As similar to the present investigation, non-significant variations were documented in different haematological markers by Flores et al. (1990) in the course of early and late stages of lactation. Similarly, Mir et al. (2008) also outlined that haematological profiles varied significantly throughout the three stages of pregnancy (early, mid and late stages) in crossbred cows. PCV, TRBC and HB levels were established to be lowest in dairy buffaloes of early stage of lactation. Similar results were obtained by Esievo and Moore (1979), who has suggested that the levels of PCV RBC, HB along with serum iron and its binding capacity and serum albumin concentration were diminished in early stage of lactation and jump up to the pre-lactation levels in the mid-lactation stage. Similarly, dwindle in the concentration of TRBC in ovine species in the early stage of lactation was also documented by Antunovic et al. (2011). On the other hand, other haematological markers such as the TLC, DLC, MCV, MCH and platelet concentrations were obtained within the ranges of normal values set down for the crossbred milch cows. Hagawane et al. (2009) documented that the mean haemoglobin concentration was dropped in the first lactation stage than second and third lactational stages in the milch buffaloes. Hussain et al. (1996) outlined similar reports that first lactational stage has non-significant influences in haemogram other than leukocytosis which is due to neutrophilia. Significantly higher concentration of cortisol and neutrophils was obtained in the current study in crossbred cows as because the corticosteroids trigger the neutrophilia through an enhanced production of neutrophils from the bone marrow or by demargination of neutrophil from the wall of blood vessel or by an amalgamation of the two above process (Lee and Kehrli 1998).
In the present study, glucose concentration was escalated as lactation stages progressed in the crossbred cows of ANI. Hypoglycemia in the first stage of lactation may be as a consequence of substantial quantity of blood glucose removal by the udder for the manufacturing of milk lactose (Hagawane et al. 2009). Similar result was documented by Filipejová and Kováčik (2009) that blood glucose concentration was significantly escalated in middle as well as lateer stages of lactation than the first or early stage of lactation. On the other hand, contrastingly, Peterson and Waldern (1981) documented that glucose concentration was homogeneous throughout the three lactation stages. Variations in the current study is accordant with previous reports obtained in the lactating mares (Heidler et al. 2002) and lactating ewes (Roubies et al. 2006). Lower blood glucose concentration (hypoglycemia) in the time of the early lactation stage is owing to usage of a colossal quantity of blood glucose by the udder for the production of lactose as well as withdrawal of higher quantity of blood glucose by the mammary gland for the production of lactose in milk (Nale 2003). Elitok et al. (2006) also documented that exponently the serum glucose concentration was declined especially at the time of dairy cattle approaching the parturition and during late stages of pregnancy suggests that speedy usage of glucose towards the terminal stage of pregnancy and initial stage of lactation in dairy cattle. Therefore, the blood glucose concentration was significantly decreased in first lactational stage and increased as stages advanced (second and third stages) in the crossbred cows of ANI.
In the current study, the triglyceride concentration was escalated as lactation stages advanced in the crossbred cows of ANI. Similar observation was documented that triglycerides exhibited a significant shoot up at the later stage than earlier stages of lactation in caprine species (Abd-El Naser et al. 2014). The decreased tendency in triglyceride concentrations in the starting stages was as a consequence of escalated demand for energy in the course of lactation and triglycerides are utilized by udder to manufacture the milk fats and their request escalated until the peak of lactation the dairy buffaloes (Karapehlivan et al. 2007).
Total cholesterol concentration was shoot up as lactation stages advanced in the crossbred cows of ANI. The decreased flow in total cholesterol concentrations were owing to the dairy animals escalated demand for energy production throughout the period of lactation (Karapehlivan et al. 2007). The inflated concentration of cholesterol with progression of lactation was a physiological and functional acclimatization to meet the lactation demands. Similarly, Ibnelbachyr et al. (2015) documented that fat concentration escalated as the lactation stages progressed. Plasma fatty acid level was decreased in the initial phase of lactation as because greater milk production triggers marshalling of the body reserves throughout the early stage of lactation. Further, higher concentrations of fatty acids after reaching the apex of lactation suggest diminished energy demand due to lower milk production as stage progressed. Throughout the early stage of lactation, milch animals may suffer a fatalistic energy balance and different magnitude of lipolysis in the fatty tissue, escalating the concentration of free fatty acids that have an antipathetic effect on the toothsome traits of milk (Strzałkowska et al. 2009).
