Introduction by decreasing the length of the long fibres in the Materials and methods

26 N .T. Mui et al. Livestock Production Science 66 2000 25 –34

1. Introduction by decreasing the length of the long fibres in the

rind. Voluntary intake by cattle was increased by Sugar cane consists of three principal fractions, 38 when the stalks were chopped to 15-cm lengths stalk, tops and green leaves. The chemical com- and the rind removed, resulting in a DM intake of position and digestibility, which differ between these 18.7 g kg body weight BW Preston, 1977. fractions have been studied by several authors. Perez The objectives of the present study were to and Garcia 1975 found that whole sugar cane identify how the particle size of different compo- contained 16 total sugars, 3.2 crude protein CP nents of the sugar cane plant influenced voluntary and 35 acid detergent fibre ADF, all expressed in feed intake of growing goats and how different rates percent of dry matter DM, and 11.3 MJ kg DM. In of CWSC inclusion influenced feed intake and the work reported by Mui et al. 1996 the DM growth rate. content was 28–29 in the leaves, 16–18 in the tops and 24–29 in the stalks. DM digestibility has been found to be between 69 and 72 for the stalk

2. Materials and methods

or stalks mixed with leaves Ffoulkes and Preston, 1979. While the digestibility of the fibre in sugar 2.1. Location and climate of the study area cane does not exceed 25, in contrast to the grasses the overall digestibility does not decrease with The experiments were conducted at the Goat and maturity. There is rather a slight increase in di- Rabbit Research Centre, Hatay province, 60 km gestibility, since accumulation of the soluble cell north-west of Hanoi. The Centre is located in the contents sugars more than offsets the decline in cell buffer zone between the mountainous area and the wall digestibility caused by lignification of the delta, 1058259 E and 218069 N, 220 m above sea structural cell wall carbohydrates Preston, 1977. level. The climate is monsoon-tropical, with a wet In the last decades much work has been done on season between April and November and a dry sugar cane, concerning digestibility, metabolism and season from December to March. Average annual effect of supplementation with non-protein nitrogen, rainfall is 1850 mm, with a mean temperature range minerals or protein-rich foliages. The studies have of 24–308C. The experiments were conducted in the generally focussed on milk and meat production in dry season. systems with dual-purpose cattle. There is, however, very little known about the feeding of chopped 2.2. Experimental animals and feeds whole sugar cane CWSC to growing and lactating goats. One hundred and fifty-six crossbred goats, F1 When evaluating tropical forages feed intake is a crosses between Bachthao as the breed of the dam very important component of the feeding value as a and three Indian breeds Barbary, Jamnapari and high feed consumption creates the necessary con- Beetal were used as experimental animals. The ditions for an increase in production McDonald et experiment started when the goats had an initial al., 1992. There are many factors affecting feed weight of 10.2–11.9 kg and were between 3.5 and 4 intake, among which different methods of processing months of age. Two animals of similar weights and have been examined to increase the feed intake. A age and, if possible, of the same sex were penned decrease in particle size by chopping or grinding together. The animals were exercised once daily for generally results in higher intakes of roughages in 1 h in a yard and were drenched against internal and small ruminants Gherardi et al., 1992; McSweeney external parasites with ivermectin 1 ml 10 kg BW and Kennedy, 1992 The methods of processing injected subcutaneously and albendazole 0.1 mg sugar cane for animal feeding have been based on kg given orally before the experiment commenced. the concept that digestibility and voluntary feed The forages used in the experiment were sugar intake would be enhanced by eliminating the more cane Saccharum officinarum, Guinea grass GG lignified part of the rind of the sugar cane stems or Panicum maximum and leaves of jack fruit Ar- N .T. Mui et al. Livestock Production Science 66 2000 25 –34 27 Table 1 30 bone meal. The chemical composition of the Chemical composition of the feeds feeds is shown in Table 1. DM OM Ash CP CF g kg g kg g kg g kg g kg 2.3. Experimental design DM DM DM DM Jack fruit 328 891 112 145 275 Concentrate 900 977 14 185 71 2.3.1. The intake experiment MUB 670 – – 370 49 Three experiments were carried out to study the Guinea grass 254 891 109 81 380 intake of three fractions of whole sugar cane leaves, Whole sugar cane 256 978 21 21 297 tops and stems chopped into different lengths. The Stalks 270 – – 17 235 animals, 108 growing goats 1–2 weeks after wean- Tops 183 – – 41 362 Green leaves 294 – – 76 393 ing, were given leaves, tops and stalks ad lib. at the rate of 150 of the fresh intake the previous day Castle et al., 1979; Forbes, 1995; Peacock, 1996. tocarpus heterophyllus. The sugar cane leaves were Each experiment lasted 19 days, with 10 days of harvested daily, while the cane tops and stalks were adaptation to the diet and 9 days of measuring intake harvested weekly. The jack fruit leaves and GG were and refusals. Samples of feed offered and refusals harvested daily early in the morning from the area were taken for DM determination every day. The around the centre. GG was cut at 35–40 days and air goats were given a basal diet of concentrate 50 dried under shade or in the house for 1 h before g day, MUB 50 g day and jack fruit foliage 400 feeding. The concentrate used in the experiments g day as a protein source, corresponding to the was produced at the centre using local ingredients requirements for growing goats at 10 kg BW and a 20 rice bran, 12 maize meal, 15 cassava root liveweight gain of 50–100 g day Devendra and meal, 