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How to cite this article: Gabriela M M, Juan F M, Víctor H S, Diana E R, Guillermo A M. Mineral Profile of Grazing Dairy Cows Feeding in Tobaccoor
Dairy Farms in the North western of Argentina. Dairy and Vet Sci J. 2018; 6(2): 555684. DOI: 10.19080/JDVS.2018.06.555684
Dairy and tobacco productions, often complementary in the same farm, represent one of the most important economies of Salta province, Argentina. The aim of this work was to evaluate plasma levels of calcium (Ca), phosphorum (P), magnesium (Mg), copper (Cu) and zinc (Zn) between dairy cows from two tobacco-dairy farms (TDF) and from two non-tobacco dairy farms (nTDF). Blood samples were obtained of 10 cows of different physiological productive periods (pre partum, fresh cow, second third of lactation and late lactation). Values Ca, Mg, Cu and Zn serum were performed by atomic absorption spectrophotometry and P values by UV-visible spectrophotometry. The relationships between variables of serum values were analyzed using linear correlation and simple linear regression; in addition, the probability of occurrence of hypocalcemia was analyzed by odds ratio (OR). Total Ca and P levels were significantly (p<0.05) different between treatments (Ca: TDF 8.40 mg/dl vs nTDF 9.64 mg/dl - P: TDF 4.74mg/dl vs nTDF 5.69mg/dl) and along periods. In both groups Ca and P concentrations decreased around calving to begin to rise gradually during postpartum. In contrast, the levels of magnesemia in the present trial did not differ between systems (TDF 2.22mg/dl vs nTDF 2.30mg/dl). No significant differences were observed in Cu and Zn levels between both production systems. Tobacco-dairy farms offers predisposing conditions to mineral imbalances, evidenced by a higher incidence of subclinical hypocalcemia and hypophosphatemia in dairy cows (OR hypocalcemia: 3.79, OR hypophosphatemia: 2.9).
In the last decade, an intensification process has been developed in the dairy production of north western Argentina. In Salta province, the bovine milk basin is located in Lerma Valley. Although it is a traditional tobacco area, it is common to find dairy cattle production annexed to this agricultural production. In the farms in which both activities are carried out, tobacco crop is generally the priority while milk production has the character of complementary activity . However, dairy production represents one of the most important regional economies in the province. Production management practices and the genetic used (Holstein, American biotype) are similar to the rest of the principal basins of the country. Dairy production has evolved from an extensive grazing system to a more mixed system,
where pastures continue to contribute about 55% of the herd’s total food intake but there is growing the use of supplements in variable proportions, as the relative stocking rate increase [1-11].
Minerals are essential for dairy cows, and the amounts found in most feeds normally are inadequate for high milk production. If these requirements are scarce, deficiency symptoms can occur. As in other parts of the world, mineral imbalances are one of the most important problem in Salta´s basin . Because minerals are required for fluid balance, blood and bone development, and for maintaining a healthy nervous system, and regulating muscles, including heart muscles, is that are no doubts about the importance of minerals on the production and in dairy herd health . Therefore, so imbalances constituting an issue of
concern associated with animal welfare and the profitability of
the sector .
Agriculture and livestock systems of the basin define
crop rotations based on management practices related to
soil conservation, so that after one or two periods of tobacco
production, the paddocks are destined to forage production with
two mainly objectives: helps in reducing soil erosion  and
to feed dairy cattle. Although there is a lot of potential in these
systems, can be exist threats that the farmers has not correctly
dimensioned the risk, for example, the potential tetanizing risk
when cows grass winter crops (oat or barley) after tobacco
The mineral content of forages varies by factors such as
species, phenological status, climatic and seasonal conditions,
soil type and fertilization [2-10,13]. Tobacco production is
characterized by high fertilization rates with nitrogen (N),
phosphorus (P) and potassium (K) due to the extractive nature of
this crop [6-23]. This practice production leads to severe mineral
imbalances in the soil  and in the pastures, and it is possible to
increase the risk of metabolic disorders in the herd.
The aim of the present work was to evaluate the differences
in the plasma levels of calcium (Ca), P, magnesium (Mg), copper
(Cu) and zinc (Zn) between dairy cows from tobacco-dairy farms
(TDF) and from non-tobacco dairy farms (nTDF).
