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Biomedical subjects

I Kyriazakis

Publications and source records attributed to I Kyriazakis.

At least 19 recordsLinked to original sources
PubMed2026

Genomic characterisation of Enterococcus cecorum isolated from broiler chickens in the United Kingdom.

Enterococcus cecorum is an important poultry pathogen associated with lameness and increased mortality, leading to major welfare and economic impacts. Treatment is often challenging because disease is frequently detected late and the organism can localise in bone and joints, limiting antimicrobial efficacy. Presence of antimicrobial resistance (AMR) genes may further complicate treatment. Despite increasing global genomic research, only one recent study has investigated the phylogeny of E. cecorum from conventional UK broiler farms, using limited samples and a restricted time frame. In this study, 283 E. cecorum isolates were analysed, including 158 from the United Kingdom and 125 global non‑UK isolates. UK isolates comprised 123 archived by the Animal and Plant Health Agency (APHA) between 2003 and 2022, predominantly from clinical outbreaks with increased welfare culling and mortality, and 35 isolates from a UK study including clinical and environmental samples. Genome sequencing was used to assess phylogeny, AMR determinants and virulence factors (VFs). Single nucleotide polymorphism phylogenetic analysis identified eight major UK lineages with limited intra‑lineage diversity, indicating that UK isolates were genetically distinct from non‑UK populations. Using a 60‑SNP threshold, APHA isolates formed 18 subclusters, consistent with long‑term persistence and recurrent farm transmission, while multiple subclusters detected on some farms suggested repeated introductions. UK isolates carried fewer AMR genes than non‑UK isolates, with erm(B), lnu(C), tet(M) and tet(L) most prevalent. Screening of VF genes identified nine genes present in all isolates, with the remainder variably distributed. A subset of 60 UK isolates was examined for 13 previously described virulence‑associated genes, with phylogenetic clustering indicating associations between gene presence or absence and clinical status or mortality classification. The capsular polysaccharide gene cpsO was assessed in this subset and most non‑clinical or environmental isolates were cpsO‑negative, although several isolates from high‑mortality outbreaks also lacked this gene. Overall, this study provides insight into the phylogeny, AMR profiles and virulence gene diversity of E. cecorum within the UK broiler sector, supporting targeted surveillance and investigation of pathogenic mechanisms.

Antimicrobial resistance↗
PubMed2001

The use of mixed distribution models to determine bout criteria for analysis of animal behaviour.

Feeding behaviour consists of feeding events, separated by non-feeding intervals. Feeding events are often clustered into bouts, which may be called meals. Grouping feeding events into meals requires the determination of a bout or meal criterion, that is, the longest interval accepted as part of a meal. Tolkamp & Kyriazakis (1999a) proposed a three-Gaussian model to estimate meal criteria. The three Gaussians each described the frequency distribution of the log(e)-transformed lengths of a population of intervals. These populations were thought to be: (1) short intervals within meals; (2) intervals within meals during which animals drink; (3) intervals between meals. This model predicted that the probability of an animal starting a meal would first increase, and then decrease with time since the last meal. This contrasts with expectations based on the satiety concept, which predicts that the probability of an animal starting a meal will increase with time since the last meal. This discrepancy is related to the symmetrical nature of the Gaussian distribution. Alternatively, the two-parameter Weibull distribution can take a skewed form and perhaps is more suitable to describe the different populations of intervals. In this study, models consisting of combinations of Gaussian and Weibull distributions were examined for their suitability to describe the observed feeding behaviour of cows. Weibulls did not improve the description of the populations of within-meal intervals, compared to Gaussians. However, the Weibull distribution was found to describe the between-meal population of intervals statistically better than the Gaussian. Additionally, this inclusion of a Weibull, as opposed to a Gaussian, resulted in predictions that were in better agreement with the satiety concept over the entire range of interval lengths observed. A model based on Gaussians to describe the within-meal populations of intervals and a Weibull to describe the population of between-meal intervals is, therefore, proposed. This model leads to biologically more satisfactory estimates of bout criteria than previous models and is likely to be applicable both across species and behaviours.

Animals↗
PubMed2001

Direct anthelmintic effects of condensed tannins towards different gastrointestinal nematodes of sheep: in vitro and in vivo studies.

