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Citrus pulp in diets for fattening lambs
Animal Feed Science and Technology, 5 (1980) 11--22
11
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
CITRUS PULP IN DIETS FOR FATTENING LAMBS
J. MARTINEZ PASCUAL and J. F E R N A N D E Z CA RMO N A
E.T.S.I. Agr6nomos, Universidad Polit$cnica, Valencia (Spain) (Received 14 November 1978; accepted for publication 12 November 1979)
ABSTRACT Martl'nez Pascual, J. and Fernandez Carmona, J., 1980. Citrus pulp in diets for fattening lambs. Anita. Feed Sci. Technol., 5: 11--22. Digestibility, N retention and energy values of isoproteic rations containing 10% alfalfa hay and a concentrate mixture (16% CP) ~vith 0, 15, 30, 45, 60 and 90% citrus pulp, were determined with 13 wethers. In a second experiment, 18 growing lambs (13.5 kg initial weight) were used to determine the values previously cited when fed on rations (16% CP) containing 0, 30 and 60% citrus pulp. Digestibility coefficients of the various feed fractions were not altered when citrus pulp was added to the diet except that for the ADF fraction which increased (P < 0.01). Organic matter and fibre digestibility were affected by age, the maximum figures being obtained with mature animals; metabolizable and digestible energy values followed a similar trend. Retention of N was inversely related to level of citrus pulp and age. Three growth trials were carried out in which daily gains, feed efficiency, dressing percentage and ruminal keratosis were studied in 108 lambs divided into groups of three and starting the experiment at an average weight of 15 kg. The animals were fed on diets containing 0--60% citrus pulp in the concentrate and 10--15% alfalfa hay. The parameters were not altered significantly up to 30% incorporation of citrus pulp, but if higher quantities were added the animal response was poorer. INTRODUCTION
Digestibility values for citrus pulp (Cp) have mainly been determined in steers. Mead and Guilbert (1926) reported coefficients as high as 89, 84 and 78 for dry matter, crude fibre and crude protein, respectively. A number of observations indicate that, when Cp replaces cereals and provides up to 70% of the total diet, DM and organic matter (OM) digestibility remain high, but may decrease slightly when Cp reaches the highest levels (Bhattacharya and Harb, 1973). Furthermore, CF digestibility values increase. On the other hand, there are few data on energy value and nitrogen retention when Cp is given to ruminants. The experiments described below consisted of two digestibility trials (Experiments I and II (a)) and three growth trials (Experiments II (b), III and
IV).
12 MATERIALS AND METHODS
Experiment I Ten wethers were housed in individual pens with faeces and urine collectors. The diets contained 90% concentrate and 10% alfalfa hay and were supplied at a level of 46.6 g/kg W°. 7s per day as reported b y Cottyn and Boucque (1969). Five concentrates with 0, 15, 30, 45 and 60% of citrus pulp and 16% crude protein were formulated in order to use the same concentrate in both fattening lamb and wether diets (Table I). The alfalfa hay contained 46.3% ADF, 17.7% CP, 23.8% CF, 2.2% EE and 90.8% OM in dry matter. Feed, faeces and urine were analysed by the methods of the Association of Official Analytical Chemists (1975) and Goering and Van Soest (1970). The combustion values of these materials, previously vacuum dried, were determined in a Gallenkamp b o m b calorimeter. Metabolizable energy (ME) values were corrected for methane losses according to the formula o f Blaxter (1964). Volatile fatty acids in the rumen fluid were determined by the method of Baumgardt (1964). A design of incomplete and balanced blocks (Cochran and Cox, 1957), was followed in two consecutive periods with four replicates for each treatment. Three more wethers were used to evaluate rations with 90% Cp, with and w i t h o u t hay, during two periods of 25 days each. These results were not included in the statistical analysis.
TABLE I Ingredients and composition of experimental diets (percentage of DM) 1 Citrus pulp (%) 0
15
30
45
60
90
Barley Maize Soya bean meal Fish meal Supplement
65.5 18.0 13.0 2.0 1.5
52.5 14.6 14.5 2.0 1.4
40.0 10.8 16.0 2.0 1.2
27.2 7.0 17.7 2.0 1.1
15.0 3.0 19.0 2.0 1.1
0 0 9.0 0 1.1
OM EE CF CP A DF ADL
95.1 3.8 5.8 16.2 7.6 1.0
93.6 4.4 6.3 16.8 10.5 1.2
91.9 4.0 7.9 15.9 14.7 1.0
90.7 3.2 8.2 15.3 17.2 0.9
88.7 3.3 9.3 15.8 21.5 1.7
86.1 2.4 12.4 10.4 26.4 1.3
' OM, organic matter; EE, ether extract; CF, crude fibre; CP, crude protein; ADF, acid detergent fibre; ADL, acid detergent lignin.
13
Experiment H Eighteen male Manchego lambs of 13.5 kg average liveweight, housed individually and divided into three groups, were offered food ad libitum until they reached 30 kg liveweight. The diets contained 0, 30 and 60% Cp as in Experiment I. T w o experimental periods of 15 days each were considered. The results were analysed statistically by the general model of variance for one factor of variation. (a) Digestibility, N retention and energy values were determined using the chemical methods described for Experiment I and t w o experimental periods of 15 days each were considered. (b) Average daily gain and dressing percentage were recorded individually whereas food intake and feed efficiency data were taken for each group. Ruminal disturbances were assessed macroscopically.
Experiment III Forty-two lambs of 17 kg initial average weight were divided into seven groups having three males each and seven having three females. Two groups of the same sex were fed with a concentrate of 0, 15 and 30% Cp and 15% of hay. Only one group of males and another of females were fed on the 45% Cp diet. F o o d intake, average daily gain, feed efficiency and dressing percentage were estimated as in Experiment II (b). The results were statistically analyzed following the general model of analysis of variance for two factors of variation with unequal number of replicates (Snedecor and Cochran, 1974).
Experiment IV Concentrates with 0, 10, 20 and 30% Cp were given with 10% hay to 16 groups of three animals, there being two groups of males and t w o of females on each diet. Growth parameters were analyzed statistically following the general model of variance for t w o factors of variation (treatment and sex). In this experiment, ruminal keratosis was studied microscopically in sections of stained ruminal epithelia according to the trichromic m e t h o d of Dualde Perez (1971). The level of keratosis was quantified by measuring the ratio of the thickness of the cornea to that of the germinative epithelia, agglutination and development of papillae. R u m e n colour was assessed by giving numerical values according to its intensity. RESULTS
Experiment I The main results appear in Table II. The digestibility coefficients for dry matter, organic matter and also nitrogen-free extract tended to decrease, but n o t significantly, as the proportion of Cp increased.
