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A feeding experiment and a digestion trial were conducted to evaluate the growth, feed intake, feed efficiency and carcass characteristics of growing finishing pigs. 48 crossbred Landrace x Large white pigs with an average body weight of 7Â±0.5 kg were divided into groups of four, balanced for ancestry, sex and body weight were used in the experiment. They were allotted to the dietary treatments in a completely randomized design with four replications. Pigs were assigned to two diets in which maize bran or wheat bran provided the energy source. A third dietary treatment where whole maize grain was used as the energy source was included for comparison. All diets were formulated to contain same levels of energy and protein. Four pigs per pen per treatment formed an experimental unit. The trial lasted for 4 months and data was collected on feed intake, weight gain. Digestibility trial was carried on two male pigs per replicate during the growth period. At the end of the growth period two pigs per treatment were slaughtered carcass characteristics determination. Average daily gain was 0.23, 0.31 and 0.13 (kg/day) for pigs fed maize bran, wheat bran and whole maize grain as dietary energy sources. Average feed intake and final body weight were significantly (P<0.05) affected by feeding on maize bran, wheat bran or whole maize. Digestibility of dry matter, crude fibre and calcium were significantly higher (P<0.05) for pigs fed maize bran than those fed wheat bran and whole maize. However, crude protein digestibility was highest (P<0.05) for the pigs fed wheat bran. There were significant differences between diets in carcass yield, ham, head, trotters, and heart weights were significant (P<0.05). Carcass composition at the 6th rib showed significant differences (P<0.05) for rib weight, rib eye muscle and other tissues. Intra-muscular fat (IMF), subcutaneous fat, and bone weight were not significantly (P<0.05) affected by diet. The results show that feeding growing pig on wheat bran diet improves ADG, feed efficiency and carcass yield. Wheat bran can therefore be substituted for maize bran depending on cost.
Key words: Wheat bran, maize bran, pigs, carcass characteristics
Production and consumption of pork in Uganda has increased substantially in the recent decade. This increased demand for pork clearly offers opportunities to expand production. The liberalization of the economy makes it increasingly essential to become competitive in the market as this can contribute significantly to the profitability of the pig industry. However, in order for the pig farmers in Uganda to fully tap this market, there is a need to improve efficiency of production. Agro-industrial cereal by-products have the potential to improve pig productivity if properly utilized. These by-products are available in Uganda, however, information pertaining to their feeding value and effect on carcass characteristics in pigs still lacks. Although cereal processing by- products are fairy priced they are variable in quality hence posing a serious challenge in their use as pig feeds. Pond (1987), asserted that agro-industrial by-products such as maize cobs, distillery, milling by-products and other fibrous feeds could be used as energy sources for pigs. In Uganda, maize bran forms the bulk of ingredients used in livestock feeds but it is higher in price compared to other cereal by-products. Wheat bran has can be used in pig diet however it level of incorporation depends on the stage of growth of the animals. Therefore care is needed when using this by product for its high in fibre which impacts on its efficiency of utilization. Muir et al. (1992) reported good performance of pigs fed this by-product. The objective of the current study were to determine the effect of maize bran and wheat bran as dietary energy sources on growth, digestibility and carcass characteristics of growing pigs.
2. Materials and methods
The experiment was conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) located 17 km North East of Kampala at an altitude of 1200 m above sea level. The area receives a bimodal type of rainfall with the first rainy season stretching from March to June and the second running from September to November. The average annual rainfall is 1500 mm and the mean daily maximum and minimum temperatures 270C and 170C respectively.
2.1 Experimental animals
Fourty eight pigs (Landrace x Large White) with an initial body weight averaging 7Â±0.5kgs were used in the study. Pigs were balanced for ancestry, sex and body weight and allotted to the experimental diets in a completely randomized design (CRD). A pen containing four animals was used as the experimental unit.
2.2 Experimental diets
Three dietary treatments were formulated based on two cereal bran i.e. MB and WB, Whole maize (WM) acted as control. The WB diet was formulated in proportions of 3: 2 for wheat bran and wheat pollard respectively. Wheat bran and pollard were obtained from local mills around Kampala. The diets were iso-proteineous and iso-caloric. They were mixed to make a 100 kg bag in proportions shown below.
2.3 Housing and management of pigs
The pigs were housed in solid floor pens fitted with water and feed troughs. The front of pens consisted of bars where as the sides were solid walls to eliminated physical contacts between pigs in adjacent pens. Each pen housed four pigs. The pigs were fed experimental diets in the morning (8:00-8:30am) and afternoon (2:00-2:30pm). The animals had free access to water always (ad libitum). The pigs were treated against ecto- and endo-parasites with IvomectinÂ® injection prior to the start of the study. They were also given an antibiotics (Tetracycline LA) injection to ensure good health.
