Effects of amount of milk, milk flow and access to a rubber teat on cross-sucking and non-nutritive sucking in dairy calves

The aim of this study was to test the effects of different amounts of milk, flow rate of milk, and access to a teat after milk intake on non-nutritive sucking on an empty teat and on cross-sucking on other calves in Bos taurus dairy calves. An additional aim was to test if calves prefer to perform non-nutritive sucking on a teat with the taste of milk or on a clean teat. First experiment involved 11 groups of three calves during gradual decrease from 5 to 2.5 and 1 to 0l of whole milk per meal twice daily. Milk flow was either 0.5 or 1l/min, and the teat buckets were either left or removed after milk intake. When the calves were fed with 5l of milk, non-nutritive sucking and cross-sucking decreased (P<0.001), compared to 1 and 2.5l. Removing the empty teat after milk intake increased cross-sucking (P<0.001). Slow milk flow reduced non-nutritive sucking after milk intake (P<0.05), but did not influence cross-sucking. Duration of recorded milk intake was similar with fast flow and 5l of milk, compared to slow flow and 2.5l of milk. The latter combination increased non-nutritive sucking and cross-sucking, suggesting that amount of milk is more important than duration of milk intake.Second experiment was carried out on 12 individually kept calves. The calves received 2.5l of milk either in an open bucket, in a rubber teat bucket, or half/half in both buckets. When not used for feeding, the open bucket and the teat bucket were filled and emptied again to make them 'tasty' with some drops of milk. The tasty teat bucket was either removed or present after milk intake. The calves had always access to a second clean teat bucket. Source of milk had no influence on recorded behaviour after milk intake. The tasty teat was sucked for twice as long as the clean one when both teats were present (P<0.001). When the tasty teat was removed, the calves increased sucking on the clean teat (P<0.001), but decreased total time spent sucking (P<0.001). We conclude that a high amount of milk and the presence of the teat bucket after milk intake reduces cross-sucking, and that a clean teat is less effective in encouraging calves to suck than a teat with taste of milk.     

Sucking behaviour of dairy calves fed milk ad libitum by bucket or teat

The milk intake and sucking behaviour of Dutch and Holstein-Friesian crossbred calves fed milk replacer ad libitum by either the bucket method (n=8) or an artificial teat (n=6) were compared. The animals were observed for 3 weeks from the age of 2 weeks, penned individually and all provided with a “dummy” (artificial) teat near the milk source within the pen.

The teat-fed calves ingested significantly more milk than the bucket-fed calves (11.9 vs. 8.0 kg/day; P<0.05), and this intake took much longer (44.2 vs. 17.7 min/day; P<0.05). In both treatment groups, milk intake was organized in “meals”. The meal criterion, separating the withinmeal and between-meal non-feeding intervals, was set at 5 min. Frequency of meals and daily total meal duration did not differ significantly. Meals occurred rather randomly throughout a 24-h period.

On average, the dummy teat was used for 13 min per day by bucket-fed calves, but for only 1 min by teat-fed calves (P<0.05). Sucking of the dummy teat was largely clustered within the meal periods.

It is concluded that in the young calf a need for sucking exists independently of milk satiation. However, the level of satiation depends on whether the calf drinks or sucks the milk. Nutritive sucking is clearly more reinforcing than non-nutritive sucking.     

Behavioural interactions between West African dwarf nanny goats and their single-born kids during the first 48 hours post-partum

