Present study reports effect lactation stages on blood metabolic profile of Mehshani buffalo. For the investigation, 18 clinically healthy lactating buffaloes were divided into three equal groups: group I (early stage), group II (mid stage) and group III (late stage).The concentration of blood glucose was lowest in early stage and increased subsequently as the lactation advances unlike the protein level. The albumin concentration was highest in early lactation stage and lowest in mid lactation. The total cholesterol was lowest in mid stage and highest in late lactation stage. The levels of BUN and uric acid were also higher in initial stage of lactation and decreased thereafter. Nonetheless, the concentration of creatinine and total bilirubin were almost similar in all the groups. However, except globulin and total cholesterol, the variations observed pertaining to other metabolites were non-significant amongst the groups. Current study thus signifies a tight homeostatic control of blood metabolites throughout the lactation period. Nonetheless, data generated may aid in assessing the metabolic health of Mehshani buffaloes.
Blood metabolic profile is commonly used as indicators of health as well as nutritional status of animals (Amle et al., 2014). It is imperative to confirm clinical diagnosis and estimate the severity of diseases (Piccione et al., 2010). Further, it also aids in diagnosis of metabolic diseases and management of infertility as well as low productivity in farm animals (Piccione et al., 2010, Kaminski et al., 2014). Amongst, the various factors affecting metabolic profile, the physiological status of animals is the predominant one (Ahmad et al., 2003). Pregnancy and lactation are two major stages in the life of dairy animals, which leads to metabolic alterations (Krajnicakova et al., 2003; Iriadam, 2007). Previous studies described the alteration in blood biochemical profile in the course of the reproductive cycle and pregnancy in farm animals including buffalo (Jain et al., 2009). Nonetheless, knowledge about the metabolic changes during different stages of lactation is of paramount importance so as to provide adequate nutrients for optimizing milk productivity of the animals. It is well known that lactation is associated with a physiologically increased rate of metabolic processes, and is characterized by a high energy requirement, especially in the early stage, when milk yield is higher (Piccione et al., 2009; Cigliano et al., 2014). Therefore, the level of blood biochemical parameters viz. glucose, total protein, A/G ratio, cholesterol, urea and uric acid changes throughout the course of lactation and are important indicators of the metabolic activity in lactating animals (Fernandez and Hoeffler, 1998; Karapehlivan et al., 2007). Since the milk yield and composition varies across the length of lactation, it is imperative to study the blood metabolites during different stages i.e. early, mid and late stage of lactation. In view of the above, present study was designed to investigate the changes in metabolic profile during different stages of lactation in Mehshani buffalo, a native milch breed of Gujarat, India.
Materials and Methods
Eighteen clinically healthy lactating Mehshani buffaloes of about 4-5 years of age were selected from the herd maintained at Livestock Research Station, SDAU, Sadarkrushinagar, Gujarat, India. The buffaloes were in various stages of lactation and based on the length of their lactation, the animals were identified as in early (7 to 105 days), mid (106 to 210 days) and late (211 to 315 days) lactation stage. Accordingly, they were categorized into three different groups of six animals each viz. group-I (early lactation), Group II (mid lactation) and Group III (late lactation).
For the investigation, about 10 ml of blood sample was collected aseptically from each animal of all the experimental groups by jugular vein puncture into serum clot activator tubes (Greiner Bio-One GmbH, Austria) to separate out the serum. Subsequently, the clear serum samples were collected in sterilized vials and stored in refrigerated condition till analyzed. The blood metabolites viz. glucose, total protein, albumin, globulin, albumin/globulin (A/G) ratio, total bilirubin, total cholesterol, creatinine, blood urea nitrogen (BUN) and uric acid were estimated using ready to use kits employing Clinical Analyzer-635 (Systronics India Ltd., India). The results were statistically analyzed using one-way ANOVA as per the method of Snedecor and Cochran (1994). P <0.05 was considered to be statistically significant.
