The mineral status in two ecosystems typical of the Iberian Peninsula was evaluated. Ecosystem I was formed by forests and ecosystem II by hilly areas. The levels of calcium, phosphorus, magnesium, iron, copper, zinc and selenium in soils, rations and serum were measured. The concentratons of iron, copper, zinc and selenium were also checked in liver. Ecosystem I showed higher values of every mineral, except for phosphorus. Seasonal differences were recorded for rations and serum, with higher values in spring. The rations produced by both ecosystems met the mineral requirements of goats in lactation. Thus, both ecosystems are suitable for the development of an ecological goat farming system. However, extra supply of minerals, particularly calcium, may be needed in the maximum productions periods.
Goat farming in the Mediterranean basin has been traditionally very important. This area accounts for an important part of the global goat stock. The importance of goat farming in this part of the world comes from two aspects. The first is the management of marginal areas, which are unsuitable for raising other domestic herbivore species. The second is to help to maintain the rural settlements, which have traditionally lost population due to the lack of local resources [
Ecological livestock rearing is an emerging face of agricultural activity that does not degrade the environment and helps in its sustainability. These benefits have been recognized by the agricultural policy of the European Union (EU), which promotes ecological practices by EU subsidies [
In the Southwest of the Iberian Peninsula, the production of domestic herbivores has adapted to the traditional Mediterranean forest, giving rise to two distinct ecosystems. The first one called “
One of the most limiting factors of these production systems would be to satisfy the requirements for essential minerals, as calcium, phosphorous, magnesium, iron, copper, zinc, and selenium, which play fundamental roles in the metabolism of goats [
The aim of this study was to check, by the evaluation of the mineral status of animals, if these two typically Mediterranean ecosystems could be managed under ecological rules.
Ecosystem I was formed by forests elevated from 300 and 600 m above sea level that had been modified by woodcutting to favour animal grazing. Ecosystem II included less modified forests, situated in hilly areas elevated from 700 to 1,200 above sea level. The soils in ecosystem I were formed by granite or slate, while in ecosystem II, the soils were predominantly slate.
Both systems presented three main components: trees, bushes, and pasture. The trees were represented by
The climate in both ecosystems was of the Mediterranean type, characterized by mild winters and dry summers. Rainfall concentrated in spring and autumn. In ecosystem I, the annual mean minimum and maximum temperatures were 10.8°C and 21.4°C, respectively, and the mean rainfall was 523 mm. In ecosystem II, temperatures were approximately two degrees less and the mean rainfall 200 mm more [
Twenty farms were selected for this experiment from the main areas of goat farming in the Southwest of the Iberian Peninsula. Ten of them belonged to ecosystem I, and the same number was representative of ecosystem II. The size of the selected flocks included the typical range in both ecosystems: small (50–200 heads), medium (300–500 heads), and large (600 heads or more). The mean altitude of the farms in ecosystem I was 450 m and in ecosystem II 900 m above sea level. The soils and the vegetation of the farms were characteristic of each ecosystem.
The nutritional practices are influenced by the climatic conditions in the Mediterranean area. There are usually two peaks of herbage growth, a minor peak between October and December after the first autumn rains and a main peak between March and June, when the herbage starts to mature and dry out. However, in ecosystem II, the maturation occurs later, and grazing is possible for longer periods.
The ration consisted of grazing and browsing on leaves and twigs of bushes, with supply of cereals and forages obtained in the same farm to improve milk production. The intake levels are not easily measured, but each goat received 800–1000 g of cereals in lactation and 300–400 g in nonproductive periods. Hay was offered ad libitum during the night. As pasture production in ecosystem I was higher, and bushes were more abundant in ecosystem II, grazing was more intensive in the first ecosystem, and the intake of ligneous vegetation was more elevated in the second ecosystem.
The management practices were very similar in both ecosystems. Goats were reared at range. After the morning milking, when they received concentrates, goats grazed and browsed on leaves. In the evening, they were guided to the shelters for the evening milking, where they were confined during the night. Kids remained in the shelters all the day, and spent the night with the does.
The reproductive management has traditionally followed a scheme of breeding periods at the end of spring and autumn, with kidding in autumn (early kidding) and in spring (late kidding). Nowadays, due to the requirements of the cheese industry, the tendency is to plan reproduction in order to have lactating does at the beginning of the summer. The mean prolificacy was 1.55 kids per doe.
“Verata” breed does and their offspring were selected for this experiment. The goats of this autochthonous breed are medium size, black, grey or, more commonly, brown. The aptitude of this breed is milk meat and the average milk production reaches 250 litres in 200–300 milking days.
Soil samples were taken from each distinct part of the farms according to the crop or land profile. These samples were composed of twelve subsamples, performed by randomly probing. Samples were transported in transparent plastic bag and kept at room temperature until analysis.
Sampling of grass was made in the parts of the farms representative of the grazing areas. The number of samples was variable according to the heterogeneity and size of the meadows. Samples of the concentrates were also taken, together with the twigs and leaves of bushes according to the consumption habits of goats. As the diet was influenced by the climatic variations, sampling included the rations of autumn and spring, which were representative of the different types of rations received through the year. Food samples were properly identified and kept at room temperature until further analysis.
Blood samples were taken according to the size of the flock in a proportion of 10%. Blood samples were obtained from does between the second and fifth delivery, selected randomly at weaning time. Samples were withdrawn from the jugular vein, put into clotting tubes, and kept at room temperature until serum separation. Analyses were conducted in the next 24 hours.