West African dwarf nanny goats and their single-born kids were tested to find out their behavioural response to separation and their mutual recognition during the first 48 h post-partum. The tests were conducted at 18, 24, 36 or 48 h post partum. Chi-square analyses were used to determine whether age, sex and birth weight of kids as well as h partum and parity of dams had an effect on post-partum bahaviours.In a preliminary study where the kids were not prevented from sucking prior to the tests, the majority of kids (93%) and does (86%) exhibited apparant minimal concern to separation (i.e., had scores of less than 3) and also failed to seek each other. When the kids were prevented from sucking 2 h prior to the tests, the couple showed some response to separation and made attempts to seek each other. This suggests that in goats the state of the neonate's nourishment and the fullness of the dam's udder may be important factors that determine the willingness of the kid and the dam to seek each other when separated. The behavioural response of 48-h-old kids to separation from their dams when they had not sucked for 2 h was significantly higher (P<0.05) than that of 18-h-old kids. The sex and birth-weight of 48-h-old kids did not affect their response to separation from their dams. Hours post-partum and parity of does did not affect their response to separation from their kids even though the proportion of does exhibiting the highest response was much higher in primiparous then multiparous animals (44% vs. 13%). Recognition of dams by kids was poor at 18 and 24 h with more than half (71%) the kids failing to recognize their dams. Dam recognition ability improved with age and at 48 h the majority of kids (88%) were able to recognize their dams. Does tested at 48 h post partum had better (P0.05) kid recognition than those tested at 18 and 24 h. The sex and birth weight of kids and the parity of dams had no effect on the mutual recognition of kids and their dams at 48 h post-partum.     

Sucking motivation and related problems in calves

Since survival of the young mammals depends on sucking success, it is assumed that sucking motivation must be strong and that sucking deprivation would result in frustration which could have a negative impact on their welfare. This concern as well as that regarding cross-sucking between calves and intersucking between older animals has stimulated research on the motivation of calves for non-nutritive sucking. Non-nutritive sucking is elicited by the ingestion of milk, and the lactose concentration in milk, rather than that of fat or protein, is the main factor stimulating non-nutritive sucking. Every time a calf drinks milk, it is stimulated to suck and deprivation of sucking may interfere with digestive processes or satiety. To understand the behaviour of the calf during nutritive sucking, we examined the effects of milk flow on calves' sucking and butting an artificial feeding system. Slowing and stopping the flow rate stimulates butting and can lengthen the duration of sucking for the meal. It also stimulates the calf to switch teats when a second teat is available. These findings are well correlated to our observations of the calf suckling a cow in experimental manipulations. The duration of the meal is not correlated with milk intake, but it is influenced by milk availability and how hungry the calf is. Furthermore, calves will butt more often when there is less milk available in the dam's udder, presumably because milk flow is slower. Consequently, it is the occurrence of butting rather than sucking duration that would be a good indicator of milk intake when the calf is suckling the dam. Finally, we recommend a combination of slower milk flow and hay feeding and the provision of a non-nutritive artificial teat to reduce the occurrence of cross-sucking following a milk meal.     

Reactivation of the quiescent corpus luteum and diapausing embryo after temporary removal of the sucking stimulus in the tammar wallaby (Macropus eugenii)

Pouch young of wallabies presumed to be carrying diapausing blastocysts were removed from the teat for times varying between 24 and 96 h and then returned to the same teat. The mothers were monitored for termination of diapause and checked for births or oestrus. In this way we were able to determine the critical time required to reactivate the quiescent corpus luteum and diapausing blastocyst after withdrawal of the sucking stimulus. When pouch young were removed from the teat for 76-96 h the corpus luteum and blastocyst were reactivated, with birth and/or oestrus occurring in 10/11 animals. When pouch young were removed for 72 h or less (n = 22) reactivation did not take place. We conclude that it takes longer than 72 h for the maternal endocrine system to become committed to reactivation. The precise sequence of endocrine events which precede blastocyst reactivation still remains to be determined.     

