Directory UMM :Data Elmu:jurnal:L:Livestock Production Science:Vol64.Issue2-3.Jun2000:

(1)

www.elsevier.com / locate / livprodsci

A comparative study of nutrient digestibility, kinetics of

degradation and passage and rumen fermentation pattern in

goats and sheep offered good quality diets

*

_´

E. Molina Alcaide , A.I. Martın Garcıa, J.F. Aguilera

´ ´ ´

Unidad de Nutricion Animal, Estacion Experimental del Zaidın (CSIC). Camino del Jueves, s /n. Armilla, Granada, Spain Received 2 November 1998; received in revised form 15 June 1999; accepted 17 August 1999

Abstract

The in vivo digestibility, the rates of fermentation and passage and the rumen fermentation pattern were compared in ˜

Granadina goats and Segurena wethers fed alfalfa hay (AH), alfalfa hay / sugar beet pulp, 4:1 (AH / SB) and alfalfa hay / sugar beet pulp / oat grain, 3:1:1 (AH / SB / OG) at approximately maintenance level. The animals were at stall and no selectivity was practised. The nylon bag technique was used to estimate the extent and fractional rate of degradation of the feed in the rumen. The fractional outflow rate of particles was determined with chromium as a marker. No significant interspecies differences in the nutrients digestibility were found. Values of potential and effective degradability and rates of degradation of both dry matter and protein were similar in goats and sheep. Also, the calculated values of the fractional rate of passage of the digesta out of the rumen were not significantly different between animal species. Ammonia-N concentrations were higher in the rumen liquor of goats than in sheep. No clear trend in the concentration of total and individual volatile fatty acids was observed when comparing goats and sheep with the exception of an increased proportion of valeric acid in the rumen liquor of sheep. From present and previous trials it is concluded that goats and sheep show equal capacities of digestion of medium to good quality diets when fed at energy maintenance level and feed selection is absent. This would validate extrapolations of feed evaluations, what implies a unique energy value.  2000 Elsevier Science B.V. All rights reserved.

Keywords: Alfalfa hay; Sugar beet pulp; Oat grain; Rumen degradation; Passage rate; Digestibility; Goat; Sheep

1. Introduction (AFRC, 1997). It devotes a section to comment on the digestive physiology of this animal species ‘in The Agricultural and Food Research Council’s view of the frequent suggestions in the literature that Technical Committee on Responses to Nutrients has in goats, digestive processes may differ in important very recently published a review on the current state aspects from those of cattle and sheep’ and another of knowledge with respect to the nutrition of the goat section to interspecies comparisons for feed intake for validation of between species extrapolations. The review on these specific subjects covers published

*Corresponding author. Tel.:134-958-57-2757; fax:1

34-958-data up to 1991. Some years later we published a

57-2753.

E-mail address: [email protected] (E.M. Alcaide) number of papers in which interspecies comparisons

(2)

between goats and sheep concerning the digestive forages than sheep, they were able to maintain a ´

physiology were made (Isac et al., 1994; Garcıa et larger rumen fill without increasing ruminal disten-al., 1994, 1995; Molina Alcaide et disten-al., 1997) when sion. This fact would contribute to increased vol-low to medium quality diets were offered. Partially untary intakes with respect to sheep. However, our this home information refers to non-producing ani- results are opposite to the information reported by mals fed at maintenance level and confined in AFRC (1997) as far as kinetics outflow is concerned metabolic crates (Isac et al., 1994) and, therefore, as they indicate shorter mean retention times of the minimizing differences in selective behaviour be- digesta in the rumen of the goats in comparison with tween animals which might account for unequal sheep. They are also contradictory concerning the digestive efficiencies. In these experiments we failed rumen fermentation pattern, although observed dif-to find interspecies differences in digestibility and ferences were of minor importance. The evidence in degradation rate when medium quality forages were this aspect is inconclusive.

