Effect of supplementing urea treated rice straw and molasses with different forage species on the performance of lambs

The UTR-molasses and forages were fed ad libitum and supplied at a level of 150% of the average consumption in the previous week. The concentrate was fixed to 1.5% of BW. The amount of concentrate was changed according changes in BW every 2 weeks after weighing.

In the digestibility trial 8 weaned male lambs with the same age and BW as the lambs in the growth trial were used in a replicated 4 x 4 Latin square design. The lambs were allocated to individual metabolic cages of 1 m x 1 m made of wood. The height of the cages was 0.5 m above the floor to be able to easily collect faeces and urine. The layout of the trial is presented in Table 1.

The diets offered and the feeding regimes were the same as in the growth trial and the digestibility experiment started 2 weeks after the feeding trial. In each period of observation, the lambs were adapted to the experimental diets for 14 days and the next 7 days were used for collecting data. Between periods the lambs were allowed 7 days for relaxing, with a normal diet of UTR-molasses, 100 g concentrate, Guinea grass and Jackfruit foliage.

Measurements and analyses

Feed offered and feed refusals were recorded daily. Water offered and refused was also measured daily during the data collection period for both the growth and the digestibility trial. In the growth trial, samples of feed offered and refused were taken weekly for analysing DM, then pooled to monthly samples for further analysis. The refusals of mixed UTR and molasses were assumed to have the same proportion of molasses as the feed offered.

The faecal samples of individual animals were taken directly from the rectum in the morning for counting gastro-intestinal parasite eggs (Nematodes, Coccidia oocysts and Cestodes). Faecal egg count (FEC) was determined using a modified McMaster method (MAFF 1977) with a lower limit of detection of 50 eggs per g of faeces. The samples of faeces (4 g) were ground and mixed with 56 ml of flotation fluid (360 g NaCl and 1 litre of water). After filtering through a tea strainer, a sub-sample was transferred to both sides of a McMaster counting chamber and allowed to stand for 5 minutes. Nematodes and Cestodes eggs and Coccidia oocysts was counted under a microscope at 10 x 10 magnification (Hansen and Perry 1994). FEC was recorded at the 10^th day after parasite treatment and then at every 4 weeks.

In the digestibility trial, the samples of feed offered and refused were taken daily during the collection periods for analysing DM, and one portion of each sample was taken and pooled to an individual weekly sample. The faeces and urine excreted by each animal was recorded twice a day at 7:00 h and 18:00 h. At each collecting time, 10% of the faeces was sampled and frozen at –20^oC. Urine was collected in a jar containing 10% sulphuric acid (urine pH<3) to preserve the nitrogen (Chen and Gomes 1992) and 10% of the total urine was also sampled every day and stored at 4^oC.

The feed offered and the refusals in both experiments were analysed for DM, CP, neutral detergent fiber (NDF), acid detergent fiber (ADF), ash and total tannins. The faeces were analysed for DM, ash, CP, NDF and ADF and the urine for N. DM was analysed according to the standard methods of AOAC (1990). DM of the UTR-molasses and forages was evaluated weekly, and daily in the rainy period. Nitrogen was determined by the Kjeldahl procedure and CP was calculated as N*6.25. NDF and ADF were determined by the methods of Van Soest et al. (1991). Total tannins were measured according to AOAC (1975). The costs of the diets were calculated using prices at the Goat and Rabbit Research Center and the local markets around the center during the experimental period.

Statistical analysis

The data were analyzed statistically by using the GLM procedure of Minitab Software, version 13.31 (Minitab  2000). Treatment means which showed significant differences at the probability level of P<0.05 were compared using Tukey’s pair-wise comparison procedures. The statistical model used in the analysis of the growth trial was:

Y_ij = m + T_i + βW_j + e_ij 

where Y_ij is the dependent variable, m is the overall mean, T_i is the effect of treatments (diets), initial weight (W_j) was used as a covariate factor in the model. The slope β describes the change in the response Y when the covariate W increases one unit and e_ij is the random error, independent and normally distributed.

The statistical model used in the analysis of digestibility trial was:

Y_ijk = m + T_i+ P_j + A_k + e_ijk

where Y_ijk is the dependent variable, T_i is the effect of treatments (different diets), P_j is the effect of period, A_k is the effect of animal and e_ijk is the random error effect.

The number of Nematode eggs was analysed using log₁₀ transformation, while Coccidia oocysts and Cestodes eggs were analysed using log₁₀ [Coccidia oocysts (or Cestodes) +1] transformation due to the fact that the data contained many zeros and were not normally distributed. The results were back-transformed by taking anti-logarithms of the least squares means and standard error of Nematodes was presented as geometric means, and Coccidia oocysts and Cestodes were presented as geometric means-1.