In vitro and in vivo studies were conducted to determine possible direct anthelmintic effects of condensed tannins towards different ovine gastrointestinal nematodes. A larval development/viability assay was used to investigate the effect of a condensed tannin extract (Quebracho) towards larvae of Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus vitrinus. The development to infective larvae and their viability was assessed in all three species and LD 50 values were calculated. The presence of Quebracho extract in the cultures decreased the viability of L3 in all species; the LD 50 were not significantly different for the different species. Forty-eight sheep were allocated to one of eight groups and were infected with a single dose of either 4000 L3 H. contortus (groups 1 and 2) or 5000 L3 T. colubriformis and 5000 L3 Nematodirus battus simultaneously (groups 3-6) or 10,000 L3 of T. circumcincta (groups 7 and 8). From day 28 until day 31 of the experiment, sheep infected with the intestinal species were drenched with Quebracho extract at 4, 8 or 16% w/w of food intake, or remained as undrenched controls; sheep infected with the abomasal species were either drenched with Quebracho extract at 8% w/w of food intake or remained as undrenched controls. All sheep were slaughtered 4 days after the end of the drenching period. Sheep infected with the intestinal species and drenched with 16% w/w Quebracho had lower FEC compared to sheep drenched with 8% w/w (P<0.05), which in turn were lower than in sheep either drenched with 4% Quebracho or which remained undrenched (P<0.05). The lowest intestinal worm burden was recovered from sheep drenched with 8% w/w Quebracho extract (P<0.05). The administration of Quebracho extract at 8% of food intake for 3 days did not affect FEC or worm burdens in sheep infected with the abomasal species compared to controls.

Animal Feed↗
PubMed2001

Does previous protein feeding affect the response of sheep towards foods that differ in their rumen availability, but not content, of nitrogen?

The objective of the experiment was threefold: (1) to test whether an 'unlearned appetite' for dietary protein exists in sheep, (2) whether such an appetite and subsequent diet selection depend on the degree of previous protein deprivation, and (3) whether the N-source in the foods offered as choice influences diet selection. Differences in protein deprivation were achieved by feeding sheep with food either with high (HP) or low (LP) protein. Sheep were fed on Food LP, either for the same period of time as sheep on Food HP or until they reached the same live-weight (LW) as sheep on Food HP. Following the feeding regimes that induced differences in animal state, sheep were given a choice between a novel low-protein food (T) or Food T supplemented with isonitrogenous amounts with one of three nitrogen sources: urea (U), casein (C), or formaldehyde-treated casein (TFC). Diet selection measured in the short-term or over the first few days did not provide any evidence in support of an unlearned appetite for protein by sheep of different states. In fact, diet selection by all animals was characterized by an avoidance of the foods supplemented with the three nitrogen sources. This avoidance was strongest for the food supplemented with formaldehyde-treated casein. Selection of considerable amounts of supplemented foods was gradual and consistent only after animals gained experience of them, i.e. were allowed to consume a single supplemented food for a period of 7 days. Following this period, animals that had previously consumed Food LP for the same period of time as animals on Food HP selected a higher proportion of the supplemented food than the other sheep. The results support the view that there is no unlearned appetite for protein in sheep, and that control over diet selection is learned.

Animals↗
PubMed2001

Influence of host nutrition on the development and consequences of nematode parasitism in ruminants.

Control of gastrointestinal nematodes of ruminants is based largely on use of anthelmintics combined, where practical, with pasture management. The increasing prevalence of resistance to anthelmintics has led to the search for alternative sustainable control strategies. Here, we consider how nutrition, as a short-term alternative, can influence the host--parasite relationship in ruminants, using gastrointestinal nematode infections of sheep as the model system. Nutrition can affect the ability of the host to cope with the consequences of parasitism and to contain and eventually to overcome parasitism. It can also affect the parasite population through the intake of antiparasitic compounds.

Animal Feed↗
PubMed2001

The expression of immunity to Teladorsagia circumcincta in ewes and its relationship to protein nutrition depend on body protein reserves.