offered. However, most of the data from our labora- With this background and given the dearth of tory were obtained in non-producing animals grazing comparative digestion studies with sheep and goats low to medium quality pastures in semi-arid lands of fed on good quality forages under conditions which

the South of Spain (Garcıa et al., 1994, 1995; Molina prevent selective intake (AFRC, 1997), the aim of Alcaide et al., 1997). In these trials some contro- the present work was to widen the range of observa-versial results were observed concerning interspecies tions from medium to high quality diets for which differences for in vitro digestibility: when grasses the hypothesis of a similar digestion capacity was were the main component ((78%) of the pasture stated, implying a unique energy value for both goats

consumed and differences in chemical composition and sheep. between the material selected were negligible, the in

vitro digestibility of dry matter (DM) and organic

matter (OM) of the material ingested by sheep was 2. Material and methods

on average 3.5 percentage units higher than that

observed for the pasture selected by goats. However, 2.1. In vivo digestibility experiments when shrubs and tree leaves accounted for the most

part of the diet ingested ((80%) the in vitro Four dry non-pregnant Granadina goats

digestibility of the forage grazed by goats was on (40.661.07 kg body weight (BW)) and four ˜

average 7 percentage units higher than that observed Segurena wethers (60.661.04 kg BW) were used to in sheep. The diet consumed by the sheep showed determine the nutrients digestibility of three different higher fibre content and degree of lignification than diets (Table 1): Alfalfa hay (AH), alfalfa hay plus the material selected by the goats. These findings sugar beet pulp in the ratio 4:1 (AH / SB) and alfalfa emphasise that differences in selective behaviour hay plus sugar beet pulp and oat grain in the ratio between animal species could account for unequal 3:1:1 (AH / SB / OG). Two wethers and two goats had digestive efficiencies. Results of the studies carried permanent ruminal cannulae. After completion of the out with grazing animals were clear to demonstrate digestibility trials cannulated animals were used to that goats had higher energy intakes than sheep determine sequentially the rate of degradation of the which could be explained by a faster rate of passage digesta in the rumen, the fermentation pattern and of particles out of the rumen and a systematic the fractional rate of passage of particles out of the

tendency (Garcıa et al., 1995; Molina Alcaide et al., rumen.

1997) for a higher rate of degradation of the material The animals were kept in individual crates and had when placed in bags suspended in the rumen. Also free access to water. In three consecutive trials, they the size of the rumen content (g dry matter) was were fed at maintenance level diets AH, AH / SB and found to be larger in goats than in sheep. So, in AH / SB / OG in two meals of equal sizes at 09:00 and agreement with relevant information reviewed by 16:00 h along with a vitamin–mineral mixture and AFRC (1997), we concluded that while goats seem daily feed intakes were individually recorded. The to have a similar capacity to digest medium quality intake of metabolisable energy for maintenance

(3)

Table 1 _{pore size was 36}_m_{. The bags were incubated during,} Ingredients (g / kg fresh matter) and chemical composition (g / kg _{4, 8, 16, 24, 48 and 72 h in the rumen of the} dry matter) of the experimental diets

cannulated animals fed one of the experimental diets

Experimental diet AH AH / SB AH / SB / OG _{containing the ingredient to be tested. Three}

con-Ingredients secutive trials were performed in which the animals

Alfalfa hay 1000 800 600 _{received diets AH, AH / SB and AH / SB / OG,} respec-Sugar beet pulp – 200 200 _{tively, at maintenance level. After incubation, the}

Oat grain – – 200

bags were washed in a washing machine during 20 min, then stomached during 5 min and, finally, dried

Chemical composition

Dry matter, g / kg fresh matter 899 903 906 at 608C. Aliquots of the remainder dry matter were

Organic matter 869 872 891 _{used for organic matter (OM) and nitrogen (N)} Crude protein 181 166 153 _{analyses. The profiles of degradation were calculated} Neutral detergent fibre 390 402 410

by the non-linear least square approach, using the

Acid detergent fibre 294 284 259

exponential model described by Ørskov and

Acid detergent lignin 65.5 59.4 50.8

N-ADF, g / 100 g total N 6.05 6.96 10.5 McDonald (1979). The effective degradability (Ed)

Gross energy, MJ / kg DM 18.4 16.5 17.9 _{in the rumen was calculated as Ed}₅_a₁_{[(b*c) /c}₁

k)] were a is the soluble fraction, b the potentially

degradable insoluble fraction, c the degradation rate

0.75

(MEm) was taken to be 374 and 421 kJ / kg BW constant and k is the passage rate of the digesta from for wethers and goats, respectively (Aguilera et al., the rumen.