Results and Discussion
The results (mean ± SE) of the blood metabolites are presented in Table 1. It is evident that there is no significant difference (P>0.05) in the concentrations of various blood metabolites amongst the three groups of lactating Mehshani buffaloes.
Table 1: Blood metabolites of three experimental groups of Mehshani buffalo
|Glucose (mg/dl)||40.67 ± 2.04a||42.5 ±4.57a||46.37± 4.31a|
|Total protein (g/dl)||8.45±0.13a||8.12±0.22a||8.01 ±0.29a|
|Total cholesterol (mg/dl)||53.21±0.45ab||50±0.28b||55.33±0.39a|
|Blood Urea Nitrogen (mg/dl)||22.67 ± 1.3a||20.5 ± 1.58a||18.89± 2.25a|
|Uric acid||0.89 ± 0.68a||0.88±0.33a||0.86±0.52a|
|Creatinine (mg/dl)||1.33 ± 0.08a||1.31 ± 0.07 a||1.30 ± 0.16 a|
|Total Bilirubin (mg/dl)||0.23 ± 0.03a||0.22 ± 0.04a||0.22 ± 0.04a|
Means with same superscript within a row do not differ significantly from each other at 0.05% level of probability
This finding corroborates the report of Hagawane et al. (2012). Present study further indicated that the mean concentration of blood glucose was lowest (40.67±2.04 mg/dl) in early stage and increased subsequently as the lactation advances. The observed values of blood glucose for mid and late stage of lactation were 42.5±4.57 mg/dl and 46.37±4.31 mg/dl, respectively. Current trend of variations are consistent with earlier report in lactating ewes (Roubies et al., 2006) and in lactating mares (Heidler et al., 2002). In contrast, glucose levels were reported to be the same throughout the three stages of lactation by Peterson and Waldern (1981); whereas, Doornenbal et al. (1988) reported somewhat higher (P<0.05) glucose concentration at parturition that declined during lactation period. The lower level of blood glucose recorded during early stage of lactation may be ascribed to the utilization of large amount of blood glucose by mammary gland for the synthesis of lactose (Schultz, 1968). It is reported that lactose synthesis and milk yield show a linear positive correlation with glucose uptake and thus the lactose synthesis potential is accompanied by greater glucose uptake by lactating mammary gland (Afshar and Fathi, 2012). The total protein level (8.45 g/dl) was found to be slightly higher in group I as compared to group II and group III animals. This observation is on the contrary to the finding of Yaylak et al. (2009), who recorded lower protein values in dry and early stages of lactation in case of Holstein cows. Krajnicakova et al. (2003) also observed an increasing trend of total protein level of serum with the progress of lactation in lactating goats and concluded that this is due to the catabolism of protein for milk synthesis. The variation may be attributed to the differences in species, nutrition, husbandry, environment and methods of assay (Beaunoyer, 1992; Osman and Albusadah, 2003). However, Hagawane et al. (2012) reported highest protein value in the early stage of lactation, which is comparable to current findings. The possible explanation for this phenomenon may be the haemoconcntration and water losses due to parturition. Further, earlier investigations have clearly shown that the expression of major milk proteins increases dramatically and in a concerted way during the onset of lactation (Bionaz and Loor, 2011). The blood albumin concentration was found to be highest in early stage of lactation and lowest in mid lactation. Conversely, the globulin concentration showed the opposite trend. Previous study reported that the albumin concentrations declined significantly (P<0.05) on the day one post-partum and a non-significant decline in the contents was observed from day two post-partum (Lone et al., 2003). These findings justify the high albumin concentration in blood during early stage of lactation observed in the current study. Our findings pertaining to albumin, globulin and A/G ratio are in consonance with the findings of Maria et al. (1990). Conversely, total colostral/milk Ig and IgG concentrations declined significantly (P<0.05) on day one post-partum and declined non significantly still further as the post-partum period increased. These findings are in agreement with Singh et al. (1982), Geene (1986) and Maria et al. (1990) in bovines. Singh et al. (1982) observed that most of the milk proteins get stabilized about a week after calving, during which period significant changes occur in the Ig levels which contribute significantly to the total proteins during that time. Abraham (1988) observed a speedy decline in the total plasma proteins and Ig concentrations within 24 h post-partum in buffaloes. Geene (1986) also reported a rapid decrease in the total Ig content in colostrum within 24 h after parturition. Maria et al. (1990) observed that colostral Ig levels decreased significantly from 1st to 5th milking (first milking within 4 h post-partum and the rest every 12 h in succession). Vann et al. (1995) also reported that total colostral Ig along with IgG decreased over time. It is obvious that the highest colostral total Ig and IgG concentrations are available on the day of parturition. The subsequent decline may be in part because of the reduction in IgG concentrations. This may be due to the reduced transfer of Ig from the maternal blood, declining synthesis by the mammary glands and/or depletion of stored Ig with the subsequent increased number of milkings.