We hypothesized that expression of immunity to gastrointestinal nematodes and its relationship with dietary metabolizable protein (MP) supply in ewes depended on body protein--but not on body fat reserves. Twin-bearing ewes were trickle infected with Teladorsagia circumcincta. Three mid-pregnancy feeding treatments were used, calculated to maintain body reserves (HH), maintain body protein- and lose body fat reserves (HL), or lose body reserves (LL), and followed by 2 isoenergetic, periparturient feeding treatments, calculated to provide either scarce (LP) or adequate (HP) amounts of MP. At the end of the mid-pregnancy feeding treatment, HL- and LL-ewes had a smaller backfat depth (approximately body fat reserves) than HH-ewes, and LL-ewes had a smaller muscle depth (approximately body protein reserves) and higher faecal egg counts (FEC) than HH- and HL-ewes. Overall, LL-ewes had higher periparturient FEC than HH- and HL-ewes, and LP-ewes had higher periparturient FEC than HP-ewes. However, LL-ewes offered the LP feed had higher periparturient FEC than ewes on any of the other combinations of feeding treatments. Feeding treatments affected plasma pepsinogen but not plasma IgA. The results support the view that body protein- but not body fat reserves may overcome consequences of dietary MP scarcity on periparturient breakdown of immunity to gastrointestinal nematodes.

Animal Feed↗
PubMed2001

The effects of condensed tannins supplementation of foods with different protein content on parasitism, food intake and performance of sheep infected with Trichostrongylus colubriformis.

The aims of the present study were to investigate (1), the potential anthelmintic properties and (2), the nutritional consequences of commercially available condensed tannins on parasitised sheep fed, ad libitum, either a high- or a low-protein food. For this purpose, forty-eight previously parasite-naïve sheep (n 12) were infected with 2000 Trichostrongylus colubriformis larvae/d for a 67-d experimental period. Two experimental foods were made: a low (L), formulated to be inadequate in meeting the requirements of growing sheep for metabolisable protein (MP), and based on wheat, citrus pulp, and oatfeed; a high (H), expected to be above the requirements of growing sheep for MP, based on similar ingredients but supplemented with protected soyabean meal. Two additional foods were made by adding 60 g Quebracho (a condensed tannins (CT) extract)/kg fresh matter to foods L and H (foods LQ and HQ respectively). This level of Quebracho supplementation has been previously shown to reduce the level of parasitism in restrictedly fed, parasitised sheep. The experiment was divided into two periods: period 1 (P1, day 1-38) and period 2 (P2, day 39-67), each one associated with different phases of an intestinal parasitic infection. Six sheep from each group were slaughtered at the end of P1, and the remaining sheep were slaughtered at the end of P2 (day 67). Although faecal egg counts (FEC; number of parasite eggs/g faeces) and total egg output were reduced in sheep offered the supplemented foods during P1 (P<0.05), worm burdens on day 38 were unaltered. Neither Quebracho supplementation nor food protein content during P2 affected FEC and worm burdens. Food intake and performance were higher in sheep offered food HQ compared with sheep offered food H (P<0.05); no differences were observed in sheep offered foods LQ and L throughout the experiment. The previously shown anthelmintic properties of CT were not observed following ad libitum intake of either low- or high-protein foods supplemented with Quebracho extract. Higher levels of CT supplementation may be required to reduce parasitism and consequently improve the performance of parasitised sheep, when fed ad libitum. Supplementation with CT conferred advantages on the performance of parasitised sheep on a high- but not on a low-protein food.

Animal Feed↗
PubMed2001

Consequences of genetic change in farm animals on food intake and feeding behaviour.

Selection in commercial populations on aspects of output, such as for growth rate in poultry. against fatness and for growth rate in pigs, and for milk yield in cows, has had very barge effects on such outputs over the past 50 years. Partly because of the cost of recording intake, there has been little or no selection for food intake or feeding behaviour. In order to predict the effects of such past, and future, selection on intake it is necessary to have some suitable theoretical framework. Intake needs to be predicted in order to make rational feeding and environmental decisions. The idea that an animal will eat 'to meet its requirements' has proved useful and continues to be fruitful. An important part of the idea is that the animal (genotype) can be described in a way that is sufficient for the accurate prediction of its outputs over time. Such descriptions can be combined with a set of nutritional constants to calculate requirements. There appears to have been no change in the nutritional constants under selection for output. Under such selection it is simplest to assume that changes in intake follow from the changes in output rates, so that intake changes become entirely predictable. It is suggested that other ways that have been proposed for predicting intake cannot be successful in predicting the effects of selection. Feeding behaviour is seen as being the means that the animal uses to attain its intake rather than being the means by which that intake can be predicted. Thus, the organisation of feeding behaviour can be used to predict neither intake nor the effects of selection on it.

Animals↗
PubMed2001

Nutrient partitioning between reproductive and immune functions in animals.