83.2 85.6 79.3 49.4 41.4 85.8 29.0 5.3 4.0 3.5
81.7 85.3 83.3 48.9 60.0 84.3 36.6 7.3 4.0 3.5
15
81.2 84.6 78.7 54.2 69.3 83.3 33.1 6.0 3.8 3.3
30
80.2 85.8 73.2 72.6 75.1 82.6 22.7 4.0 3.9 3.4
45
78.7 86.0 72.6 57.5 76.3 83.0 24.3 4.3 3.8 3.2
60
NS NS * NS ** NS NS NS NS NS
Significance of differences
NS = non-significant. *, P < 0.05. **, P < 0.01. 1 T h e r a t i o n s w i t h 90% Cp were n o t i n c l u d e d in statistical analysis, means_+ SE. 2 C o n c e n t r a t e given alone, w i t h o u t hay.
Digestibility (%) DM OM EE CF ADF N R e t a i n e d N (%) (g/day) DE (kcal/gDM) ME (keal/gDM)
0
Cp in c o n c e n t r a t e (%)
0.13 1.56 0.83 1.77 1.16 0.58 3.38 O.57 0.01 0.02
SE
NS NS ** NS ** NS NS NS NS NS
Linear effect
E x p e r i m e n t I. Digestibility, n i t r o g e n r e t e n t i o n , a n d digestible a n d m e t a b o l i z a b l e e n e r g y f o r w e t h e r s
T A B L E II
NS NS NS NS NS
NS
NS NS
Second order effect
78.1-+ 1.3 85.8-+ 0.7 56.0-+ 3.5 70.1-+ 2.0 76.1_+ 3.5 73.6-+3.5 25.1_+5.5 3.4_+ 1.0 3.6-+ 0.05 3.2+- 0.05
90
78.5+1.7 8 6 . 5 -+ 1.2 60.9_+ 3.9 71.5-+3.3 80.7-+ 1.0 71.2-+2.6 31.5-+1.1 3.7_+2.5 3.7+-0.05 3.2-+0.05
902
Cp in c o n c e n t r a t e (%)1
15 The digestibility of crude fibre increased when more Cp was added to the ration and this rise was even greater for the 90% Cp ration. If the latter value is corrected for the digestibility of soya bean fibre, a crude fibre digestibility of 78% is estimated for pure Cp (Fig. 1). The ADF coefficients increased from 41.4% to 76.3% when Cp content was raised from 0 to 60% (P < 0.01) and to 80% for pure pulp. Nitrogen digestibility decreased with increasing level of Cp b u t the differences were not significant. The values decreased from 85.8% in a ration w i t h o u t pulp to 83.0% in the 60%-Cp ration, although this contained 6% more soya bean meal than the former. Digestible and metabolizable energy values fell slightly when the percentage of pulp was increased. Values for pure pulp calculated for the ration containing 90% Cp were 3.6 and 3.1 Mcal/kg. 90
-/
C F' D
/
a~ ' ~ .
/ •~
15
30
o~
/*5
60
% Cp
90
Fig. 1. Crude fibre digestibility in sheep. X, lambs, Experiment II(a), Period I; e, lambs, Experiment II(a), Period II; o, adults, Experiment I; *, adults, Bhattacharya and Harb (1973); n, adults, Devendra (1973).
Experiment II (a) The digestibility of DM, OM, NFE and N did not differ significantly (Table III). As in Experiment I, the digestibility of ether extract and fibre increased with pulp level (P < 0.01). Digestibility of both fibre fractions, CF and ADF, also showed an obvious improvement from Period I to Period II~ as can be seen in Fig. 1. The nitrogen balance was clearly positive and decreased with increasing Cp (P < 0.05). These values were similar in the t w o periods, despite the differences in the level of intake. Figures for retained N (%) showed a clearer picture, declining when Cp levels were raised, and always higher in Period I. Digestible and metabolizable energy value of diets were affected significantly b y treatments, being higher with the 30% Cp ration and lower in Period I than Period II. The acetic/propionic ratio in the ruminal fluid was 1.5, 2.4 and 3.2 (P<0.05) in lambs given 0, 30 and 60% Cp, respectively.
76.0 78.1 75.5 34.3 34.1 72.8 54.0 10.9 3.4 3.0
75.2 78.5 73.9 49.8 62.1 70.7 48.2 8.3 3.6 3.2
30
72.6 76.6 67.5 57.2 69.3 70.6 43.5 7.7 3.3 2.8
60
NS ffi n o n - s i g n i f i c a n t . *, P < 0 . 0 5 . **, P <: 0 . 0 1 .
DM OM EE CF ADF N R e t a i n e d N (%) (g/day) D E (kcai/gDM) M E (kcal/gDM)
Digestibility(%)
0
Cp in d i e t (%)
Period I
NS NS ** ** ** NS ** * ** **
Significance of differences
0.89 0.56 0.83 1.20 1.25 0.39 0.48 0.31 0.07 0.05
SE
NS NS ** ** ** NS ** ** ** **
Linear effect
NS NS ** ** ** NS NS ** ** **
Second order effect
80.0 79.3 78.6 44.2 39.0 76.2 39.9 11.0 3.6 3.2
0
78.1 80.2 71.9 59.6 67.2 73.0 41.0 9.1 3.8 3.3
30
Cp in d i e t (%)
Period II
76.5 79.6 64.3 68.0 77.1 72.6 29.9 6.7 3.5 3.0
60
NS NS ** ** ** NS NS * ** **
Significance of differences
E x p e r i m e n t H (a). Digestibility, n i t r o g e n r e t e n t i o n , a n d d i g e s t i b l e a n d m e t a b o l i z a b l e e n e r g y f o r g r o w i n g l a m b s f o r P e r i o d s I a n d II
T A B L E III
0.79 0.61 0.78 0.61 0.61 O.64 2.38 0.60 O.O4 0.04
SE
NS NS ** ** ** NS NS ** NS **
Linear effect
NS NS * ** ** NS NS NS NS **
Second order effect
17
Experiment H (b) There were no significant differences (Table IV) except for feed efficiency, but the diets with more Cp showed worse results. Hay intake varied from 9.6% of the diet w i t h o u t pulp to 11.4% of the diet with 60% pulp. The level of ruminal keratosis increased as the a m o u n t of Cp in the ration was raised. In some cases there was a low level of keratosis in lambs fed on diets containing 0 and 30% Cp. All the lambs which had eaten concentrate wit~, 60% Cp had more keratosis, and in one it was very severe. T A B L E IV Growth of lambs in Experiment II (b) Cp in diets (%)
Total intake (g DM/day)
Average daffy gain (g/day) Feed efficiency Dressing percentage
0
30
60
Significance of difference
999 312 3.2 49.2
913 272 3.4 48.8
928 234 3.9 48.2
NS NS * NS
SE
Linear effect
Second order effect
23.12 13.45 0.11 0.55
NS NS ** NS
NS NS NS NS
NS = non-significant. *, P < 0.05. **, P < 0.01.
