Effect of jackfruit leaves on feed utilization and ruminal fermentation of growing goats

Lam Phuoc Thanh, Pham Truong Thoai Kha, Pham Van Trong Tinh¹ and Tran Thi Thuy Hang¹

Department of Animal Sciences, College of Agriculture, Can Tho University, Viet Nam
phuocthanh@ctu.edu.vn
¹ Department of Agricultural Technology, College of Rural Development, Can Tho University, Viet Nam

Abstract

This study aimed to evaluate effect of jackfruit leaves (JF) replacing for Para grass (PG) on intake, digestibility, nitrogen balance and ruminal fermentation in growing meat goats. Four male Boer goats, 4 months old, were used in a 4×4 Latin square design. A basal diet consisted of pelleted concentrate and PG (C:F 30:70). The treatments were 4 levels of JL (0, 50, 75 and 100%) replacing PG on a DM basis (equivalent to: 0, 36.9, 52.7 and 70.3% of diet DM on basis of actual intakes during the experiment). Result showed that replacement of JL for PG in the diets increased (p<0.01) DM intake (DMI), accounting for 27.8, 54.9, 54.2% increase in diet containing 36.9, 52.7 and 70.3% JL compared with diet contained only PG. Goats fed 70.3% JL in the diet decreased (p<0.05) NDF digestibility by 41.3% compared with those fed only PG. Nitrogen retention showed the greater values (p=0.06) in goats fed JL diets (8.77-9.76 g/d) compared with goats fed only PG (4.31 g/d). A greater live weight gain (p=0.08) of goats consumed JL-diets, accounting for 87.8-131 g/d increase compared to goats fed only PG. Total VFA and NH₃-N concentrations were not affected, but blood urea nitrogen decreased linearly (p<0.01) by increasing levels of JL in the diets. Overall, combined data suggest that substitution of JL for PG at 75 and 100% in the diets of growing meat goats reduces nutrient digestibility, but improves nutrient intake, nitrogen retention and live weight gain without affecting ruminal fermentation. Thus, feeding JL instead of PG in growing meat goats would get positive efficiency of feed local resources and animal performance.

Key words: digestibility, jackfruit leaves, meat goats, nitrogen balance, ruminal fermentation

Introduction

Domesticated ruminants, including meat and dairy goats contribute immensely to sustainable food and nutrition systems because these ruminants can convert low-value human-inedible feed input into high-value human-edible protein output in the form of meat and milk (Ben Salem and Smith, 2008; Enahoro et al 2019; Salami et al 2019). In recent years, livestock population has been driven rapidly by increasing demand for animal proteins due to a concomitant rise in population, urbanization and household income. Livestock production systems demand high energy inputs, land, chemicals and water – all of which are becoming increasingly scarce (Preston, 2009). Meanwhile, some tropical regions (e.g., Viet Nam) are characterized by long dry season with inconsistent rainfall patterns, which makes challenging to get enough forage for the maintenance of small ruminants. Distel et al (2020) suggested that replacement of simple traditional forage by complementary forage species that enable ruminants to select a diet in benefit of their nutrition, health, whilst reducing the negative environmental impacts caused by agricultural systems. Therefore, an approach promoting to improve efficient use of feed local resources is very necessary. In this regard, jackfruit (Artocarpus heterophyllus) leaves (JL), a fodder tree leaves, can be used as an alternative forage source for traditional grasses in goat production. This foliage characterized by great contents of dry matter (33.2%), crude protein (16.6%) and neutral detergent fiber (52.6%) (Mui et al 2002) compared to more common forage crops for ruminant feed such as Para grass (Brachiaria mutica) (Mui et al 2002), Napier grass (Maleko et al 2019) and Guinea grass (Oliveira et al 2020). Moreover, JL also has high content of insoluble protein (Kouch et al 2003) and phenolic compounds, e.g. tannins (Pal et al 2015).