The physiological processes that underlie the reproductive cycle impose considerable metabolisable protein (MP) demands on a female, especially during the periparturient period. When MP supply falls short of MP demand (i.e. MP becomes scarce), certain, if not all, bodily functions are expected to be penalised. It has been proposed that partitioning of scarce MP is prioritised to reproductive rather than to immune functions. In other words, at times of MP scarcity, the penalty on expression of immunity would be expected to be greater than that on reproduction. This hypothesis forms a nutritional basis for the occurrence of periparturient breakdown of immunity to parasites (BIP), which can be observed in many host-parasite systems. In the present review we explore this nutritional basis, using periparturient sheep infected with the abomasal nematode Teladorsagia circumcincta as an example, and attempt to quantify its occurrence. Evidence supporting the nutritional basis of periparturient BIP is reviewed, covering experiments in which nutrient supply (from both exogenous and endogenous sources) and/or nutrient demand were manipulated. Quantitatively, MP requirements for expression of immunity to T. circumcincta were estimated to be about 1 g/kg metabolic body weight (body weight 0.75) per d, approximately 5% of the maximum MP requirements of periparturient sheep. The major component of this requirement was assumed to be for replenishing irreversible plasma protein losses into the gastrointestinal tract. Although confirmation of this estimate is required, such estimates may be used to improve the known MP requirements of periparturient animals, enabling the extent and the consequences of periparturient BIP to be minimised.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Can an increased intake of metabolizable protein affect the periparturient relaxation in immunity against teladorsagia circumcincta in sheep?

Within the overall hypothesis that the periparturient relaxation of immunity (PPRI) to gastrointestinal parasites has a nutritional basis, we studied whether an increased intake of metabolizable protein (MP) could affect the expression of immunity to Teladorsagia (Ostertagia) circumcincta of twin-bearing and -rearing Greyface ewes. Two sets of iso-energetic diets were formulated to provide either 85% (L-) or 130% (H-) of the MP requirements during the last 6 weeks of pregnancy (-P) and the first 6 weeks of lactation (-L). Thirty ewes were allocated to LP or HP. Six ewes of each group were slaughtered after lambing (S(0)); the remaining 24 ewes of each group were allocated to either LL or HL, thus creating four treatment combinations during lactation (LP/LL, LP/HL, HP/LL and HP/HL; n=12). Six ewes of each treatment combination were slaughtered at Week 3 (S(3)) or at Week 6 (S(6)) in lactation. The HP ewes were heavier at lambing, produced heavier lambs, had lower faecal egg counts (FECs), a lower concentration of plasma pepsinogen, a higher concentration of plasma albumin during late pregnancy and more abomasal globule leukocytes (GLs) but similar worm burdens at S(0) compared to the LP ewes. The LP/HL and HP/HL ewes had a higher calculated milk production than the LP/LL and HP/LL ewes. FECs increased for each treatment combination during the first 3 weeks of lactation. This increase concurred with fewer abomasal GLs at S(3) compared to S(0). The LP/HL and HP/HL ewes had a higher proportion of immature worms and more abomasal GLs than the LP/LL and HP/LL ewes at S(6). The FECs continued to increase during the second 3 weeks of lactation for the LP/LL ewes only, which concurred with an elevated plasma pepsinogen concentration and an absence of abomasal GLs at S(6). The plasma pepsinogen concentration decreased rapidly for the LP/HL ewes during lactation. We conclude that an increased intake of MP could enhance the expression of immunity to T. circumcincta of twin-bearing and -rearing Greyface ewes.

Animal Feed↗
PubMed2000

Effects of short-term exposure to condensed tannins on adult Trichostrongylus colubriformis.

Twelve parasite-naive sheep were used to study the possible direct anthelmintic effect of a condensed tannin extract (quebracho) on the population and fecundity of the intestinal nematode Trichostrongylus colubriformis. The sheep were infected with a single dose of 20,000 L3 of T colubriformis. Twenty-eight days later, six of them were drenched daily for a week with quebracho extract at 8 per cent by weight of their food intake. All lambs were then slaughtered, and their small intestines removed to estimate the worm burdens and the numbers of eggs in utero. Two days after the first drench with tannin extract the faecal egg counts of the treated sheep were approximately 50 per cent of those of the control sheep (P<0.01), but there was no further reduction with continued drenching. In the treated sheep the worm burdens and number of eggs per gram faeces per worm were reduced by 30 per cent compared with the controls (P<0.05), but the sex ratios, the number of eggs in utero and length of the worms were not affected by drenching with tannin.