If pigs are to fully express their potential for weight gain, intake must meet their nutritional requirement (Whittemore, 1993). In the current study, pigs fed whole maize had the lowest average daily feed intake levels (ADFI) compared to those fed maize bran and wheat bran as energy sources. As such, average daily gain and feed to gain ratio were lower for these pigs compared to those fed maize bran and wheat bran diets. The low intake demonstrated by the pigs fed whole maize diet might have resulted in decreased intake of CP and DE hence their lower weight gain compared to the maize bran and wheat bran diets. Adesehibwa (1992) reported that pigs fed diets of low CP grew slowly.
Despite diets being formulated on isoproteinic and isocaloric basis, whole maize diet had lower CP implying that, the nutritional demands for the pigs fed on this diet were not met, hence their constant slow growth rate (Kyriazakis, et al., 1999). It is possible that feed intake was less than the desired level for the animals to achieve full their genetic potential.
The digestibility of nutrients (DM, CP) from whole maize based diets were lower than maize bran and wheat bran based diets, implying that, palatability and acceptability were low for this diet compared to that of maize bran and wheat bran diets hence the lower average daily gain (ADG). The reason for this is probably due to the poor quality of CP, which may have decreased growth and hence efficiency of gain. Adesehibwa (1992) indicated that low levels of dietary protein are required to maximize growth and efficiency of gain for a protein source with well balanced amino acids in contrast to that with a poor amino acid balance where more levels of dietary protein are required. Additionally, Conrad (1984) reported that, the amino acid requirement expressed as a percentage of the diet decreased as the pig becomes heavier, that the requirements are greatest during the rapidly growing stages of the young animal. This implies that, since the pigs were started as weaners and therefore still growing, they were negatively impacted by this low protein hence the low gains exhibited.
On the other hand, maize diets have been reported to have starch encapsulated by NSP present in it, hence hampering its gastro-intestinal tract digestibility (Slaughter et al., 2001; Svihus et al., 2005). They further stressed that, in maize diets most of the EE was encapsulated inside the grain hence making it not readily available for digestion. All of these may have therefore contributed to the overall poor performance of pigs fed whole maize based diets.
Some authors have reported maize as a standard with which to compare the performance of other feed stuffs while others have criticized its use as sole dietary ingredient (Okai et al., 2005; Vasal, 2006; Moeser et al., 2002). However, in the present study pigs on whole maize based diets performed poorly in terms of growth and weight gain despite it not being a sole dietary ingredient.
The performance of pigs fed diet containing wheat bran was superior to those containing maize bran and whole maize (control) despite the higher CF content of wheat bran diet (Table 5). This is probably due to the higher palatability and acceptability of the wheat bran diet to pigs as partly demonstrated by its high intake and average daily gain (ADG). Hedemann et al, (2006) reported that feeding pigs high insoluble dietary fibre sources improves gut morphology and stimulate mucosal enzyme activity which might improve nutrient digestibility and piglet growth. In their work, Langlois et al, (1987) reported that wheat bran induced an increase in volume (+115%) and protein output (+36%) of the pancreatic juice and that all enzyme activities were enhanced by intake of wheat bran. This could have further enhanced its digestibility by the animals. Brannon, (1990) also demonstrated that, exocrine secretion are dietary dependent and is aimed at improving digestibility and nutrient absorption by the GIT.
4.2 Effect of cereal bran on nutrient digestibility
Digestibility determination is essential in order to define the efficiency of utilization of nutrients in the feed. Pigs fed diets based on maize bran had higher fibre digestibility (Table 3). This implies these pigs had greater contribution to their net energy requirement resulting from VFAs produced from digestion of CF in the hind gut. Kass et al. (1980) estimated the contribution of VFAs from fibre fermentation to be about 5%-28% of the net energy requirement of the growing pig. Utilisation of crude fiber by non ruminants has been shown to vary considerably according to the fibre source (Freira et al., 2000; Galassi et al., 2004), degree of lignification (Forbes and Hamilton, 1952), level of inclusion (Farrell and Johnson, 1970), and the extent of processing (Saunders et al., 1969). This could probably explain why fiber digestibility differed.
The digestibilities of nutrients in wheat bran based diets with exception of CP were lower than maize bran based diets (Table 4). The depression in digestibility of chemical components could be due to the decrease in the mean retention time of this diet in the GIT (Hansen et al., 1992) brought about by higher levels of fiber in wheat bran based diets compared to maize bran based diets. The crude fiber level for maize grain based diet (control) was lower than maize bran and wheat bran diets but its digestibility was the lowest among the diets. This could partly be explained by the low average daily feed intake exhibited by the animals on this diet. This further implies that the animals were taking in lower nutrient/KgDM as compared to those fed maize bran and wheat bran diets.
