MATERIALS AND METHODS

For the purpose of this experiment, eighteen entire Sudan Baggara bulls were selected at average live weight 200±7.56 kg and 1.5 year old. The animals were then identified by ear tags and divided into two treatment groups of 9 animals each, each group is subdivided into three subgroups of three bulls each penned together in (4x3 m) pen at the premises of Animal Production Research Centre (APRC) at Hillat Kuku. The pens were equipped with feeding trough, water troughs, with clean fresh water available all over the day and night. The experiment continued for 70 days during July-November 2005. An adaptation period of three weeks was allowed to subject the animal to a resting period during which they undergo compensation for any possible feed restriction and to adapt the ruminal micro-flora to the experimental diets. Two experimental diets were formulated in a Complete Diet System (CDS), with similar ingredient composition, iso-nitrogenous and iso-caloric but with different formulation method and physical form. Diet (A) was computed by hand and than rechecked by computer in an unpelleted form (mash form). Diet (B) was formulated and processed in a pelleted form by Kenana Sugar Company using animal feed industry. Both diets composed of 15% Sugarcane Baggase (SCB) as the basal roughage component, it was already air dried and ground. Dried green alfalfa was given once a week at a rate of 2 kg/head. The chemical composition of the diets was obtained by using the standard procedure of the official method for analysis of the association of official analytical chemist (AOAC, 2000). The Metabolizable Energy (ME) content of the diet was calculated as described by MAFF (1976).

ME (MJ/kg) = 0.012 CP + 0.031 EE + 0.005 CF + 0.014 NFE

Measurement collected were, weighing of animals which performed weekly, daily feed intake, daily Body Weight Gain (BWG)and Feed Conversion Ratio (FCR) were recorded. Feed intake was determined daily as the differences between feed offered and refusals. Samples for DM determination were taken from feed refusal at weekly interval, live animal weights were recorded to the nearest 5 kg prior to the morning feed using bridge balance of 1500 kg maximum capacity load of 5 kg division. Animals were night fasted and weight was taken in the morning before feeding.

RESULTS

Results obtained in this study showed no significant different (p>0.05) in the average initial live weight between the 2 treatment groups. The differences of the Average Daily Gain (ADG) and the total gain were not found to be significant (p>0.05) between bulls fed diet (A) and (B). The feed intake data presented in Table 3 showed that, the means of the Dry Matter Intake (DMI) between the treatment groups were not found to be significantly (p>0.05) influenced by the dietary treatment but bulls fed the unpelleted diet (A) showed higher total DMI compared to bulls fed the pelleted diet (A). Bulls fed the (A) showed higher average DMI as 8.94 kg/head/day on DM basis over these fed diet (B) as 5.9 kg/head/day. Again the DMI as percentage of body weight was found to be higher in bulls fed diet (A) compared to these fed diet (B) but the difference was not found to be significant (p>0.05). Although, the 2 diets composed of the same ME value, but bulls fed diet (A) seemed to score more ME intake values over those fed diet (B). On the other hand the crude protein intake between the treatment groups was almost similar and the difference was not found to be significant (p>0.05) (Table 4).

Table 1:	Feed ingredients of the experimental diets

Table 2:	Chemical composition of the experimental diets

Table 3:	Feedlot performance of Sudan Baggara bulls fed pelleted and unpelleted baggase based diet
±SEM: Standard error of means; ns: Not significant, **Significant (p<0.01), Sig.= Significance

Calculations of the ratio between the crude protein intake and the metabolizable energy intake revealed higher ratio in bulls fed the unpelleted diet (A) over bulls fed the pelleted diet (B). The feed conversion ratio between the 2 treatment groups was significantly (p>0.05) improved. This was obviously seen in bulls fed the pelleted diet (B) over those fed the unpelleted diet (A). Bulls fed the unpelleted diet (A) reached finishing target weight earlier than those fed the pelleted diet (B) but the difference was not significant (p>0.05).

