An assessment of current dietary amino acid recommendations for the growing meat rabbit based on whole body amino acid composition: a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
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Date
1986
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Massey University
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Abstract
Reservations regarding the amino acid levels recommended by
the National Research Council [NRC] (1977) and the Societe de
Chime Organique et Biologique [AEC] (1978) for the growing meat
rabbit, prompted the use of rabbit whole body amino acid
composition values as a first approximation toward determining the
ideal dietary amino acid balance, relative to lysine, for this
species.
In the absence of whole body amino acid composition data for
the growing rabbit, a technique was established for the processing
and subsequent chemical analysis of the rabbit whole body. Using
the established technique, twelve 53-day-old New Zealand White
rabbits were prepared and representative whole body tissue samples
were analysed to determine their amino acid contents.
The determined overall mean essential amino acid composition
of rabbit whole body (g/kg dry matter) was, lysine 5.05;
histidine 2.54; isoleucine 2.57; leucine 5.67; phenylalanine
3.66; tyrosine 2.82; threonine 3.24; valine 3.16; arginine
5.48; methionine 1.49; and cystine 2.32. A comparison of these
determined rabbit whole body amino acid values, relative to
lysine, compared with the recommendations of NRC (1977) and AEC
(1978), suggested, that the published requirements were
overgenerous. In a subsequent study, aimed at determining whether
the published dietary amino acid recommendations were indeed
excessive, 81 five-week-old New Zealand White rabbits were fed one
of a series of nine iso-caloric diets with progressively reduced
amounts of crude protein (159 to 97 g/kg) but a fixed level of
lysine (6.5 g/kg).
Over a 40-day period the growth performance of the rabbits
was similar on the first six diets of the series, but thereafter
with decreasing dietary crude protein content there was a linear
decrease in growth rate and concomitant increase in the feed
conversion ratio.
Urinary nitrogen and urinary urea excretion measured during
the experimental period declined progressively from the first to
the sixth diet of the series and then plateaued, findings which
are in general agreement with the growth performance data.
Urinary creatinine excretion showed a decline across diets,
indicating, that the rabbits on the higher protein diets were
leaner than their counterparts on the diets of lower crude
protein.
As the gross amino acid composition of the first diet in the
series equated with that of published recommendations, while that
of diet six approximated rabbit whole body amino acid composition,
it appears that the recommendations are overgenerous and that the
dietary ideal amino acid balance may not be far removed from that
of rabbit whole body composition. The need for further research
to confirm these findings and define more exactly the dietary
ideal amino acid balance for the growing rabbit is emphasized.
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Keywords
Rabbits, Amino acids, Feeding and feeds, Animal nutrition