Stefan Jurjanz

Drinking Behavior of Lactating Dairy Cows and Prediction of Their Water Intake

The water intake of 41 lactating dairy cows managed according to current dairy farm practices was individually and continuously monitored to 1) investigate drinking behavior and 2) determine factors affecting water intake. The cows were housed in a free-stall barn and fed once daily with a corn silage and concentrate-based total mixed ration (48% dry matter content; 20.6 +/- 3.3 kg/d of dry matter intake). Cows were milked twice daily, with a yield of 26.5 +/- 5.9 kg/d. The daily free water intake (FWI) was 83.6 +/- 17.1 L, achieved during 7.3 +/- 2.8 drinking bouts. The drinking bout water intake was 12.9 +/- 5.0 L. Almost three-fourths of the FWI occurred during working hours (0600 to 1900 h). Consumption peaks corresponded to feeding and milking times. More than one quarter of the daily FWI was met during the 2 h after each milking. About 75% of the present cows visited the watering point at least once during the 2 h after the evening milking. It is probable that drinking behavior evolved with lactation, but further studies are required to identify the relationship between lactation stage and drinking behavior. The most relevant factors affecting the daily FWI of lactating cows were best combined according to the following predictive equation: (R(2) = 0.45; n = 41 cows, n = 1,837): FWI, L/d = 1.53 x dry matter intake (kg/d) + 1.33 x milk yield (kg/d) + 0.89 x dry matter content (%) + 0.57 x minimum temperature ( degrees C) - 0.30 x rainfall (mm/d) - 25.65. The results obtained using these equations were in agreement with the equations developed by other researchers.

Variations of trans Octadecenoic Acid in Milk Fat Induced by Feeding Different Starch-Based Diets to Cows

The impact of starch sources differing in their velocities of ruminal degradation on the milk fat of dairy cows was studied. The animals received diets containing a slowly degradable (potatoes) or rapidly degradable (wheat) starch concentrate (40% of the dry matter) in a total mixed diet. Milk fat was the only animal performance factor affected: Cows produced significantly less milk fat when fed the wheat diet than the potato diet (−3.3 g/kg, −122 g/d; P<0.05). With the wheat diet, milk fat was poorer in short-chain FA and richer in unsaturated longchain FA, especially in trans octadecenoic acid (4.4 vs. 2.7% of the total FA, P<0.05). A very large increase in the isomer trans-10 18∶1 (+1.46% of the total FA) was observed. Because no difference in volatile FA concentrations in the rumen was revealed, the increase in trans octadecenoic acids, and particularly the isomer trans-10 18∶1, was associated with the larger postprandial drop in ruminal pH with wheat. Similar concentrate levels and FA profiles in both diets indicated that the decrease in milk fat was due to changes in the ruminal environment. Quicker degradation of wheat starch, and hence a greater drop in pH with this diet associated with the absence of any effect on volatile FA, strengthen the hypothesis developed in the literature of enzyme inhibition via increased levels of trans octadecenoic acids, especially the trans-10 isomer. Hence, milk fat can be decreased with rapidly degradable starch sources and not only with high levels of concentrates in the diet or added fat. More detailed work is necessary to elucidate the microorganisms involved and to determine whether metabolic pathways similar to those reported for high-concentrate diets are involved.

Relative bioavailability of soil-bound polycyclic aromatic hydrocarbons in goats

This study aimed at determining the relative bioavailability (RB) of three soil-bound PAH model compounds (phenanthrene [PHE], pyrene [PYR] and benzo[a]pyrene [BaP]) in four lactating goats. RB was estimated by comparing the urinary or milk excretion of the major mono-hydroxylated metabolites of PAHs after ingestion of PAH spiked-soil and -oil feeds. A series of three increasing doses were orally administered in order to estimate the dose response of the two different matrices. The results of this study reveal that urinary excretion prevailed compared to milk excretion (30-fold higher). The recovery rate of mono-hydroxylated metabolites of PAHs in urine and milk indicate that PYR was absorbed at a minimum level of 36%. 3-OH PHE excreted in urine suggests a minimal absorption of at least 5% for PHE. 3-OH BaP remained under the limits of detection and quantification and no RB could be calculated for this compound. RB of soil-bound PYR compared to PYR in oil was 61% and 50% in milk and urine, respectively. Thus, a significantly reduced RB of PYR in soil has been shown. On the other hand, no significant differences were observed between oil and soil for urinary 3-OH PHE (RB=100%). These results show that the soil matrix significantly reduces the bioavailability of certain PAHs. The decrease of bioavailability seems to be dependent on the compounds, i.e. higher for PYR than for PHE. This study also suggests that soil ingestion should be taken into account in risk assessment studies.