Effect of milkflow rate and presence of a floating nipple on abnormal sucking between dairy calves

The aim of this study was to investigate if access to an artificial teat compared to an open bucket would decrease abnormal sucking in calves held in pairs, and if the calves would perform less abnormal sucking if they spent more time drinking or sucking the milk. In total 16 calves of Swedish Red and White cattle housed in pairs were used. The eight groups were given 2.5l of whole milk per calf, twice a day in one of the following treatments; bucket with fast flow (control), bucket with slow flow, floating nipple with fast flow and floating nipple with slow flow. All groups were subjected to the four different treatments in a random balanced order. Two buckets were connected with a rubber pipe in order to control the milk flow. In the fast treatments, the milk poured from one bucket to the other in 40s, and in the slow treatments the milk poured from one bucket to the other in 10min. Each group had the treatment for 6 days before behavioural observations were done on day 7. These were made by instantaneous recordings at 20s intervals for 30min, starting when the calves received their milk in the morning and afternoon. The number of recordings of abnormal sucking was lower than the control in all treatments (P<0.001). The lowest recording of abnormal sucking was found, when the calves had both a floating nipple and a slow flow. Sucking on other objects in the pen had the highest number of recordings, when they had a nipple and a fast flow (P<0.01), but the sucking on the empty nipple represented 95% of this category. The calves tended to lick and bite more on the bucket, the nipple and pen fittings in the two treatments with fast flow (P<0.1) than in the slow treatment with nipple. It is concluded that both the performance of sucking and the time taken to ingest milk are important in order to decrease abnormal sucking between calves.     

Behavioural interactions between West African dwarf nanny goats and their twin-born kids during the first 48 h post-partum

West African dwarf nanny goats and their twin-born kids were tested to determine their behavioural response to separation and their mutual recognition during the first 48 h post-partum. Does and their kids were given scores ranging from 1 to 5, depending on how they performed in the tests. Animals that showed maximum response and recognition ability were given a score of 5, while those with minimum response and recognition ability scored 1. The kids were prevented from sucking 2 h prior to the tests, which were carried out at 18, 24, 36 and 48 h post-partum. Chi-square procedure was used to determine whether age, sex and birthweight of kids as well as hours post-partum and parity of dams had any effect on these post-partum behaviours. Out of 48 twin-born kids tested, 32 (67%) responded actively to separation from dams (i.e. had scores of 3 or more). The age, sex and birthweight of kids did not significantly affect (P>0.05) their response to separation from their dams. The hours post-partum and the parity of does also did not affect their response to separation from their kids. The dam recognition ability of twin-born kids was very poor. Out of a total of 48 kids tested, only 17 (35%) were able to recognize their dams (i.e. had scores of 3 or more). Even at 36 h, only four out of 14 (26%) could recognize their dams. It was only at 48 h that the majority of kids tested (i.e. 75%) successfully identified their dams. At 48 h, the dam recognition ability of kids was significantly better (P<0.05) than that of 18-h-old kids. Sex and birthweight of 24-48-h-old twin-born kids did not significantly affect (P>0.05) their ability to recognize their dams. The majority of does tested (i.e. 20 out of 24) were able to recognize their twin-born kids. The hour post-partum and parity of does did not significantly affect (P>0.05) their kid recognition ability.     

Reduction in cross-sucking in calves by the use of a modified automatic teat feeder

Cross-sucking may be a problem in group-housed calves fed by automatic teat feeders. In the present study, the behaviour of calves fed by a conventional feeder with an open feeding stall (n=15 calves) was compared with the behaviour of calves fed by a modified feeder, closing in the rear after the calf has entered (n=14 calves). It was found that the calves fed by the feeder with the closed stall stayed longer in the feeding stall following milk ingestion (P<0.001), showed longer bouts of non-nutritive sucking directed to the teat after milk ingestion (P<0.005) and performed less cross-sucking in the first 15min after milk ingestion (P<0.001) than calves fed by the feeder with the open stall. The design of the feeder had, however, no significant influence on the incidence of cross-sucking performed without close temporal association with milk ingestion. As the modification in the feeding stall reduces cross-sucking and is not costly, it should be feasible to introduce it in practice.     

Comparison of two surgical techniques for mastectomy of goats

Two different techniques for mastectomy were carried out on 14 goats with gangrenous mastitis. The animals were randomly assigned to one of two groups containing seven goats each. The first group was operated via a classical surgical mastectomy technique (either bilateral (n=5) or unilateral (n=2)). The second group was operated via vascular ligation of the external pudendal blood vessels and milk vein and amputation of the affected teat (either bilateral (n=3) or unilateral (n=4)). Comparison between the two groups was carried out. Vascular ligation and teat amputation proved to be an effective, quick, safe, and less expensive technique for mastectomy in goats. Ligation of udder vasculature was less traumatic than surgical amputation and the stress on the patient was minimal.     

