Previous research has shown that even small numbers of lung and gastro-intestinal (GI) nematodes cause sub-clinical infections during autumn and can reduce voluntary feed intake (VFI) and liveweight gain (LWG) post-weaning in farmed deer. However, little is known about the effect of parasitism on growth of young farmed deer prior to weaning (summer and early autumn). At present, the control of deer parasites is largely by anthelmintic treatment. Alternatively, chicory sown as a pure sward has been shown to reduce parasitism and increase post-weaning growth of deer compared with perennial ryegrass-based pasture, although, neither forage plantain nor the inclusion of chicory in a pasture mix have yet been evaluated in this context. In addition, it has been suggested that to achieve a high pregnancy rate early in the mating season, deer calves should be weaned prior to mating to optimise nutrition and body condition of the hinds. At present there is no adequate evidence in the published literature to justify this. Two experiments were conducted in 2005 and 2006 respectively. The first experiment investigated the impact of early or late pre-rut weaning, with and without anthelmintic treatment, on parasitism and growth (LWG g/day) of deer calves during summer and early autumn. Weaning date effects on hind reproductive parameters were also investigated. The second experiment was a preliminary investigation to compare the effect of grazing permanent perennial ryegrass pasture (Lolium perenne) with chicory (Cichorium intybus) narrow-leaved plantain (Plantago lanceolata) and pasture mixes based on short-rotation tetraploid ryegrass (TSR-mix; nil endophyte) or long-rotation tetraploid ryegrass (TLR-mix; low endophyte), with both mixes sown with the same clover (white and red) and chicory, on post-weaning growth and endoparasitism of weaned farmed red deer calves in autumn. In 2005, seventy-six deer calves were randomly allocated in a 2x2 factorial design, involving sex, genotype, weaning date (February 17 or March 17), treatment with either topical moxidectin (0.5mg/kg) on January 14 and February 25 or no anthelmintic treatment. Liveweight gain, faecal gastrointestinal egg counts (FEC) and lungworm larval counts (FLC), haematological parameters and serum proteins concentrations (i.e., total protein, albumin and globulin) of calves were measured. Mixed-age adult hinds (64) were used to investigate the effect of weaning date on internal parasitism, conception date and pregnancy rate determined by ultrasound scanning. These hinds were not given anthelmintic treatment, but FLC and FEC were determined on January 12, February 17, March 17, March 31 and May 4. All deer rotationally grazed permanent perennial ryegrass-based pasture (Lolium perenne) together until weaning at which point calves were removed to separate but similar pasture. Calves weaned in March had a higher LWG to March 31 than those weaned in February (P<0.0001). Faecal larval count in treated calves was zero, but FEC remained similar to the untreated control calves, regardless of when they had been treated (average 136 epg, range 0-600 epg in mid February and average 92, range 0-350 epg at the end of March). Treated calves had higher serum albumin, and lower serum globulin concentrations than the untreated control group (albumin, 36.2 ± 0.3 vs 35.2 ± 0.3g/L; P<0.001; globulin, 23.9 ± 0.4 vs 25.5 ± 0.4g/L; P<0.005). In hinds, FLC averaged 5 lpg (range 0 – 122) and FEC averaged 26 (range 0- 200) with no significant relationship between weaning date and either FLC or FEC. No effect of weaning date on conception rate or date was observed. This study showed that pre-rut weaning date, (although confounded by weaning process management) and sub-clinical parasitism during summer and early autumn may influence LWG in young farmed deer. The failure of moxidectin to reduce FEC to zero raises the question of the efficacy of this macrocyclic lactone anthelmintic against GI nematodes in farmed deer and/or emergence of farmed deer GI nematode resistance. Potential diagnostic parameters such as serum albumin concentration, which was reduced in untreated control deer, warrant further investigation for clinical diagnostic use in farmed deer. The study also highlighted the need for further research to demonstrate the advantages or disadvantages of pre-rut weaning on growth of deer calves and hind reproduction. The 2006 grazing experiment investigated the effect of pasture species grazed on post-weaning growth and endoparasitism of farmed red deer from 3- 6 months of age. Ninety-five red deer calves were randomly allocated to five groups based on sex, LW, FEC and FLC. These calves rotationally grazed either a permanent pasture based on perennial ryegrass, chicory, narrow-leaved plantain, or one of two pasture mixes based on either a short-rotation tetraploid ryegrass (TSR-mix) or long-rotation tetraploid ryegrass (TLR-mix). Both mixes included the same white clover, red clover and chicory. All deer were initially treated with an anthelmintic (albendazole), with subsequent trigger treatment withheld until weight loss or clinical parasitism was observed. Anthelmintic trigger treatment (albendazole) was given on an individual animal basis. The anthelmintic trigger treatment and LWG data in this study suggest that plantain, TLR- and TSR-mixes and chicory may all have a role in aiding control of endoparasitism in young growing deer in autumn in deer production systems based on permanent perennial ryegrass-based pasture with low anthelmintic input. However, any potential effects of forage feeding value and anti-parasitic plant compounds of chicory, plantain and pasture-forage mixes on parasitism and growth could not be separated in this study. It is therefore acknowledged that these observations are preliminary and based on a design intended only to establish whether further replicated studies are warranted, particularly with plantain and pasture mixes. However, the study has shown that pasture species, either sown as a pure crop or in a pasture mix can influence LWG, resilience to internal parasitism and requirement for anthelmintic use in young farmed deer. Data from the first experiment (2005) has shown that pre-rut weaning date and sub-clinical parasitism during summer and early autumn can influence LWG in young farmed deer while the trigger treatment and LWG data from the second experiment (2006), suggest that plantain, TLR-and TSR-mixes and chicory may have a role in aiding control of internal parasitism in young deer in autumn. The outcome of the second experiment has application to deer production systems with low anthelmintic input. Serum protein and haematological parameters investigated in both studies demonstrated the need for further research to establish diagnostic markers for both sub-clinical and clinical internal parasitism in farmed young deer.