Four dairy farms were selected, two corresponding to TDF
and nTDF. The average production for herds was 7979 ±638 litres
of milk per lactation. Cows (n= 40) of two or more lactations
were sampled 4 times through the year. At each time, 10 cows
of different physiological productive periods were chosen at
random. These periods were: pre partum (approximately 21 days
before the probable calving date), early lactation or fresh cow
(during the first 30 days of lactation), second third of lactation
(between 90 and 120 days postpartum) and late lactation
(between 200-305 days in milk). All samples corresponded to
cows with 2 or more lactations.
Dairy cattle feeding were similar in the four farms sampled.
During the lactation period the diet was constituted between
25-30% by pastures (fundamentally alfalfa), 30% of corn silage
and 40-45% of concentrates (expeller of soya, soy bean and
corn grain), while during the pre-calving period diet consisted
in 50% corn silage, 30% wheat straw, 15% soybean expeller
and 5% wheat bran. During all production stages and in all
farms commercial mineral salts were supplied according to the
manufacturer’s recommendations. In addition, two of the dairy
farms evaluated (one corresponding to the TDF group and the
other to the nTDF group) used anionic salts during pre-calving.
Blood samples were obtained by jugular vein puncture. Serum
was extracted by centrifugation for 10 minutes at 1500 rpm. The
concentrations of Ca, Mg, Cu and Zn were measured by flame
atomic absorption spectrophotometry and P determinations
were made by UV-visible spectrophotometry according to the
The relationships between variables of serum values
were analyzed using linear correlation (Pearson) and simple
linear regression; in addition, the probability of occurrence of
hypocalcemia was analyzed by odds ratio. Differences between
variables and lactation periods were examined by analysis of
variance, Tukey test and Chi square using Fisher’s test. Statistical
differences were considered significant at P<0.05. Statistical
package InfoStat  was used
The reference values to consider clinical and subclinical
hypocalcemia were <5.5 and from 5.5 to <8.5mg/dL respectively
[15,16]. For Mg, hypomagnesemia was considered at values lower
than 1.8mg/dL. For hypophosphatemia and hyperphosphatemia
the reference values were <4 and> 6.18mg/dL respectively .
Cu level were considered adequate when concentration was
higher than 60μg /dl while for Zn the minimum value accepted
as ideal was 90μg /dl .
Table 1 shows the results obtained regarding the serum
calcium concentration in both treatments and throughout the
entire sampling period. Concerns to the levels of calcemia,
statistically significant differences were detected not only
between groups but also in all the productive stages considered.
The average values obtained for the TDF treatment were
compatible with a subclinical hypocalcemia condition, being in
turn the period of fresh cow in which the lowest concentration
of calcium was detected. This decrease in Ca concentrations
around calving to begin to rise gradually during postpartum was
recorded in both groups, but always with lower values for the
Means with a different letter within the same row are different (P<0.05).
Like in this trial, Albornoz  reported for dairy cows in
grazing conditions a decrease in Ca levels near calving for a
subsequent increase during postpartum. On the other hand, the
values obtained for nTDF group were similar to those observed
by Albornoz et al.  for dairy cattle in semi-pastoral systems
(9.32 ± 0.08). The incidence of subclinical hypocalcemia was
62.5% in the TDF and 44% in the nTDF (Chi 60.2, p <0.0001),
with a highest probability of occurrence in the first group (OR:
3, 79). These differences were detected in all evaluated periods,
and therefore they would not be due to the productive levels
associated to each stage (Table 2).
The values of phosphorus obtained throughout all the
periods are presented in Table 3. As was for the level of Ca in
blood, P mean concentration throughout the entire trial was
statistically different and lower in nTDF treatment. In turn, the
fluctuation of P values in both groups was similar, resulting
in a decrease in values around the birth to begin to rise later
during the postpartum, Albornoz et al.  also reported similar
behaviour for this mineral. Despite this dynamic, it should be
mentioned that in both groups and throughout the sample
period, the average values obtained were within the range of
normality proposed by Goff .
Means with a different letter within the same row are different (P<0.05).