1986, 1991). The ME content was estimated to be 9

MJ / kg dry matter (DM) for diets AH and AH / SB 2.3. Composition of the rumen liquor and 10.5 MJ / kg DM for diet AH / SB / OG,

irre-spective of the animal species to be fed. Therefore, Samples of rumen content from the goats and air-dry matter intake of diets AH and AH / SB was on wethers fitted with ruminal cannulae were taken once

0.75

average 46 and 52 g / kg BW for wethers and at day, 2 h after feeding, during two consecutive

0.75

goats, respectively, and 40 and 45 g / kg BW days at the end of the experiments described in when diet AH / SB / OG was assayed. Each trial Section 2.2. They were strained through a layer of included a 15-day adaptation period and a 10-day cheesecloth and the pH of the filtrate was immedi-collection period. Daily total faeces, urine and feeds ately determined. An average composite sample of refusal were individually collected and then, weighed the squeezed liquor per sampling day and animal and 10, 20 and 30% of daily collection, respectively, species was built up. Aliquots of the composite were stored at 2208C. Samples of the ingredients samples were used for the determination of ammonia were also daily collected, pooled and kept at 2208C nitrogen (NH –N) and total volatile fatty acids3

for analysis. The coefficients of digestibility of (VFA) and their individual concentrations were also nutrients and the energy values of the experimental measured. The remainders of these filtrates were diets were obtained from measurements of nutrients freeze dried to determine DM, OM and total nitrogen and gross energy intake and losses in faeces and (TN) contents.

urine, when appropriate. Energy losses as methane

were calculated as described by Aguilera and Prieto 2.4. Fractional passage rate (1991).

After 20 days of consumption of each experimen-2.2. Rumen degradation tal diet (AH, AH / SB and AH / SB / OG), 25 g of chromium mordanted fibre (Uden et al., 1980) of the Bulked samples of alfalfa hay, sugar beet pulp or corresponding experimental diet were directly placed oat grain were mill ground through a 2 mm screen in the rumen of each animal immediately before and aliquots of approximately 2 g were placed in feeding. Faeces were individually taken by rectal nylon bags which measured 7310 cm and whose grab sampling at 6, 9, 12, 24, 28, 32, 48, 53, 72 and

(4)

79 h after dosage of the mordanted material and formed with animal species as main effect. For stored at 2208C until analysed. The fractional rate degradability profile two replicates of four combina-of passage from the rumen (k) was calculated as the tions of treatments (incubated feed / diet offered) slope of the regression of the logarithm of chromium within animal species were used. Differences be-concentration in faeces with time post dosing. The tween means were tested by the Bonferroni test. A equation log Ye 5log Ae 2kt was used, where loge one-way ANOVA was also made to determine the

Y and log A are the natural logarithms of chromiume statistical significance of dietary treatment (AH vs. concentration in faeces and t is the time after the AH / SB) when alfalfa hay was incubated in the administration of the marker. rumen of the animals.

2.5. Analytical procedures

3. Results

Samples of feed and feed refusals daily taken from individual animals during the in vivo trials were

3.1. In vivo digestibility experiment thawed and mixed before analyses. Corresponding

samples of faeces were freeze-dried. They were mill

The coefficients of apparent digestibility of nu-ground (1 mm) and analysed for dry matter (DM),

trients and the energy values of the experimental organic matter (OM), crude fat (CF) according to the

diets obtained in goats and sheep are shown in Table methods recommended by AOAC (1975); total and

2. In the course of the digestibility trials small cell walls attached nitrogen (TN and N-ADF,

respec-quantities (,80 g) of refusals were sporadically tively) were analysed according to the methodology

observed in some animals, both in wethers and goats, described by Prieto et al. (1990); gross energy (GE)

and no interspecies differences could be established. was determined in an adiabatic bomb calorimeter;

As planned, the supplementation of alfalfa hay with neutral detergent fibre (NDF), acid detergent fibre

20% sugar beet pulp or 40% mixture 1:1 sugar beet (ADF) and acid detergent lignin (ADL) were

ana-pulp and oat grain increased the digestibility of lysed by the method of Van Soest et al. (1991).

organic matter (DOM). Values found ranged between Samples of the undegraded fractions of dietary

0.667 and 0.768 according to the type of diet, ingredients obtained during the in situ trials and of

implying ME content expected for good quality the strained rumen fluid were also analysed for DM,

diets. The effect of the dietary treatment on the OM and N content.

apparent digestibility of nutrients was highly signifi-The analyses of Cr O2 3 content in mill ground

cant (P,0.001). On the contrary, no significant samples of mordanted diets and of faeces from the

differences (P.0.05) in nutrients and energy di-passage rate trial were performed according to the

gestibility between goats and sheep were found. procedure described by Aguilera et al. (1988).

