Effect of Feeding Acacia as Supplements on the Nutrient Digestion, Growth Performance, Carcass Traits and Some Blood Constituents of Awassi Lambs under the Conditions of North Sinai

MATERIALS AND METHODS

This study was carried out at the experimental farm of Animal Production Department, Faculty of Environmental Agricultural Sciences, El-Arish, Suez Canal University during the period from 2006 to 2007. The climatic characteristic of this region is semi-arid (Long. 33.75 E, Lat. 31.27 N) with an average annual rain in fall of about 94 mm (average 10 years from 2000 to 2009) in North Sinai (CLAC, 2008).

Plant material: Acacia saligna (leaves and twigs) were harvested daily at morning from the farm of Animal Production Department. These plants were collected by hand, then air-dried until DM content was around 450 g kg^-1 feed.

The experimental work of this study was divided into two successive parts. During the first period, digestibility and nitrogen balance trails were conducted before the commencement of the feeding trial to evaluate the four experimental diets. Three ram lambs with an average live body weight of 38 kg were used to estimate the digestibility coefficients of the diets. They were individually kept and fed in metabolic crates. The digestibility trial consisted of 14 days as a preliminary period followed by 7 days as a collection period. The control ration (T1) was a basal diet consisting of CFM and rice straw to cover their nutritional requirements according to NRC (1985). Rations 2, 3 and 4 consisted of CFM to cover 80, 60 and 40% of the TDN requirements and were offered air-dried acacia, respectively.

The daily CFM of rations were offered in almost two equal parts at 8:00 am and 4:00 pm whereas acacia was offered ad lib. 9:00 am Refusals were collected just before offering the next days. During the collection period, total daily faces output was collected and 10% sample was taken. And acacia were first dried at 65°C for 48 h. The final dry matter of feed and faces were determined after drying in a forced air oven at 105°C for 24 h. Dried samples were mixed and ground through in a wily mill with a 2 mm screen. Dry samples were kept in a plastic vials at room temperature for the chemical analysis. Total daily urinary excreted from each ram lambs were collected in jar containing 100 mL of 20% H₂SO₄ to prevent ammonia loss. Daily samples of 10% were taken from each animal.

During the second part, the effect of the control ration, 2^nd and 3^rd rations on growth performance, carcass characteristics, some blood metabolites and economical evaluation were (ration 4 was discarded). Eighteen newly weaned Awassi lambs (16 weeks of age) were divided according to body weight into three similar groups of six lambs each. The three groups were assigned at random to receive the three experiments rations for 12 weeks. The average initial body weights of lambs for T1 (control), T2 and T3 were 23.38, 23.04 and 24.41 kg, respectively.

The lambs of the control ration (T1) was fed a basal ration consisting of concentrate feed mixture and rice straw to cover their nutritional requirements according to NRC (1985) which was adjusted every two weeks according to body weight and growth rate. Second and 3rd rations were fed CFM to cover 80 and 60% of the Total Digestible Nutrient (TDN) requirements and were offered air-dried acacia ad libtum.

The lambs were drenched against internal parasites before the start of the experimental. The animals were watered. natural saline well water containing 3400 ppm. The analysis of drinking under ground water was carried out to Page et al. (1982).

The animals of each group were fed and housed in a 6x10 m² semi-open shaded pens.

Animals were individually weighed at the beginning of the experiment then every two weeks and daily gain was calculated for each animal.

Mineral and vitamins blocks were fixed among cages to enable the animals to lick when ever they required. Samples of the experimental ingredients, acacia was taken for chemical analysis at the beginning of the collection period of the digestibility trials and the chemical of the consumed rations were calculated.

Slaughtering procedure and carcass measurements: At the end of the growth experiment, three male animals in each group were randomly selected for slaughter. The lambs were fasted for at least 12 h and body weight recorded before slaughtering. The body was weighed again after bleeding, skinned eviscerated and the skin, head, fore feet, hind feet and the viscera were removed. Weight of the gut content was calculated as the difference between full and empty weight. The weight of other components of offal or non-carcass parts such as kidney and pelvic fat and different organs (liver, spleen, lung and trachea diaphragm, heart, kidneys and testes) were recorded.

