An interdisciplinary approach to controlling chikungunya outbreaks on French islands in the south-west Indian ocean.

The outbreak of chikungunya that occurred on French Island territories in the southwest Indian Ocean in 2005 and 2006 caused severe morbidity and mortality. In the aftermath, French authorities set up a scientific task force including experts in epidemiology, public health, entomology, virology, immunology, sociology, animal health, community and hospital medicine. The mission of the task force was to conceive and propose research programs needed to increase understanding of the disease and epidemic and to help public health officials in improving epidemic response measures. The purpose of this article is to describe the findings of the task force at the end of its two-year existence and initial outcomes in the the areas studied. Discussion emphasizes topics requiring further study.

Impact on productivity of peri-parturient rise in fecal egg counts in Creole goats in the humid tropics.

The control of gastrointestinal nematodes requires an understanding of their epidemiology so that particular parasite stages can be targeted. Dam infection during early lactation is one example of this in ruminant nematode infections. The existence of the peri-parturient relaxation in immunity and its impact on productivity were examined in a Creole goat flock from Guadeloupe, exposed to mixed natural infection (predominantly Haemonchus contortus and Trichostrongylus colubriformis). A total of 1,511 l were obtained from 909 does resulting from 463 dams and 150 sires. Fecal and blood samples were collected at kidding before anthelmintic drenching, 4 and 6 weeks after kidding. The traits analyzed were logarithm transformed fecal egg counts (FEC), packed cell volume (PCV), and logarithm transformed blood eosinophilia counts (EOS) for does at each sampling point and changes in these during the postpartum period. With the exception of the PCV values measured at kidding, lactating does had significantly higher FEC and lower PCV than control dry does at every sampling point. Geometric means of FEC in lactating does were 819 +/- 174, 677 +/- 146 and, 699 +/- 160 eggs per gram (EPG) at kidding, 4 and 6 weeks after kidding respectively. Geometric means of FEC in dry does were 187 +/- 57, 89 +/- 28, 133 +/- 43 at these time points, respectively. EOS differences were not consistent between groups and probably not specific enough for variations in Creole goats' peri-parturient rise to be discussed. As does aged, their egg output decreased and primiparous does always had greater egg output than multiparous ones. Overall, does' FEC at 4 weeks after kidding decreased by 1.3% each year. The higher the litter size, the higher the FEC at kidding and inverse applied for PCV measurements. Does that stopped lactating had significantly lower FEC and higher PCV values than lactating does with low milk yields. Higher infection rates during early lactation in Creole goats were recorded in does with lower maternal ability assessed by the average daily weight gain of kids between 10 and 30 days of age. Kids from dams with higher FEC (i.e. >600 EPG higher than corresponding does) had 17% lower average daily weight gain between 30 and 70 days postpartum and were approximately 1 kg lighter at weaning than kids from dams with lower FEC. Thus, it is clear that a peri-parturient rise in FEC exists in Creole goats. By controlling the intensity of this peri-parturient rise in FEC, herd health and productivity could be substantially improved.

Population evolution of the free-living stage of goat gastrointestinal nematodes on herbage under tropical conditions in Guadeloupe (French West Indies).

In Guadeloupe (French West Indies), paddocks were contaminated with gastrointestinal helminth eggs by young goats during the rainy season and the dry season. The evolution of L3 population size on herbage was followed over a period of 56 days. The major genera were Haemonchus and Trichostrongylus. It was shown that the L3 appeared on herbage 7-14 days after the beginning of contamination (DAC), and the L3 population sizes were maximal between the 14th and the 21st DAC. The maximum duration of larval survival ranged between 49 and 56 days. There was a marked depressive effect by the dry season on eggs hatching and L3 development with some arrested egg hatching in Trichostrongylus. The climatic events and the amount of dry matter on pastures during the grazing period appeared as the main important factors which could interfere with the overall evolution of the L3 population size and there was no preferential direction of L3 migration from faeces to herbage.

Pasture populations of cattle nematode larvae in Guadeloupe (French West Indies).

The development of numbers of third-stage (L3) larvae of gastrointestinal nematodes after pat (faeces) deposition by heifers is described, using a mathematical model, for seven experiments carried out in Guadeloupe (French West Indies). A dramatic rise in L3 population size occurred on herbage near pats, 17-25 days after pat deposition. There was no clear relationship between climatic data and L3 population dynamics. However, 5 successive days of rainfall induced the resumption of larval migration in two experiments. Changing the unit of expression of L3 population size (100 L3 m-2 vs 1000 L3 per kg DM) did not alter estimates of the model parameters. The evolution of L3 population of Haemonchus and Cooperia were similar.

