Introduction compare the protein and protein-free dry matter Materials and methods

186 S . Terramoccia et al. Livestock Production Science 65 2000 185 –195

1. Introduction compare the protein and protein-free dry matter

degradability of three feeds in rumen of cattle, The protein rumen degradability, representing one buffalo and sheep and the relationship between the of the most important features in animal feeding, has rumen degradation rate and the passage rate of solids been studied for many years Chalupa, 1975; Smith, and fluids. 1975; Ørskov and McDonald, 1979; Tamminga, 1979; Verite et al., 1987 and continues to be studied up to the present. In order to measure the amount of

2. Materials and methods

undegraded protein, especially for proteinous feeds, the rumen degradability of protein has become one The experiment was carried out on four Mediterra- of the most significant parameters in the new feed nean buffalo Bubalus bubalis bulls 417.1614.2 evaluation systems: AFRC 1992, NRC 1985 and kg, four Friesian bulls 509.2633.7 kg and four INRA 1988. With regard to rumen degradation, Delle Langhe rams 70.664.4 kg, fitted with soft only cattle and sheep are more frequently studied silicone ruminal cannulas 10 cm internal diameter while experimental data regarding buffalo species is for buffalo and cattle, 4 cm internal diameter for very limited; a few trials on buffalo protein rumen rams; Bar Diamond, Parma, ID, USA and fed four degradability have been carried out in Asia Kumar diets with different forage:concentrate ratios 1 5 and Walli, 1988; Chaubility et al., 1991 and in 87.5:12.5; 2 5 75.0:25.0; 3 5 62.5:37.5; 4 5 0.75 Europe Infascelli et al., 1995. Moreover, regarding 50.0:50.0. The animals received 50 g DM kg carbohydrate rumen degradability, less data is avail- per day adaptation period: 15 days and the diets able for all ruminants. had the same crude protein content 140 g kg DM. According to Bartocci et al. 1997 buffalo retains The feeds utilized in the diets were alfalfa hay and ingesta in the rumen–reticulum longer than cattle, maize silage always given in the same ratio, 65:35 although the retention time in the whole digestive on the DM basis, and pelletted concentrate. The tract was less, due to the shorter residence time in chemical composition of feeds and diets were de- the gut. In addition, the different rumen microflora in termined according to Martillotti et al. 1987. the two species Puppo and Grandoni, 1994; Puppo The same feeds concentrate and alfalfa hay, et al., 1999 and different ruminal contractions, milled on screen [ 2.5 mm, and chopped maize which are more intense in buffalo than cattle Ken- silage, frozen and ground for 20 s on screen [ 5 nedy et al., 1992, could have an influence on protein mm, used in the formulation of the four diets, were and carbohydrate rumen degradation. incubated separately in the rumen, using the nylon These above mentioned characteristics have de- bag technique 3 g DM of duplicated samples for termined the opportunity to verify the differences each incubation time; bag pore size 41 mm, bag total 2 among animal species regarding the rumen degra- surface area 320 cm , width:length ratio 1:1.6, round dation of nutrients. base. As the relationship between the rumen degradation To establish the differences between the species, rate and the rumen passage rate constant of solids the degradation value at zero time was obtained by was verified only in cattle and sheep Martz and inserting the bags into the rumen for 3 min; the other Belyea, 1986; Shaver et al., 1988; Susmel et al., incubation times were 2, 4, 8, 24, 48 and 72 120 1990b, the comparison of both these parameters was only for hay h. The zero time bags were washed by taken into account in the case of buffalo. Regarding hand with cold water and all the other bags in the the relation between the rumen degradation rate and washing machine with cold water for 15 min and the rumen passage rate constant of fluids, no refer- subjected to centrifugation; then they were dried ence was found for ruminants. overnight at 658C in a forced-air oven, according to Due to the physiological differences among the the Ørskov and McDonald 1979 procedure. considered animal species and the necessity of Besides the crude protein CP content in the having to evaluate feeds for the formulation of the residues of the three incubated feeds, the loss of appropriate diets, the aim of the present paper is to protein-free dry matter PFDM from each bag was S . Terramoccia et al. Livestock Production Science 65 2000 185 –195 187 also calculated to determine the rumen degradability cattle received 300 g alfalfa hay mordanted with ´ at different incubation times. Na Cr O according to Uden et al. 1980 pro- 2 2 7 Rumen degradability of crude protein was ob- cedure, and 50 g of Co-EDTA dissolved in 300 ml tained by CP 2 CP CP 3 100, whereas the distilled water while rams received 75 g mordanted 1 2 1 protein-free dry matter degradability at different alfalfa hay and 20 g Co-EDTA dissolved in 100 ml incubation times was calculated by the following distilled water. Grab samples of faeces were col- equation: lected at 0, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 34, 40, 44, 48, 54, 60, 68, 80, 92, 104, 116, 128, DM 2 CP 2 DM 2 CP DM 2 CP 3 f g 1 1 2 2 1 1 140 and 152 h post dosing. Faeces were dried and 100 after mineralization at 4508C, were solubilized and analyzed for Cr and Co by atomic absorption accord- where DM , CP are DM and CP g of feed before 1 1 ing to the Williams et al. 1962 method. The k 1 incubation and DM , CP are DM and CP g after 2 2 values for solid particles were obtained with the incubation, respectively. multicompartmental model Dhanoa et al., 1985 The amount of degraded carbohydrates structural while the k for fluids were obtained by the G4 1 and unstructural can be obtained by multiplying model Pond et al., 1988 as reported by Amici et al. PFDMD as calculated below with the sum of crude 1997. fiber and nitrogen free extracts; this parameter thus Statistical differences among the species or the obtained is necessary, together with that of degraded diets were found by analysis of variance using a crude protein, for the purpose of estimating the monofactorial model by SAS GLM procedure; fur- amount of digestible protein in the gut of microbial thermore a bifactorial model factor species: buffalo, origin ASPA Feeding Commission, 1994. cattle, sheep; factor passage rate constant: ex- Each set of data were fitted using the following perimental k , theoretical k has also been utilized 1 1 exponential model Ørskov and McDonald, 1979: to estimate the effect of both considered factors on effective degradability. dgt 5 a 1 b 1 2 exp 2ct f g Since the values regarding the passage rate con- where ‘‘dgt’’ is the rumen degradability at time stant k for fluids were obtained in tandem with k 1 1 ‘‘t’’, ‘‘a’’ is the rapidly soluble fraction at zero time, values for solids, correlations between ‘‘c’’ and ‘‘b corresponding to the first value of the asymptotic 100c’’ as amount of the degradable fraction curve on the ordinate axis, ‘‘b’’ was the potentially degraded per unit of time vs. ‘‘k ’’ either for solids 1 degradable fraction, ‘‘c’’ was the degradation rate or for fluids were executed using the SAS CORR constant of fraction ‘‘b’’ and ‘‘t’’ was the incubation procedure. time; the procedure used was SAS NLIN, Marquardt algorithm SAS, 1993. The effective rumen degradability of crude protein

3. Results and discussion