Experiment III The average daily gain of males varied from a m a x i m u m of 272 g with the 15% Cp diet, to a minimum of 127 g with the 45% Cp diet. The same trend was observed with females (Table V). There were differences between sexes in feed efficiency and ADG (P < 0.01), and in food intake and dressing percentage (P < 0.05). The sex X treatment interactions were n o t significant. As in Experiment II (b), the hay refused was gradually lowered as the percentage of pulp was increased. So the real intake of hay (% of concentrate) in males was 12.8, 14.2, 14.8 and 15.1 with 0, 15, 30 and 45% Cp, respectively. The same trend was observed in females.
Experiment IV As in Experiment III, males grew more than females and differences between sexes were significant (P < 0.01). The results were not altered for males when more Cp was added to the diet, but for females they tended to become worse (Table VI). There were no significant differences in the degree of keratosis, developm e n t and agglutination of papillae in the different groups. Some differences were registered (P < 0.05) as regards colour.
18 TABLE V G r o w t h o f l a m b s in E x p e r i m e n t III Cp in diet (%) 0 15 30 45
Sex
Total intake (g D M / d a y )
Gain (g/day)
Feed efficiency
Dressing percentage
Male Female Male Female Male Female Male Female
929 824 942 845 955 820 778 821
259 188 272 199 256 171 127 143
3.6 4.5 3.5 4.3 3.6 4.9 5.5 5.7
55.8 56.5 53.3 56.7 54.7 54.3 53.9 56.6
Treatment difference SE t r e a t m e n t Linear e f f e c t Second order effect Sex d i f f e r e n c e SE sex SE t r e a t m e n t X sex
NS 21.7 ** NS ** 15.4 30.8
** 2.16 ** NS ** 1.53 3.05
** 0.13 ** ** ** 0.09 0.18
NS 0.11 ** NS ** 0.07 0.15
NS = non-significant. **, P < 0.01.
g/day
3OO ~
p
[E d
2oo 100
\
~
e
0
10
x % Cp
p
rfI 9 40
50
60
Fig. 2. Daily w e i g h t gain in lambs. E x p e r i m e n t s II(b), III a n d IV.
Two more lambs, not included in the statistical analysis, were fed on diets containing 30% Cp w i t h o u t hay and they presented a m a x i m u m level of hyperkeratosis; intake and daffy gain were clearly lower. DISCUSSION
It seems that the dry or organic matter of citrus pulp is as digestible as that of cereals, as the addition of Cp did not alter digestibility. The values obtained for growing lambs are lower than those of Experiment I, or those published by Devendra (1973) for castrated rams.
19 TABLE VI G r o w t h o f l a m b s in E x p e r i m e n t IV Cp in diet (%) 0 10 20 30
Sex
Total intake (g D M / d a y )
Gain (g/day)
Feed efficiency
Dressing percentage
Male Female Male Female Male Female Male Female
960 823 1033 830 956 775 988 805
298 236 316 217 311 208 300 200
3.0 3.2 3.1 3.5 2.8 3.5 3.0 3.8
54.7 54.7 51.6 56.7 53.0 55.3 54.9 53.7
NS 11,6 NS NS ** 8.2 14.9
NS 0.15 NS NS ** 0.11 0.21
Treatment difference SE t r e a t m e n t Linear effect Second order effect Sex d i f f e r e n c e SE sex SE t r e a t m e n t × sex
NS 24.6 NS NS ** 16.0 32.0
NS 0.57 NS NS ** 0.41 0.81
NS = non-significant. **, P < 0.01.
The trend in the digestibility of CF showed that the fibre fraction of Cp is clearly more digestible than that of cereals. However, the greater total content of fibre in the rations containing pulp would contribute to a better ruminal degradation of this fraction, and there is the effect of calcium hydroxide mentioned in a previous paper. There was an interval of one month between Periods I and II of Experiment II, and the higher digestibility of OM and fibre in the second period would correspond to greater rumen development. It is accepted that ruminal function is well established between the 8th and 12th weeks of age, the latter age being reached in the second period studied. Ether extract was of low digestibility, which could be ascribed to the high content of essential oils and calcium in citrus pulp. The apparent digestion of nitrogen was poor and tended to decrease with the incorporation of more Cp, despite the higher proportions of soya bean protein (56% in the 60% Cp ration}. The nitrogen of Cp is slightly digestible, as is shown by the values for the diet containing 90% Cp or by that calculated for the pure pulp (64.5%) and it agrees with some earlier work. Ammermann et al. (1963a), studying dried citrus seed meal, reported that nitrogen digestibility was 56% and biological value 46% when the meal supplied 88% of the total protein in the ration. The retention of nitrogen fell as the proportion of citrus pulp increased, which would be further evidence of the low quality of the protein, as mentioned above. It is reasonable to expect that the utilization of the digested nitrogen
20
declines as the animal grows owing to the fact that the absolute amount of digested N is clearly higher, whereas N retention is similar in both Periods I and II (Experiment II (a)) and lowest for wethers (Experiment I). The digestible and metabolizable energy figures determined in Experiment II (a) were lower than those obtained with mature animals, although the results are closer for the animals near 30 kg live weight (Period II, Experiment II (a)). Once faeces and urine energy losses are calculated (Table VII), it is evident that the faecal losses decrease as the animal grows. The urine losses, stated as a percentage of the digested energy, are also smaller in growing lambs, in agreement with their higher urine N o u t p u t and lower N retention compared to the wethers utilized in Experiment I. Conversely, the losses of energy as methane are lower because DE appears in Blaxter's formula as a positive item. Nevertheless, energy losses in urine and methane together do not reach the faecal loss, and the deduced values of ME are highly affected by the digestibility of OM, which increases with the age of lambs. TABLE VII Experiments I and II (a). Energy lost in faeces (FE) and urine (UE) as percentages of gross energy (GE) and digestible energy (DE) Cp in diet (%) 0