Additionally, pigs fed diets based on wheat bran had heavier empty stomachs, large intestines, hearts and kidneys than those fed maize bran and maize grain (control) diets. This suggests that, the pigs were able to adjust anatomically to gain nutritional benefits from fibrous materials by increasing their feed intakes in an effort to compensate for the low energy of the diet. This is consistent with findings of Pond et al, (1980) who reported an increase in length of the large intestine of pigs fed on high fiber diets. These changes are a reflection of increase in size (hypertrophy) of particular tissues of the organ in response to increased amount of work performed by these organs in drying, mixing, shaping, moving and expelling large amounts of un- digested residues. Additionally, pigs fed diet based on wheat bran had the highest average daily feed take compared to those fed maize bran and whole maize suggesting that level of intake may also have influenced the relative organ weights of these pigs. This is in line with the findings of Gómez et al, (2002) who reported feeding level as one the factors lead to increase of organ weights in p
4.3 Effect of cereal brans on carcass and non carcass characteristics of growing pigs
Pigs fed a diet based on wheat bran based had higher live weight and consequently higher carcass yield. This is demonstrated by their high average daily gain (ADG) and average daily feed intake (ADFI), implying that most of the nutrients digested were absorbed and assimilated into body tissues as compared to pigs fed other diets.
The empty stomach, large intestine, heart and kidney were significantly higher for the pigs fed maize bran and wheat bran based diets than those fed whole maize based diets (Table 5). This could be attributed to the crude fiber level content in the experimental diets used. In the current study, maize bran and wheat bran diets had higher crude fiber (CF) levels and consequently lower DE than whole maize diets. This further reinforces other findings by Shi and Noblet (1994),Canh et al, (1998) and Davidson et al, (1998) that, cereal brans are characterized by varying levels of fiber which negatively impacts energy and nutrient utilisation by pigs. Consequently, this increases waste production and nutrient excretion.
Ma et al, (2002) reported significant changes in the mass of the gastrointestinal tract and other intestinal organs as a result of feeding diets based on 5% wheat bran, as a source of high insoluble fibre to pigs. The increase in the stomach and large intestine weights for maize bran and wheat bran diets observed in the current study is in line with the finding of Shurson et al., (2000) and Jorgensen et al., (1996). Our findings however, contrasts with the works of Cunningham et al, (1961) and Gargallo & Zimmerman (1980), who reported very little or no change in the organs of pigs given diets containing increased levels of Lucerne, wheat bran cellulose and sunflower hulls.
Dietary fibre has been found to negatively impact on energy content of the diet. Pigs adapt to high fiber by increasing their food intakes in an effort to compensate for the low energy of the diet. This is achieved by an enlargement of some or all organs of the gastro intestinal tract. Jorgensen et al, (1996) reported significant heavier stomach, ceacum, and longer colon in growing finishing pigs fed diets containing higher dietary fiber. Generally, changes in the size and weight of gastro-intestinal organs are believed to reflect a hypertrophy of particular tissue of the organ in response to increased amount of work performed by these organs in drying, mixing, shaping, moving and expelling large amounts of undigested residues.
Carcass length in this study was similar across all diets despite pigs fed wheat bran being heavier. Ham weight increase was in tandem with slaughter weight. This could have been entirely dependent on the breed (Fisher et al., 2003). In the present study, weights of loin, and shoulder did not increase with slaughter weight.
4.4 Effect of diets based on cereal brans on carcass tissue composition
Pigs fed wheat bran diet had higher rib and eye muscle weights (Table 6). This demonstrates that the rate of muscle accretion was higher in these pigs. This further implies that the nutrients in this diet were digested efficiently, absorbed and assimilated into body tissues as compared to those fed maize bran and whole maize (control) diets.
The influence of diets on intra-mascular fat (IMF) was found to be non significant across diets. Intra-mascular fat content is linked to texture (Kriestensen et al., 2002; Teye et al., 2006), though not tested in this study, it implies tenderness of pork was similar across all diets. Since the animals were subjected to the diets at 2.5 months (weaners) and slaughtered at four months (growing stage) most of the energy must have been used for growth and less was available for store as body fat. The lower subcutaneous fat and back fat thickness clearly demonstrates that since animals were still growing and therefore using more energy for this process less was available for body store.
The use of cereal agro-based by-products for improved pig production in Uganda remains a challenge. However, results from the current studies have revealed that if carefully incorporated in pig feeds, cereal by-products have the potential to improve pig production. Pigs fed diet where wheat bran served as an energy source had higher average daily gain (ADG) and better FCR compared to those fed maize bran and maize grain (control). This clearly shows that under proper usage this by-product can significantly improve pig production. Results on carcass characteristics also showed higher rib weight, rib eye muscle and muscle weight by wheat bran fed pigs compared to those fed on maize bran, maize grain based diets. This further demonstrates considerable scope for increased and more efficient utilization wheat bran in pig feeds. It is also important to note that feed stuffs from animal origin are expensive than those from the plant origin, therefore, if efficiently utilized, agro-industrial cereal by-products would not only cut down feed costs (improve net profits) but also reduce competition between human beings and pigs for convention fees stuffs like maize and soybean meal. Further studies are also recommended on more effective methods of combining cereal by-products for improved pig performance as they represent a vast animal feed resource which is not yet fully exploited.