Total protein and globulin were escalated and albumin concentration was declined as stages of lactation advanced in the crossbred cows of ANI. Similar information was documented by Krajnicakova et al. (2003) in lactating dairy goats that enhanced flow pattern of serum total protein with the advancement of lactation in milch goats and it marked that higher flow of protein is as consequence of protein catabolism for milk synthesis and production. Similar to the result of present study, Filipejová and Kovacik (2009) also documented that total protein concentration was significantly escalated in the mid and late lactation stages than in initial stage of lactation. In spite of proportionally decreased protein percentage documented by Strzałkowska et al. (2009) at initial and mid-lactation phases, they support the accretion of protein concentrations with the advancement of lactation. On the other hand, Hagawane et al. (2009) documented that throughout the early stage of lactation, serum total protein concentrations were moderately raised and this escalates in total protein value might be imputed to the haemo-concentration and water losses happened in postpartum.
In the present study, the creatinine concentration was declined as lactation stages progressed. The noticeable elevated creatinine concentration at the initial stage of lactation may be accredited to the uterine involution and myometrium protein mortification (Bell et al. 2000). Kronfeld (1982) communicated inflated serum creatinine concentrations during the summit of lactation in HF cows.
The BUN concentration was escalated as lactation stages advanced in the crossbred cows of ANI. BUN concentration was outstandingly dropped down in the early stage of lactation could be either because of shoot up of deamination or escalated protein intake (Hagawane et al. 2009). The BUN concentrations documented in the present study at various phases of lactation were inflated than those obtained in earlier researches (Hagawane et al. 2009). Several earlier investigators have documented that serum urea concentration is regulated by the days in milk in buffalo species (Serdaru et al. 2011). The concentration of serum blood urea nitrogen is considered to be a marker of total protein uptake. Alterations in the serum blood urea contentment throughout the lactation period could be dependent upon milk synthesis and milk yield (El-Sherif and Assad 2001). The decreased flow pattern in urea concentrations presumably accompanied with make use of urea for protein synthesis/manufacturing on rumen-hepatic pathway owing to compensation of the low protein intake throughout the initial lactation stage (Yokus et al. 2006). Hagawane et al. (2009) documented that the blood urea nitrogen concentrations vary remarkably amongst the different phases of lactating buffaloes. It is also inscribed that the efficiency for usage of metabolisable protein for milk synthesis or production is not so much as that of maintenance (McDonald et al. 1995). Therefore, as the milk production/yield escalates, the average protein utilization effectiveness declines which in turn lead to significantly higher drainage of nitrogen in the form of urea by way of urine and milk (Roy et al. 2003). An escalate in urea value was additionally noted in the initial two months of lactation (Ndibualonji and Godeau 1993) and obtained to be summit at third months of postpartum, which declined gradually thereafter (Rajcevic et al. 1993). Throughout the early stage of lactation, milk urea level was decreased (Whitaker et al. 1995). Similar reports were documented in the present study in crossbred cows of ANI.