Goats can feed more types of grass compared with other ruminant species (Shaheen et al 2020). Van et al (2005) concluded that goat diet containing many kinds of foliage potential resulted in higher intake compared to feeding the foliage alone. In Viet Nam, 38% jackfruit trees (approximate 30,000 hectares) are cultivated in Mekong delta, a down south region. To our knowledge, no reports have been published on the replacement of traditional forage in goat diets by JL which is more specifically forage in tropical countries, particularly Mekong Delta – Viet Nam, where this forage material is readily available with large amount and can be a very low-cost and viable alternative for goat feeding. Thus, this study aimed to evaluate effect of replacement of JL for Para grass (PG) on intake, digestibility, nitrogen (N) balance, and ruminal fermentation in growing goats. The hypothesis was that increasing supplement of by-pass protein from JL, digestibility would not be an index of nutritive value, which is generally believed.

Materials and methods

Study site

The studies were conducted in Vietnam at Can Tho University Farm (Hoa An campus), Phung Hiep district, Hau Giang province, 40 km south-west of Can Tho city, a center of Mekong Delta in Viet Nam. The experimental site is between the coordinates 9°47′ N latitude and 105°28′ E longitude, and at an elevation of 2 m below sea level. The area receives about 1,800 mm of rainfall per year. The climate is tropical monsoon, with a wet season between May and November and a dry season from December to April. The mean daily temperature ranges from 20°C to 35°C.

Animal, experimental design and diet

Four male Boer goats (Photo 1), 4 months old, and 15.1 ± 1.41 kg body weight were housed in individual cages (1.2m × 0.6m × 1.2m, L×W×H) and fed a basal diet of Para grass and concentrate. Animals were allocated to 4 treatments in a 4×4 Latin square design. The treatments were 4 levels of JL (0, 50, 75 and 100%) replacing PG on a DM basis (equivalent to: 0, 36.9, 52.7 and 70% of diet DM on basis of actual intakes during the experiment). Each experimental period was lasted for 14 days including 7 days for adjustment and 7 days for sampling. Diets were offered in equal amounts twice daily at 07:30 and 17:30 h. The concentrate used in the experiment was mixed and pelleted from ingredients including 29.6% soybean meal, 37.7% ground corn, 30% rice bran, 0.6% limestone, 0.3% DCP, 0.5% NaCl, and 1.4% premix of mineral and vitamin (as DM basis). The foliage of jackfruit was pruned from 3-5 years old trees (Photo 2) ensuring that some branches were left for continued growth. The leaves were separated from the branches (Photo 3) and offered to the goats. Para grass was cut daily at 30-40 days regrowth and chopped before feeding. Both JL and PG were collected from the areas around Can Tho University Farm.

Photo 1. Goats in the study	Photo 2. Jackfruit trees
Photo 3. Jackfruit leaves

Sampling and measurements

From d8 to d12, data on feed offered and refused as well as total fecal and urine outputs were recorded daily for each goat during a 5-d period. Feces were collected in wire-screen baskets placed under the floor of the cages, and urine was collected through a funnel into plastic buckets containing 50 mL of 10% H₂SO₄. The acidification to keep the final pH of urine below 3 was necessary to prevent loss of volatile ammonium and microbial degradation. Representative samples (10%) of feeds, feces, and urine were collected over 5 consecutive days, stored at −20°C, and pooled for chemical analysis. On d13, blood samples were collected before the morning meal for analysis of blood urea nitrogen (BUN) concentration. Briefly, blood was withdrawn from the jugular vein into evacuated tubes containing lithium heparin, immediately placed on ice, and centrifuged at 4,500×g for 5 min. On d14, rumen fluid samples were collected at 0, 3 and 6 h post morning feeding using a 100-mL syringe. The rumen fluid was immediately determined pH value. The subsample was then filtrated through a clean double layer of cotton cloth, and the liquid fraction was acidified with 1M H₂SO₄ (9:1 w/w), centrifuged at 10,000×g for 15 minutes and stored at −20°C for analyses of VFA and NH₃-N concentrations. Body weight at the beginning and end of the experimental period was also recorded.