Blood samples were taken monthly before morning feeding. Blood samples were by jugular puncture from 3 animals from each group. Within one hours of collection, the samples were centrifuged at 3000 rpm for 10 min. The serum was separated and stored at -20°C until analysis. The results of the 3 months samples were averaged.

Serum total protein, albumin, total lipids, glucose, cholesterol, urea, creatinine, ALT, GPT, AST and GOT levels were determined colorimetrically using commercial kits Bio-Merieus, Laboratory Reagent and products, France. The globulin values were obtained by subtracting albumin values from protein values.

Samples of feeds, faces and urine were chemically analyzed according to AOAC (1990). All animals were kept under the same managerial and environmental conditions.

Data were subjected to statistical analysis by the SAS (1996) computer program using the General Linear Models (GLM). Differences between treatments means were tested for using Duncan multiple range test (Duncan, 1955).

RESULTS AND DISCUSSION

Chemical of the ingredients and the experimental rations: The chemical composition of the ingredients used to formulate the experimental rations (Table 1), was within the normal ranges published in Egypt (El-Shaer et al., 1984; MAO, 1997; Mousa and Shetaewi, 2002; Mousa and El-Shabrawy, 2003) and Bhatta et al. (2005) and Van Thanh et al. (2005).

Table 1 shows that Crude Fiber (CF) was higher in acacia than CFM, while Ether Extract (EE), crude protein, Nitrogen Free Extract (NFE) and ash were lower than CFM. The values were 1.75, 13.07, 53.61 and 8.07% for acacia vs. 2.90, 17.30, 58.39 and 9.81 for CFM, resp. These results are in agreement with those reported by Mousa and El-Shabrawy (2003).

The proximate analyses of the consumed experimental rations are also shown in Table 1. The control ration (T1) had higher DM% then rations 2, 3 and 4 because of the higher moisture content in acacia. Ration 4 had lower CP, EE and ash contents but higher CF than other rations.

Digestibility coefficients and nutritive values: Digestion coefficients of the experimental rations are presented in Table 2. Differences were observed in the digestion coefficients of DM, OM, CP, EE, CF and NFE among rations 1, 2, 3 and 4.

Table 1:	Chemical composition of the ingredients and calculated chemical composition of the consumed rations (%)
*Ration 1 Concentrate feed (CFM) plus rice straw, *Ration 2 Concentrate feed (CFM) plus ad lib acacia (20%), *Ration 3 Concentrate feed (CFM) plus acacia ad lib (40%), *Ration 4 Concentrate feed (CFM) plus acacia ad lib (60%), *Gross energy concentration (MJ kg-1 DM), calculated according to MAFF (1975) using the equation GE MJ kg-1 DM = 0.0226CP+0.0407EE+0.0192CF+0.0177NFE, Where, CP, EE, CF and NFE are presented as g kg-1 DM

Table 2:	Digestion coefficients and nutritive values of the experimental rations
A, B, C, D: Means bearing different superscripts within the same row are significantly different at p<0.01, a,b: Means bearing different superscripts within the same row are significantly different at p<0.05

The digestibility coefficients of DM, OM, CP and CF were significantly (p<0.01) higher in ration 2 (CFM to cover 80 and 60% of the TDN requirements and acacia ad lib) than 4 (CFM to cover 40% of the TDN requirements and acacia ad lib. There was no differences among EE digestibility of rations 1, 3 and 4, but EE digestibility (67.2) was low (p<0.05) for ration 2 compared to other rations. These results agree with the data of Mousa and El-Shabrawy (2003) who found that the digestibility coefficients of DM, OM, CP, EE, CF and NFE of diet consisted of Concentrate Feed Mixture (CFM) to cover 70% of the TDN requirements of kids and green acacia ad lib were lower than those of the control diet. On the other hand, Mugweni et al. (2001) reported that the dry matter digestibility of acacia/maize mixture was similar to maize alone (62.2 vs. 63.8%), both higher than the Leucaena/maize mixture (57.6%).

