Ingestão de proteína para cordeiros da Raça Santa Inês: digestibilidade e desempenho

Abstract

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.