Individual and total VFA in aliquots of strained rumen liquor were determined by gas

chromatog-raphy (Isac et al., 1994) and NH –N by the tech-3 3.2. Rumen degradation nique described by Weatherburn (1967).

Table 3 presents estimates of the degradability of 2.6. Statistical analyses dry matter (DMD) and crude protein (CPD) of the dietary ingredients assayed in goats and sheep. The GLM procedure of the SAS (1987) was used Considerable differences between dietary ingredients to evaluate statistically the effects of animal species in values of both soluble and potentially degradable and dietary treatment. The data from the in vivo insoluble fractions of dry matter and crude protein experiment were analysed by means of a two-way were observed. No interspecies differences in po-ANOVA, while for validation of statistical differ- tential (a1b) and effective degradability and in rate

ences in degradability profile or rate of passage of of degradation of both dry matter and protein were digesta one-way analyses of variance were per- found (P.0.05).

(5)

Table 2

The apparent digestibility (%) and the energy value of good quality diets in goats and sheep (n54)

a b

Experimental diet : AH AH / SB AH / SB / OG Level of significance

Animal species: Goats Sheep Goats Sheep Goats Sheep SEM Diet (D) Animal D3AS species (AS)

Dry matter 63.4 63.5 66.9 68.2 72.6 72.9 0.58 *** NS NS

Organic matter 66.7 67.4 70.7 71.4 76.2 76.8 0.54 *** NS NS

Crude protein 82.0 83.0 78.0 78.3 74.6 75.6 0.44 *** NS NS

Neutral detergent fibre 52.3 53.2 54.0 54.6 68.0 70.1 0.90 *** NS NS

Acid detergent fibre 47.1 48.9 48.3 49.1 71.8 78.1 1.29 *** NS NS

Acid detergent lignin 16.8 15.9 11.9 2.90 37.0 40.0 1.79 *** NS NS

Gross energy (GE) 64.4 64.9 65.4 66.3 73.5 74.4 0.62 *** NS NS

Digestible energy (DE), 11.8 12.1 10.9 10.8 13.2 13.3 MJ / kg dry matter

Metabolisable energy (ME), 9.59 9.83 8.60 8.74 11.0 11.1

MJ / kg dry matter

ME / GE3100 52.1 53.6 52.3 52.9 61.0 62.1 ME / DE3100 81.0 81.5 79.1 81.1 83.2 83.4

AH: alfalfa hay; AH / SB: alfalfa hay plus sugar beet pulp, 4:1; AH / SB / OG: alfalfa hay plus sugar beet pulp and oat grain, 3:1:1.

NS, not significant; ***, P,0.001.

SEM: standard error of the means.

Calculated assuming: Methane energy (kJ / day)579.110.09753digestible energy intake (Aguilera and Prieto, 1991). Table 3

Rumen degradation profiles of alfalfa hay, sugar beet pulp and oat grain in goats and sheep offered good quality diets. Effect of the animal species

b c

Animal species: Goats Sheep Average values SEM LS

Diet offered : AH AH / SB AH / SB / OG AH AH / SB AH / SB / OG

Incubated Alfalfa hay Alfalfa hay Sugar beet Oat grain Alfalfa hay Alfalfa hay Sugar beet pulp Oat grain ingredient: pulp

