Evaluation of trace element status of organic dairy cattle.

The present study aimed to evaluate trace mineral status of organic dairy herds in northern Spain and the sources of minerals in different types of feed. Blood samples from organic and conventional dairy cattle and feed samples from the respective farms were analysed by inductively coupled plasma mass spectrometry to determine the concentrations of the essential trace elements (cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), iodine (I), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se) and zinc (Zn)) and toxic trace elements (arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb)). Overall, no differences between organic and conventional farms were detected in serum concentrations of essential and toxic trace elements (except for higher concentrations of Cd on the organic farms), although a high level of inter-farm variation was detected in the organic systems, indicating that organic production greatly depends on the specific local conditions. The dietary concentrations of the essential trace elements I, Cu, Se and Zn were significantly higher in the conventional than in the organic systems, which can be attributed to the high concentration of these minerals in the concentrate feed. No differences in the concentrations of trace minerals were found in the other types of feed. Multivariate chemometric analysis was conducted to determine the contribution of different feed sources to the trace element status of the cattle. Concentrate samples were mainly associated with Co, Cu, I, Se and Zn (i.e. with the elements supplemented in this type of feed). However, pasture and grass silage were associated with soil-derived elements (As, Cr, Fe and Pb) which cattle may thus ingest during grazing.

Identifying sources of metal exposure in organic and conventional dairy farming.

In humans the main route of exposure to toxic metals is through the diet, and there is therefore a clear need for this source of contamination to be minimized, particularly in food of animal origin. For this purpose, the various sources of toxic metals in livestock farming (which vary depending on the production system) must be taken into account. The objectives of the present study were to establish the profile of metal exposure in dairy cattle in Spain and to determine, by chemometric (multivariate statistical) analysis, any differences between organic and conventional systems. Blood samples from 522 cows (341 from organic farms and 181 from conventional farms) were analysed by inductively coupled plasma mass spectrometry to determine the concentrations of 14 elements: As, Cd, Co, Cr, Cu, Fe, Hg, I, Mn, Mo, Ni, Pb, Se and Zn. In conventional systems the generally high and balanced trace element concentrations in the mineral-supplemented concentrate feed strongly determined the metal status of the cattle. However, in organic systems, soil ingestion was an important contributing factor. Our results demonstrate that general information about the effects of mineral supplementation in conventional farming cannot be directly extrapolated to organic farming and special attention should be given to the contribution of ingestion of soil during grazing and/or ingestion of soil contaminated forage.

Helminth infections on organic dairy farms in Spain.

The aim of this study was to assess the prevalence of the major helminth infections affecting organic dairy cattle in northern Spain. Milk and faecal samples were obtained from 443 milking cows. Ostertagia ostertargi and Fasciola hepatica exposure was assessed by detection of specific antibodies in milk samples and F. hepatica infection was diagnosed by the detection of coproantigens in faecal samples. Dictyocaulus viviparus and Calicophoron daubneyi infections were diagnosed by conventional coprological techniques. The prevalence of infections caused by F. hepatica was considerable low, but similar to data reported from conventional farming in the same area. The prevalence rate of C. daubneyi infection was higher than previous data mirroring an increase of the prevalence that was also reported in other European countries in recent years. Specific antibodies against O. ostertargi were detected in all herds and the median levels of antibodies, determined by ELISA, exceeded the thresholds indicating milk production losses. The prevalence of D. viviparus was almost negligible. For each parasite, an ordinal logistic-regression analysis was used to assess the risk of infection by taking into account the administration of effective anthelmintics and the number of lactations. Treatment of cows with fasciolicides decreased the risk of F. hepatica infection in multiparous cows, whereas treatment with oxiclozanide or albendazol did not decrease the risk of C. daubneyi infection or O. ostertargi exposure, respectively. The study findings demonstrate that helminth infection in organic dairy farming is similar or even lower than previous data reported from conventional farming. Special attention should be paid to the impact of these infections on milk production.

Effects of different strategies of mineral supplementation (marine algae alone or combined with rumen boluses) in organic dairy systems.