Administration, Topical↗
PubMed2000

Variation between individuals and the consequences for diet selection by groups of animals.

We describe a model to predict the diet selection of a population of animals, based on simple assumptions about the characteristics of the individuals in a population, including the variation between them. Individuals are characterized by three parameters with biological relevance; a nutrient (protein) requirement, an ability to discriminate between foods of different protein contents and a need to collect information about both foods. Each animal selects perfectly a diet that avoids both a deficiency and an excess of protein, where this is possible. To construct the population two further assumptions are made. The first is that the values of each parameter are drawn from uncorrelated normal distributions subject to the values being logically possible. The second is that, for different mean values for the population, the standard deviation is directly proportional to the mean so that the coefficient of variation is independent of the mean. The model was used to predict the outcomes of six hypothetical experiments, using 100 individuals on each treatment, where the values of the three parameters were systematically varied. In the experiments one food was always of low protein content while the protein content of the other was the treatment variable. The quantitative effects of varying either the mean value of the parameters, or their variation, on both the mean composition of the diet selected, and on its variation, were not possible to predict without using the model. The shape of the population response was different to that for any individual. Extensions to the model may be able to increase its relevance to practical issues of diet selection. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Consequences of long-term feeding with condensed tannins on sheep parasitised with Trichostrongylus colubriformis.

Naive wethers were used to investigate the long-term effects of dietary condensed tannins from Quebracho extract, during an intestinal parasitic infection in sheep. Sheep were allocated to eight groups; seven groups were daily infected with 3000 L(3) Trichostrongylus colubriformis for 10 weeks and the eighth group was the uninfected control. The 10-week experiment was divided into two periods; Period 1 (P(1), week 1-5) corresponded to high worm establishment and acquisition of immunity, whereas Period 2 (P(2), week 6-10) to the established worm population and expression of host immunity. Three experimental foods with similar composition were formulated: Q0, Q3 and Q6. Their difference was in the content of Quebracho extract which was 0, 30 and 60 g per kg fresh matter, respectively. All foods were offered at an allowance of 3.5% of sheep liveweight. During P(1), parasitised sheep were offered one of the three experimental foods and during P(2) they either remained on the same food or changed food according to the design (P(1)-P(2)): Q0-Q0, Q0-Q3, Q0-Q6, Q3-Q0, Q3-Q3, Q6-Q0, Q6-Q6. Control sheep were offered the allowance of Q0 throughout. Sheep that consumed Q3 and Q6 reduced their faecal egg counts (FEC) compared to sheep offered Q0, during both periods (P<0.05). No differences were observed in the FEC between sheep offered Q3 and Q6. The changeover from Q0 in P(1) to either Q3 or Q6 during P(2), was accompanied by a reduction in FEC (P<0.05), whereas an increase in FEC was observed when food changed from Q3 or Q6 to Q0 (P<0.05). Worm burdens and fecundity at the end of the experiment were reduced in sheep offered foods Q3 and Q6 compared to sheep offered Q0. A significant decrease in liveweight gain and in food conversion efficiency of parasitised sheep offered Q3 and Q6 compared to sheep offered Q0, was observed in P(1) (P<0.05) but not in P(2). By the end of the experiment control sheep had achieved higher liveweight and converted food more efficiently than parasitised sheep (P<0.05). In conclusion, evidence for a long-term effect of Quebracho extract, during both the initial establishment and on the established T. colubriformis population in sheep, was provided by the present study. It is suggested that the effect observed was a direct anthelmintic effect of the condensed tannins included in sheep diets.

Animal Feed↗
PubMed2000

Temporal effects of protein nutrition on the growth and immunity of lambs infected with Trichostrongylus colubriformis.