However, if the individual values are considered in both
treatments there are animals with serum levels of P below the
normal limits (Table 4 & 5). The phosphatemia registered two
types of imbalances: around 17% of the animals presented
hypophosphatemia, while 23.2% hyperphosphatemia. In
turn there were differences between the groups, a higher
proportion of hypophosphatemic cows in the TDF (27%) than
in the nTDF (11%) (Chi 17.01, p <0.0001) were detected. The
OR value obtained indicates that cows from TDF are 2.90 times
more likely to have hypophosphatemia. These differences were
repeated in all periods evaluated. Conversely, when evaluating
the proportion of hyperphosphatemic cows the largest number
of animals in this condition was identified in the nTDF (32%)
while in the TDF it was 10.8% (Chi 23.7, p <0.0001). Thus, the OR
indicates that cows from the nTDF are 3.84 times more likely to
suffer hyperphosphatemia (Table 5).
Horst & Goff [19,20] indicate that phosphatemia is influenced
by the physiological state of the animals and the amount of milk
produced, although the content of the mineral in the food is one
of the most relevant factors in the determination of the level of
serum phosphorus. So that, it can be suggested that the diets
in the TDF are more deficient in P than those from nTDF. This
excess of P observed in the nTDF would lead to greater excretion
of it in the faeces and consequently to the soil and forages
The average values of magnesium concentration in blood
throughout the entire trial period and for both treatments are
presented in Table 6.
At no time and in any of the treatments there were significant
differences regarding the blood magnesium content. In turn, even
when average magnesemia values remained within the range of
normality proposed by Kaneko et al.  (1.7 to 3.0mg/dL), they
were significantly lower during pre-calving (Table 6). Values
similar to those obtained in the present trial were reported by
Albornoz et al.  for animals under semi-pastoral systems.
Despite the fact that the average values were found within
what was considered adequate, 17.8% of the animals sampled
showed hypomagnesemia (105/587) (Table 7). Similar results
have been registered by Suarez & Martínez  who reported
values of up to 46% of subclinical hypomagnesemia in dairy
herds of Salta´s basin.
Goff  mentions that, although hypomagnesemia in dairy
herds can be sporadic and of variable incidence, it is possible
that it affects up to 20% of grazing cows, a percentage similar
to that obtained in the present trial. Recent studies indicate that
hypomagnesemia affects calcium homeostasis, increasing the
risk of hypocalcemia. This is because low magnesemia reduce
the response of tissues to PTH and active vitamin D. In contrast
with Ca and P concentrations, the levels of hypomagnesemia in
the present trial did not differ between systems (TDF: 19% vs
nTDF: 16.7%, Chi 0.53, p <0.47), even when production stages
were considered (Table 6). Hypomagnesemia usually occurs at
the beginning of lactation, although it can also occur at the end of
pregnancy, in animals that graze fast-growing forages with high
concentrations of potassium and nitrogen and low levels of Mg
and sodium .
At evaluate serum Cu levels between TDF and nTDF, no
significant differences were found between sampling periods
(p <0.2801), whereas significant differences (p <0.0002) were
observed when average value was considerate. In spite of this,
the average values of cupremia were within the established
reference limits (TDF: 74.7±16μg / dl, nTDF: 79.8±40μg / dl).
Similarly, Zn serum concentration was found between the limits
established as normal (TDF: 110±34μg / dl, nTDF: 109±31μg/
dl). No significant differences were observed between treatments
(p <0.5658) or production stages (p <0. 0246).
At comparing the proportion of animals that were below the
reference values in Cu (p <0.28) and Zn (p <0.89), no significant
differences were observed between TDF and nTDF. Only just near
10% of the animals were below the normal limit (Cu: 10.3%, Zn:
7.5%). This result is encouraging, since Cu and Zn are essential
microelements for antioxidant function, and play a fundamental
role in the immune system in dairy cows.
This research demonstrates that tobacco-dairy farms offers
predisposing conditions to mineral imbalances, evidenced by
a higher incidence of hypocalcemia and hypophosphatemia in
dairy cows (OR hypocalcemia: 3.79, OR hypophosphatemia: 2.9).
However, non-tobacco dairy farms offer a higher proportion of
hyperphosphatemic cows (OR: 3.84). Interestingly, no significant
differences were observed in the Cu and Zn levels between both
production systems [24-27].
Based on the results obtained it is suggested continue to
deepen on the particular features of dairy production associated
with tobacco crop and the possible consequences on the mineral
imbalances in dairy cattle.