Chemical analysis

Feed, feed refusal, and feces samples were first dried in a forced-air oven at 60°C for 48 h and then ground to pass a 1-mm screen (Cutting Mill SM 100, Retsch, Haan, Germany) before analysis. Chemical analyses of the diet, refusals, and feces were determined according to standard methods of AOAC (1991) for dry matter (DM), organic matter (OM), total mineral (Ash), crude protein (CP) and ether extract (EE). The solubility of the protein was determined by method of Whitelaw and Preston (1963). Neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were analyzed following the methods of Van Soest et al (1991). Determination of tannins in the feeds was done following the method of AOAC (1995). Concentration of BUN in plasma samples were determined using a biochemical analyzer (XL 200, Erba, India). Ruminal pH was determined by a pH meter (HI5222, Hana Instruments, US). Ruminal NH₃-N concentration was analyzed using the Kjeldahl methods (AOAC, 1991).

Concentrations of individual VFA were analyzed using a Thermo Trace 1310 GC system (Thermo Scientific, Waltham, MA, USA) equipped with a flame ionization detector. The inlet and detector temperature were maintained at 220°C. Aliquots (1 μL) were injected with a split ratio of 10:1 into a 30m × 0.25mm × 0.25μm Nukol fused-silica capillary column (Cat. No: 24107, Supelco, Sigma-Aldrich, St. Louis, MO, USA) with nitrogen carrier gas set to a flow rate of 1 mL/min and initial oven temperature of 80°C. The oven temperature was held constant at the initial temperature for 1 min, and thereafter increased at 20°C/min to a temperature of 180°C and held for 1 min, and increased at 10°C/min to a final temperature of 200°C, and a final run time of 14 min (Bharanidharan et al 2018). Individual VFA peaks were identified based on their retention times, compared with external acid standards including acetic, propionic, butyric, valeric, iso-butyric and iso-valeric (Sigma-Aldrich, USA).

Statistical analysis

Statistical tests were performed using SAS University Edition 2019 (SAS Institute Inc., Cary, NC, USA). Data were statistical analyzed using the General Linear Model procedure. The statistical model was Y_ijk = µ + A_i + D_j + P_k + ε_ijkl, where Y_ijk = the dependent variable, A_i = the effect of animal (i = 1-4), D_j = the effect of diet (j = 1-4), P_k = the effect of period (k = 1-4), and ε_ijk = the residual effect. Data on ruminal fermentation patterns were analyzed using a Mixed model with the repeated measures (hours). The statistical model was Y_ijklm =μ + A_i + P_j +D_k + T_l + (D ×T)_kl + ε_ijklm, where Y_ijklm = the dependent variable, μ = the overall of mean, A_i = the random effect of animal, P_j = the fixed effect of period, D_k = the fixed effect of diet, T_l = the fixed effect of time (hour), (D×T)_kl = the fixed effect of interaction between diet and time, and ε_ijklm = the random residual error. Significant differences among diet means were statistically compared using Tukey. Differences were declared significant at p<0.05, and tendency was declared at 0.05≤p<0.1.

Results and discussion

Composition of diet ingredients and of the diets

The CP level (% in DM) was low for both PG (11.8%) and JL (12.9%) thus about 50% of the dietary CP was supplied by the concentrate (Table 1). Jackfruit leaves had lowest protein solubility (27.6%) while this was 42.0 and 66.3% in PG and concentrate, respectively. Kouch et al (2003) showed that protein solubility in JL was 33.7%. Lignin content in JL was 19.1% while this was only 14.2 vs. 8.32% in concentrate and PG, respectively. Moreover, total tannins were 11.6% in JL, remarkably higher than those in concentrate and PG (0.88 vs. 3.47%).