30
60
FE/GE
Lambs, Period I Period II Wethers
24.7 22.7 24.2
20.3 19.4 20.1
16.5 16.8 15.5
F E/ DE
Lambs, Period I Period II Wethers
32.8 29.4 31.9
25.5 24.1 25.1
19.8 20.2 18.3
UE/DE
Lambs, Period I Period II Wethers
2.6 2.9 3.7
3.2 3.7 4.6
3.2 3.1 5.0
Values for ME, calculated from the equation of the O. Kellner Institute, are a b o u t 5% (0% Cp) and 12% (30 and 60% Cp) lower than those determined experimentally. Citrus pulp is a product hardly comparable to standard concentrates, because it is easily fermentable, and that formula underestimates methane losses. The incorporation of large proportions of Cp in the diet decreases dally gain of y o u n g lambs, b u t the results frequently follow a curvilinear pattern to give maxima when 10--15% Cp is added (Fig. 2). The average dally gain and feed efficiency values are, in general, within the normal limits elsewhere, b u t they are not comparable to those quoted by
21 Loggins et al. (1964, 1968), Ammerman et al. (1963b) and Chicco et al. (1973), since the lambs used by those workers were 4 months old at the beginning of the fattening period. We may conclude t h a t the incorporation of Cp up to levels of 30% does not alter daily gain, feed efficiency and dressing percentage. Intake and weight gain are closely related. The increasing a m o u n t of fibre of the diets might have reduced intake, but the digestibility of Cp was too high to impose physical limits and also the digestibility of CF in the rations increased as the proportion of Cp increased. However, fibre decreases fattening efficiency. Welch and Smith (1971} reported that Cp gave a longer chewing time than cereal but it was lower when long hay was offered. It was observed t h a t lambs ate more hay when rations with more Cp were supplied. Nevertheless, the pulp is an ingredient with low content of cell walls in spite of its high fibre percentage. A m m e r m a n et al. (1963c) reported a marked parakeratosis in the rumen of steers given Cp with little or no hay; later papers agreed with their findings. This trend was shown in our experiments, although there were no significant differences. The severity of rumen parakeratosis was greatest with 30% Cp and no hay. Regardless of the level of Cp in the diet, severe parakeratosis was not found when lambs ate chopped hay. Loggins et al. (1968) also noticed the most acute cases in lambs consuming an all-concentrate pelleted diet (74% citrus pulp), but A m m e r m a n et al. (1963b) considered that the ruminal epithelium of two lambs given only concentrate (66% citrus pulp) was normal. Frequently hyperkeratosis is related to agglutination of papillae caused by food. In our experiments this effect was not found, perhaps because of the relatively large particle size of the ground pulp used. ACKNOWLEDGEMENTS The authors are indebted to Prof. R. Romero for his help with the statistical analysis, the Instituto Nacional de Investigaciones Agrarias for providing housing facilities, A. Gargallo for his care of the animals and A. Climent for technical assistance. REFERENCES Ammerman, C.B., Van Walleghem,P.A., Easley, J.F., Arrington, L.R. and Shirley, R.L., 1963a. Dried citrus seeds -- nutrient composition and nutritive value of protein. Fla. Agric. Exp. Stn. J., Ser. No. 1783. Ammerman, C.B., Loggins, P.E. and Arrington, L.R., 1963b. Comparative feeding value of dried citrus pulp and ground snapped corn for fattening lambs. Fla. Agric. Exp. Stn., Mimeo Ser. No. 63-13. Ammerman, C.B., Van Walleghem,P.A., Palmer, A.Z., Carpenter, J.W., Hentges, J.F. and Arrington, L.R., 1963c, Comparative feeding value of dried citrus pulp and ground corn and cob meal for fattening steers. Anita. Sci., Mimeogr. Rep., AN 64-8, Univ. Florida. Association of Official Analytical Chemists, 1975. Official Methods of Analysis 12th edn. Washington.
22 Baumgardt, B.R., 1964. Practical observations on the quantitative analysis of free volatile fatty acids in aqueous solution by gas--liquid chromatography. Dep. Dairy Sci., Bull. No. 1, University of Wisconsin, U.S.A. Bhattacharya, A.N. and Harb, M., 1973. Dried citrus pulp as a grain replacement for Awasi lambs. J. Anita. Sci., 36: 1175--1180. Blaxter, K.L., 1964. Metabolismo Energ~tico de los Rumiantes. Ed. Acribia-Zaragoza, p. 193. Chicco, C.F., Duque, C.M., Shultz, E. and Shultz, T.A., 1973. Yucca, citrus pulp and molasses for fattening lambs. Agron. Trop., 23: 587--592. Cochran, W.G. and Cox, G.M., 1957. Experimental Designs. 2nd edn., Wiley, New York. Cottyn, B.G. and Boucque, Ch.V., 1969. Digestibilit~ et valeur alimentaire de pellets de pulpes s~ch~es d'agrumes. Rev. Agric., 11--12; 1543--1551. Devendra, C., 1973. Effect of citrus meal on digestibility of sheep diet. Trop. Agric., 50: 221--224. Dualde Perez, D., 1971. Modificaci0n al m~todo de Gallego para ~ coloraci0n de tejidos en general. Veterinaria, XXXVI: 207--212. Goering, H.K. and Van Soest, P.J., 1970. Forage fibre analyses. Agric. Res. Serv., U.S. Dep. Agric., Agriculture Handbook No. 379. Loggins, P.E., Ammerman, C.B., Arrington, L.R., Moore, J.E. and Simpson, C.F., 1964. Feeding value of pelleted rations high in citrus by-products and corn for fattening lambs. Fla. Agric. Exp. Stn., Mimeogr. Rep. AN 65-6. Loggins, P.E., Ammerman, C.B., Moore, J.E. and Simpson, C.F., 1968. Effect of feeding long hay or sodium bicarbonate with ground or pelleted diets high in citrus pulp, on lamb performance. J. Anim. Sci., 27: 745--750. Mead, S.W. and Guilbert, H.R., 1926. Digestibility of certain fruit by-products. Part I. Dried orange pulp and raisin pulp. Univ. California Bull. No. 409. Snedecor, G.W. and Cochran, W.G., 1974. M~todos estadfsticos. 6th edn., C.E.C.S.A. M~jico. Welch, J.G. and Smith, A.M., 1971. Effect of beet pulp and citrus pulp on rumination activity. J. Anim. Sci., 33: 472--475.
