INFLUENCE OF DIFFERENT SOURCES OF ZINC SUPPLEMENTATION ON ITS BIOAVAILABILITY IN LACTATING CATTLE
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Date
2019
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Publisher
ICAR-NDRI, KARNAL
Abstract
The present study was conducted to determine the bioavailability of zinc from
three different organic (zinc glycine (ZnG) and zinc propionate (ZnP), zinc
hydroxy methionine (ZnM)) and one inorganic (zinc sulphate (ZnS)) sources. The
experiment was carried on 30 KF lactating cattle for the period of 160 days
starting from mid lactation (100 days) to end lactation (260 days). The animals
were subjected to the pre-trial period (PT) of three weeks at the beginning of the
trial. The animals were then grouped on the basis of body weight and milk yield
into five (n=6 animals) groups viz control, zinc sulphate, zinc glycine, zinc
propionate and zinc methionine. All the experimental animals were fed basal
diets (32.2 ppm zinc) fulfilling their requirement in energy and protein as per
ICAR (2013). The pre-trial period (PT) was followed by the periods of zinc
supplementations except in control group (C). Animals were supplemented with
the zinc three times (S1-50, S2-50 and S3-100) interspersed with the two nonsupplementation
periods (NS1 and NS2). Low dose zinc (50 ppm) was
supplemented in the first two supplementation periods (S1-50 and S2-50) and
high dose (100ppm) zinc was supplemented in third period (S3-100). Samples
were collected at the end of each period and in the middle of first
supplementation period, each period was designated as PT, 21S1-50, 42S1-50,
NS1, S2-50, NS2 and S3-100. In each supplementation period (21S1-50, 42S1-
50, S2-50 and S3-100) blood samples were collected at 0, 6, 12 and 24h post
supplementation of zinc. Humoral and cell mediated immunity of the
experimental animals were studied in the first (S1-50) and last (S3-100)
supplementation periods. During first and last supplementation periods, two
metabolic trials were conducted to determine digestibility, nutrient intake,
nitrogen balance and mineral balance. Results revealed that zinc
supplementation had no effect on dry matter and nutrient intake. Milk yield
declined from mid to late lactation in all groups but the decline was least in zinc
propionate correlating with the lowest somatic cell count. Plasma alkaline
phosphatase activity increased significantly (P<0.05) in the zinc supplemented
groups in all periods after 42S1-50 and it decreased linearly in control group.
The plasma metallothionine-1A concentration increased significantly (P<0.05) in
organic zinc supplemented groups at low dose level and in all groups at high
dose level. Catalase, SOD and FRAP was higher while TBARS tend to be lower
in organic zinc supplemented groups. Cortisol concentration decreased
significantly (P<0.05) while Total Ig and IgG increased in organic zinc
supplemented groups. The cell mediated immunity (percent change in skin
thickness) increased nearly to its double after 6h of injection in all groups
especially zinc propionate group thereafter it slowly reversed to normal levels at
48h. Humoral immunity determined by log2 titre against sheep RBC was
significantly higher on 14 and 21 days in zinc propionate group at both low and
high doses. Plasma zinc increased significantly (P<0.05) with the
supplementation of zinc at day 42 (42S1-50) of supplementation irrespective of
source. Plasma zinc concentration in the control group had shown a declining
trend. Zinc supplementation had no effect on plasma calcium, iron and copper
levels. Plasma zinc levels peak at 6h post supplementation and fell back to the
basal level at 24h in all supplemented groups. However, in organic
supplemented groups it tended to be higher during all the supplementation
periods. RBC zinc was higher in organic supplemented groups at high dose
supplementation during S3-100. Zinc supplementation irrespective of source and
dose had no effect on digestibility of nutrients, nutrient intake, nitrogen balance
and mineral balance (calcium, copper and iron). However, zinc absorption in all
the supplemented groups was higher, the value being highest in zinc propionate
group at both low and high dose supplementation. The retention of zinc was
higher in zinc supplemented groups than the control group. The expression of
MTI gene was significantly higher in zinc propionate group at higher dose of
supplementation and the expression of ZnT1 gene was higher in organic zinc
supplemented groups at higher dose of supplementation. Results indicate that
zinc supplementation irrespective of source at 50ppm is essential for the
lactating cattle and the duration of zinc supplementation had greater impact than
the dose. Organic sources of zinc have higher bioavailability than the inorganic
source and among the organic sources zinc propionate tend to have higher
bioavailability probably due to different method of absorption and metabolism.