Herbage density of third-stage larvae of goat strongyles during the dry season in Guadeloupe.

The objective of this study was to determine the main sources of variation in herbage densities of infective third stage larvae of goat strongyles during the marked dry season of 1994 in Guadeloupe (FWI). Herbage samples were collected for L3 density (LD) determination by an accurate method, 4 times at 4-week intervals in 58 paddocks of 21 farms spread out in five regions of the archipel of Guadeloupe. At the same time, FEC of each grazing animal and fecal culture for parasite genus determination according to sex and age were carried out. Stocking rate, dry matter content of soil, and daily climatic data were also recorded. An index of egg development in larvae (IEDL) was calculated as the ratio of LD to the eggs deposed during the 4th, 3rd, and 2nd weeks before sampling. Medians of LD in herbage were 3397, 1853, 1410, and 324 L3/kg DM for all parasites, Haemonchus, Trichostrongylus, and Oesophagostomum, respectively. Date of sampling, region, and irrigation practice in the northern windward region were the main sources of variation in LD and in frequency of each parasite. LD decreased as the dryness lasted, but it remained important (500 L3/kg DM) despite the drought. LD in windward regions were higher than in other regions. The region, the farm, and the paddock were the main sources of variation of IEDL. LD of each parasites were inversely correlated to global radiation recorded 1 to 3 weeks before herbage sampling, but no relation was found with rainfall data. Trichostrongylus frequency in L3 population increased as the dryness lasted. A dryness axis was extracted from environmental variables (climatic data, dry matter of soil, duration of dryness) by a multiple factorial procedure. LD and Haemonchus frequency in L3 population were inversely correlated to dryness axis (p < 0.01). In contrast, Trichostrongylus frequency was positively correlated to the dryness component.

Genetic variability in resistance of Creole goats to natural infection with trichostrongylids in Guadeloupe.

The objective of this study was to show the existence of genetic variability in resistance of Creole goats to natural infection with intestinal nematodes. Four successive cohorts of male and female kids were reared from weaning during 9 months in intensive pangola pastures (stocking rate 1.4 t/ha, regrowth of 21 days, 300 kg N/ ha/year of fertilization). All cohorts considered, 203 offsprings from 13 bucks and 149 goats were used in the experiment. Animals were treated with an oral dose of ivermectin every seven weeks, from 3 to 11 months of age. They were sampled for fecal egg counts (FEC) and packed cell volume (PCV), 6 weeks after drenching, when 6 and 10 months old. Haemonchus contortus and Trichostrongylus colubriformis were the predominant species. Data of one cohort when 6 months of age and another one when 10 months old were not included in calculations because a self-cure occurred during a rainy season. Estimated means of FEC after square-root transformation were 1054 and 711 respectively for 6-month-old and 10-month-old kids. Phenotypic correlations between FEC and PCV were -0.46 (p < 0.001) and -0.29 (p < 0.01) when 6 and 10 months old, respectively. FEC repeatabilities estimated as variance ratio were 0.47 and 0.06 for within-age measures (data recorded at one week interval) and between age measures (6 vs. 10 months) respectively. No sire effect was significant for PCV. Sire effect on FEC was more significant when 6 months old (p < 0.03) than when 10 months old (p < 0.15). Further studies are now being carried out to confirm this genetic determinism of resistance to natural infection with strongyles in Creole goats.

Development of a single dilution ELISA to detect antibody to Dermatophilus congolensis in goat and cattle sera.