Results

Chemical composition of the feeds

The chemical composition of the feeds is shown in Table 2.

The growth experiment: feed intake, nutrient intake, water consumption, LWG and feed conversion ratio

The amount of UTR-molasses offered was significantly different among treatments (Table 3).  The highest amount of DM offered was in the control diet, significantly higher than in the diets UTR-S and UTR-C, but similar to the UTR-J diet. The total amount of DM offered was highest for the diet UTR-J, significantly higher than for UTR-S, UTR-C and the control diet. However, there were no significant differences between the UTR-C and the control diet.   

The total DMI recorded for the animals fed the diet UTR-J (739 g) was significantly higher than for the diets UTR-C (573 g) and UTR-S (613 g), but was not significantly different from the control diet (676 g). The UTR-molasses intake was lower for the treatments UTR-S and UTR-C and higher for the control and UTR-J treatments. There was, however, no significant difference in intake of UTR-molasses among the UTR-S, UTR-C and UTR-J treatments.

The daily DMI ranged from 3.3% to 4.4% of BW and was not significantly different among treatments. Amount of DM consumed in percent of DM offered ranged from 65% to 77% and was also not significantly different.

The water consumption was highest in the animals fed the control diet and the UTR-J diet (1090 g) but was significantly lower for the diets UTR-S (790 g) and UTR-C (630 g). There was no significant difference between the UTR-S and UTR-C diets. The water intake ranged from 1.1 kg to 2.8 kg/kg DMI. The CP intake was significantly lower in the UTR-S diet compared to the UTR-J (118 g) and the control diets (108 g), but the CP intake from the UTR-C diet was not  significantly different from the other diets (104 g). The NDF consumed was significantly lower for the UTR-C diet compared to the other diets. The intake of total tannins in the UTR-J diet was 25.7 g/day, significantly higher compared to the UTR-C (12.1 g/day) and UTR-S (9.7 g/day) diets. The estimation of energy intake showed that there was no significant difference in energy intake among treatments and that energy intake ranged from 5.9 to 6.5 MJ/day.

Changes in LWG and feed conversion ratio (FCR) are presented in Table 3. There was no difference in the initial BW or the final BW. The LWG ranged between 70.0  and 77.7 g/day and was not significantly different among diets. The FCR of DM was significantly lower for the UTR-C diet compared to the UTR-J diet but was similar to the other diets; the FCR of CP was significantly higher for the UTR-J diet compared to the other diets.

The growth experiment: effect of the different experimental diets on internal parasites

The effect of the different experimental diets on internal parasites is shown in Figures 1 to 3.   In general, the number of parasite eggs from internal parasites was low in all experimental diets. In the diets which contained total tannins, the number of eggs was reduced or slightly increased during the period from start to 70 days of experiment. The numbers of Nematode eggs in the UTR-J and UTR-C were reduced from 1877 and 3504 eggs/g faeces at the first time of counting to 1235 and 2556 eggs/g faeces after 60 days, respectively, and increased slightly after 70 days of experiment to 2946 and 3047 eggs/g faeces. In the diets without or with low content of total tannins (control diet and UTR-S), the number of Nematode eggs increased during the time of the experiment.

Figure 1. Effect of different experimental diets on number of Nematodes, in the faeces of growing lambs.

Figure 2. Effect of the different experimental diets on number of Coccidia oocystts, in the faeces of growing lambs

Figure 3. Effect of the different experimental diets on number of Cestodes, in the faeces of growing lambs

The digestibility experiment

The daily intake, apparent digestibility and nitrogen balance are presented in Table 5. The intake of UTR-molasses was highest in UTR-J, significantly different from the control, UTR-S and UTR-C diets. The total DMI of all diets ranged from 810 g to 1057 g/day, and was significantly higher for the UTR-J diet compared to the other diets. The digestibility of DM (and OM) was similar for the control 633 g/kg (675) and the UTR-C 604  (635) diets, but was significantly higher than for the UTR-S, 548  (581) and UTR-J, 540 (576), diets. However, the CP digestibility did not show the same trend as for the DM digestibility. The CP digestibility of the UTR-J diet was significantly lower than for the other diets, which were not significantly different from each other. The results were the same for the NDF digestibility. The ADF digestibility was not significantly different among treatments.

The N intake was higher and similar in the diets UTR-J, UTR-C and control, and lower in the diet UTR-S. The N retention was positive in all diets, ranging from 9.8 g to 10.9 g/day, and was not significantly different between diets. The economic outcome of feeding the different diets is shown in Table 8. The cost/kg LWG of the control diet was higher than for all the experimental diets. If the cost/kg LWG of the control treatment was fixed to 100% the costs of the diets UTR-S, UTR-C and UTR-J were 90.5%, 56.2% and 35.7%, respectively.