Intake

Replacement of JL for PG in the diets increased (p<0.01) DM intake (DMI), accounting for 27.8, 54.9, 54.2% increase in diet containing 36.9, 52.7 and 70.3% JL compared with diet contained only PG (Table 2). There was a quadratic regression between level of JL in diet and DMI with y = − 0.0227x² + 6.3341x + 566.33 and R² = 0.94 (Figure 1). That increased nutrient intake in goats fed JL diets in this study was similar to the result in goats of Das and Ghosh (2007), but was different from the result of Mui et al (2002), where increasing JL replaced for concentration caused a linear reduction of DM and CP intakes in goats. Malik et al (2017) found no change in DMI of sheep fed JL replaced for wheat bran. Kibria et al (1994) showed that JL are highly palatable and thus goats consumed higher amount of feeds offered. Other factors affecting feed intake in this study may also include other substances such as volatile oils or phenolic compounds in JL. Pal et al (2015) showed that JL contained 40.1% total phenolics comprised of 12.9% non-tannin phenolics.

Figure 1. Curvilinear trend in DM intake as Jackfruit leaves place Para grass in the diet of goats

Total-tract digestibility and nitrogen balance

There was a negative linear regression between level of JL in diet and DM digestibility (y = − 0.1213x + 64.73; R² = 0.98; Figure 2). Goats fed 70.3% JL in the diet decreased (p<0.05) NDF digestibility by 41.3% compared with those fed only PG (Table 3). The NDF digestibility showed a negative linear trend as increased JL in the diets (y = − 0.3494x + 62.713; R² = 0.97; Figure 3). Nitrogen (N) intake increased (p<0.01) by 58.8% in diet containing 70.3% JL compared with only PG-contained diet. Feeding increased amounts of JL in the diet increased linearly (p <0.01) fecal N, and the extent of the increase was greater for 70.3% JL in diet (10.2 g/d) compared without JL in diet (3.96 g/d); however, N excretion via urine was linearly lower (p<0.01) in JL diets (3.10-3.42 g/d) compared with PG diet (5.75 g/d). Nitrogen retention showed the greater values (p=0.06) in goats fed JL diets (8.77-9.76 g/d) compared with goats fed only PG (4.31 g/d). With only a 14-day duration of each period, we could also detect a greater live weight gain (p =0.08) of goats consumed JL-diets, accounting for 87.8-131 g/d increase compared with goats fed only PG. Figures 4 shows a very close relationship between level of JL in the diet and nitrogen retention (y = − 0.0017x ² + 0.1911x + 4.284; R² = 0.99), whereas a close relationship between level of JL in the diet and live weight gain is presented in Figure 5 (y = − 0.0575x² + 5.3508x + 44.116; R² = 0.98).

Figure 2. Negative linear trend in DM digestibility as Jackfruit leaves replace Para grass in the diet of goats	Figure 3. Negative linear trend in NDF digestibility as Jackfruit leaves replace Para grass in the diet of goats
Figure 4. Curvilinear trend in N retention as Jackfruit leaves replace Para grass in the diet of goats	Figure 5. Curvilinear trend in live weight gain as Jackfruit leaves replace Para grass in the diet of goats