11
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
CITRUS PULP IN DIETS FOR FATTENING LAMBS
J. MARTINEZ PASCUAL and J. F E R N A N D E Z CA RMO N A
E.T.S.I. Agr6nomos, Universidad Polit$cnica, Valencia (Spain) (Received 14 November 1978; accepted for publication 12 November 1979)
ABSTRACT Martl'nez Pascual, J. and Fernandez Carmona, J., 1980. Citrus pulp in diets for fattening lambs. Anita. Feed Sci. Technol., 5: 11--22. Digestibility, N retention and energy values of isoproteic rations containing 10% alfalfa hay and a concentrate mixture (16% CP) ~vith 0, 15, 30, 45, 60 and 90% citrus pulp, were determined with 13 wethers. In a second experiment, 18 growing lambs (13.5 kg initial weight) were used to determine the values previously cited when fed on rations (16% CP) containing 0, 30 and 60% citrus pulp. Digestibility coefficients of the various feed fractions were not altered when citrus pulp was added to the diet except that for the ADF fraction which increased (P < 0.01). Organic matter and fibre digestibility were affected by age, the maximum figures being obtained with mature animals; metabolizable and digestible energy values followed a similar trend. Retention of N was inversely related to level of citrus pulp and age. Three growth trials were carried out in which daily gains, feed efficiency, dressing percentage and ruminal keratosis were studied in 108 lambs divided into groups of three and starting the experiment at an average weight of 15 kg. The animals were fed on diets containing 0--60% citrus pulp in the concentrate and 10--15% alfalfa hay. The parameters were not altered significantly up to 30% incorporation of citrus pulp, but if higher quantities were added the animal response was poorer. INTRODUCTION
Digestibility values for citrus pulp (Cp) have mainly been determined in steers. Mead and Guilbert (1926) reported coefficients as high as 89, 84 and 78 for dry matter, crude fibre and crude protein, respectively. A number of observations indicate that, when Cp replaces cereals and provides up to 70% of the total diet, DM and organic matter (OM) digestibility remain high, but may decrease slightly when Cp reaches the highest levels (Bhattacharya and Harb, 1973). Furthermore, CF digestibility values increase. On the other hand, there are few data on energy value and nitrogen retention when Cp is given to ruminants. The experiments described below consisted of two digestibility trials (Experiments I and II (a)) and three growth trials (Experiments II (b), III and
IV).
12 MATERIALS AND METHODS
Experiment I Ten wethers were housed in individual pens with faeces and urine collectors. The diets contained 90% concentrate and 10% alfalfa hay and were supplied at a level of 46.6 g/kg W°. 7s per day as reported b y Cottyn and Boucque (1969). Five concentrates with 0, 15, 30, 45 and 60% of citrus pulp and 16% crude protein were formulated in order to use the same concentrate in both fattening lamb and wether diets (Table I). The alfalfa hay contained 46.3% ADF, 17.7% CP, 23.8% CF, 2.2% EE and 90.8% OM in dry matter. Feed, faeces and urine were analysed by the methods of the Association of Official Analytical Chemists (1975) and Goering and Van Soest (1970). The combustion values of these materials, previously vacuum dried, were determined in a Gallenkamp b o m b calorimeter. Metabolizable energy (ME) values were corrected for methane losses according to the formula o f Blaxter (1964). Volatile fatty acids in the rumen fluid were determined by the method of Baumgardt (1964). A design of incomplete and balanced blocks (Cochran and Cox, 1957), was followed in two consecutive periods with four replicates for each treatment. Three more wethers were used to evaluate rations with 90% Cp, with and w i t h o u t hay, during two periods of 25 days each. These results were not included in the statistical analysis.
TABLE I Ingredients and composition of experimental diets (percentage of DM) 1 Citrus pulp (%) 0
15
30
45
60
90
Barley Maize Soya bean meal Fish meal Supplement
65.5 18.0 13.0 2.0 1.5
52.5 14.6 14.5 2.0 1.4
40.0 10.8 16.0 2.0 1.2
27.2 7.0 17.7 2.0 1.1
15.0 3.0 19.0 2.0 1.1
0 0 9.0 0 1.1
OM EE CF CP A DF ADL
95.1 3.8 5.8 16.2 7.6 1.0
93.6 4.4 6.3 16.8 10.5 1.2
91.9 4.0 7.9 15.9 14.7 1.0
90.7 3.2 8.2 15.3 17.2 0.9
88.7 3.3 9.3 15.8 21.5 1.7
86.1 2.4 12.4 10.4 26.4 1.3
' OM, organic matter; EE, ether extract; CF, crude fibre; CP, crude protein; ADF, acid detergent fibre; ADL, acid detergent lignin.
13
Experiment H Eighteen male Manchego lambs of 13.5 kg average liveweight, housed individually and divided into three groups, were offered food ad libitum until they reached 30 kg liveweight. The diets contained 0, 30 and 60% Cp as in Experiment I. T w o experimental periods of 15 days each were considered. The results were analysed statistically by the general model of variance for one factor of variation. (a) Digestibility, N retention and energy values were determined using the chemical methods described for Experiment I and t w o experimental periods of 15 days each were considered. (b) Average daily gain and dressing percentage were recorded individually whereas food intake and feed efficiency data were taken for each group. Ruminal disturbances were assessed macroscopically.
Experiment III Forty-two lambs of 17 kg initial average weight were divided into seven groups having three males each and seven having three females. Two groups of the same sex were fed with a concentrate of 0, 15 and 30% Cp and 15% of hay. Only one group of males and another of females were fed on the 45% Cp diet. F o o d intake, average daily gain, feed efficiency and dressing percentage were estimated as in Experiment II (b). The results were statistically analyzed following the general model of analysis of variance for two factors of variation with unequal number of replicates (Snedecor and Cochran, 1974).
Experiment IV Concentrates with 0, 10, 20 and 30% Cp were given with 10% hay to 16 groups of three animals, there being two groups of males and t w o of females on each diet. Growth parameters were analyzed statistically following the general model of variance for t w o factors of variation (treatment and sex). In this experiment, ruminal keratosis was studied microscopically in sections of stained ruminal epithelia according to the trichromic m e t h o d of Dualde Perez (1971). The level of keratosis was quantified by measuring the ratio of the thickness of the cornea to that of the germinative epithelia, agglutination and development of papillae. R u m e n colour was assessed by giving numerical values according to its intensity. RESULTS
Experiment I The main results appear in Table II. The digestibility coefficients for dry matter, organic matter and also nitrogen-free extract tended to decrease, but n o t significantly, as the proportion of Cp increased.
