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Biomedical subjects

I Kyriazakis

Publications and source records attributed to I Kyriazakis.

7 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↗
PubMed1992

The growth of mammals following a period of nutritional limitation.

A theory of predicting the growth of an animal following a period of nutritional limitation is proposed here. The theory consists of the following three propositions. Proposition 1: there is a scale of size, such that the growth rate following a period of nutritional limitation is that of normal animals at the same size. Proposition 2: any abnormalities in body composition at the end of the period of limitation will be corrected over time. Proposition 3: the rates at which abnormalities in body composition at the end of the period of limiting conditions are corrected, are always set by the conditions of rehabilitation. The propositions are connected with three other problems viz normal growth, growth under some limitation and the conditions needed by an animal to perform at its potential. These problems are dealt here by: (i) using a simple description of normal growth, (ii) considering the limitation by its effects rather by attempting to predict the effects of a given limitation, and (iii) using simple assumptions about protein and energy scales and requirements. The predictions of the theory are compared with experimental data, and a good qualitative agreement is found. Important conclusions from the theory are: (a) that it is essential to measure as fully as may be the state of the animal at the end of the period of limitation and to compare it with the state of normal animals and (b) that careful attention needs to be given to the choice and the description of the treatment, or preferably treatments, during the rehabilitation period.

Animals↗
PubMed1992

Selection of a diet by growing pigs given choices between foods differing in contents of protein and rapeseed meal.

The objective of the experiment was to test whether the rules that appear to underlie diet selection by pigs given choices between two foods of different crude protein (CP) content, persist when a rapeseed meal with possible goitrogenic effects is included in one or both foods. Forty-four pigs were given access to one food, or to two foods as a choice, from 12-30 kg liveweight. The foods were the combinations of two levels of CP (140 and 300 g CP/kg food) and two levels of inclusion (0 and 180 g/kg food) of a rapeseed meal, which resulted in foods L, H, LR, HR; in addition the equal parts mixture of foods L and H was also made (food M). The treatments were: access to a pair of foods as a choice, pairs LH, LR, H, LHR and LRHR (n = 6 per treatment) or access to a single food L, LR, M, H and HR (n = 4 per treatment). The inclusion of the rapeseed meal did not significantly affect the rates of food intake and liveweight gain of the pigs given access to one food. Pigs given a choice between a rapeseed-based food and another one (pairs LRH and LHR), showed a significant preference for the food without it. The rejection of the foods with rapeseed meal was such that it overpowered the physiological need of the pig to select a diet that would meet its CP requirement. When the two foods differed only in CP content (pairs LH and LRHR) pigs were able to select a diet whose composition changed systematically as they grew, and supported rapid growth. The diet selection of the choice-fed pigs is consistent with the idea that pigs, given a choice between a potentially harmful food and a non-harmful one, will favour the latter irrespective of its nutritional properties, only if it is assumed that the inclusion of rapeseed meal had a detrimental effect on the single fed pigs, which could not be seen in their performance as measured by the rates of food intake and liveweight gain.

Animals↗
PubMed1992

The effects of varying protein and energy intakes on the growth and body composition of pigs. 1. The effects of energy intake at constant, high protein intake.

The objective of the present experiment was to define the form of the relationship between varying levels of energy intake at constant, high protein intake and the performance of young pigs. By doing so it was expected that we could distinguish between four models that predict the pig's responses to its diet as rates of protein and lipid retention. Forty young pigs were assigned at 12 kg live weight either to an initial slaughter group (n 8) or to one of four allowances of starch intake at a constant intake of a high-protein feed (with 345 g crude protein (nitrogen x 6.25)/kg food). Half the pigs were killed after 4 weeks and half after 8 weeks on the treatments; at each slaughter point on each treatment half the pigs were entire males and half were females. Increasing the intake of starch (energy) resulted in significant increases in the rates of live weight, empty-body, protein and lipid gains of pigs slaughtered at both stages. There was no minimum positive lipid:protein ratio in the gain of the pigs. Male pigs deposited more protein and less lipid than females but this effect of sex on protein and lipid retention was seen only on the two highest allowances of starch intake. The calculated efficiency of protein utilization increased with increasing starch intake up to a maximum of 0.81, when probably the energy:protein in the diet became non-limiting. The results led to the rejection of two of the models that predict the rates of protein and lipid retention as responses to protein and energy intake, but the two remaining models could not be rejected, at least qualitatively.

Animals↗
PubMed1992

The effects of varying protein and energy intakes on the growth and body composition of pigs. 2. The effects of varying both energy and protein intake.

The objective of the experiment was to define the form of the relationship between varying levels of protein and energy intake and the performance of young pigs. Forty-four young-pigs were assigned at 12 kg live weight for 6 weeks either to an initial slaughter group (n 8) or to one of the nine feeding treatments (n 4); three allowances of a high-protein food with 355 g crude protein (nitrogen x 6.25; CP)/kg (P1, P2, P3) at three levels of feeding (L, M and H). Each feeding level was met by supplementing the allowance of feed P with the appropriate amount of starch and each treatment had two males and two females. The rate of protein deposition was not affected by feeding level at the two lowest allowances of basal feed P (P1 and P2), but it increased with increasing the feeding level for the pigs on treatment P3. Males deposited more protein than females, but this effect was more pronounced with treatment P3. The rate of lipid deposition increased with each increase in the level of feeding and decreased with increasing the allowance of feed P. The calculated efficiency of protein utilization (ep) was expressed as a function of the energy:protein ratio in the feed (MJ metabolizable energy/kg digestible CP). The best model to describe the relationship was a linear-plateau model, with the maximum value for ep of 0.814 at 73 MJ/kg. This relationship provided the basis of a model that could predict the response of a growing pig to its diet as rates of protein and lipid retention.

Animals↗
PubMed1991

The ability of pigs to control their protein intake when fed in three different ways.

The ability of pigs to control their protein intake was tested in three different ways. When pigs were offered access to single feeds of different protein contents, at a constant liveweight of 20 kg, they increased their daily feed intake as the protein content of their feed was decreased (long-term protein intake regulation). When the protein content of their feed was altered daily, pigs consumed consistently higher amounts of feed when they had access to a low protein feed rather than to a high protein one (short-term protein intake regulation). When, finally, they were given a choice between two feeds of different protein contents, pigs selected a diet that met their protein requirements (as judged by their growth rates and feed efficiencies) and avoided excess of protein intake, but only if they had had previous experience of both feeds. It is suggested that pigs first need to learn about the feeds that are subsequently offered as a choice, before they can make correct dietary choices.

Animal Feed↗