Discussion

Chemical composition of the feeds

The CP of UTR with 4% of urea was 113 g/kg DM, lower than reported by Khang and Dan (2001) (132 g/kg DM) and higher than the 96 g/kg DM obtained by Do et al. (2002), but similar to the results reported by Selim et al. (2004). The variation in CP concentration in the urea treated rice straw can depend on the rice straw varieties used, fertilisation and harvesting period (Shen et al 1998). The CP content of the Stylosanthes forage was 154 g/kg DM, lower than reported by Phengsavanh and Ledin (2003) and Mupangwa et al. (2000) (190 g/kg DM), but higher than the 124 g/kg reported by Villaquiran and Lascano (1986). The CP concentration in the Stylosanthes forage is mainly affected by the harvesting frequency. According to Tarawali (2005) the CP concentration of Stylosanthes is around 170 g/kg DM, but can decrease very fast from 188 g at a harvesting frequency of 2 months to 94 g/kg DM at a harvesting frequency of 4 months. The Cassava foliage had a CP content of 202 g/kg DM in the present study. This value is lower than the results reported by Vongsamphanh and Wanapat (2004) (230 g to 258 g/kg DM) in different Cassava varieties, by Khang and Wiktorsson (2006) (215 g) and by Phengvichith and Ledin (2007), (211g). However, it is in the range of CP content of Cassava foliage of 146 g to 361 g/kg DM, reported by Oyenuga (1968), Seerley (1972) and Devendra (1977). The CP content in the Jackfruit foliage was 148 g/kg DM. This result is in agreement with values obtained by Mui et al. (2001), Mui et al. (2002) and Van et al. (2005), but it is higher than the 129 g reported by Das and Ghosh (2007). The difference in CP concentration of the foliages could be a result of differences in the proportion of leaves and stems in the harvested material, or in the method of sampling. It also could be affected by the harvest stage, since CP is normally higher in young compared to mature foliages.

The content of total tannins in the Jackfruit in this study was 48 g/kg DM. This is in agreement with the values reported by Van et al. (2005) and Van et al. (2006) of 40 to 42 g/kg DM. The total tannin in the Cassava foliage was 23 g/kg DM, lower compared to the results reported by Netpana et al. (2001), Wanapat et al. (2001) and Dung et al. (2003) with 33 g, 31 g and 39 g/kg DM, respectively. The different content of total tannins could be due to stage of plant growth, season of collection or proportions of the foliage materials sampled (Makkar and Becker 1998; Salem  2006. Mupangwa (2000) found 15.6 g/kg DM of total tannins in Stylosanthes hay, and the Stylosanthes forage in this study contained 16 g/kg DM. The total concentration of tannins in the forages did not seem to have any negative effects on intake or performance of the lambs. Barry and McNabb (1999) concluded that the concentration of condensed tannins in Lotus corniculatus (30 g to 40 g/kg DM) in the diet of sheep increased the absorption of essential amino acids without affecting voluntary feed intake and feed conversion ratio but the performance of sheep was depressed at the level of 75 g to 100 g/kg DM of condensed tannins in the diet.

Effect of supplementation with protein rich forages on DMI, LWG, digestibility and economic efficiency.

In this experiment, using protein rich forages (Stylosanthes, Cassava and Jackfruit) as a replacement for the concentrate in the diet of sheep resulted in no significant differences between the experimental and control treatments in relation to g DMI per kg BW. The total DMI in g/kg BW of lambs fed the diets UTR-S, UTR-C and UTR-J, were 34 g, 33 g and 44 g, respectively. Phengsavanh and Ledin (2003) found that the total DMI of goats was improved to nearly 30 g/kg BW when supplementing 40% Stylosanthes forage in the diet, and 41 g/kg BW by West African dwarf goats when fed Stylosanthes hamata cv. Verano mixed with guinea grass (Bamikole et al.  2001). Dung et al. (2003) indicated that the g DMI/ kg BW of growing goats fed a basal diet of guinea grass and Cassava chip was 34 g, when 25% of concentrate supplementation in the diet was replaced by Cassava hay. Similar DMI in g/kg BW of lambs compared to the present study was indicated by Van et. al. (2007) (47 g/kg BW), when offering diets of Jackfruit, sugarcane and concentrate. The difference in the DMI could be due to characteristics of the animal species or of the feeds in the diet (McDonald et al.  2002). According to NRC (1985) and Gatenby (1991) the DMI of sheep normally ranges from 15 g to 30 g/kg BW, but in good feeding conditions and with feeds with high intake characteristics, the DMI of sheep could reach 40 g to 50 g per kg BW.