In the present study, concentration of the liver functional enzymes (AST, ALT and ALP) was declined as lactation stages advanced; however, non-significant variation was obtained among the three stages of lactation in crossbred cows of ANI. Similarly, Serdaru et al. (2011) documented that these serum intra-cellular enzymes (AST, ALT and ALP) were significantly (p < 0.05) declined in the lactating than in dry buffalo groups. AST and ALP are supposed to be efficient biomarkers to ascertain the energetic and mineral variation (Mundim et al. 2007). Alterations in functions of these liver functional enzymes may also be associated to decrease dry matter intake during parturition which in turn stimulate the hepatic lipidosis and changes the normal functionality/activities of the liver (Greenfield et al. 2000). However, no evidences were documented in the literature to describe the associateship of the noted trends of differences in the levels of these liver functional enzymes with various phases of lactation. An escalation in ALT and AST concentrations and their activity in blood throughout lactation is suggestive of increment in hepatic metabolism in ovine species (Antunovic et al. 2011). On the other hand, Yaylak et al. (2009) documented that the lactation stage influences the AST and ALT levels and their activities remarkably. Plasma ALP activity demonstrated a well-defined and progressively declined from calving. This may be accredited to declining placental ALP concentration and activity in postpartum period following in decline the plasma ALP activity (Heller and Joshi 2006).
In the current study, depletion of calcium, phosphorous and magnesium concentrations was escalated during early stage than at second or third stage of lactation. This may be due to uncontrolled flow of blood calcium reserve by way of colostrum and milk during the early stage of lactation. As the lactation stage progresses, the blood calcium concentration is climbed, which is in concurrence with the documentations of Nale (2003). Nehra (2016) documented a remarkable decline in serum calcium concentration throughout the early lactation stage. It may be due to the lactating dairy cows retrieve continuously and constantly from the distress of parturition and post-partum and uncontrolled requirement of calcium for beginning of lactation. The decline in calcium concentrations may be the result of the diminished absorption and assimilation of food metabolites from the gastro-intestinal precursor, uncontrolled wastes through urine and more particularly overabundance of supplying mineral constituents into milk (Hagawane et al. 2009). Hagawane et al. (2009) documented that there was a decline in calcium concentration during the early lactational stage (8.19 ± 0.83 mg/dL) than those in normal apparently healthy buffaloes (11.21 ± 0.19 mg/dL). Further, Hussain et al. (2001) specified that peak level of calcium was noted in pre-partum stage at month 8 of gestation and bottom concentration was obtained at parturition and immediate post-partum. Earlier researchers (Moghaddam and Hassanpour 2008; Yokus and Cakir 2006) documented that calcium concentrations were diminished at post-partum than throughout the pregnancy period.
In the present investigation, diminishing of phosphorous concentration was escalated during the initial stage than second or third stage of lactation in the crossbred cows of ANI. Decreased concentrations of phosphorus in the earlier lactational stages might be due to the prerequisite of it for the synthesis of colostrum and increased carbohydrate metabolism (Serdaru et al. 2011). Hagawane et al. (2009) documented that the serum phosphorus concentration in the initial stage of lactation was remarkably decreased than in the normal healthy control buffaloes.
In lactating bovines, a multiplex interrelationship of various principal metabolic hormones (prolactin, thyroid hormones and glucocorticoids) accelerates mobilization of principal substrates for milk production or synthesis during the process of galactopoiesis (Tucker 1981). Thyroid hormones (TSH, T3 and T4) have a predominant contribution in the formation and development of the udder or mammary gland in mammalian species (Ramos et al. 2000). Concentration of thyroid hormones was escalated as lactation stages advanced. There were outstandingly reduced the concentration of thyroid hormones during the early and at peak lactation stage than in mid or late lactation stages, when (second and third stages) milk production significantly declined. It might be intimated that the decreased serum thyroid hormone concentrations in early and at peak lactation stage in the present investigation are due to an adaptive decline in synthesis and secretion rate of thyroxine and changed T4 to T3 transformation in the extra-thyroidal tissues. The recession of thyroid secretion rate in the initial stages of lactation is probably due to the inadequate fuel supply to the non-mammary tissues due to the nutrient utilization by the intensively lactating udder and to the declared energy deficit state throughout the period of greatest lactational accomplishment. Similar observation documented in dairy Baladi goats that a remarkable escalation of triodothyronin at the third or