Generally, the coefficients of DM, OM, CP, CF and NFE decreased with increasing acacia inclusion in the diet. The best CP digestibility (75.07) was that of ration 1 (control) followed by rations 2, 3 and 4 (68.51, 64.81 and 59.67, respectively).

The adverse effect of acacia the digestibility of the ration should be ascribed to the inhibitory effect of its high tannin content on microbial activity (Malechek and Provenza, 1981). The type of tannin, the level and activities of tannin in browse are variable leading to varied effects on the reduction of digestibility (Ebong, 1995).

On the other hand, Sanon et al. (2008b) reported that the Acacia senegal leaves with high cp content had good intake characteristics and showed high nutrient digestibility. It seems that the protein in acacia is poorly digested by sheep and goats owing to the presence of tannins (4-11%) DM basis (Degen et al., 1995; Abou El-Nasr et al., 1996).

Anti-nutritional factors such as condensed tannins protect plants from degradation in the rumen. They are reported to form combination with proteins in the rumen rendering them unavailable for digestion and consequently increase their out put in faces (Robins and Brooker, 2005).

Feeding values: The feeding values of, ration 1 (control) and 2 had the highest (p<0.01) TDN value followed by ration 3 then ration 4 which had the lowest TDN value The superiority of the rations 1 and 2 in TDN is mainly due to their almost equal high CFM contents. On the other hand, rations 3 and 4 contained high levels of acacia which reflected lower TDN value. Regarding the DCP% of the four experimental rations (Table 2), it was clear that the differences among the four rations were significant (p<0.01). The highest value was that of ration 1 (control) followed by ration 2, 3 and 4. The low DCP% value of ration 4 may be due to its high level of acacia which contains a high value of tannins therefore is showed the lowest value of CP digestibility, as reported by Mousa and El-Shabrawy (2003). The present findings are in agreement with those reported by Abou El-Nasr et al. (1996) and Mohamed (1996).

The absence of negative effects of tannin on intake could be attributed to the relatively low quantity of tannin ingested and/or to the effect of drying the acacia before feeding. Barry et al. (1986) reported that less than 40% of tannin in the ration was beneficial to ruminants. Igwebuike et al. (2008) reported that the growing rabbits can tolerate 40% Acacia alibido pods in their diets without adverse effect on nutrient digestibility and blood parameters.

Nitrogen balance: The date of N-balance recorded for the four experimental rations are reported in Table 3.

Table 3:	Nitrogen balance of lambs fed the experimental rations
A, B, C, D: Means with different superscripts within the same row are significantly different at p<0.01

In all animals on the four rations were in N. balance. The highest N intake was recorded for ration 1 followed by group 3, 2 and 4. The amounts excreted in the feces are reflected on the CP digestibility coefficients. Fecal-N was highest with ration 4 including high levels from acacia compared with rations 1, 2 and 3.

The negative effect of acacia tannins on N-balance was demonstrated in numerous studies on sheep and goats (Reed et al., 1990; Degen et al., 1995; Ben Salem et al., 1999a, b, 2000, 2002a, 2005). In addition, acacia leaves contains in average 20% of its total N bound to fiber (N-ADF) as reported by Ben Salem et al. (1995).

The present findings are in agreement with those reported by Woodward and Reed (1997) and Mousa and El-Shabrawy (2003).

The amount excreted in the urine was highest with ration 1 which received the highest N-intake.

Ben Salem et al. (2005) reported that lambs fed on acacia diet retained less nitrogen than those on the oat hay diet (p<0.001). While, Sotohy et al. (1997) reported that absorbed and retained nitrogen (g/d) were decreased with increasing levels of Acacia nilotic (tannin-rich plants) by Baladi goats in Assuit.

The value of N-balance/N-absorbed (the biological values) was also improved as acacia inclusion was increased.

The growth trial:
Live body weight and daily gain: The Awassi lambs used in the experiment were of North Sinai type especially in Rafah, Shiekh Zeyuied and El-Arish regions, this breed is well adapted in the semi-arid zones, Awassi sheep have a high potential for milk production (Guirgis, 1988).

The final weights and daily gain of lambs were not significantly affected by three experimental rations during the whole experimental period (Table 4).