A solid phase immunosorbent assay to detect antibodies to Dermatophilus congolensis in ruminant sera was developed to be used as a single dilution ELISA in large epidemiological surveys. Optimal conditions for the test are described. The use of blocking proteins to reduce non specific binding was necessary. Non fat dry cow milk and fetal calf serum were the only two efficient blocking agents out of six tested. Comparison of 4 antigenic fractions obtained after sonication and differential centrifugations of D. congolensis cultures showed that cell-wall (CW) or membrane (M) enriched preparations were more specific than a crude extract (CR) or a soluble (S) antigen. Whole spores and filaments performed poorly as antigens. The best sensitivity and specificity of the ELISA were obtained when the cut-off point of positivity was fixed at mean absorbance of negative sera + 2.58 sd. The specificity was then 97.6% either with M or CR antigen. The sensitivity was improved from 93.4% with CR to 98.2% with M antigen. Threshold values for a positive test varied between the 3 geographical areas tested. CW and M were also the most efficient antigens for discerning between serotypes of D. congolensis. The precision of the test was evaluated with CR antigen and expressed in residual expressed in residual coefficient of variation (CV). The precision was CV = 5.1% when each serum was titrated in duplicate and the antibody levels were expressed in absorbances. The expression of antibody levels in arbitrary standard units estimated from calibration curves reduced the precision (CV = 13.8%). Several methods were tested to decrease between plate variability but these did not greatly improve the reproducibility since it was shown that the main source of variation was within the plate.

Comparison of the resistance to sympatric and allopatric isolates of Haemonchus contortus of Black Belly sheep in Guadeloupe (FWI) and of INRA 401 sheep in France.

The resistance of a tropical breed of sheep towards the nematode parasite Haemonchus contortus (Hc) was compared to that of a European breed after artificial infection with the parasite following a 2 x 2 x 2 experimental design: two isolates (Hc Gua from Guadeloupe versus Hc Fra from France), two breeds each reared in their native habitats (Black Belly (BB) in Guadeloupe, FWI, INRA 401 reared in France), and two groups of lambs with differing infection status (one naive, i.e. infected for the first time during the experiment, and one primed, i.e. which had previously received doses of 5000 L3 on Days -35 and -32 before the infection during this experiment). Both groups were composed of 10 male lambs, which were 20 weeks of age when they were given a dose of 10,000 L3 of the relevant isolate on Day 0. Resistance was assessed by regular fecal egg counts (FECs) and blood samples, and worm counts were processed on Day 35 p.i. The FEC was lower in the BB than in INRA 401 lambs, lower in the primed than naive groups, and lower in Hc Fra than in Hc Gua. The eosinophil count remained unchanged in the naive INRA 401 groups, but increased in all the other groups. The hematocrit fell after infection, but the live weight was not affected by the infection. Worm burdens were 1868 and 5237 in the naive BB and INRA 401 groups, respectively, and 596 and 4835 in the primed BB and INRA 401 groups. The daily production of eggs per Hc Gua female worm was 1.5-fold that of Hc Fra. The number of worms had no effect on worm length or Hc in utero egg count in the BB sheep, but a positive and significant correlation between these two traits was seen in the INRA 401 lambs. These findings are indicative of innate resistance, and confirmed the high acquired resistance of the BB sheep to both sympatric and allopatric isolates of Hc. The regulation of worm population and fecundity differed in the BB and INRA 401 sheep.

Gastro-intestinal parasitism of cattle in native pasture grazing system in Guadeloupe (French West Indies).

Gastro-intestinal parasitism of creole cows and calves, Limousin x creole cross calves and Brahman x creole cross calves was recorded during seasons of calving in a native grazing system in Guadeloupe, a wet tropical area. Calvings were pooled during the dry season for two herds and during the rainy season for two other herds. For each calving season, calves of one herd were drenched monthly with anthelmintic. A marked periparturient rise in egg excretion was observed in cows. Coccidial infection was always present in calves, but no clinical signs were observed. The main parasites during the first 2 months of life were Strongyloides papillosus and Toxocara vitulorum. Then, Haemonchus placei, Trichostrongylus spp. and Cooperia spp. were the dominant species encountered. Brahman cross calves were the most heavily infested animals. There was no clear relationship between third stage larvae (L3) population size on pasture and worm burdens in calves, except during the second month of life. Despite medium levels of infestation, parasitism inhibited the growth of creole calves: -10.5 kg of bodyweight at weaning (-59 g day-1 of daily bodyweight gain from birth to weaning). The pathological effects of subclinical parasitism were confirmed by a lower packed cell volume and albuminaemia in parasitized calves than in treated calves.

Comparison of methods for counting third stage larvae of gastrointestinal nematodes of small ruminants in tropical pastures.

