Effect of plane of nutrition on energy and nitrogen retention and on plasma urea concentrations in Southdown ram hoggets from high and low backfat selection lines

摘要

Abstract Tweuty-four Southdown ram hoggets (12 each from the Massey University high and low backfat selection lines) were offered lucerne chaff at 0.7 or 1.2 times maintenance requirement in a balanced factorial design. Energy and nitrogen (N) balances were measured over a 10-day period. Rams were then placed on a 2-hourly feeding pattern and differences in plasma hormone and metabolite concentrations were examined. No differences were observed between selection lines in components of energy or N balance at 0.7 maintenance. Low (backfat) line rams offered 1.2 maintenance exhibited greater diet selection than high (backfat) line rams with the result that they had lower energy intake and energy retention (intake less faecal and urinary losses). N intakes were also lower in low line rams at 1.2 maintenance but, because of their (not significantly) lower urinary N excretion, there were no differences between lines in N Despite lower energy retentions, low line rams exhibited higher concentrations of glucose i...