30 groundnut cake, 10 soy bean meal, 4 McLeroy, 1982; Table 2. fish meal, 3 salt and 6 minerals. The molasses– The foliage was given as small bunches hanging urea blocks MUB consisting of 35 rice bran, above the feeding troughs of the pen. The sugar cane 10 urea, 15 minerals, 5 salt and 35 molasses was chopped with a machete. Sugar cane leaves, tops were also made at the centre. The mineral mixture in or stems were offered three times daily, one-third in the concentrate and the MUB was 70 CaCO and the morning 07:00 h together with the MUB, one- 3 Table 2 The diets in the growth and the digestibility experiment and the recommendations for DM intake and requirements of growing goats Feed g day BW 10 kg 12.5 kg 15 kg 20 kg DM CP DM CP DM CP DM CP Concentrate 45 8 67 12.5 90 16 135 25 MUB 33 12 33 12 33 12 67 24 Jackfruit 130 19 130 19 130 19 260 38 Basic diet, total 208 39 235 43.5 257 47 462 87 75 CWSC GG 620 705 770 1380 of total diet DM Total DM fed 828 940 1027 1842 Intake of DM and requirement of CP , growth 50 –100 g day a After Devendra and 505 40 545 44 584 47 663 53 McLeroy 1982 a After Peacock 1996 300 43 375 47 450 51 600 59 a Digestibility of CP estimated to 0.7. 28 N .T. Mui et al. Livestock Production Science 66 2000 25 –34 third at noon 12:00 h together with the concentrate intervals during the whole experimental period 110 and the rest in the afternoon 18:00 h together with days, always before the morning feeding. jack fruit foliage. All the feeds were fed in separated troughs. The animals had free access to fresh water 2.3.3. The digestibility experiment and a mineral lick with the composition 70 Six male goats were chosen for a digestibility trial. Ca PO , 15 NaCl and 15 cement as a binding 3 4 2 The goats were randomly allocated to same six diets agent. The liveweights were recorded before and as in the growth experiment Table 2 and with the after the experiments. same feeding and management routines as in the In the first part of the experiment 36 goats were intake experiment. The experiment consisted of 9 fed green sugar cane leaves, harvested at the normal days adaptation followed by 7 days collection, harvesting time. The goats were divided randomly repeated for three periods using the same animals but into six groups of three males and three females. The with a new random allocation for each period. All sugar cane leaves were chopped into five different animals were penned in digestibility crates during the lengths; 5, 10, 15, 20, 25 cm and one group was experiment but were allowed 10 days of free feed- given whole leaves. ing grazing between the collection periods. In the second part of the experiment 36 goats were During the collection period, feed offered and randomly divided into three groups of 12 goats refusals of CWSC, GG, jack fruit foliage, concen- seven males and five females. The goats were fed trates and MUB were measured and faeces were sugar cane tops chopped three different ways: i collected. Samples of feed and refusals were taken 1–3-cm slices, ii 15-cm lengths and split into two for analysis of content of DM, CP and crude fibre parts, iii 20-cm lengths and split into four parts. CF. The faeces were weighed every day at 07:00 h In the third part of the experiment 36 goats were then mixed thoroughly and 10 was taken for DM randomly divided into three groups of 12 goats eight determination at 608C. The samples were analysed males and four females. The goats were fed sugar using the standard methods of AOAC 1985. The cane stalks chopped three different ways: i 1–3-cm digestibility coefficients for DM DDM, CP DCP slices, ii 20-cm lengths and rind removed, iii and CF DCF of the total diet were calculated as 15-cm lengths and split into four parts but with the described by McDonald et al. 1992. rind remaining. 2.4. Statistical analysis 2.3.2. The growth experiment In the growth experiment the effect of the level of The data from the experiments were analysed CWSC inclusion on growth and feed intake was using Minitab Software 1994. The results from the examined. Based on the results from the intake intake and the growth experiment were analysed experiment the smallest particle size 1–3 cm was using one-way analysis of variance. The treatment chosen for the experiment. A completely randomized means which showed significant differences at the design was used and 48 goats were allocated to six probability level of P , 0.05 were compared with treatments five males and three females per treat- each other using the Fisher pairwise comparison ment, where CWSC was combined with GG at six procedures. different ratios. The same feeding and management The model used in the analysis was: routines as in experiment 1 were used. The diets in the experiment and the requirements for growing Y 5 m 1 T 1 e ij i ij goats are presented in Table 2. The ratios of CWSC GG on a DM basis of 0 100, 20 80, 40 60, 60 40, where Y is the jth observation of the ith treatment, ij 80 20 and 100 0, corresponded to 0, 15, 30, 45, 60 m is the general mean, T is the effect of the ith i and 75 CWSC in total dietary DM. The amount of treatment, and e is the random error effect. ij DM and CP was chosen to cover requirements for The results from the growth experiment were maintenance and growth of goats at different live subjected to an analysis of variance for a completely weights. The animals were weighed at 2-week randomised design. The data were corrected by N .T. Mui et al. Livestock Production Science 66 2000 25 –34 29 covariance using initial weight as independent vari- where Y is the jth observation of the ith treatment, a able adjusting feed intake, live weight gain and feed the intercept, b the slope of Y against the corre- i conversion ratio FCR calculated as total DM intake sponding value of X , X the effect of the ith i i divided by total liveweight gain of the animals for treatment, and e the random error effect. ij the overall experimental period. The model used was:

3. Results