The accuracy and the precision of a simple and reliable technique for the extraction and the counting of third stage larvae densities of gastro-intestinal strongyles of ruminants from pasture samples are assessed in tropical conditions, i.e. for pangola pastures and for the genera of Haemonchus and Trichostrongylus. To separate the larvae from herbage samples, water washings obtained by a centrifuge spin-dryer were put to sediment in disposable plastic bags. The extraction and counting of larvae from sediments were achieved by exhaustion of sediments with repeated sucrose/water interface procedures. The recovery rate of third stage infective larvae (L3) added to the sediment was 79.1% (+/- 9.49%). The accuracy, estimated as recovery rate of L3 added to herbage samples, was 76.5 (+/- 11.31%). The recovery by the sedimentation method was 3.5 times higher than that of a filtering method through a 20 microns sieve. The detection limit was estimated to be 130 L3 kg-1 dry matter. Precision, estimated as the residual standard deviation of duplicate assays, was 1857 L3 kg-1 dry matter (mean 9164 L3 kg-1 dry matter). Results obtained in routine epidemiological surveys of gastro-intestinal strongylosis of small ruminants in West Africa and in the West Indies demonstrated the usefulness of the technique.

Experimental infection of Black Belly and INRA 401 straight and crossbred sheep with trichostrongyle nematode parasites.

Compared to INRA 401 lambs reared in France, Black Belly (BB) lambs reared in Guadeloupe (F.W.I.) were highly resistant to both primary and secondary experimental infection with Haemonchus contortus. To investigate this huge inter-breed difference, a nucleus flock of BB was constituted, and experiments were conducted to: (i) confirm this difference in lambs born in France, (ii) check whether it was similar for Trichostrongylus colubriformis and Teladorsagia circumcincta, and (iii) find out whether this difference was age-related. Forty BB lambs, 84 F1 lambs (BB siresxINRA 401 ewes) and 88 INRA 401 lambs born in two cohorts were used in an experimental design involving three host breeds, both genders and two age-groups (3.5- and 7-month-old when first infected). The limited availability of BB lambs made the study incomplete. Infection consisted of the administration of two doses of 10,000 infective larvae of one of the nematode species, separated by an anthelmintic treatment and an interval of 1 week before the second dose was administered. Fecal egg counts (FECs) were done on Days 28 and 35 after each infection; ewe lambs of the INRA 401 and F1 breeds were necropsied, the worm burden was established, the length of the female worms measured and the eggs in utero counted. For H. contortus and T. colubriformis, the FEC was lower in the BB than in the INRA 401 lambs, and the FEC found for the F1 lambs was intermediate. For T. circumcincta, only data for the F1 and INRA 401 lambs were available, and the FECs for these breeds were the same. In all three breeds, the FEC determined after the second dose was significantly lower than that found after the first dose in the ewe lambs, but not in the ram lambs. Infecting the lambs when they were 7- instead of 3.5-month-old significantly lowered egg excretion of both parasites in the F1 (P<0.0001), but not the INRA 401 lambs. Worm numbers in the F1 and in the INRA 401 ewe lambs confirmed the FEC data, many F1 lambs being free of T. colubriformis. The H. contortus female worms were shorter and had fewer eggs in utero in the F1 than in the INRA 401 lambs. A higher proportion of T. circumcincta was at the fourth larval stage in the F1 lambs. In conclusion, the BB breed is much more resistant than INRA 401 to H. contortus, with the F1 lambs being more like the BBs after the second dose. This difference was also found for T. colubriformis and, to a lesser extent, for T. circumcincta.

Mortality of Creole kids during infection with gastrointestinal strongyles: a survival analysis.

Mortality due to strongyles infection in small ruminants is a critical component of flock productivity in a tropical climate. In goat production, few experiments have been conducted to estimate the variability of this trait. A survival analysis study was carried out in the Creole experimental flock of INRA-Gardel (Moule, Guadeloupe) to identify management and genetic factors influencing mortality of kids reared at pasture and infected with gastrointestinal strongyles, predominantly Haemonchus contortus and Trichostrongylus colubriformis. Survival curves from 3 and 11 mo of age were analyzed for 837 kids sired by 48 bucks and 250 does. The causes of death were recorded. Mortality due to gastrointestinal strongyles was the variable considered. The flock management included drenchings with levamisole every 8 wk. Fecal egg counts and packed cell volume were regularly measured after 7 wk of natural infection. All but 6.7% of the records were uncensored, with an average failure time of 165 d. The probability of death following gastrointestinal infection was more than three times greater in males than in females. Kids raised by their mother before weaning had a lower (P < 0.05) relative risk of dying than those reared in nursery (0.40 vs. 1). Parity of the dam and litter size effects were not significant. The risk of death was reduced by approximately 80% during the 3 wk that followed a drenching (P < 0.01). Risk decreased by about 25% for each additional kilogram of body weight at weaning. Live weight, fecal egg counts, and packed cell volume all had significant effects on risk of death when introduced as time-dependent covariates in the model (P < 0.0001 for live weight and packed cell volume, and P < 0.01 for fecal egg counts). The estimated genetic variability was small and inaccurate. These results demonstrated that risk of death from gastrointestinal infection could be reduced with appropriate flock management. High infection levels increased the risk of death, but they were not the direct cause. The important mediation of reduced body weight and anemia in likelihood of death is highlighted. More data are needed to better assess the possibility for genetic improvement of viability in Creole kids during gastrointestinal strongyle infection.