Samples from livers were taken at the slaughterhouse from kids weaned 21 days after birth and fed only milk. The number of samples was proportional to the number of animals slaughtered and the size of the flock. Samples were frozen at −40°C until analysis.
Minerals were determined in the soils and rations by atomic absorption (Perkin Elmer 550, IZASA, Sevilla, Spain) after the pretreatment of the sample and extraction techniques [
An experienced team of observers performed a clinical monitoring of the goats in the experiment in order to detect possible clinical manifestations of mineral deficiency during the last period of gestation and the lactation.
In the calculation of the means values of mineral content in the ration, it has been taken into account the contribution of the different ingredients making up the rations. The grass accounts for 75% of the ration and the concentrates for 25%. Thus, the mean mineral contents of the rations are weighted means and not merely arithmetic means. The differences in the mean concentration of minerals in soils, ration, serum, and liver between the different ecosystems and sampling seasons (spring or autumn) were evaluated by an interactive two-way analysis of variance. The G-stat 2.0 statistical package was used for this study [
The mean concentrations of calcium, magnesium, iron, copper, zinc, and selenium obtained in the soils were significantly higher in the farms of ecosystem I than in the farms of ecosystem II (Table
Mean concentration (mean ± SD) of minerals in the soils.
Mineral | Ecosystem | Comparison | ||||
I | II | Ecosystem | Season | |||
Spring | Autumn | Spring | Autumn | |||
Ca (ppm) | NS | |||||
P (ppm) | NS | |||||
Mg (ppm) | NS | |||||
Fe (ppm) | NS | |||||
Cu (ppm) | NS | |||||
Zn (ppm) | NS | |||||
Se (ppm) | NS |
The differences in the mineral composition of the rations in ecosystem I and ecosystem II resembled the differences in the soils (Table
Mean concentration (mean ± SD) of minerals in the rations.
Mineral | Ecosystem | Comparison | ||||
I | II | Ecosystem | Season | |||
Spring | Autumn | Spring | Autumn | |||
Ca (% DM) | ||||||
P (% DM) | ||||||
Mg (% DM) | ||||||
Fe (% DM) | ||||||
Cu (ppm) | ||||||
Zn (ppm) | ||||||
Se (ppm) |
The highest values in the serum were obtained in ecosystem I, except for phosphorus (Table
Mean concentration (mean ± SD) of minerals in serum.
Mineral | Ecosystem | Comparison | ||||
I | II | Ecosystem | Season | |||
Spring | Autumn | Spring | Autumn | |||
Ca (mg/dL) | ||||||
P (mg/dL) | ||||||
Mg (mg/dL) | ||||||
Fe ( | ||||||
Cu ( | ||||||
Zn ( | ||||||
Se ( |
The results of iron, copper, zinc, and selenium concentration obtained in the liver samples (Table
Mean concentration (mean ± SD) of trace elements in liver (ppm DM).
Mineral | Ecosystem | Comparison | ||||
I | II | Ecosystem | Season | |||
Spring | Autumn | Spring | Autumn | |||
Fe | NS | |||||
Cu | NS | |||||
Zn | ||||||
Se |
The statistical appraisal of the means of mineral concentration in the soils did not reveal significant differences between seasons (Table
The mineral content of the ration provided in the farms in autumn was significantly different from the ration supplied in spring, with higher means in the last season (Table
The presence of seasonal variations in the mineral composition of the rations consumed by the goats was indicative of a better supply of minerals in the spring. This finding was in accordance with the changes reported for the mineral concentration of pasture in spring [
Significant differences between seasons were found for the serum concentrations of all the minerals studied, with higher values in spring (Table
The concentration of zinc and selenium in the liver was significantly higher in spring, but iron and copper did not present seasonal differences (Table
The values found for calcium in the soil (Table
Ecosystem I produced rations that met the requirements of lactation in goats for magnesium and iron, almost covered the need for phosphorus, copper, zinc, and selenium, and did not reach the minimum calcium requirements (Table
Mean serum concentrations of phosphorus, magnesium, iron, and zinc were in the normal range (Table
The low concentration of calcium in the soils (Table
The adequate values reported for phosphorus and magnesium were the result of the level of these elements in the soils and the ration. In the case of phosphorus, it might relate to the ability of goats to select the vegetal species with the highest concentration in this mineral and the high ratio of phosphorus absorption in this species [
The values reported for calcium and phosphorus in the serum yielded a calcium/phosphorus ratio from 1.5/1 to 0.9/1, which may be considered inadequate [
The serum concentrations of the trace elements (Table
Our results of copper, zinc, and selenium in the serum could be considered as the minimum of the normal range [
Marginal selenium levels were detected. These values were compatible with the previous history of selenium-related diseases. However, in the interpretation of these results the adaptation to the supply of rations with low selenium content should be taken into account [
Iron concentration in the liver was in the normal range. Copper, zinc, and selenium were slightly over the lower limit of the range (Table
The rations produced by ecosystem I met the mineral requirements of goats in lactation, particularly in spring. Ecosystem II provided rations with lower mineral content, especially in autumn.
Both ecosystems were prepared for the development of ecological goat farming system, but some corrective measures should be applied in the gestation and lactation. These control programmes should be aimed to increase the mineral content of the rations in two ways: fertilizing the soils to enrich the mineral content of the local forages and crops or importing ecologically produced concentrates from areas with adequate mineral concentration in the soils.
The authors acknowledge the support of the Regional Government and European Social Fund (PRI97D036) in the funding of this study and the valuable technical assistance of the Agricultural Laboratory Services of the Regional Government of Extremadura (Spain).