The blood total cholesterol was lowest in mid stage and highest in late stage of lactation. The trend in variation of total cholesterol may be ascribed to the buffaloes increased requirement for energy during lactation. Karapehlivan et al. (2007) found that triglycerides are used by mammary gland to form the milky fats and their request increase until the peak of lactation. Probably the high starting values found here are linked to a not yet high milk production; indeed at 30th day. When lactation comes to their, triglycerides show a remarkable decrease. The higher level of cholesterol with advancement of lactation was a physiological adjustment to meet the lactation requirements (Lone et al., 2003).
Similarly, the mean value of BUN and uric acid were also recorded to be apparently higher in initial stage of lactation and decreased as the lactation progresses. This may hold well in relation to observed apparently increased level of total protein. The BUN values observed in the present study at different stages of lactation were higher than those reported in earlier investigation (Hagwane et al., 2012). Reinartz and Hofmann (1989) also found that serum urea concentration was significantly influenced by the lactation stage. It is recorded that the efficiency for utilization of metabolisable protein for milk production (0.68) is less than that of maintenance (1.00) (McDonald et al., 1995). So, as the milk production increases, the overall protein utilization efficiency decreases, which consequently leads to more drainage of nitrogen in terms of urea through urine and milk (Roy et al., 2003). An increase in urea value was further observed in the first 8 weeks of lactation (Ndibualonji and Godeau, 1993) and found to be peak at 12 weeks postpartum, which decreased slowly thereafter (Rajcevic et al., 1993). However, other researchers found a different trend of variation in case of BUN. During the first month of lactation lower milk urea (MU) concentration was recorded by Carlsson et al. (1995). Likewise, Whitaker et al. (1995) also reported that cows in early lactation often have much lower MU level. In contrast, no relation was reported between urea concentration in milk and stage of lactation by Erbersdobler et al. (1990) and values were relatively constant between 200 to 300 mg/l. Similarly, Coustumier (1996) also found no correlation between lactation stage and urea levels except just after calving. Similar to our study, Schepers and Meijer (1998) also observed that stage of lactation had no significant influence on BUN and thus on MU concentration. Hence, in the light of varying observations of different researchers, a systemic and critical investigation may be established in this aspect. The concentration of creatinine and total bilirubin were found to be almost similar in all the three groups of buffalo.
It is concluded that stage of lactation does not significantly affect the blood metabolic profile of lactating Mehshani buffaloes. The limited sensitivity of these blood parameters to stage of lactation in clinically normal dairy animals is not surprising because, most of these parameters are under the homeostatic control systems (Cozzi et al., 2011). Nonetheless, data generated during the current study may be useful as reference values for the scientific community as this is the first study of its kind in case of Mehshani buffalo. Further, blood profile has traditionally been used to assess the metabolic health status of the animals; hence the present investigation may also be helpful in this regard. In addition, this study may also assist the nutritionists to formulate ration for optimum productivity of the Mehshani buffaloes since blood-biochemical analytes are being widely considered to identify dietary causes of diseases leading to low productivity.