Evaluation of Urea Treated Acacia nilotica Pods as a Feed for Grower Lambs

Sheep rearing forms the major source of livelihood providing both employment and income to landless, resourceless rural masses in many regions of India. The impact of reducing the feed cost and increasing the feed efficiency is likely to be enormous in economic sheep production. Feeding non conventional feeds as supplements is an important means of achieving reduction in overall feed costs. Tree pods are one such non conventional protein rich feed resources that could be harnessed as a feed ingredient in sheep production. In many areas in India, farmers collect the fruits of Acacia sp. and feed their sheep or the grazing sheep are taken directly to the trees and fed with naturally fallen or knocked down fruits. Topps and Oliver (1978) had suggested that the pods of Acacia sp. could very well serve as potential source of protein for diets based on poor quality cereal crop residues. Punj (1988) assessed that about 60,000 tonnes of Acacia nilotica pods are annually available in India. Milled Acacia nilotica pods with seeds could provide supplement similar to maize bran (Gohl, 1981) and adult sheep could be maintained by feeding these pods (Prabhakara Rao and Anjaneya Prasad, 1978). Babul (Acacia nilotica) pods could be safely included up to 16.5% in the total mixed ration (TMR) of pregnant goats (Raju Kushwaha et al., 2012) and lactating goats (Raju Kushwaha and Rai, 2011) without affecting their performance. As the protein content in the fruits of Acacia nilotica is high, its palatability is also high and they may be suitable protein supplements for dry season diets; however presence of high amount of tannins tends to reduce the feeding value (Mohamed Abdalla et al., 2014). Addition of 4% urea at high moisture (55%) and storage for 10 days resulted in considerable detannification (Total phenols 88%, Condensed tannins 100%) of mature oak leaves. This approach could become a practical method for detannification at farm level with the added advantage of increased nitrogen content (Makkar and Singh, 1993). Moreover, urea could provide nitrogen through ammonia that could be converted to microbial protein thereby providing additional protein to the host animal (Castro et al., 1999). Adopting this principle, the total tannins were chemically reduced to a great extent and protein content was considerably enhanced in Acacia nilotica pods up on treatment with 5% urea and storage for 14 days at 40% moisture level (Chellapandian and Balachandran, 2004). Though many workers have observed the utility of raw Acacia nilotica pods as a noteworthy feed for small ruminants, the information on nutritive value of urea treated pods is lacking.  Hence the present study was undertaken to evaluate the nutritional potential of urea treated Acacia nilotica pods at different dietary levels for supporting growth and nutrient utilisation in lambs.

The feeding experiment in sheep with inclusion of Acacia nilotica pods in concentrate mixture was undertaken in an organized farm in Tirunelveli district of Tamil Nadu during the year 2019. The laboratory analytical works related to this experiment was done at the Department of Animal Nutrition, Veterinary College and Research Institute, Tirunelveli. Acacia nilotica pods were collected, sun dried and ground in a hammer mill to pass through medium mesh screen (2 mm) and preserved. The ground pods and seeds were treated in bulk with urea. To every 100 kg of the ground feed, 5 kg urea was added in a solution of 51 litres of water to achieve a moisture level of 40 per cent. The urea solution was sprayed, the feed was thoroughly mixed and stored for 14 days in tightly secured polythene bags. After 14 days of storage, the bags were opened and the treated feed was shade dried for about one hour. Then the urea treated pods (UTP) was incorporated in three experimental concentrate mixtures @ 0, 15 or 30 per cent (R1, R2, R3) replacing deoiled rice bran. The concentrate mixtures were made isoproteinic and isocaloric by adjusting the level of inclusion of other feed ingredients. The cost of the three concentrate mixtures-R1, R2 and R3 was Rs.19.25, Rs. 18.00 and Rs.17.20 respectively. Napier Bajra hybrid grass (CNCO4) harvested at about 75 to 80 days of growth and chopped in a chaff cutter into pieces (2-3 cm length) was provided as the basal roughage component in the rations. The ingredient composition of the experimental concentrate mixtures with different level of urea treated pods (UTP) are given in Table 1. The experimental concentrate mixtures and CNCO4 grass were analyesd for proximate composition (AOAC, 2012).



Fifteen ram lambs of native Kilakarsal breed of about six months of age and with an average initial body weight of 9.39±0.28 kg were used in this experiment. The lambs were divided on the basis of body weight into three groups with five lambs per dietary group in a completely randomized design. Prior to the experiment, the lambs were drenched with a broad spectrum anthelmintic. The lambs were housed in individual pens and fed with the experimental rations for a period of 70 days. All the lambs were provided with clean drinking water throughout the day during the entire trial period. Daily record of feed consumption was maintained. The lambs were weighed at fortnightly intervals. At the end of the feeding experiment, digestion trial was conducted using the same ram lambs. A preliminary period of 15 days followed by a collection period of 7 days was adopted. Twenty per cent of the dung voided was sampled and stored at-20°C. The samples were analysed for proximate composition (AOAC, 2012) and the digestibility of nutrients in the three experimental rations were determined. The data collected in the study were analysed as per methods suggested by Snedecor and Cochran (1994).