Assessment of genetic variability of resistance to gastrointestinal nematode parasites in Creole goats in the humid tropics.

Goat production is widespread in the tropics. Goats are very susceptible to gastrointestinal nematode infection, but there is less evidence of their genetic resistance. Genetic resistance of Creole goats to gastrointestinal nematodes has been studied at Guadeloupe in the French West Indies since 1995. The objective of this research was to investigate genetic variation for resistance to gastrointestinal nematode infection, in order to introduce this trait into breeding schemes. Genetic variability was assessed within a Creole experimental flock. Forty-nine sire groups were characterized at weaning and 55 during fattening after weaning. Kids were naturally infected, mainly by Haemonchus contortus and Trichostrongylus colubriformis. Fecal egg counts were determined once at weaning and every 6 and 7 wk after drenching during fattening. Blood samples were collected every 7 wk during fattening for determination of packed cell volume. Live weights were recorded at weaning and at the beginning and middle of every infection period during fattening. Genetic parameters were estimated using the REML for multivariate animal models. The heritability estimate for transformed fecal egg count was 0.37+/-0.06 at weaning. During fattening, it increased from 0.14+/-0.05 at 4 mo to 0.33+/-0.06 at 10 mo. Heritabilities of packed cell volume ranged from 0.10 to 0.33. At weaning, maternal heritability of fecal egg count reached 0.26 and direct heritability 0.20. After 6 mo of age, maternal effects were found to be unimportant for fecal egg count and packed cell volume. Live weights presented significant genetic variability. Genetic relationships between fecal egg counts and live weight in infected pastures were never significant. Genetic correlations between packed cell volume and live weight decreased from 0.47 to 0.10 from weaning to 10 mo of age. These results demonstrated the feasibility of breeding for improved resistance to nematodes in Creole kids.

From isolates to a synthetic laboratory population: maintenance of variability in the nematode Haemonchus contortus.

Haemonchus contortus isolates were collected from goats of five locations with different climatic characteristics in Guadeloupe archipelago. They were investigated for morphology, morphometrics and allozyme diversity after passage in immunosuppressed lambs using long acting corticoids. The basic aim of the work was to construct a synthetic strain in laboratory conditions which was representative of the isolates. The isolates were only slightly different although climatic conditions were very different. The resemblance of isolates might be due to the practice of goat exchanges between farms or to their insular origin. However the isolate from a smaller island (Les Saintes) was different (mostly on morphometrics) from all the others originating from Guadeloupe main Island. The first assemblage in laboratory resulting from the installation from a mixture of the five isolates was not very representative, whereas the next generation (synthetic strain) resembled all the isolates as shown from allozyme study. Female fecundity and length in established synthetic strain were lower than that recorded in isolates, indicating a decrease in fitness, possibly due to the stability of experimental environment. The representativity of the synthetic strain was good but the strain could still evaluate on further passages and should be evaluated on a large number of generations maintained in laboratory.

A semi-automated method for the determination of total iodine in milk.

A method for determination of iodine in milk is described. This method involves the destruction of organic matter by alkaline incineration and automated spectrophometric determination of iodide based on the Sandell and Kolthoff's reaction. The recoveries of added iodide before calcination were between 90.05 +/- 7.36% and 97.14 +/- 4.56% (mean +/- S.D.). The coefficient of variation ranged from 2.15 to 7.21% according to the iodine content of the milk. The limit of detection was estimated to be around 2 micrograms/kg.

