diets respond similar and had no stress on claves. In the current study, the observed number of platelets in calves was in range of 596-660 x 10⁹/L in different dietary regimes. The number of platelets was in range as described by previous study (Knowles et al., 2000). The decrease in mean corpuscular volume in HME diet of calves was associated with higher number of red blood cells and hemoglobin. Our findings were also in consistent with the findings of previous researcher (Egli and Blum, 1998; Knowles et al., 2000). The decrease meancorpuscular hemoglobin concentration and increase in thrombocytocrit  in calves fed HME could be explained by the mechanism of body to increase the red blood cells number to maintain a normal hemoglobin concentration. Lower hemoglobin concentration in MME fed animals could also be explained by lower CP concentration of diet. As the composition of MME diet shows less CP contents (20.77%) as compare to LME (23.17%) and HME and Rotimi et al., (2018) reported that hemoglobin concentration reduced by the low protein diet.
       
In current study total serum total protein, albumin, globulin, total glycerides, low density lipoprotein and free fatty acid was not affected by dietary treatment. Our findings were similar with the findings of Quigley et al., (2006) who reported increase in nutrient in calf’s daily intake had no effect on serum total protein, albumin, globulin, total glycerides, low density lipoprotein and free fatty acid. However, the higher blood urea nitrogen in MME diet as compare to HME diet could be explained by the previous study of Dominic et al., (2014) who reported that increasing energy level in the diet decreases the concentration of blood urea nitrogen. If this is the case, blood urea nitrogen should be less in calves fed MME diet as compare to LME diet calves. This could also be explained by the study of Dominic et al., (2014) who reported that increasing the level of CP in the diet of animals results in higher blood urea nitrogen. In current study, the CP concentration of MME diet was 20% while the LME diet had 23.17% protein that could be reason of higher blood urea nitrogen concentration of LME diet. The activity of lactate dehydrogenase in calves were similar among the dietary treatments. Our findings were similar with the findings of Egli and Blum (1998) who reported that lactate dehydrogenase remains same in calves on different dietary regimes. Similar, concentration of aspartate aminotransferase was indication that heart, skeletal muscle and liver cells undergoes similar changes with dietary treatments in calves.
       
Similar response of hormone and antioxidant in current study due to various dietary treatments explored that during weaning, change in energy level in the diet of calves had no influence on growth hormone, growth and antioxidant activity. It could further explain, change in energy level might have no effect on rumen development, nutrient absorption and hence growth of calves.

This work was funded by ‘National Key Research and Development Program of China (2017YFD0502005)’ and ‘The Key Research and Development Project of Hunan Province, China” (No.2 017NK1020) and ‘Hunan Modern Agricultural Technology System of Herbivora’ and‘Hunan Co-Innovation Center of Animal Production Safety’.