Dry matter Goats Sheep

a (%) 2.24 25.8 10.7 52.6 6.35 20.0 11.2 64.7 22.8 25.6 5.86 NS

b (%) 67.8 37.5 81.5 42.5 67.7 47.2 84.2 28.4 57.3 56.9 5.41 NS 21

c (h ) 0.091 0.086 0.047 0.025 0.087 0.095 0.031 0.029 0.062 0.061 0.0080 NS

RSD 2.66 2.24 3.91 4.73 1.94 1.37 2.99 0.58

Ed (%) 51.6 53.1 59.2 74.3 55.8 58.0 59.5 81.5 59.6 63.7 2.68 NS Crude protein

a (%) 17.3 29.6 27.4 82.2 22.8 49.2 27.2 89.9 39.1 47.3 7.16 NS

b (%) 76.4 64.9 65.2 12.0 70.1 36.3 69.1 5.10 54.6 45.2 7.16 NS 21

c (h ) 0.111 0.063 0.056 0.038 0.106 0.086 0.022 0.043 0.067 0.064 0.0084 NS RSD 1.97 1.99 4.78 0.72 4.70 1.76 2.87 0.79

Ed (%) 75.8 72.6 68.9 89.6 76.6 77.8 61.0 93.4 76.7 77.2 2.71 NS

AH: alfalfa hay; AH / SB: alfalfa hay plus sugar beet pulp, 4:1; AH / SB / OG: alfalfa hay plus sugar beet pulp and oat grain, 3:1:1.

SEM: standard error of the means.

Level of significance: NS, not significant.

Residual Standard Deviation.

3.3. Composition of rumen fluid 2 h after feeding from goats and wethers fed the diets tested. The sampling procedure followed did not In Table 4 mean values are given for the chemical allow a statistical treatment to be performed. Never-composition of pooled samples of rumen fluid taken theless, it was clear that goats showed higher

(6)

con-Table 4

Average composition of spot samples of rumen liquor of goats and sheep offered good quality diets

Experimental diet : AH AH / SB AH / SB / OG

Animal species: Goats Sheep Goats Sheep Goats Sheep

DM, g / 100 g fresh matter 4.72 1.62 5.49 2.05 2.77 3.43

MO, g / 100 g dry matter 57.5 53.2 65.0 47.6 65.5 73.6

N, g / 100 g dry matter 5.60 3.26 4.30 2.57 4.94 5.47

pH 6.64 6.63 6.54 7.07 6.29 6.05

N–NH , mg / 100 ml3 34.6 12.3 27.0 3.66 14.2 5.95

VFA, mmol / l 93.7 86.0 86.6 60.9 75.1 93.1

C2, mmol / l 61.5 57.8 55.1 39.6 48.8 59.8

C3, mmol / l 21.1 15.6 18.5 11.8 14.0 17.4

IC4, mmol / l 0.89 1.20 1.65 0.93 0.50 0.70

C4, mmol / l 7.90 8.35 7.69 5.37 10.3 12.9

IC5, mmol / l 0.98 1.14 2.07 1.14 0.36 0.49

C5, mmol / l 1.32 1.95 1.62 2.05 1.26 1.77

Taken 2 h after feeding.

AH: alfalfa hay; AH / SB: alfalfa hay plus sugar beet pulp, 4:1; AH / SB / OG: alfalfa hay plus sugar beet pulp and oat grain, 3:1:1.

centrations of NH –N than sheep. However, no3 4. Discussion

systematic trend between animal species in the

concentration of total and individual volatile fatty In this study no interspecies differences in appar-acids was observed, except an increased proportion ent digestibility of nutrients between goats and sheep of valeric acid in the rumen liquor of sheep irre- have been found. It must be emphasised that the spective of the diet consumed. animals consumed the same feed and no selection took place. Our results compare well with those 3.4. Fractional passage rate published by Ndosa (1980) and Mohammed (1982) who found no differences in the apparent digestibili-The calculated values of the fractional rate of ty of organic matter between sheep and goats fed passage of the digesta out of the rumen (k) for goats good quality forages (pelleted dried grass and pel-and for sheep (Table 5) were not significantly leted dried alfalfa, respectively). The results obtained different (P.0.05). Mean retention time of the in the present trials and those found in a previous digesta in the rumen of goats and wethers was 33 work from our laboratory (Isac et al., 1994) with

and 40 h, respectively. A tendency to slow outflow Granadina goats and Segurena wethers fed medium rate was noticed when sugar beet pulp or sugar beet quality alfalfa hay (DOM, 0.58) and vetch straw pulp and oat grain was incorporated to alfalfa hay. (DOM, 0.58), support observations made by Uden