That decreased NDF digestibility with increasing levels of JF in the diet was supported by Das and Ghosh (2007). For this reason, JL contained high insoluble protein which escaped from the rumen took with its particles of fiber which would be digested with lesser efficiency than if they had been digested in the rumen. A remarkable decrease in NDF observed in JL diets could be also a result of higher intakes of ADF and ADL. Moreover, the higher tannin content in JL (11.6%) compared with that in PG (3.47%) was also a factor to reduce nutrient digestibility. High dietary CT had been showed to decrease extremely in vitro DM degradability in four ruminant species (Bueno et al 2020). Similar result was found in the study of Pal et al (2015). Tannins depress fiber digestion by forming complexes with lignocellulose and hence prevent microbial digestion (Piñeiro-Vázquez et al 2015). Moreover, tannins have been implicated for their inhibitory effects on nutrient digestion because tannins have high ability to bind protein at- and post-rumen which led to decrease apparent protein digestibility and increase excretion of N via feces (Patra and Saxena, 2011). In the current study, shifting pattern of nitrogen excretion from urine to feces is beneficial environmentally. In fact, urinary nitrogen is mainly in the form of urea, which is more rapidly hydrolyzed to ammonia and nitrified to nitrate, whereas fecal nitrogen is largely in the organic form, which is less volatile. Therefore, decreased nitrogen excretion via urine could reduce ammonia and nitrous oxide emissions into the atmosphere. The greater fecal N excretion with increasing rates of JL (high contains of tannins) in the current study was similar to previous studies in meat goats and dairy cows (Animut et al 2008; Grainger et al 2009).

Ruminal fermentation patterns

Interactions between diet and sampling time (h) for rumen fermentation characteristics were not significant. Therefore, only averages of VFA measurements at the different sampling times are presented in Table 4. Total VFA and NH₃-N concentrations were not affected by feeding JL in the diets. Concentration of BUN reduced linearly (p<0.01) by 1.76 and 2.05-folds in goats fed 52.7 and 70.3% relative to goats fed PG alone. There was a negative linear trend in BUN when increasing level of JL in goat diets (y = − 0.0002x² − 0.051x + 8.3146;
R² = 0.97; Figure 6).

Figure 6. Negative linear trend in BUN as Jackfruit leaves replace Para grass in the diet of goats

Das and Ghosh (2007) found no effect on ruminal VFA concentration of growing goats when JL was used at 50% in the diet. Similar result was observed in a study of Dschaak et al (2011), where dairy cows supplemented with 3% condensed tannin extract had no change on total VFA and NH ₃-N concentrations. However, Roca-Fernández et al (2020) reported that feeding condensed tannins at 3.80-7.56% in the diets reduced strongly ruminal VFA concentration. That reduced BUN concentration in goats fed 52.7 and 70.3% JL in the diet is negative effects of insoluble protein and tannins on goat health in these diets. High insoluble protein in JL reduced ruminal protein degradation and therefore ruminal NH₃-N concentration. The complexes formed between tannins and proteins render them inaccessible to rumen degradation and favor post-rumen release, thereby reducing ammonia concentration in the rumen (Ningrat et al 2016) and urea concentration in blood. However, no reduction of ruminal NH ₃-N concentration was found in this study. It was explained partially that the greater ingested nutrients in JL could compensate for low rumen degradability of this feed, which led to maintain concentrations of VFA and NH₃-N in the rumen. Moreover, it is probably that phenolic compounds in JL might stimulate protein synthesis of rumen microbes. Jayanegara et al (2011) found that concentrations of total tannins and condensed tannins in leaves had positively correlate with bacterial populations. With the higher nutrient ingest, the greater number of ruminal microbes could help to increase total nutrient fermentability in the rumen.

Conclusion

• Increasing replacement of JL for PG in the diet of growing goats increased DMI from 27.8-54.9%, but decreased digestibility of NDF. Nitrogen retention increased by 103-126% when growing goats were fed JL diets. Ruminal fermentation products remained unchanged regardless of JL rate in the diets.
  
  
• Based on the findings of this study, it is concluded that substitution of JL for PG at 75 and 100% in diet DM of growing meat goats containing 30% concentrate is effective in reducing urinary N excretion while allowing improvement in DM intake and live weight gain without affecting ruminal fermentation. Our findings challenge current accepted generalization on the use of digestibility as an index of nutritive value in ruminants when high by-pass CP and tannin feeds reduce nutrient digestibility, but increase N retention and live weight gain.

Acknowledgement

This study was supported in part by the Can Tho University Improvement Project VN14-P6 supported by a Japanese ODA Loan under Grant No. A9.

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