83.2 85.6 79.3 49.4 41.4 85.8 29.0 5.3 4.0 3.5
81.7 85.3 83.3 48.9 60.0 84.3 36.6 7.3 4.0 3.5
15
81.2 84.6 78.7 54.2 69.3 83.3 33.1 6.0 3.8 3.3
30
80.2 85.8 73.2 72.6 75.1 82.6 22.7 4.0 3.9 3.4
45
78.7 86.0 72.6 57.5 76.3 83.0 24.3 4.3 3.8 3.2
60
NS NS * NS ** NS NS NS NS NS
Significance of differences
NS = non-significant. *, P < 0.05. **, P < 0.01. 1 T h e r a t i o n s w i t h 90% Cp were n o t i n c l u d e d in statistical analysis, means_+ SE. 2 C o n c e n t r a t e given alone, w i t h o u t hay.
Digestibility (%) DM OM EE CF ADF N R e t a i n e d N (%) (g/day) DE (kcal/gDM) ME (keal/gDM)
0
Cp in c o n c e n t r a t e (%)
0.13 1.56 0.83 1.77 1.16 0.58 3.38 O.57 0.01 0.02
SE
NS NS ** NS ** NS NS NS NS NS
Linear effect
E x p e r i m e n t I. Digestibility, n i t r o g e n r e t e n t i o n , a n d digestible a n d m e t a b o l i z a b l e e n e r g y f o r w e t h e r s
T A B L E II
NS NS NS NS NS
NS
NS NS
Second order effect
78.1-+ 1.3 85.8-+ 0.7 56.0-+ 3.5 70.1-+ 2.0 76.1_+ 3.5 73.6-+3.5 25.1_+5.5 3.4_+ 1.0 3.6-+ 0.05 3.2+- 0.05
90
78.5+1.7 8 6 . 5 -+ 1.2 60.9_+ 3.9 71.5-+3.3 80.7-+ 1.0 71.2-+2.6 31.5-+1.1 3.7_+2.5 3.7+-0.05 3.2-+0.05
902
Cp in c o n c e n t r a t e (%)1
15 The digestibility of crude fibre increased when more Cp was added to the ration and this rise was even greater for the 90% Cp ration. If the latter value is corrected for the digestibility of soya bean fibre, a crude fibre digestibility of 78% is estimated for pure Cp (Fig. 1). The ADF coefficients increased from 41.4% to 76.3% when Cp content was raised from 0 to 60% (P < 0.01) and to 80% for pure pulp. Nitrogen digestibility decreased with increasing level of Cp b u t the differences were not significant. The values decreased from 85.8% in a ration w i t h o u t pulp to 83.0% in the 60%-Cp ration, although this contained 6% more soya bean meal than the former. Digestible and metabolizable energy values fell slightly when the percentage of pulp was increased. Values for pure pulp calculated for the ration containing 90% Cp were 3.6 and 3.1 Mcal/kg. 90
-/
C F' D
/
a~ ' ~ .
/ •~
15
30
o~
/*5
60
% Cp
90
Fig. 1. Crude fibre digestibility in sheep. X, lambs, Experiment II(a), Period I; e, lambs, Experiment II(a), Period II; o, adults, Experiment I; *, adults, Bhattacharya and Harb (1973); n, adults, Devendra (1973).
Experiment II (a) The digestibility of DM, OM, NFE and N did not differ significantly (Table III). As in Experiment I, the digestibility of ether extract and fibre increased with pulp level (P < 0.01). Digestibility of both fibre fractions, CF and ADF, also showed an obvious improvement from Period I to Period II~ as can be seen in Fig. 1. The nitrogen balance was clearly positive and decreased with increasing Cp (P < 0.05). These values were similar in the t w o periods, despite the differences in the level of intake. Figures for retained N (%) showed a clearer picture, declining when Cp levels were raised, and always higher in Period I. Digestible and metabolizable energy value of diets were affected significantly b y treatments, being higher with the 30% Cp ration and lower in Period I than Period II. The acetic/propionic ratio in the ruminal fluid was 1.5, 2.4 and 3.2 (P<0.05) in lambs given 0, 30 and 60% Cp, respectively.
76.0 78.1 75.5 34.3 34.1 72.8 54.0 10.9 3.4 3.0
75.2 78.5 73.9 49.8 62.1 70.7 48.2 8.3 3.6 3.2
30
72.6 76.6 67.5 57.2 69.3 70.6 43.5 7.7 3.3 2.8
60
NS ffi n o n - s i g n i f i c a n t . *, P < 0 . 0 5 . **, P <: 0 . 0 1 .
DM OM EE CF ADF N R e t a i n e d N (%) (g/day) D E (kcai/gDM) M E (kcal/gDM)
Digestibility(%)
0
Cp in d i e t (%)
Period I
NS NS ** ** ** NS ** * ** **
Significance of differences
0.89 0.56 0.83 1.20 1.25 0.39 0.48 0.31 0.07 0.05
SE
NS NS ** ** ** NS ** ** ** **
Linear effect
NS NS ** ** ** NS NS ** ** **
Second order effect
80.0 79.3 78.6 44.2 39.0 76.2 39.9 11.0 3.6 3.2
0
78.1 80.2 71.9 59.6 67.2 73.0 41.0 9.1 3.8 3.3
30
Cp in d i e t (%)
Period II
76.5 79.6 64.3 68.0 77.1 72.6 29.9 6.7 3.5 3.0
60
NS NS ** ** ** NS NS * ** **
Significance of differences
E x p e r i m e n t H (a). Digestibility, n i t r o g e n r e t e n t i o n , a n d d i g e s t i b l e a n d m e t a b o l i z a b l e e n e r g y f o r g r o w i n g l a m b s f o r P e r i o d s I a n d II
T A B L E III
0.79 0.61 0.78 0.61 0.61 O.64 2.38 0.60 O.O4 0.04
SE
NS NS ** ** ** NS NS ** NS **
Linear effect
NS NS * ** ** NS NS NS NS **
Second order effect
17
Experiment H (b) There were no significant differences (Table IV) except for feed efficiency, but the diets with more Cp showed worse results. Hay intake varied from 9.6% of the diet w i t h o u t pulp to 11.4% of the diet with 60% pulp. The level of ruminal keratosis increased as the a m o u n t of Cp in the ration was raised. In some cases there was a low level of keratosis in lambs fed on diets containing 0 and 30% Cp. All the lambs which had eaten concentrate wit~, 60% Cp had more keratosis, and in one it was very severe. T A B L E IV Growth of lambs in Experiment II (b) Cp in diets (%)
Total intake (g DM/day)
Average daffy gain (g/day) Feed efficiency Dressing percentage
0
30
60
Significance of difference
999 312 3.2 49.2
913 272 3.4 48.8
928 234 3.9 48.2
NS NS * NS
SE
Linear effect
Second order effect
23.12 13.45 0.11 0.55
NS NS ** NS
NS NS NS NS
NS = non-significant. *, P < 0.05. **, P < 0.01.