Table 5

Mean values of the fractional rate of passage (k) of particles out of the rumen of goats and sheep offered good quality diets. Effect of the animal species

a b c

Experimental diet : AH AH / SB AH / SB / OG Average value SEM LS

Animal species: Goats Sheep Goats Sheep Goats Sheep Goats Sheep 21

k, h 0.034 0.032 0.032 0.023 0.024 0.020 0.030 0.025 0.003 NS

AH: alfalfa hay; AH / SB: alfalfa hay plus sugar beet pulp, 4:1; AH / SB / OG: alfalfa hay plus sugar beet pulp and oat grain, 3:1:1.

SEM: standard error of the means.

(7)

and Van Soest (1982) and Antoniou and Had- wethers and goats reveal a normal fermentation jipanayiotou (1985) and allow us to conclude that pattern expected to be observed when there is no sheep and goats have a similar capacity to digest shortage in the supply of available nitrogen. Al-forages of medium to good nutritional quality and, though these spot samples may not be representative therefore, that extrapolations of feed energy values of the diurnal variation in composition of rumen from one to the other animal species could be liquid they are perfectly valid for interspecies com-validated. However, it should be stressed that in parisons, as was observed in a previous study of our grazing animals or whenever interspecies differences laboratory carried out in goats and sheep fed lucerne in selective feeding are apparent unequal digestive hay, vetch straw or their 1:1 mixture (Isac et al., capacities between goats and sheep are likely to 1994). Our present study shows that pH was in the

occur (Garcıa et al., 1994; Molina Alcaide et al., range of values appropriate for an optimal activity of 1997). Observations made with low quality diets cellulolytic microflora. Differences observed be-have shown significant interspecies differences tween goats and sheep in rumen fermentation param-favourable to goats (Domingue et al., 1991; Murphy eters were of minor importance, a fact which seems et al., 1996). There is also information, which to be expected when medium to high quality diets indicates that goats show significantly higher nutrient are offered (Watson and Norton, 1982; Antoniou and

´ digestibility than sheep when fed good quality alfalfa Hadjipanayiotou, 1985; Isac et al., 1994; Garcıa et hay (Reid et al., 1990). al., 1995). However the ammonia-N content in the In agreement with the results found in previous rumen liquor of goats was always much greater than studies of our group (Isac et al., 1994), the observa- in sheep and accounted for a rather fixed proportion tions made in the present work corroborate the lack of the total-N fraction (0.13–0.10) in contrast with of significant differences between goats and sheep the wide range of values found in sheep (0.23–0.03). regarding the rate of degradation and the effective Whether this could be indicative of interspecies degradability either for the dry matter or crude differences in N recycling or in efficiency of micro-protein fractions of the forages offered. These results bial protein synthesis is a subject which deserves are also in agreement with the observations of further attention.

Hadjipanayiotou et al. (1988) concerning moderately In the present trials the observed fractional outflow good quality feeds. Only in co-grazing animals rates lay in the range of values expected for forages degradation rates of dry mater tended to be higher in fed at approximately maintenance intake (ARC, goats than in sheep when the quality of the available 1984). There is limited information concerning

pasture declined with maturity (Garcıa et al., 1995). rumen turnover time in goats and sheep. Previous The same trend was observed when shrubs and tree comparative studies of ruminal kinetics carried out in leaves account for a great proportion of the vegeta- our laboratory with unrestrained animals have dem-tion and, consequently, high contents of lignin and onstrated similar outflow rates of stained particles in non-available nitrogen were found in the pastures goats and sheep (Isac et al., 1994) in agreement with consumed (Molina Alcaide et al., 1997) and an- present results. On the contrary, goats at pasture tinutritive compounds, like tannins, were probably showed faster passage rates consistent with the present; in other words, when goats exhibited a increased daily feed intakes observed in comparison

selective capacity which allowed them to ingest a with sheep (Garcıa et al., 1995). Therefore, it seems diet with a higher protein and lower fibre contents that when stall-feeding impairs selective feeding than sheep. The increase in rate of disappearance behaviour or when animals are given medium to high from nylon bags is indicative of improved microbial quality forages similar ruminal retention times are to activity. This stimulation of microbial activity could be expected. Other authors reported slower (Ndosa, be attributable to the presence of true protein, 1980; Doyle and Egan, 1980; Watson and Norton, increased N or easily digestible cell wall. 1982; Domingue et al., 1991) or faster (Huston et al., In our study the analyses made in the average 1986; Katoh et al., 1988) rates of passage of digesta samples of rumen liquor taken 2 h after feeding from out of the rumen in goats than in sheep. The results