DISCUSSION

The feedlot performance data presented in Table 3 showed no significance (p>0.05) difference in the initial and final body weights, the Average Daily Gain (ADG) and the total gain. Bulls fed diet (B) ate less amount of feed than those fed diet (A) (Table 3 and 4) even though the 2 diets were similar in feed ingredients composition and (ME) content, but the difference was not found to be significant (p>0.05). This might be attributed to the physical nature of the two diets as diet (A) is in mash (unpelleted) form and diet B is pelleted. This fact also could be attributed to the lowered CF content of diet B (9.28) compared to the synonymous diet A (13.84).

Table 4:	Feedlot performance of Sudan Baggara bulls fed pelleted and unpelleted baggase based diet
±SEM: Standard error of Mean;, ns: Not significant

Lowered CF content might have reduced the sensitivity of the rumen receptors to stretch or touch and hence the DMI as reported by Forbes (1986). Another possible factor was the animal behavior and or individually as reported by Huntington and Burns (2007) that reduced DMI was attributed in part to animal behavior. For Sudan Baggara bulls, pellets were new type of feed and animal often exhibit reluctance to accept a new feed as reported by Cheeke (2005) and Chapple et al. (1987). Similarly, Baker et al. (1955), Hale et al. (1969) and Church and Kellems (1998) reported that while pelleting high concentrate ration might markedly improve feed efficiency, gain was usually reduced due to the lowered feed intake. The reason for this is unknown but may be due to shift in Volatile Fatty Acids (VFA) production and this is found to be inline with Illius and Jessop (1996).

Earlier studies of Weir et al. (1959), Beardsley et al. (1959), Church and Fox (1959) and McCroskey et al. (1961) showed more variable results and depressed feed intake in cattle fed pelleted rations. Bulls fed the pelleted diet (B) spent more time chewing and secreted more saliva before swallowing the bolus. This might be related to the particle size, of the pellet (9 mm) or to the increased (NDF) of diet B which might lead to toughness of the pellet (Table 2). This observation agreed with the findings of many researchers (Sudweeks et al., 1981; Beauchemin and Buchanan-Smith, 1996; Loginbuhl et al., 2000) who reported that chewing time/kg of DMI decreased as DMI increased and vice versa. Other workers (Kellems and Church, 1998; Beardsley, 1964; Reddy, 2004) stated that feed intake, daily gain and FCR of cattle and sheep were increased when the roughage was pelleted.

Ensminger et al. (1990) reported that pelleting diets low in forage has no adverse effect on rations containing a low level of CF and there was no advantage in pelleting feed for beef and swines. This discrepancy with the former studies could be attributed to the fact that DMI could be influenced by many possible parameters such as textural characteristics of the feedstuffs which determine its degree of acceptance, initial body weight feeding period, environmental conditions, metabolic body size, crude fibre content and rumination time.

These parameters might impose individual or additive effect.

In this study, the reported values for DMI for Sudan Baggara bulls fed diet (B) were similar to those reported for the same breeds by Itidal (2004). Similarly the reported DMI for the other group fed diet A were in line with those reported by Eltahir (1994); Mohamed (1999) and Intesar (2002).

The average daily gain (ADG) reported for Sudan Baggara bulls in this study were higher than those reported by Mohamed (1999); Intesar (2002) and Itidal (2004) and were in line with ADG for Sudan Baggara bulls reported by many other researches.

The Feed Conversion Ratio (FCR) value decrease when it indicates efficient feed utilization. This was clear in bulls fed the pelleted diet B (Table 3) where bulls fed this diet efficiently (p<0.05) utilized feed (FCR = 5.72 g/DM/kg mass gain) compared to bulls fed diet A. This improvement in FCR might be attributed in part to the absence of selective feeding behavior of bulls fed the pelleted diet (B) as pelleting markedly improve feed efficiency (Church and Kellems, 1998; Beardsley, 1964; Baker et al., 1995). This finding could be attributed in part to the high protein content of the diet (16.43%) which agreed with Cobic et al. (1980) who reported that FCR was most efficient in animal fed the highest CP level (14.3-16.6%) in DM of the ration. Bulls fed diet (A) reached the finishing target weight earlier than those fed diet B (Table 3) but ate more feed than bulls fed diet (B).