Generally lambs fed ration 3 (40% acacia) had the highest body weight followed by ration 2 (20% acacia) then those fed ration 1 (control). The highest values of Total Weight Gain (TWG) and Daily Gain (DG) were shown for ration 3 (15.65 kg and 186.31 g/d), respectively. While, the intermediate values was recorded for ration2 (14.21 kg and 171.9 g/d, resp.) and the lowest total gain and daily gain were recorded for control ration (13.48 kg and 160.47 g/d), respectively.

Table 4:	Growth performance of lambs as affected by feeding diets containing different levels of acacia (X-±SE) from 16 to 28 weeks of age
All difference between three rations were not significant p<0.05

Table 5:	Performance of lambs fed the experimental rations

Similar trends were obtained by Shetaewi et al. (2001), Mousa and El-Shabrawy (2003) and Yousef (2005) reported that the concluded that up to 40% acacia leaves could be used and safely in the diet of rabbits without adversely affecting their reproductive under subtropical conditions. Abd-Alla et al. (2007) and Abdel-Samee et al. (2008) reported that feeding Acacia saligna improved productivity of heat stressed growing lambs and increased (p<0.05) daily gain and relative growth rate by 15.48 and 16.0%, respectively.

DM intake and feed conversion: The average of dry matter intake by lambs given ration 1 (control) compared to rations 2 and 3 supplemented with acacia are present in Table 5. The DM intakes (kg/heed/d) were 1.182, 1.123 and 1.186 kg for lambs fed rations 1, 2 and 3, respectively. Feed conversions in terms kg feed kg^-1 gain of were 7.37, 6.53 and 6.37 for rations 1, 2 and 3, respectively. These values were worse than those obtained by Momani Shaker et al. (2002, 2003) for Awassi ram lambs. However, similar results were reported by Harb (1994) who found the feed conversion of Awassi male lambs to be 6.55 in an experiment lasting for 154 days with high concentrate rations.

Daily TDN and DCP intakes (g/head/d) were 734, 697 and 712 and 147, 124 and 121, for rations 1, 2 and 3, respectively. Daily intake from CFM and acacia by Lambs for ration 3 could cover their nutritional requirements (maintenance and growth) according to NRC (1985) from TDN for sheep. However, these values of TDN from acacia could cover 40% TDN from nutritional requirements. These obtained results are in agreement with those reported by EL-Lakany et al. (1991), Mousa and Shetaewi (2002), Mousa and El-Shabrawy (2003) and Yousef (2005). The corresponding TDN intake/kg gain was 4.6, 4.05 and 3.82 kg and DCP intake/kg gain were 0.91, 0.72 and 0.65.

This indicated better feed conversion as DM, TDN and DCP intakes/kg gain for ration 3 (40% acacia) compared with lambs fed ration 2 and the control. In general, feed conversion improved by increasing acacia ratio up to 40%.

Economical evaluation: The obtained results of economical for lambs fed the experimental diets are presented in Table 6. Data revealed that ration 1 (control) was the highest in feed cost to give kg gain (8.89 LE) followed by ration 2 (6.61 LE) and ration 3 (5.74 LE).

Table 6:	Economical efficiency for lambs fed the experimental rations
Price of 1 kg DM feed for CFM and rice straw were 1.40 and 0.15 LE, respectively. Total feed cost = Price of 1 kg DM feedxtotal dry matter consumed. Feed cost/kg gain = Total feed cost/Total body weight gain. Price of 1 kg Live body weight = 20 LE at the time of the experiment. Total interest = (price of 1 kg live body weightxTotal gain kg) – (total feed cost). Interest/kg gain = Price of 1 kg live body weight gain-feed cost/kg gain

The highest cost of one kg gain for the ration was mainly due to the high proportion and price of CFM which increased the total cost of the diet by increasing of CFM in diet. While, lower cost of one kg gain for ration 2 and 3, was due to the lower price of acacia and to the low proportion of the expensive CFM, which reduced the total cost of the diet by increasing the acacia, which was associated with the highest daily gain and the best feed conversion.

Addition of acacia to the diet resulted in an improvement of interest/kg gain. The improvements were 20.52 and 28.35 for rations 2 and 3 above the control diet.