(8)

Doyle, P.T., Egan, J.K., 1980. Intake and digestion of herbage

found by Ndosa (1980) and Doyle and Egan (1980)

diets by Angora goats and Merino sheep. Proc. Austr. Soc.

are unexpected in view of the concomitant higher

Anim. Prod. 13, 521.

intakes they observed in goats than in sheep. _{Garcıa, M.A., Aguilera, J.F., Molina Alcaide, E., 1995. Voluntary}_´ From present and previous trials it is concluded _{intake and kinetics of degradation and passage of} unsup-that goats and sheep show equal capacities of plemented and supplemented pastures from semiarid lands in

grazing goats and sheep. Livest. Prod. Sci. 44, 245–255.

digestion of medium to good quality diets when fed

Garcıa, M.A., Isac, M.D., Aguilera, J.F., Molina Alcaide, E.,

at energy maintenance level and selectivity is not

1994. Rumen fermentation pattern in goats and sheep grazing

practised. This would validate extrapolations of

pastures from semiarid lands unsupplemented or supplemented

quality evaluations concerning the content of digest- _{with barley grain or barley grain-urea. Livest. Prod. Sci. 39,} ible nutrients and feed energy value. _81–84.

Hadjipanayiotou, M., Koumas, A., Georghiades, E., Hadjidemet-riou, D., 1988. Studies on degradation and outflow rate of protein supplements in the rumen of dry and lactating Chios ewes and Damascus goats. Anim. Prod. 46, 243–248. Acknowledgements _{Huston, J.E., Rector, B.S., Ellis, W.C., Allen, M.L., 1986.}

Dy-namics of digestion in cattle, sheep, goats and deer. J. Anim.

The authors acknowledge financial support by Sci. 62, 208–215. ´

Isac, M.D., Garcıa, M.A., Aguilera, J.F., Molina Alcaide, E.,

´ ´

Comision Interministerial de Ciencia y Tecnologıa

1994. A comparative study of nutrient digestibility, kinetics of

(CICYT; Project ref. AGF92-0334). They are also

digestion and passage and rumen fermentation pattern in goats

grateful to E. Colmenero for skilled technical assis- _{and sheep offered medium quality forages at the maintenance} tance. _{level of feeding. Arch. Anim. Nutr. 46, 37–50.}

Katoh, K., Sato, F., Yamazak, A., Sasaki, Y., Tsuda, T., 1988. Passage of indigestible particles of various specific gravities in sheep and goats. Br. J. Nutr. 60, 683–687.

Mohammed, H.H., 1982. Energy requirements for maintenance References _{and growth: comparison of goats and sheep. Ph.D. Thesis,}

University of Reading, UK. ´

AFRC Technical Committee on Responses to Nutrients, 1997. The Molina Alcaide, E., Garcıa, M.A., Aguilera, J.F., 1997. The nutrition of Goats, Nutrition Abstracts and Reviews (Series B). voluntary intake and rumen digestion by grazing goats and Report No. 10, vol. 67, pp. 765–830. sheep of a low-quality pasture from a semi-arid land. Livest. Association of Official Analytical Chemists (AOAC), 1975. Prod. Sci. 52, 39–47.

Official Methods of Analysis, 12th ed. Association of Official Murphy, K.S., Reddy, M.R., Reddy, G.V.N., 1996. Nutritive value Analytical Chemists, Washington, USA. of supplements containing poultry dropping / litter for sheep Agricultural Research Council, 1984. The Nutrient Requirements and goats. Small Rum. Res. 21, 71–75.

of Ruminant Livestock. Supplement no. 1. Commonwealth Ndosa, J.E.M., 1980. A comparative study of roughage utilisation Agricultural Bureaux, Slough, UK. by sheep and goats. M. PhD. Thesis, University of Reading, Aguilera, J.F., Prieto, C., 1991. Methane production in goats given UK.

diets based on lucerne hay and barley. Arch. Nutr. 41, 77–84. Ørskov, E.R., McDonald, I., 1979. The estimation of protein ´

Aguilera, J.F., Molina, E., Prieto, C., Boza, J., 1986. Estimacion degradability in the rumen from incubation measurements ´

de las necesidades energeticas de mantenimiento en ganado weighted according to rate of passage. J. Agric. Sci. 92, ˜

ovino de raza Segurena. Arch. Zootec. 35, 89–96. 499–503.

