Two experiments were conducted to evaluate whether the meeting or not of the
demand of rumen degradable protein (RDP) in association with meeting or
surplus conditions of metabolizable protein (MP) affected the dry matter intake,
digestibility of nutrients and performance in sheep fed tropical Grass in different
stages of maturation (Cynodon – hight e low ADF) according to the
recommendations of the AFRC system. In the digestibility and nitrogen balance
trial, one group of twelve Santa Inês sheep lambs were utilized in to times, the
experimental design was randomized in factorial design 2x2x2, with two
Nutritional Plans (PN- A: meeting RDP and PN-B: not meeting RDP), two
tropical grass (hay of Cynodon) with high and low ADF and sex (males: 32,4 kg
± 1,67 e females: 34,1kg ± 3,6). For the performance trial, 24 lambs of Santa
Inês breed, with an average initial weight of 23,9 kg ± 4,86 (male) and 24,5 kg ±
3,75 (female) in a completely randomized design were utilized in the same
factorial design. The treatments promoted differences (P<0,05) as regards dry
matter intakes in both experiments in favor from the factors: meeting RDP,
males lambs and Cynodon with low ADF. However, no differences were
observed (P>0,05) on weight gain and feed conversion in the two nutritional
plans (PN- A: 232,41 g/day e PN- B: 201,25 g/day).The weight gain and feed
conversion was 239 e 194 g/day; 4,34 e 5,14 kg DM/kg weight gain for males
and females, respectively. The digestibility of dry matter and fibrous fractions
were affected by the distinct balance conditions between the nutritional plans of
RDP. But there weren’t observed differences (P>0,05) in nitrogen retention
when expressed like N retained/N absorbed between the both nutritional plans.
There was a significant reduction in urinary nitrogen excretion when RDP was
restricted in the diet, However, could be observed interactions (roughage vs.
nutritional plane) on N retained/ N absorbed showing the effect of fiber dietary
digestibility. The restriction of rumen degradable protein (RDP) in sheep
growing lambs, did not changes the weight gains and depress the nitrogen
urinary excretion.
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