This study was designed to evaluate the effect of marine algae supplementation alone or in combination with a regular mineral supplement (rumen boluses) to improve the mineral status in organic dairy cattle and their effect on the milk mineral composition, milk production, composition (% of fat and protein) and quality (SCC). Thirty-two Holstein Friesian lactating cows were randomly selected and assigned to the algae (A), boluses (B), algae+boluses (AB) and control group (C). For the algae groups (A, AB), a supplement composed of Sea Lettuce (80%), Japanese Wireweed (17.5%) and Furbelows (2.5%) was formulated to be given to the cows at the rate of 100 g/animal per day (A1) for the length of 4 weeks. In the second half of the experiment (weeks 5-8), the algae mixture was reformulated and the proportion of Furbelows was increased from 2.5% to 5.0% with a subsequent decrease of Lettuce to 77.5% (A2). In the boluses group (B), each cow received 2 boluses after calving. Blood (serum) and milk samples were collected at 2 and 4 week intervals, respectively, and analysed for trace element concentrations by ICP-MS. Information related to the milk composition and SCC during a 305-day lactation for each animal were obtained from the Dairy Records Management System. The supplementation with algae, boluses or the combination of both treatments showed a statistically significant effect on the iodine (algae), selenium (boluses) and cobalt (algae+boluses) status of the animals. In milk, treatments had a statistical significant increase on iodine, and a tendency to increase selenium concentrations. The assayed algae mixture combined with another source of selenium could be an effective tool to improve the mineral status in serum and milk.

The use of seaweed from the Galician coast as a mineral supplement in organic dairy cattle.

This study was designed to assess the value of seaweeds from the Galician coast as a source of minerals (especially iodine (I) but also other micro-minerals) in organic dairy cattle. It was conducted in an organic dairy farm in the Lugo province that typically represents the organic milk production in NW Spain. The animal's diet consisted mainly of local forage (at pasture or as hay and silage in the winter) and 5 kg of purchased concentrate/day per animal (representing 23.5% of feed intake). Based on the mineral composition of the diet, the physiological requirements and the EU maximum authorised levels in feed, a supplement composed by Sea Lettuce (Ulva rigida) (as flakes, 80%), Japanese Wireweed (Sargasum muticum) (flakes, 17.5%) and Furbelows (Saccorhiza polyschides) (powder, 2.5%) was formulated to give 100 g/animal per day. Sixteen Holstein Friesian lactating cows were randomly selected and assigned to the control (n=8) and algae-supplemented groups (n=8). Both groups had exactly the same feeding and management with the exception of the algae supplement, which was mixed with the concentrate feed and given to the animals at their morning milking for 10 weeks. Heparinised blood (for plasma analysis) and milk samples were collected at 2-week intervals and analysed for toxic and trace element concentrations by inductively coupled plasma-mass spectrometry or inductively coupled plasma-optical emission spectrometry. The algae supplement significantly improved the animals' mineral status, particularly I and selenium that were low on the farm. However, the effect of the algae supplement on the molybdenum status in cattle needs further investigation because of its great relevance on copper metabolism in ruminants. The I supply deserves special attention, since this element is at a very high concentration in brown-algae species and it is excreted in the milk proportionally to its concentration in plasma concentrations (mean ± s.e. in the algae-supplemented and control groups were 268 ± 54 and 180 ± 42 µg/l, respectively).

Essential trace and toxic element concentrations in organic and conventional milk in NW Spain.

Dietary composition and husbandry practices largely determine essential trace element status and toxic element exposure of livestock, and consequently their concentrations in animal products. This study evaluates the main essential trace (Co, Cr, Cu, Fe, I, Mn, Mo, Ni, Se and Zn) and toxic (As, Cd, Hg and Pb) element concentrations in milk from organic and conventional farms in NW Spain (n=50). Milk samples were acid digested and analyzed by ICP-MS. Essential trace element concentrations in organic milk were significantly lower compared to conventional milk, this was especially evident for elements that are routinely supplemented at high concentrations in the conventional concentrate feed: Cu (41.0 and 68.9µg/L in organic and conventional milk, respectively), Zn (3326 and 3933µg/L), I (78 and 265µg/L) and Se (9.4 and 19.2µg/L). Toxic metal concentrations in milk were in general very low and no statistically significant differences were observed between organic and conventional milk. In addition, the mineral content of organic milk showed a seasonal pattern, the significantly higher As (65%) and Fe (13%) concentrations found in the winter sampling possibly being related to a higher consumption of concentration feed and soil ingestion when grazing.