Aguilera, J.F., Prieto, C., Molina, E., Lachica, M., 1988. A Prieto, C., Aguilera, J.F., Lara, L., Fonolla, J., 1990. Protein and micromethod for routine determination of chromic oxide in energy requirements for maintenance of indigenous Granadina nutrition studies. Analusis 16, 454–457. goats. Br. J. Nutr. 63, 155–163.

Aguilera, J.F., Lara, L., Molina, E., Prieto, C., 1991. Energy Reid, R.L., Jung, G.A., Cox-Ganser, J.M., Rybeck, B.F., Tow-metabolism of the growing Granadina goat at fasting and nsend, E.C., 1990. Comparative utilization of warm- and cool-maintenance. Small Rumin. Res. 5, 109–115. season forages by cattle, sheep and goats. J. Anim. Sci. 68, Antoniou, T., Hadjipanayiotou, M., 1985. The digestibility by 2986–2994.

sheep and goats of five roughages offered alone or with Statistical Analysis System Inst. (SAS), 1987. User’s Guide: concentrates. J. Agric. Sci., Camb. 105, 663–671. Statistics. SAS Inst., Cary, NC.

Domingue, B.M.F., Dellow, D.W., Barry, T.N., 1991. Voluntary Uden, P., Van Soest, P.J., 1982. Comparative digestion of timothy intake and rumen digestion of a low quality roughage by goats (Phleum pratense) fibre by ruminants, equinus and rabbits. Br. and sheep. J. Agric. Sci. 117, 111–120. J. Nutr. 47, 267–272.

(9)

Uden, P., Colucci, P.E., Van Soest, P.J., 1980. Investigation of Watson, C., Norton, B.W., 1982. The utilization of pangola grass chromium, cerium and cobalt as markers in digesta. Rate of hay by sheep and Angora goats. Proc. Aust. Soc. Anim. Prod. passage studies. J. Sci. Food Agric. 31, 625–632. 14, 467–473.

Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for Weatherburn, M.W., 1967. Phenol-hypochlorite reaction for de-dietary fiber, neutral detergent fiber, and nonstarch polysac- termination of ammonia. Analyst Chem. 39, 971–974. charides in relation to animal nutrition. J. Dairy Sci. 74,

(1)

79 h after dosage of the mordanted material and formed with animal species as main effect. For

stored at 2208C until analysed. The fractional rate degradability profile two replicates of four

combina-of passage from the rumen (k) was calculated as the tions of treatments (incubated feed / diet offered)

slope of the regression of the logarithm of chromium within animal species were used. Differences

be-concentration in faeces with time post dosing. The tween means were tested by the Bonferroni test. A

equation log Ye 5log Ae 2kt was used, where loge one-way ANOVA was also made to determine the

Y and log A are the natural logarithms of chromiume statistical significance of dietary treatment (AH vs.

concentration in faeces and t is the time after the AH / SB) when alfalfa hay was incubated in the

administration of the marker. rumen of the animals.

2.5. Analytical procedures

3. Results Samples of feed and feed refusals daily taken from

individual animals during the in vivo trials were

3.1. In vivo digestibility experiment thawed and mixed before analyses. Corresponding

samples of faeces were freeze-dried. They were mill

The coefficients of apparent digestibility of nu-ground (1 mm) and analysed for dry matter (DM),

trients and the energy values of the experimental organic matter (OM), crude fat (CF) according to the

diets obtained in goats and sheep are shown in Table methods recommended by AOAC (1975); total and

2. In the course of the digestibility trials small cell walls attached nitrogen (TN and N-ADF,

respec-quantities (,80 g) of refusals were sporadically

tively) were analysed according to the methodology