The aim of this research was to determine whether metabolisable protein supply during the early period of infection with Trichostrongylus colubriformis influenced resilience and the later stages in the development and magnitude of host resistance in previously nematode-naïve lambs. Eighty TexelxGreyface lambs were fed pelleted feeds calculated to provide grossly different amounts of metabolisable protein. Sixty of the lambs received a trickle infection of T. colubriformis and 20 lambs were kept as uninfected controls. There were four initial groups, namely infected or uninfected and fed either a moderate or a high protein feed. After 5weeks of infection, a further four groups were established by changing the feed of half of the animals fed the moderate protein feed to the high protein feed and of half of the animals fed high protein to the moderate protein feed. Live weight gain and feed conversion ratio were greatest for lambs fed the high protein feed and were reduced by infection. Faecal egg counts, worm burdens and per capita fecundity of adult female nematodes were unaffected by changes to metabolisable protein supply. Decreasing metabolisable protein supply following 5weeks of infection reduced live weight gain without any effect on resistance to T. colubriformis. Haematological variables, indicative of improved resistance, were also largely unaffected by metabolisable protein supply. It is concluded that the requirements of immune function probably had priority over those of growth and that the metabolisable protein supply provided by the moderate protein feed was sufficient to account for the requirements for the expression of immunity. It is probable that the potential for metabolisable protein supply to enhance resistance to infection from T. colubriformis is dependent on the levels and magnitude (i.e. in relation to maintenance requirements) of metabolisable protein supply being compared and the demand of other competing physiological functions.

Animals↗
PubMed2000

Analysis of the feeding behavior of pigs using different models.

Short-term feeding behavior is conventionally analysed using random process models. The assumption underlying these models have recently been questioned and this article describes the application of both random, and more biologically based, models to the feeding behavior of pigs. Feeder visits of 16 growing pigs, housed individually from 17 to 52 kg live weight, were recorded electronically over a continuous period of 35 days. Daily food intake increased linearly with time, but there was considerable individuality in the degree of order. Pigs made between 18.8 and 80.3 (mean 47.9) daily visits to the feeder. Intervals between visits could be described by two log-normal distributions. Two Gaussian density functions were fitted to the distribution of the log-transformed intervals. For the combined data from all animals the within- and between-meal intervals were 11.2 s and 100.1 min, respectively. A model with three Gaussian functions gave an improved fit to the interval distribution. The within and between meal intervals were then estimated to be 4.2 s and 93.9 min, respectively. The middle distribution of intervals ranged from 0.5 to 38.1 min. The intervals were also described by random process models; again, a three-process model gave an improved fit compared to a two-process model. The mean estimated number of meals per day from the three Gaussian model was 14.3, and from the three process random model, 16.3. A biological interpretation of the three types of interval suggests that: (1) pigs eat in meals separated by long intervals; (2) meals consist of clusters of eating bouts separated by shorter intervals, sometimes associated with drinking; (3) within each eating bout short intervals occur as pigs constantly move in and out of the feeder. It remains unclear what underlies the observed patterns of eating.

Animals↗
PubMed2000

The biologically relevant unit for the analysis of short-term feeding behavior of dairy cows.

To determine whether visits or meals are the most biologically relevant unit of short-term feeding behavior, we analyzed 209,025 records of visits to feeders by 37 cows. Two feeds were used that differed in protein content. Cows were divided into control groups for the low and high protein feeds and a choice group that had access to both. Daily number of visits and intake per visit were very variable. Cows fed low protein feed had lowest daily intakes, but single-visit characteristics were poorly correlated with daily intake. The probability of cows ending a visit did not change greatly with visit length. Log-normal models were used to estimate individual meal criteria (44.7+/-2.1 min), and visits were grouped into meals. Meal duration (36.9+/-1.3 min) and daily number of meals (6.1+/-0.1) were not affected by treatment. Feeding rate and intake per meal were lowest for cows fed low protein feed. Meal size decreased systematically during the day. The probability of cows ending and starting a meal increased with meal length and interval between meals, as predicted by the satiety concept. Meals are, therefore, a biologically relevant unit of short-term feeding behavior and visits are not.

Animal Feed↗
PubMed1999

Nutrition-parasite interaction.

The interactions between host nutrition and parasitism in ruminants are viewed within a framework that accounts for the allocation of scarce nutrient resources, such as energy and protein, between the various competing body functions of the host. These include functions that are the direct result of parasitism. Since it is proposed that the host gives priority to the reversal of the pathophysiological consequences of parasitism over other body functions, it is to be expected that improved nutrition will always lead to improved resilience. On the other hand, it is proposed that the function of growth, pregnancy and lactation are prioritised over the expression of immunity. Thus, improved nutrition may affect the degree of expression of immunity during these phases. The framework is useful at highlighting areas of future research on host/parasite/nutrition interactions. Its suggestions can account for the observations of the periparturient relaxation of immunity in reproducing females, as well as the reduction in worm burden in small ruminants supplemented with additional protein. Although developed for gastrointestinal nematodes in ruminants, the concepts of the framework should be applicable to the interactions of nutrition in other parasitic diseases.

Animal Nutritional Physiological Phenomena↗