The DMI from Stylosanthes and Cassava was 19 g/kg BW and from Jackfruit 26 g/kg BW. Forage from Stylosanthes, Cassava and Jackfruit made up 58%, 56% and 59%, respectively, of the total DMI. If judged by the DMI it can be concluded that Jackfruit has better intake characteristics than Cassava and Stylosanthes. Keir et al. (1997), Mui et al. (2001), Kouch et al. (2003), Van et al. (2005) and Das and Ghosh, (2007) also concluded that foliage from Jackfruit is an excellent feed for ruminants, with high intakes. However, the DM content in Jackfruit in present study was 2.0 and 1.6 times higher than in Cassava and Stylosanthes, respectively. The higher water content could have had a negative effect on the feed intake from Cassava and Stylosanthes. The differences in water content in the forages resulted logically in significantly different water consumption, higher in the diets UTR-J and control. According to McDonald et al. (2002) the animal obtains water from three sources: drinking water, water in the feeds and metabolic water. In a cool environment, non-lactating sheep need between 1 to 2 litres of water/kg DMI. If a sheep eats green grass or other feeds with high water content (at least 60%), it reduces the requirement for drinking water (Gatenby 1991).

The LWG of the lambs was not significantly different among the treatments in spite of the protein sources being different and the total CP intake being lower in the diet UTR-S compared to the other diets. The LWG was similar to the result obtained by Binh et al. (2003), who found that the LWG of Phan Rang lambs was around 68 g to 73 g/day. The CP digestibility was significantly higher in the diets UTR-C, UTR-S and control compared to UTR-J and the N content in the urine and faeces was higher in the diet UTR-J, so even if the CP intake was high in the UTR-J diet this did not result in any higher N-retention or better growth.

The CP and MJ ME consumed in this study was sufficient for lambs of 20 kg of BW gaining 50 g per day in all treatments according to the nutrient requirement of sheep as reported by Paul et al. (2003) so unless there were appreciable differences in the utilization of the nutrients no differences in LWG could be expected.

The economic efficiency was highest when feeding the diet UTR-J, but the FCR for DM and CP was significantly higher for the diet UTR-J. The costs of the diets were based on the prices of the feeds at the Goat and Rabbit Research Center, which means that the results are valid for the local situation but may be different in other conditions.

Effect of secondary compounds (total tannins) in protein rich forages on the infection by internal parasites.

The Nematode egg counts/g faeces of the sheep were reduced during the time of the experiment after 10 days to 60 days for animals fed the diets containing tannins. The number of parasite eggs in this study was similar to the results reported by Dung et al. (2003), where the Nematode egg count in the faeces of weaned goats was lower in the groups fed the diet of Cassava hay, Cassava chip, guinea grass and concentrate compared to the diet without Cassava hay, but higher than the results reported by Van et al. (2006), when goats were fed Acacia foliage supplemented with Paragrass and concentrate. Since the animals were de-wormed at the start of the experiment, fed a presumably clean basic feed (UTR) and the forages were cut, not grazed, high levels of parasite eggs would not be expected. Hoskin et al. (1999) found that when red deer consumed forages high in condensed tannins, the gastrointestinal worm burden, including T. circumcincta and Trichostrongylus axeis was reduced. Sheep grazing on forage high in condensed tannins (Lotus spp. forage), had a lower number of O.circumcinct worms compared to animals grazing on forages low in condensed tannins (Nieze et al. 1998). The FEC in the faeces of goats were reduced when diets were supplemented with Cassava hay (Netpana et al.  2001) or Cassava foliage (Seng and Rodriguez  2001). The faecal parasite egg counts of goats were lower in the diets with foliages of Cassava, Jackfruit or Leucaena compared to feeding Guinea or Ruzi grass (Lin et al.  2003). Athanasiadou et al. (2001) found that FEC in sheep faeces was lower when the sheep were drenched with condensed tannins extract. According to Barry and MacNabb, (1999) the tannins form complexes with the dietary proteins and these complexes reduce nematode viability. The effect of condensed tannins may be an interaction of condensed tannins with the external surface of larvae (Kahn and Diaz-Hernandez  2000).

Conclusions

• Stylosanthes forage and Cassava and Jackfruit foliage could be used as protein sources in a diet based on urea treated rice straw and replace a commercial concentrate without any effect on the live weight gain of the sheep.

• Feeding Stylosanthes forage and Cassava and Jackfruit foliage in the daily diet of sheep is very easy to apply for farmers, and a reduced price of products will lead to an improvement of the economical efficiency compared to concentrate supplementation.

• Using forages containing tannins such as Jackfruit or Cassava can possibly reduce the number of internal parasites with time.  

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