The proximate composition of the experimental concentrate rations and CNCO₄ grass are presented in Table 2 on % DMB. Since formulated as isoproteinic and isocaloric rations, there was no significant difference in the proximate composition of the experimental concentrate mixtures. CP, CF, EE, NFE and TA contents of CNCO4 grass were 10.21, 30.48, 2.14, 40.97 and 16.20 respectively which correlated well with the earlier report of Chellapandian and Arulnathan (2016).



The average dry matter intake (DMI), average daily gain (ADG) and feed efficiency of the lambs fed with experimental rations are presented in Table 3. The DMI worked out to be 64.90, 65.84 and 65.43 g/kg W 0.75 in lambs fed with rations containing 0, 15 and 30% UTP in the concentrate mixture respectively. The observed dry matter intake (3.55-3.58% body weight) was within the range suggested as DMI for growth by Kearl (1982) for ruminants in tropical countries (1.1%-4.1% body weight). Similar high DMI in sheep had been previously reported by Reddy and Reddy (1989) and Kantwa et al., (2006) for complete ration containing groundnut hulls and fresh green Mulberry leaves respectively. The corresponding values for ADG in the present study were 48.14, 47.43 and 48.57 g. The DMI and ADG were not altered significantly by the inclusion of urea treated pods in the concentrate mixture. The feed efficiency in terms of DMI required to gain one kg body weight were 8.28, 8.58 and 8.35 kg which did not vary between the treatment groups. The protein to energy ratio in the experimental rations consumed by the animals in different treatment groups was almost similar (1:32, 1:28, 1:25) which had resulted in similar performance in terms of body weight gain and feed efficiency. The feed cost per kilogram live weight gain was Rs.114.67, Rs.109.38 and Rs.101.65 in lambs fed with rations containing 0, 15 and 30% UTP in the concentrate mixture respectively. Feed cost was observed to decrease with increase in level of UTP in the ration and was significantly (P£0.05) low at 30% inclusion level.



The digestibility coefficients of nutrients and the nutritive value (DCP, TDN) of the three experimental rations are given in Table 4. Dry matter digestibility decreased with inclusion of UTP in rations, though with non-significant difference between groups. The dry matter digestibility was lowest in the ration with 30% UTP. Similar decrease in DM digestibility was observed by Makkar and Singh (1993) in urea treated oak leaves stored more than five days. Inclusion of UTP stored for a longer period (14 days) could be the reason for the observed low DM digestibility of the experimental rations. The organic matter digestibility decreased with increased level of inclusion, the reduction being significant (P≤0.05) only up to 15% level. The crude protein digestibility increased from 46.31 to 48.31 and 52.10% as the level of inclusion of UTP increased from 0 to 15 and to 30%. However, the dry matter digestibility and crude protein digestibility did not differ significantly between the groups. Similarly increase in crude protein digestibility was also observed by Puga et al., (2001) in sheep supplemented with controlled release urea which was attributed to the availability of additional non protein nitrogen to ruminal bacteria for microbial protein synthesis. This could also be due to the effect of tannins in the pods that caused increase in the amount of ruminal by-pass protein available for post ruminal digestion (Atiba et al., 2021) The crude fibre digestibility which was 44.46% at 0% inclusion decreased significantly (P≤0.05) to 35.87% at 15% inclusion and remained similar at 30% inclusion (33.77%). Similar low digestibility trend was observed in NFE also. Low crude fibre digestibility (48.7%) was also reported by Paswan et al., (2017) for concentrate mixture with 30% untreated Acacia nilotica pod meal fed to goats. Abdullah et al., (2018) has noted that there was a general tendency of decreasing digestibility of crude fibre with increasing level of A.nilotica pods in the concentrate mixture of sheep ration and attributed it to the activities of tannin content of the ration. Berhe Weldegebriel and Yadav (2017) had also reported significantly (P<0.01) lower NDF and ADF digestibility in rams fed rations supplemented with high level of Acacia seyal pods replacing wheat bran and attributed it to the fact that Acacia species possess a variety of physical and chemical compounds causing reduction in the palatability and nutritive value. However, the poor digestibility of DM, fibre and NFE in this study might also be attributed to the presence of high level of structural carbohydrates in the pods compared to the deoiled rice bran which was replaced by the pods in the experimental rations. The untreated Acacia nilotica pods as analysed by Chellapandian and Murugan (2003) was found to contain high level of structural carbohydrates - 10.29% lignin, 14.43% cellulose and only 12.12% hemicellulose in their cell wall. DCP of experimental rations increased significantly (P≤0.05) as the level of UTP in the concentrate mixture increased which could be attributed to the increased crude protein digestibility. The TDN decreased significantly (P≤0.05) at 15% level and remained unaffected thereafter. Reduced digestibility of crude fibre and NFE resulted in decrease of the TDN content. The narrowing down of the nutritive ratio with increased level of UTP could be attributed to higher levels of DCP.

From the results of body weight gain, feed efficiency and nutritive value, it was inferred that Acacia nilotica pods treated with 5% urea at 40% moisture and stored for 14 days could safely be included up to 30 per cent level in the concentrate mixture of growing lamb ration replacing deoiled rice bran without any adverse effect on their growth performance. Inclusion of urea treated pods in lamb rations proved to be beneficial in terms of considerable reduction in feed cost.

The authors are thankful to the Dean, Veterinary College and Research Institute, Tirunelveli, Tamil Nadu for providing the necessary facilities.

All authors declared that there is no conflict of interest.