Simulation of infestation risk of cattle by gastro-intestinal trichostrongylids in a tropical humid climate.

The population dynamics of trichostrongylid third stage larvae (L3) around bovine dung were fitted with non-linear models (marginal law) in tropical humid climate in different climatic situations. These marginal models were combined with the survival duration of pats, the weight of cows, the number of pats per cow and per day, the stocking rate and the herbage mass availability, taking into account the patchy grazing behaviour of cattle in order to estimate infestation probability of cattle by third stage larvae. The infestation risk was computed for different ages of herbage regrowth and grazing times in rotational grazing systems. The infestation risk was found to range between 0 to 1400 L3 per kg of dry matter of grass and per day depending on the marginal law. The grazing time, the age of herbage regrowth and the forage availability were the main factors of variation of the infestation risk.

Milk iodine residues after a post-milking iodophor teat-dipping.

When udders were washed before milking, a post milking teat-dipping with a 5,000 mg available iodine/l iodophor induced an iodine residue of 33 to 54 micrograms l/kg in milk. The iodine contents of the first jets of milk were 1.08 to 8.27 times higher than those of average milk. However, the bulk of iodine residues in milk seemed to be an iodine transfer across teat skin to milk. From these data, iodophor teat-dipping cannot be considered as a threat for public health in France.

Experimental coccidiosis in goats. 1. Experimental model. Effects of parasitism on the feeding behaviour and the growth of animals; intestinal lesions.

Experimentally infecting goats with three species of coccidia (Eimeria ninakohlyakimovae, E. arloingi, E. christenseni) and placing them in metabolism cage helped us to obtain a parasitic development which was significant and continuous. This development is not necessarily accompanied by clinical symptoms. However slight constipation and not diarrhoea was observed. Feed consumption is reduced and a subsequent reduction in the rate of growth is observed. As far as the feeding behaviour is concerned, the reduction in the rate of growth is compensated by the animals choosing those parts of their ration which are most easily digested.

Experimental coccidiosis in goats. 2. Effect of parasitism on nutritional balances and some blood parameters.

Experimental infection of goats with three species of coccidia (E. ninakohlyakimovae, E. arloingi, E. christenseni) caused a significant modification in apparent digestibility of dry matter, organic matter and crude fibre but only mild clinical effects. Nitrogen balance became negative and there was a decrease in serum albumin and glucose concentration and packed cell volume. These modifications may be partially explained by the fall of dry matter intake, the change in dry matter content of faeces and the disturbances of intestinal functions.

Iodine nutrition in ewes: effects of low to high iodine intake on iodine content of biological fluids in pregnant and lactating ewes.

In a first experiment, 2 groups of 46 and 47 multiparous ewes received diets which provided an iodine intake of 0.36 and 0.26 mg/kg dry matter (group C) and, 2.01 and 1.94 mg/kg (group D), respectively, for pregnancy and lactation. In a second experiment, 3 groups of 10 nulliparous ewes received diets which provided an I intake of 0.13 and 0.12 mg/kg dry matter (group A), 0.22 and 0.20 mg/kg dry matter (group B), and 10.77 and 8.88 mg/kg dry matter (group E), respectively, for pregnancy and lactation. Observations and sampling were carried out on the ewes from the first third of pregnancy to the 2nd and the 6th week of lactation. The diets provided adequate nutrition for pregnant and lactating ewes. Dietary I content had no effect on the dry matter intake, the size or the weight of the litter and the length of pregnancy. Plasma inorganic iodine (PII) was less affected by the I intake during lactation than during pregnancy. The excretion of I in milk induced a decrease in PII between pregnancy and lactation. The I in urine expressed as microgram I/g creatinine was largely affected by the intake. Colostrum I was 6.7, 4.0, 1.2, 1.3 and 1.5 times higher in groups A, B, C, D and E than the I in milk collected 1 week postpartum. Milk iodine (MI) content and the ratio MI/PII were markedly dependent on the I intake. During pregnancy, plasma T4 concentration decreased for each group. Plasma T4 concentration remained low during lactation in the low I intake group, whereas it increased at the same time in the other groups. The plasma T3 concentration decreased at the 6th week of lactation in the highest I intake group. Experimental values showed that 0.12 mg I/kg dry matter induced depletion in the I stocks of pregnant and lactating ewes, whereas an I intake above 10 mg I/mg dry matter disturbed the metabolism of thyroid hormones.