later stages of lactation. Accordant with these research results, Pezzi et al. (2003) documented diminished serum T3 value at the initial stage of lactation. Similarly, Dalvi et al. (1995) documented decreased concentrations of T3 and T4 throughout the early stages of lactation because of the secretion and release of these metabolic hormones in milk during the biosynthesis process of milk by the udder as noted in the present study. A similar effect of escalated plasma thyroxine concentration with advancement of lactation was documented by Akasha et al. (1987). Sharma and Joshi (2006) also demonstrated that reduced plasma thyroxine concentration was correlated significantly with increased lactational performance probably due to higher utilization of plasma thyroxine in high milk producers. A predominant function of the thyroid hormones (T3 and T4) is noted in the normal body metabolism favoring all the anabolic and catabolic processes (Rudas and Pethes, 1990), which could also describe the greater concentrations seen in the late stages of lactation in the current study. Thyroid hormones regulate the milk synthesis as well as magnitude and duration of milk synthesis and are obligatory for the continuation of lactation (Park and Lindberg 2005). The inflated concentrations of these metabolic hormones in the crossbred cattle throughout the 2nd and 3rd stage of lactation throw back the greatest metabolic activity of the udder for milk synthesis and production. It is also demonstrated by the truth that highest daily milk production in the crossbred cows is achieved during second month of lactation (Singh et al. 1996). Hormone concentrations of T3 and T4 escalated while prolactin declined with progression of lactation in the present study in the crossbred cows. In the mammary gland, thyroid hormones assist in the differentiation and development of the epithelial cells (Capuco et al. 2008). Distinct in-vivo and in-vitro investigations have confirmed that exogenous administration of thyroid hormones can enhance the milk production or synthesis by potentiating other lactogenic and galactopoietic hormones (Bhattacharjee and Vonderhaar 1984). Similarly, Gueorguiev (1993) documented that high milk yielding cows expressed lower blood T4 and T3 concentrations and higher ratio of T 4: T3 in the lactation period of 1–80 days than those of low milk yielding cows indicated the variances in the thyroid hormones metabolism accompanied with milk synthesis intensity. It has also been documented that an escalated transformation of thyroxine to triiodothyronine has occurred in the udder, however, not in other organs (Kahl et al. 1992) marked that these thyroid hormones were more beneficial for the high milk yield or production in dairy cows. This signifies organ-specific alterations in T3 production, which is indispensable to reinforce the metabolic demands of lactation (Kahl et al. 1992).
Prolactin performs role in mammogenesis and lactogenesis in mammalian species including cattle, empowering the mammary cells to metamorphose completely at parturition and commencing the genesis of substantial milk secretion. Prolactin in plasma seems to reflect straightforwardly the demands of mammary gland cells to triggers the metabolic process in milk synthesis and secretion (Akasha et al. 1987). The contribution of prolactin in galactopoesis and its associateship with milk production or yield is not yet acknowledged. In the present study, prolactin concentration has been decreased gradually as stages of lactation advanced in the crossbred cows of ANI. The elevated concentration of plasma prolactin throughout the first stage of lactation also indicates that its circulatory quantity is essential at the climax of lactation. The squashing of prolactin with injection of brmocryptine during the initial stage of lactation in turn has declined milk yield and production with low concentration of protein and lactose in milk (Singh and Ludri 1999). Plasma prolactin concentration declined remarkably from first to second and then to third stage in crossbred cows marking that suckling and milking procedures are predominant excitant for higher blood circulatory prolactin concentrations (Arya 1990). Milking or suckling presses/triggers prolactin release and this release diminishes as lactation progressed (Beck et al. 1979), which is homogeneous to the observations in the present study in crossbred cows.
In the present study, the stress hormone, cortisol has been subsided gradually and continuously as stage of lactation progressed in the crossbred cows of ANI. Cortisol acts throughout the puberty, gestation and lactation in association with other endocrine hormones and assists in the growth and development of udder and also in the synthesis and production of milk. The elevated concentrations of plasma cortisol throughout the period of lactation also indicates that its blood circulatory concentration is essential during the summit of lactation or milk production. Low cortisol concentration during third stage of lactation was accompanied with decreased milk yield and in summer season as its concentration is also influenced by environmental variables such as temperature, relative humidity and light hours (Ludri and Sharma 1985).