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.
Kahn
L P
LP
Animal Nutrition and Health Department, Animal Biology Division, Scottish Agricultural College, West Mains Rd, Edinburgh, UK. lkahn2@metz.une.edu.au
Kyriazakis
I
I
Jackson
F
F
Coop
R L
RL
D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000097:blood; D004044:Dietary Proteins / Q000494:pharmacology*; D004435:Eating; D004804:Eosinophils; D005243:Feces / Q000469:parasitology; D005260:Female; D007958:Leukocyte Count / Q000662:veterinary; D010270:Parasite Egg Count / Q000662:veterinary; D010758:Phosphorus / Q000097:blood; D012709:Serum Albumin / Q000378:metabolism; D012756:Sheep / Q000254:growth & development* / Q000276:immunology* / Q000469:parasitology; D012757:Sheep Diseases / Q000276:immunology / Q000503:physiopathology*; D014253:Trichostrongylosis / Q000276:immunology / Q000503:physiopathology / Q000662:veterinary*; D014254:Trichostrongylus / Q000276:immunology / Q000502:physiology; D014508:Urea / Q000097:blood; D014935:Wool / Q000254:growth & development
D004044:Dietary Proteins; D012709:Serum Albumin; D010758:Phosphorus; D014508:Urea; D002118:Calcium