Dairy ruminant exposure to persistent organic pollutants and excretion to milk.

Human activities produce polluting compounds such as persistent organic pollutants (POPs), which may interact with agriculture. These molecules have raised concern about the risk of transfer through the food chain via the animal product. POPs are characterised by a strong persistence in the environment, a high volatility and a lipophilicity, which lead to their accumulation in fat tissues. These compounds are listed in international conventions to organise the information about their potential toxicity for humans and the environment. The aim of this paper is to synthesise current information on dairy ruminant exposure to POPs and the risk of their transfer to milk. Three major groups of POPs have been considered: the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), the polychlorobiphenyls (PCBs) and the polycyclic aromatic hydrocarbons (PAHs). The results show that contamination of fodder and soil by these compounds is observed when they are exposed to emission sources (steelworks, cementworks, waste incinerators or motorways) compared with remote areas. In general, soil contamination is considered higher than plant contamination. Highest concentrations of POPs in soil may be close to 1000 ng/kg dry matter (DM) for PCDD/Fs, to 10 000 mg/kg DM for PAHs and 100 μg/kg DM for PCBs. The contamination of milk by POPs depends on environmental factors, factors related to the rearing system (fodder and potentially contaminated soil, stage of lactation, medical state of the herd) and of the characteristics of the contaminants. Transfer rates to milk have been established: for PCBs the rate of transfer varies from 5% to 90%, for PCDD/Fs from 1% to 40% and for PAHs from 0.5% to 8%. The differential transfer of the compounds towards milk is related to the hydrophobicity of the pollutants as well as to the metabolic susceptibility of the compounds.

Direct determination of recombinant bovine somatotropin in plasma from a treated goat by liquid chromatography/high‐resolution mass spectrometry

Recombinant bovine somatotropin (rbST) is used in dairy cattle to enhance milk production. Despite the ban on this hormone in some countries, especially in Europe, there is so far no method available for the direct detection of rbST either in milk or in plasma. An analytical strategy has been developed to analyze rbST in plasma, including a purification procedure based on a precipitation with ammonium sulphate, followed by a solid-phase extraction (SPE)-based clean-up on C4 sorbent and precipitation with cold methanol. The hormone was then digested with trypsin and analyzed by liquid chromatography/high-resolution mass spectrometry (LC/HRMSn) on a linear ion trap coupled with an Orbitrap. The tryptic N-terminal peptide, specific to the difference between the endogenous and recombinant form of the somatotropin, was fragmented and product ions were analyzed at high mass resolution. Applying this approach to goat plasma allowed the direct detection of 10 ng mL(-1) of rbST in fortified samples. It also showed the presence of rbST in plasma collected from a goat treated with the hormone, even 2 days after administration. These results are of a great interest in the field of somatotropin control and undoubtedly constitute a first step in the development of a method for the detection of rbST not only in bovine plasma, but also in other biological matrices such as milk.

Polychlorinated biphenyl and low polybrominated diphenyl ether transfer to milk in lactating goats chronically exposed to contaminated soil.

This study investigated milk excretion kinetics of PCBs, tetra-BDE (BDE 47), and penta-BDE (BDE 99) in goats exposed to contaminated soil under controlled conditions. The animals were fed (80 days) with feed containing 5% of contaminated soil. During this exposure period, milk was analyzed weekly. At the end of the experiment the PCBs and PBDEs retained in hepatic and adipose tissues were also determined. The soil-milk carry over rates (CORs) of PCBs ranged from 6 to 62%. This result suggests that a large part of ingested soil-bound PCBs was recovered in milk. Significantly different levels between the congeners were reported in the tissues (fat, liver). BDE 47 and 99 excretions in milk achieved a plateau after 2 weeks of exposure, and their corresponding CORs were about 30%. These two congeners showed a significantly (P < 0.05) lower accumulation in the adipose tissue than the major PCB congeners. The concentrations of BDE 47 and 99 in the liver were the same as PCB concentrations. This result suggests that the low brominated congeners are submitted to the metabolism more extensively than the major PCBs.