Experiment III The average daily gain of males varied from a m a x i m u m of 272 g with the 15% Cp diet, to a minimum of 127 g with the 45% Cp diet. The same trend was observed with females (Table V). There were differences between sexes in feed efficiency and ADG (P < 0.01), and in food intake and dressing percentage (P < 0.05). The sex X treatment interactions were n o t significant. As in Experiment II (b), the hay refused was gradually lowered as the percentage of pulp was increased. So the real intake of hay (% of concentrate) in males was 12.8, 14.2, 14.8 and 15.1 with 0, 15, 30 and 45% Cp, respectively. The same trend was observed in females.
Experiment IV As in Experiment III, males grew more than females and differences between sexes were significant (P < 0.01). The results were not altered for males when more Cp was added to the diet, but for females they tended to become worse (Table VI). There were no significant differences in the degree of keratosis, developm e n t and agglutination of papillae in the different groups. Some differences were registered (P < 0.05) as regards colour.
18 TABLE V G r o w t h o f l a m b s in E x p e r i m e n t III Cp in diet (%) 0 15 30 45
Sex
Total intake (g D M / d a y )
Gain (g/day)
Feed efficiency
Dressing percentage
Male Female Male Female Male Female Male Female
929 824 942 845 955 820 778 821
259 188 272 199 256 171 127 143
3.6 4.5 3.5 4.3 3.6 4.9 5.5 5.7
55.8 56.5 53.3 56.7 54.7 54.3 53.9 56.6
Treatment difference SE t r e a t m e n t Linear e f f e c t Second order effect Sex d i f f e r e n c e SE sex SE t r e a t m e n t X sex
NS 21.7 ** NS ** 15.4 30.8
** 2.16 ** NS ** 1.53 3.05
** 0.13 ** ** ** 0.09 0.18
NS 0.11 ** NS ** 0.07 0.15
NS = non-significant. **, P < 0.01.
g/day
3OO ~
p
[E d
2oo 100
\
~
e
0
10
x % Cp
p
rfI 9 40
50
60
Fig. 2. Daily w e i g h t gain in lambs. E x p e r i m e n t s II(b), III a n d IV.
Two more lambs, not included in the statistical analysis, were fed on diets containing 30% Cp w i t h o u t hay and they presented a m a x i m u m level of hyperkeratosis; intake and daffy gain were clearly lower. DISCUSSION
It seems that the dry or organic matter of citrus pulp is as digestible as that of cereals, as the addition of Cp did not alter digestibility. The values obtained for growing lambs are lower than those of Experiment I, or those published by Devendra (1973) for castrated rams.
19 TABLE VI G r o w t h o f l a m b s in E x p e r i m e n t IV Cp in diet (%) 0 10 20 30
Sex
Total intake (g D M / d a y )
Gain (g/day)
Feed efficiency
Dressing percentage
Male Female Male Female Male Female Male Female
960 823 1033 830 956 775 988 805
298 236 316 217 311 208 300 200
3.0 3.2 3.1 3.5 2.8 3.5 3.0 3.8
54.7 54.7 51.6 56.7 53.0 55.3 54.9 53.7
NS 11,6 NS NS ** 8.2 14.9
NS 0.15 NS NS ** 0.11 0.21
Treatment difference SE t r e a t m e n t Linear effect Second order effect Sex d i f f e r e n c e SE sex SE t r e a t m e n t × sex
NS 24.6 NS NS ** 16.0 32.0
NS 0.57 NS NS ** 0.41 0.81
NS = non-significant. **, P < 0.01.
The trend in the digestibility of CF showed that the fibre fraction of Cp is clearly more digestible than that of cereals. However, the greater total content of fibre in the rations containing pulp would contribute to a better ruminal degradation of this fraction, and there is the effect of calcium hydroxide mentioned in a previous paper. There was an interval of one month between Periods I and II of Experiment II, and the higher digestibility of OM and fibre in the second period would correspond to greater rumen development. It is accepted that ruminal function is well established between the 8th and 12th weeks of age, the latter age being reached in the second period studied. Ether extract was of low digestibility, which could be ascribed to the high content of essential oils and calcium in citrus pulp. The apparent digestion of nitrogen was poor and tended to decrease with the incorporation of more Cp, despite the higher proportions of soya bean protein (56% in the 60% Cp ration}. The nitrogen of Cp is slightly digestible, as is shown by the values for the diet containing 90% Cp or by that calculated for the pure pulp (64.5%) and it agrees with some earlier work. Ammermann et al. (1963a), studying dried citrus seed meal, reported that nitrogen digestibility was 56% and biological value 46% when the meal supplied 88% of the total protein in the ration. The retention of nitrogen fell as the proportion of citrus pulp increased, which would be further evidence of the low quality of the protein, as mentioned above. It is reasonable to expect that the utilization of the digested nitrogen
20
declines as the animal grows owing to the fact that the absolute amount of digested N is clearly higher, whereas N retention is similar in both Periods I and II (Experiment II (a)) and lowest for wethers (Experiment I). The digestible and metabolizable energy figures determined in Experiment II (a) were lower than those obtained with mature animals, although the results are closer for the animals near 30 kg live weight (Period II, Experiment II (a)). Once faeces and urine energy losses are calculated (Table VII), it is evident that the faecal losses decrease as the animal grows. The urine losses, stated as a percentage of the digested energy, are also smaller in growing lambs, in agreement with their higher urine N o u t p u t and lower N retention compared to the wethers utilized in Experiment I. Conversely, the losses of energy as methane are lower because DE appears in Blaxter's formula as a positive item. Nevertheless, energy losses in urine and methane together do not reach the faecal loss, and the deduced values of ME are highly affected by the digestibility of OM, which increases with the age of lambs. TABLE VII Experiments I and II (a). Energy lost in faeces (FE) and urine (UE) as percentages of gross energy (GE) and digestible energy (DE) Cp in diet (%) 0