Piglet growth before and after weaning in relation to a qualitative estimate of solid (creep) feed intake during lactation: a pilot study

The experimental objectives were to verify whether a qualitative measure of creep feed consumption using a dye was related to performance, and associate this with teat order. Indigo carmine (5 g/kg) was added to a starter diet between days 12 and 31 (weaning) of lactation. On days 19, 23, 27 and 31, faeces from each piglet were assessed for colouration. Each piglet was categorized as a 'good', 'moderate' or 'small/non' eater of feed. There were no differences in pre-weaning growth rate between categories. Piglets classed as 'good' or 'moderate' eaters in lactation grew fastest (p = 0.009) in the first three days after weaning, but between days 4 and 7, the highest growth rate occurred in 'moderate' eaters. 'Small/ non' eaters grew slower (p < 0.01) between weaning and 28 days after weaning. Piglets drinking milk from anterior teats were heavier at weaning (p < 0.001) and for the first 14 days after weaning (p = 0.104) compared to piglets sucking posterior teats. Data from this study demonstrated that creep feed intake of piglets could qualitatively be assessed using indigo carmine, and that this categorization was related to performance in the immediate post-weaning period.     

The triradiate sucking pharynx in animal phylogeny

Independent sucking/swallowing pharynges, as found in members of at least ten animal phyla, are pharynges that are opened by muscles that are not attached to the outer body wall. Their musculature is derived from either mesoderm or ectoderm, the latter taking the form of a myoepithelium. I review results of previous work on the morphology of independent sucking/swallowing pharynges among invertebrates and provide new information on the ultrastructure of the pharynx of the cyclostome bryozoan Crisia eburnea. The various morphologies of this type of pharynx have been used in some phylogenetic considerations, but only the myoepithelial sucking pharynx with a triradiate lumen was considered significant in analyses of relationships between phyla. However, I argue that this shape is the only one that makes an efficient suction pump, and this, together with different orientations of the myoepithelial pharyngeal pump and its phylogenetic distribution, indicates that the triradiate myoepithelial pharynx has evolved convergently in a number of lineages.     

Teat-seeking or pre-sucking behaviour in newly-born lambs: Possible effects of maternal skin temperature

The possibility that thermal cues play a part in the teat-seeking behaviour of newly-born lambs was investigated. Measurements show that the external surfaces of a lactating ewe vary in temperature, highest readings being obtained from the inguinal cavity at the base of the udder. Experiments show that, before sucking, lambs stay longer in a warm compartment than in a cool one, also that they become more active when their muzzles are placed in contact with a warm smooth surface than they do when placed in contact with a cool smooth surface. The activity evoked resembles that of newlyborn lambs searching for the teat.     

Differential effects of undernutrition during pregnancy on the behaviour of does and their kids at parturition and on the establishment of mutual recognition