Contamination of free-range ducks by chlordecone in Martinique (French West Indies): A field study

The former use of chlordecone (CLD) in the French West Indies has resulted in long-term pollution of soils and subsequently of food chains. In contaminated areas, free-range ducks used to control weeds in orchards may be exposed to CLD through polluted soil ingestion. The question arises whether they may be consumed. Muscovy ducks were raised on a guava orchard planted on a soil moderately contaminated (410 μg CLD/kg dry matter). Ducks were raised indoor up to 6 weeks of age and allowed to range freely outdoors thereafter. Twenty-nine females were sequentially slaughtered by groups of 2 to 5 ducks, after 4, 16, 19, 22 or 26 weeks spent in the orchard or after 16-17 weeks in the orchard followed by 3, 6 or 9 weeks in a closed shelter for depuration. CLD concentration increased from 258 to 1051, 96 to 278, 60 to 169 and 48 to 145 μg/kg fresh matter (FM) as the exposure through grazing increased from 4 to 22 weeks, in liver, abdominal fat and leg with and without skin, respectively. Eggs collected in the orchard contained up to 1001 μg CLD/kg FM. All these values exceeded the Maximum Residue Limit (MRL) of 20 μg/kg FM. CLD concentration in all tissues was divided by around 10 within the 9-week confinement period. Despite this quite rapid decontamination, it is estimated that 12-13 weeks would be required to achieve the MRL in liver and in eggs, and 5-6 weeks in leg muscle. Such durations would be too long in practice. Thus, the consumption of products from free-range ducks should be avoided, even in areas mildly contaminated with CLD.

Relative bioavailability of soil-bound polychlorinated biphenyls in lactating goats

Livestock may be exposed to organic pollutants via ingestion of contaminated matrices such as fodder or soil. The question on contribution of soil-bound polychlorinated biphenyls (PCB) to livestock exposure was not yet considered. The aim of this study was to assess the relative bioavailability of soil-bound PCB by assessing milk excretion of indicator PCB (I-PCB) after ingestion by goats of graded levels of PCB (mainly PCB forms 153, 180, and 138) in soil-contaminated feeds or in oil-contaminated feeds. Eight multiparous Alpine goats were grouped in 4 pairs on the basis of body weight and milk yield. In each pair, one goat was assigned to the soil feeds and the other one to the oil feeds. The experiment consisted of a 7-d adaptation period, followed by a 96-d exposure period. The exposure period was divided into 3 successive 32-d periods during which each goat received either 3 soil feeds or 3 oil feeds, distributed in increasing rank of contamination. During the last week of each 32-d period, milk from each goat was collected during 3 successive 24-h periods, stored at -20°C, and freeze dried before analysis (extraction by accelerated solvent extraction, followed by gas chromatography-mass spectrometry analysis). Bioavailability of I-PCB from soil or spiked oil feeds was estimated by means of the slope-ratio method from I-PCB concentration in milk in response to ingested I-PCB. Relative bioavailability was found to vary from 36 to 50% for PCB 118, 138, and 153 and it was 73% for PCB 180. When considered globally, the response obtained with the I-PCB was estimated to 51%. Relative bioavailability was not established for PCB 52 and 101, compounds known to be readily cleared and showing low concentrations in milk. For PCB 28, no significant interaction was found between matrix and dose. This experiment reveals that PCB bound to soil are potentially liberated from soil during the digestive process and may undergo absorption, distribution, metabolism, and excretion. Thus, soil has to be considered as a risk matrix for ruminants and rearing practices in contaminated areas should strictly reduce the risk of soil ingestion by the ruminants.

Soil intake of lactating dairy cows in intensive strip grazing systems.