Similar results were reported by Mousa and El-Shabrawy (2003) who found that cost of feeding/kg gain was reduced when CFM was substituted by acacia in ration of Damascus kids.

Carcass characteristics: The effects of diets on carcass and organ weights are shown in Table 7. The averages of fasting weight; hot carcass and dressing out percentage of ration 3 were higher than those of the other rations, with no significant differences among them. The dressing percentages (including tail fat) were 52.51 and 50.28% in lambs fed experimental rations 3 and 2, respectively when compared with lambs of the control group (48.28%) but with no significant differences. These results agree with those of Momani Shaker et al. (1997, 2002), Allam et al. (2005) and Sanon et al. (2008b).

Dressing percentage in cold condition in the ranged from 50.13 to 52.43% for fat tailed Awassi ram lambs Momani Shaker et al. (2002). Also, Allam et al. (2005) reported that the average slaughter weight, average carcass weight and average dressing percentage were 42 kg, 21.57 kg and 51.35%, respectively for Saedi lambs. Mohamed et al. (2005) reported that the dressing percentage of lambs ranged from 49.44 to 51.67. On the other hand, Abdel Monein (2009) reported that the dressing percentage were 56.2, 53.3 and 53.10 for Ossimi, Barki and Rahmani ram lambs under intensive productions, El-Asheeri et al. (2006) found that the dressing percentage was approximately similar for Rahmani (49.1%) and Ossimi (49.8%) ram lambs.

The highest dressing percentage of carcass without tail fat was 48.28 and 46.04% in carcass of experimental ration 3 and 2 when compared with carcass of control ration 43.89%. These results agree with the data of Yayneshet et al. (2008), who found that the dressing percent for male goats increased with increased level of acacia etbic fruit supplement (1.5% on body weight basis).

Table 7:	Effect of feeding the experimental diets on carcass and organ weight of lambs
A, B: Means bearing different superscripts within the same row are significantly different at p>0.01, a, b: Means bearing different superscripts within the same row are significantly different at p>0.05

Similar, results were reported by Momani Shaker et al. (2003) who found that the average dressing percentage of Awassi ram lambs was 43.49%.

The head and legs weights did not show remarkable change among groups. Also, other offal's and organs (liver, kidneys, heart and lungs and testes) did not record any differences among rations.

Data in Table 7 showed that the internal fat and kidney fat were significantly (p<0.05 and p<0.01) the highest, being 1.59 and 0.53 kg, respectively in carcass of lambs fed experimental ration 3. The corresponding values for lambs fed rations 2 and 1 were 0.81, 0.242, 0.507 and 0.188 kg.

In general all organs appeared normal with no apparent lesions. It appeared therefore that of acacia in the ration had no deleterious effects on carcass quality.

Blood serum parameters: Table 8 shows the blood serum parameters in terms of total protein, albumin, globulin, urea, cholesterol, total lipids, glucose, creatinine, SGOT and SGPT concentrations when growing lambs were fed the experimental.

No significant (p>0.05) changes concerning these metabolites were found.

The values of total protein and their fractions, urea, cholesterol, glucose, creatinine, SGOT and SGPT concentrations were within the normal range reported by Mousa and Shetaewi (2002) on ewes fed acacia. Gabr et al. (2005) and Al-Shanti and Abo Omar (2005) reported similar results with growing lambs.

Table 8:	Some blood serum constituents of lambs fed the experimental rations
All difference among the three rations were not significant (p>0.05)

Generally, the values obtained of blood constituents indicated normal physiological and healthy status of lambs fed both rations containing acacia.

This study indicates that feeding Awassi lambs on diets including up to 40% of the TDN requirements from acacia did counter act their feedlot performance. Therefore, the use of acacia tested in the current experiment can be recommended for use by local farmers for lamb production under North Sinai conditions which should reduce their cost of meat production. During the dry season acacia remain green and maintain a relatively high crude protein content and is commonly used as protein and energy supplements for small ruminants during this period. This is supported by the findings of Youssef et al. (2003) who reported that acacia saligna shrubs showed a great potentiality as fodder for growing sheep under arid and saline conditions of Egyptian desert.