We investigated whether undernutrition during the second half of pregnancy impaired the behaviour of does and their kids at parturition and early mutual recognition. Twenty-two control and 22 underfed mixed-breed, multiparous dairy goats were used, together with their respective kids (control, n = 31: nine singles, 16 twins and six triplets; underfed, n = 32: 11 singles, 18 twins and three triplets). Undernutrition involved limiting protein and energy intake at 70% of the nutritional requirements for maintenance and foetal growth from day 70 of pregnancy until birth. The behaviour of mothers and their two first-born kids was observed for 90 min from the birth of each kid. Maternal olfactory recognition of the kid was assessed at 4 h post partum by testing selective nursing behaviour. Non-olfactory recognition was assessed at 8 h in a two-choice test excluding olfactory cues. In kids, preference for the mother was assessed in a two-choice test at either 12 or 24 h post partum. Bodyweight of does and kids were lower in the underfed group up to 2 weeks post partum. At parturition, licking, maternal bleating frequency and latency to nursing did not differ between nutritional groups. Control kids were faster than underfed kids to stand, search for and reach the udder, but underfed kids bleated more and tended to spend more time at the udder. Both control and underfed does accepted their own kid and rejected the alien in the selectivity test at 4 h. In contrast, at 8 h post partum, only control goats showed a significant preference for their own kid in the non-olfactory recognition test. Both control and underfed kids showed a preference for their own mother at 12 and 24 h and undernutrition during pregnancy had little influence on the performance of kids. However, 12 h-old underfed kids tended to be less active than control kids and visited their own mothers less than control kids. There were no significant correlations between the behaviour of the mother or of the kid at parturition and their performance in the discrimination tests. Overall, undernutrition in the second half of pregnancy appears to be more detrimental for the behaviour of the mother than for the kid. Furthermore, it has more impact on the establishment of maternal non-olfactory recognition than on maternal care at parturition or the establishment of maternal selectivity.     

Effectiveness of selected premilking teat-cleaning regimes in reducing teat microbial load on commercial dairy farms

Aims: To determine the effectiveness of premilking teat‐cleaning regimes in reducing the teat microbial load and effect on milk quality. Methods and Results: The effectiveness of several premilking teat‐cleaning regimes in reducing teat microbial load was assessed using 40 cows on each of the four commercial UK dairy farms with herringbone parlours during two sampling periods. In the first experiment, all the treatments reduced teat total viable count (TVC), but there was no significant difference between the hypochlorite wash and dry wipe, iodine dip and dry and alcohol‐medicated wipe or dry wipe alone. In the second experiment, the chlorine wash and dry wipe was significantly more effective in reducing teat TVC than a water wash and dry, chlorine dip and dry or a dry wipe. There was no relationship between cleaning regime and milk TVC, Enterobacteriaceae or Escherichia coli levels. Conclusions: All of the cleaning techniques studied reduced teat microbial load, however, the chlorine wash and dry was the most effective. Significance and Impact of the study: The premilking teat‐cleaning techniques studied reduced the teat microbial load and therefore reduced the potential for milk contamination; however, a wash including an effective disinfectant followed by a dry wipe was the most effective.     

Variability of breast sucking, associated milk transfer and the duration of lactational amenorrhoea.

Quantitative relationships between physical parameters of sucking, milk transfer and the duration of amenorrhoea were examined in normal mother-baby pairs under exclusive breastfeeding. Sucking pressures were recorded twice on the second and once on the fifth month after birth, during complete breastfeeding episodes, by means of a catheter attached to the nipple and connected to a pressure transducer, the signals of which were analysed by computer. Babies were weighed before and after each sucking episode to estimate milk transfer. In the first nursing episode after noon, 2-month-old babies sucked from 140 to > 800 times during 4-15 min from the first breast, obtaining from 20 to > 100 g milk. The physical parameters of sucking and milk transfer exhibited high inter-individual but low intra-individual variabilities. There were significant differences in the physical parameters of sucking and milk transfer efficiency between first and second breast and between the second and fifth months after birth. Milk transfer efficiency was inversely correlated with time occupied by non-sucking pauses > or = 1.5 s, and was directly correlated with mean intersuck intervals in the first breast and with duration of the sucking episode, number of sucks, mean pressure and area under the pressure curve in the second breast. There was no correlation between the physical parameters of sucking and duration of lactational amenorrhoea (n = 62). However, significantly more mothers had amenorrhoea lasting > 180 days among those whose babies spent a longer proportion of the nursing episode in non-sucking pauses > or = 1.5 s. This finding indicates that sensory stimulation of the nipple produced during a nursing episode by stimuli other than sucking itself may have an important role in sustaining lactational amenorrhoea. It is concluded that nursing episodes have a complex structure that allows the development of a breastfeeding phenotype in each mother-baby pair, exhibiting important inter-individual variability. The present analysis does not support the contention that this source of variability accounts for the variability in the duration of lactational amenorrhoea.     