Involuntary soil intake by cows on pasture can be a potential route of entry for pollutants into the food chain. Therefore, it appears necessary to know and quantify factors affecting soil intake in order to ensure the food safety in outside rearing systems. Thus, soil intake was determined in two Latin square trials with 24 and 12 lactating dairy cows. In Trial 1, the effect of pasture allowance (20 v. 35 kg dry matter (DM) above ground level/cow daily) was studied for two sward types (pure perennial ryegrass v. mixed perennial ryegrass-white clover) in spring. In Trial 2, the effect of pasture allowance (40 v. 65 kg DM above ground level/cow daily) was studied at two supplementation levels (0 or 8 kg DM of a maize silage-based supplement) in autumn. Soil intake was determined by the method based on acid-insoluble ash used as an internal marker. The daily dry soil intake ranged, between treatments, from 0.17 to 0.83 kg per cow in Trial 1 and from 0.15 to 0.85 kg per cow in Trial 2, reaching up to 1.3 kg during some periods. In both trials, soil intake increased with decreasing pasture allowance, by 0.46 and 0.15 kg in Trials 1 and 2, respectively. In Trial 1, this pasture allowance effect was greater on mixed swards than on pure ryegrass swards (0.66 v. 0.26 kg reduction of daily soil intake between medium and low pasture allowance, respectively). In Trial 2, the pasture allowance effect was similar at both supplementation levels. In Trial 2, supplemented cows ate much less soil than unsupplemented cows (0.20 v. 0.75 kg/day, respectively). Differences in soil intake between trials and treatments can be related to grazing conditions, particularly pre-grazing and post-grazing sward height, determining at least in part the time spent grazing close to the ground. A post-grazing sward height lower than 50 mm can be considered as a critical threshold. Finally, a dietary supplement and a low grazing pressure, that is, high pasture allowance increasing post-grazing sward height, would efficiently limit the risk for high level of soil intake, especially when grazing conditions are difficult. Pre-grazing and post-grazing sward heights, as well as faecal crude ash concentration appear to be simple and practical tools for evaluating the risk for critical soil intake in grazing dairy cows.

DAIRY LIVESTOCK EXPOSURE TO PERSISTENT ORGANIC POLLUTANTS AND THEIR TRANSFER TO MILK: A REVIEW

The main emission sources of Persistent Organic Pollutants (POPs) should be attributed to Human activities although certain natural events may also enhance their production. After emission, these compounds can be potentially transferred to the food chain via interactions with livestock systems. POPs are characterized by some volatility, strong persistence in the environment, and a high lipophilicity, which leads to their accumulation in fat tissues. These molecules have raised concern about the risk of transfer through the food chain via the animal product. POPs are listed in several international conventions dealing with their potential toxicity for humans and the environment. This paper synthesizes current information on dairy ruminant exposure to POPs and the risk of their transfer to milk. Five major families of POPs have been considered: the two groups of dioxins and furans (PCDD/Fs), the Poly Chloro Biphenyls (PCBs), the Polycyclic Aromatic Hydrocarbons (PAHs) and the emerging family of Poly-Bromo-Diphenyl-Ethers (PBDE). Dairy ruminants are mainly exposed to theses POPs by oral ingestion, other contamination ways are considered as minor. The contamination of roughage and soil by these compounds is observed when they are exposed to emission sources (steelworks, cement works, waste incinerators or motorways) compared to remote areas. Concentrations in soil can be higher than in plants, especially for very persistent halogened compounds. Highest concentrations of POPs in soil may be close to 1 μg per kg dry matter for PCDD/Fs and PBDEs, 100 μg/kg dry matter for indicator PCBs, 10 g/kg dry matter for PAHs. The contamination of milk by persistent organic pollutants depends on environmental factors, which are related to the rearing system (feeding system, access to contaminated soil or not, stage of lactation, udder health of the animals) and of the characteristics of the considered contaminants (their chemical properties like molecular weight, halogenations, lipophilicity and metabolic susceptibility). Established transfer rates to milk were lowest for PAHs (generally less than 1%), mainly due to other excretion pathway like urine but also to a certain proportion of metabolization. Transfer rates of halogenized compounds were generally higher: for PCBs the rate of transfer varies widely from 5% to 90%, and for the PCDD/Fs from 1% to 40%. Further studies should clarify the effect of hydroxyl-metabolites of PAHs on Human health and precise the transfer rates of PBDEs where only few data are available.