Feed conversion efficiency in sheep genetically selected for resistance to gastrointestinal nematodes

Context It has been indicated that there might be an antagonism between selection for gastrointestinal nematode resistance and high productivity feed conversion efficiency in ruminants. Aims This study aimed to determine whether genetic nematodes would alter the intake of sheep with or without infection Haemonchus contortus. Methods Sixty-seven Corriedale lambs (357 ± 14 days old) derived from flocks genetically selected resistant (n= 29) susceptible (n = 38) (GIN) were evaluated individual dry-matter (DMI), ratio (FCR) residual (RFI). Considering bodyweight (BW), GIN line sires, males allotted one three outdoor pens females two, each pen being equipped five automated feeding systems two automatic weighing platforms record BW. Feed (lucerne haylage, crude protein 20.5%, metabolisable energy 9.2 MJ/kg DM) water offered ad libitum. The experiment was conducted periods. First, animals maintained worm-free (14 acclimatisation 44 records) then, Period 2 (42 days), artificially infected 6000 L3 Worm egg counts recorded on Days 9, 23, 27, 30, 42 post-infection. While DMI, FCR, average daily gain BW analysed using a generalised linear model including dams age, as fixed effects, RFI only line. Key results In both periods, did not have significant (P > 0.05) effect RFI, count different < Day 23 post-infection (Period 2), higher Conclusions most important finding this is breeding GIN-resistant negative when FCR 1-year old fed libitum high-protein diet. Implications Breeding internal does affect productivity.