The effect of electrical field strength on activation and development of cloned caprine embryos

The activation procedure used in nuclear transfer (NT) is one of the critical factors affecting the efficiency of animal cloning. The purpose of this study was to compare the effect of two electrical field strengths (EFS) for activation on the developmental competence of caprine NT embryos reconstructed from ear skin fibroblasts of adult Alpine does. The NT embryos were obtained by transfer of the quiescent fibroblasts at the fourth passage into the enucleated metaphase II (M II) oocytes. Four to five hours after electrical fusion, the NT-embryos were activated by EFS either at 1.67 or at 2.33 kV/cm and immediately incubated in 6-DMAP (2 mM) for 4 h. The cleavage rate of the NT-embryos activated with 2.33 kV/cm was greater than that activated with 1.67 kV/cm after in vitro culture for 18 h (65.6% versus 19.6%, p < 0.001). No pregnancy was found in 14 recipient does after transferring 51 NT embryos at 1-2 cell stages activated with 1.67 kV/cm. In contrast, two of the seven recipients were pregnant and gave birth to three kids after transferring 61 NT embryos at 1-2 cell stages activated by 2.33 kV/cm. The birth weights of three cloned kids were within the normal range of Alpine goats. However, one kid died 1h after birth while the remaining two are still healthy. DNA analysis by polymerase chain reaction (single-strand conformation polymorphism, SSCP) confirmed that the three kids were genetically identical to the nuclear donor.     

QTL for the heritable inverted teat defect in pigs

The mothering ability of a sow largely depends on the shape and function of the mammary gland. The aim of this study was to identify QTL for the heritable inverted teat defect, a condition characterized by disturbed development of functional teats. A QTL analysis was conducted in a porcine experimental population based on Duroc and Berlin Miniature pigs (DUMI). The significant QTL were confirmed by linkage analysis in commercial pigs according to the affected sib pair design and refined by family-based association test (FBAT). Nonparametric linkage (NPL) analysis revealed five significant and seven suggestive QTL for the inverted teat defect in the porcine experimental population. In commercial dam lines five significant NPL values were detected. QTL regions in overlapping marker intervals or close proximity in both populations were found on SSC3, SSC4, SSC6, and SSC11. SSC6 revealed QTL in both populations at different positions, indicating the segregation of at least two QTL. The results confirm the previously proposed polygenic inheritance of the inverted teat defect and, for the first time, point to genomic regions harboring relevant genes. The investigation revealed variation of the importance of QTL in the various populations due to either differences in allele frequencies and statistical power or differences in the genetic background that modulates the impact of the liability loci on the expression of the disease. The QTL study enabled us to name a number of plausible positional candidate genes. The correspondence of QTL regions for the inverted teat defect and previously mapped QTL for teat number are in line with the etiologic relationship of these traits.     

Dairy goat kids fed liquid diets in substitution of goat milk and slaughtered at different ages: an economic viability analysis using Monte Carlo techniques