30
60
FE/GE
Lambs, Period I Period II Wethers
24.7 22.7 24.2
20.3 19.4 20.1
16.5 16.8 15.5
F E/ DE
Lambs, Period I Period II Wethers
32.8 29.4 31.9
25.5 24.1 25.1
19.8 20.2 18.3
UE/DE
Lambs, Period I Period II Wethers
2.6 2.9 3.7
3.2 3.7 4.6
3.2 3.1 5.0
Values for ME, calculated from the equation of the O. Kellner Institute, are a b o u t 5% (0% Cp) and 12% (30 and 60% Cp) lower than those determined experimentally. Citrus pulp is a product hardly comparable to standard concentrates, because it is easily fermentable, and that formula underestimates methane losses. The incorporation of large proportions of Cp in the diet decreases dally gain of y o u n g lambs, b u t the results frequently follow a curvilinear pattern to give maxima when 10--15% Cp is added (Fig. 2). The average dally gain and feed efficiency values are, in general, within the normal limits elsewhere, b u t they are not comparable to those quoted by
21 Loggins et al. (1964, 1968), Ammerman et al. (1963b) and Chicco et al. (1973), since the lambs used by those workers were 4 months old at the beginning of the fattening period. We may conclude t h a t the incorporation of Cp up to levels of 30% does not alter daily gain, feed efficiency and dressing percentage. Intake and weight gain are closely related. The increasing a m o u n t of fibre of the diets might have reduced intake, but the digestibility of Cp was too high to impose physical limits and also the digestibility of CF in the rations increased as the proportion of Cp increased. However, fibre decreases fattening efficiency. Welch and Smith (1971} reported that Cp gave a longer chewing time than cereal but it was lower when long hay was offered. It was observed t h a t lambs ate more hay when rations with more Cp were supplied. Nevertheless, the pulp is an ingredient with low content of cell walls in spite of its high fibre percentage. A m m e r m a n et al. (1963c) reported a marked parakeratosis in the rumen of steers given Cp with little or no hay; later papers agreed with their findings. This trend was shown in our experiments, although there were no significant differences. The severity of rumen parakeratosis was greatest with 30% Cp and no hay. Regardless of the level of Cp in the diet, severe parakeratosis was not found when lambs ate chopped hay. Loggins et al. (1968) also noticed the most acute cases in lambs consuming an all-concentrate pelleted diet (74% citrus pulp), but A m m e r m a n et al. (1963b) considered that the ruminal epithelium of two lambs given only concentrate (66% citrus pulp) was normal. Frequently hyperkeratosis is related to agglutination of papillae caused by food. In our experiments this effect was not found, perhaps because of the relatively large particle size of the ground pulp used. ACKNOWLEDGEMENTS The authors are indebted to Prof. R. Romero for his help with the statistical analysis, the Instituto Nacional de Investigaciones Agrarias for providing housing facilities, A. Gargallo for his care of the animals and A. Climent for technical assistance. REFERENCES Ammerman, C.B., Van Walleghem,P.A., Easley, J.F., Arrington, L.R. and Shirley, R.L., 1963a. Dried citrus seeds -- nutrient composition and nutritive value of protein. Fla. Agric. Exp. Stn. J., Ser. No. 1783. Ammerman, C.B., Loggins, P.E. and Arrington, L.R., 1963b. Comparative feeding value of dried citrus pulp and ground snapped corn for fattening lambs. Fla. Agric. Exp. Stn., Mimeo Ser. No. 63-13. Ammerman, C.B., Van Walleghem,P.A., Palmer, A.Z., Carpenter, J.W., Hentges, J.F. and Arrington, L.R., 1963c, Comparative feeding value of dried citrus pulp and ground corn and cob meal for fattening steers. Anita. Sci., Mimeogr. Rep., AN 64-8, Univ. Florida. Association of Official Analytical Chemists, 1975. Official Methods of Analysis 12th edn. Washington.
22 Baumgardt, B.R., 1964. Practical observations on the quantitative analysis of free volatile fatty acids in aqueous solution by gas--liquid chromatography. Dep. Dairy Sci., Bull. No. 1, University of Wisconsin, U.S.A. Bhattacharya, A.N. and Harb, M., 1973. Dried citrus pulp as a grain replacement for Awasi lambs. J. Anita. Sci., 36: 1175--1180. Blaxter, K.L., 1964. Metabolismo Energ~tico de los Rumiantes. Ed. Acribia-Zaragoza, p. 193. Chicco, C.F., Duque, C.M., Shultz, E. and Shultz, T.A., 1973. Yucca, citrus pulp and molasses for fattening lambs. Agron. Trop., 23: 587--592. Cochran, W.G. and Cox, G.M., 1957. Experimental Designs. 2nd edn., Wiley, New York. Cottyn, B.G. and Boucque, Ch.V., 1969. Digestibilit~ et valeur alimentaire de pellets de pulpes s~ch~es d'agrumes. Rev. Agric., 11--12; 1543--1551. Devendra, C., 1973. Effect of citrus meal on digestibility of sheep diet. Trop. Agric., 50: 221--224. Dualde Perez, D., 1971. Modificaci0n al m~todo de Gallego para ~ coloraci0n de tejidos en general. Veterinaria, XXXVI: 207--212. Goering, H.K. and Van Soest, P.J., 1970. Forage fibre analyses. Agric. Res. Serv., U.S. Dep. Agric., Agriculture Handbook No. 379. Loggins, P.E., Ammerman, C.B., Arrington, L.R., Moore, J.E. and Simpson, C.F., 1964. Feeding value of pelleted rations high in citrus by-products and corn for fattening lambs. Fla. Agric. Exp. Stn., Mimeogr. Rep. AN 65-6. Loggins, P.E., Ammerman, C.B., Moore, J.E. and Simpson, C.F., 1968. Effect of feeding long hay or sodium bicarbonate with ground or pelleted diets high in citrus pulp, on lamb performance. J. Anim. Sci., 27: 745--750. Mead, S.W. and Guilbert, H.R., 1926. Digestibility of certain fruit by-products. Part I. Dried orange pulp and raisin pulp. Univ. California Bull. No. 409. Snedecor, G.W. and Cochran, W.G., 1974. M~todos estadfsticos. 6th edn., C.E.C.S.A. M~jico. Welch, J.G. and Smith, A.M., 1971. Effect of beet pulp and citrus pulp on rumination activity. J. Anim. Sci., 33: 472--475.