The aim of this study was to analyze the economic viability of producing dairy goat kids fed liquid diets in alternative of goat milk and slaughtered at two different ages. Forty-eight male newborn Saanen and Alpine kids were selected and allocated to four groups using a completely randomized factorial design: goat milk (GM), cow milk (CM), commercial milk replacer (CMR) and fermented cow colostrum (FC). Each group was then divided into two groups: slaughter at 60 and 90 days of age. The animals received Tifton hay and concentrate ad libitum. The values of total costs of liquid and solid feed plus labor, income and average gross margin were calculated. The data were then analyzed using the Monte Carlo techniques with the @Risk 5.5 software, with 1000 iterations of the variables being studied through the model. The kids fed GM and CMR generated negative profitability values when slaughtered at 60 days (US$ −16.4 and US$ −2.17, respectively) and also at 90 days (US$ −30.8 and US$ −0.18, respectively). The risk analysis showed that there is a 98% probability that profitability would be negative when GM is used. In this regard, CM and FC presented low risk when the kids were slaughtered at 60 days (8.5% and 21.2%, respectively) and an even lower risk when animals were slaughtered at 90 days (5.2% and 3.8%, respectively). The kids fed CM and slaughtered at 90 days presented the highest average gross income (US$ 67.88) and also average gross margin (US$ 18.43/animal). For the 60-day rearing regime to be economically viable, the CMR cost should not exceed 11.47% of the animal-selling price. This implies that the replacer cannot cost more than US$ 0.39 and 0.43/kg for the 60- and 90-day feeding regimes, respectively. The sensitivity analysis showed that the variables with the greatest impact on the final model’s results were animal selling price, liquid diet cost, final weight at slaughter and labor. In conclusion, the production of male dairy goat kids can be economically viable when the kids diet consists mainly of either cow milk or fermented colostrum, especially when kids are slaughtered at 90 days of age.     

Strongyloides ratti: reversibility of immune damage to adult worms

Transplantation experiments were conducted to assess the reversibility or irreversibility of the damage sustained by Strongyloides ratti during infections in the rat host. Worms of different ages from primary and secondary infections were recovered from their original hosts and transplanted surgically into naive rats. The size and fecundity of normal (Days 6–11 postinfection) worms were maintained after transfer. Damaged worms from primary infection (Days 22–26) showed complete recovery of size and fecundity within 10 days of transfer; damaged worms from a secondary infection (Days 6–7) also showed functional recovery but to a lesser extent. The ultrastructural changes observed mainly in the intestine of damaged worms from primary infections, prior to their transfer, were, however, only partially ameliorated following transplantation into new naive hosts; there was no complete return to structural normality. On the other hand, second infection worms did show almost complete ultrastructural recovery. The course of a transplanted infection established with either damaged or normal worms was similar to infections established percutaneously. Increase in the size of transplanted infections from 100 to 250 worms per recipient did not alter the dynamics of the host/parasite relationship. There was no evidence of adaptation in S. ratti and damaged worms, when transplanted into naive rats, were as successful as normal worms in protecting the host against a subcutaneous larval infection. The implications of this work on the present understanding of the phenomenon of autoinfection in experimental rodent strongyloidiasis are discussed.     

Description and validation of a novel technique to study the bacterial flora of the teat duct of ewes

We describe a new technique that may be used for studying the bacterial flora of the teat duct in live ewes, and we present evidence regarding its accuracy, safety and repeatability. A sterile, plastic, 20 G catheter is used for sampling. The catheter stylet is taken out and the plastic catheter cut with a sterile blade to a length of 2 mm. In order to ensure accurate and consistent cutting of the catheter at the desired length, a sterilized ruler is placed beside the catheter. The whole procedure is carried out under aseptic conditions, on sterilized surgical screens. Before sampling, a thorough disinfection with povidone iodine scrub solution of the teat apex and the lower (1 cm) part of the teat skin is carried out. The catheter is held by the investigator from the cannula hub; then, it is inserted into the teat, rolled around the internal teat wall, in order to sample the mucosa and then withdrawn. Material collected on the tip of the catheter is plated onto bacteriological media. The sensitivity of the technique compared to a method that detects the bacterial flora of the teat after slaughter of the animals (scratching of the teat mucosa by means of a scalpel blade) was 99.1% for field samples and 100% for experimental samples; specificity of the technique was 90.7 and 100%, respectively, kappa coefficient between results of the two methods was 0.9045. The safety of the technique was assessed in an investigation, where ewes were repeatedly (eight times) sampled by means of this technique, throughout their lactation; in no case was clinical or subclinical mastitis recorded. Finally, the repeatability of the method was assessed in 37 paired samples, obtained 30–40 min apart; a 100% match was recorded between bacteriological results of the two samplings of each pair. We conclude that the method can be useful in research studies, in order to obtain information regarding bacterial ecology and dynamics inside the teat of ewes.