| Citation |
The effects of diets with four different protein sources were determined with respect to average daily gain, feed conversion ratio, back fat thickness and economic benefits in growing pigs. The four treatments were based on cassava root meal as energy source: A control treatment (FM) was cassava root meal plus marine fish meal; Treatment BM was cassava root meal plus catfish broken meat by-product meal; Diet OE was cassava root meal plus oil extracted catfish by-product meal and Diet BH was cassava root meal plus bone and head catfish by-product meal. The four diets were fed to twenty four growing pigs in a Complete Randomized Block design with four treatments and six replications, and the experimental unit was one pig.
There were differences among the diets in the average daily gain (ADG), dry matter intake (DMI), feed conversion ratio (FCR) and back fat thickness, with a descending trend from BM, OE, FM and BH (P<0.05). The DMI, ADG, back fat thickness and iodine number were highest in BM (1955 g, 629 g, 13.7 mm and 52.8, respectively) (P<0.05) and lowest in BH (182 g, 925 g, 7.81 mm and 40.1, respectively) (P<0.05). FCR in BM was the lowest (3.13 kg/kg gain and highest in BH 5.31 kg/kg gain) (P<0.05). The feed cost per kg weight gain of pigs in BM was lowest (P<0.05). The gross income and net benefit per pig of BM were higher than the other diets (P<0.05). It can be concluded that the growth performance and economic benefit of the treatment with catfish broken meat by-product meal (BM) were highest, followed by OE, FM and BH.
Pig production in the Mekong delta increased strongly by 25.5 % between 2000 and 2006. However, during the same period production in Cantho Province decreased by 45 %, and continued to decline, by 4.3 % annually between 2006 and 2008 (Vietnam Statistical Yearbook, 2008).
According to Nguyen Thi Thuy et al (2007) catfish residue meals contain high levels of minerals and concentrations also were shown to vary considerably among by-products and factories. For example, ash contents ranged from 3.5 to 33.8 % depending on catfish by-product, and calcium and phosphorus concentrations ranged from 7 to 13 %, and 2 to 3 %, respectively, which means that catfish by-products are a good source of macro- minerals for growing pigs and sows.
The nutritive value of any protein is directly related to the amino acid composition of that protein. A protein that does not contain the proper amounts of amino acids will be imbalanced. Tra catfish by-product meal (broken meat and skin) contains an excellent balance of essential amino acids, especially with respect to lysine and methionine (Nguyen Thi Thuy et al 2007).
According to Le Thi Men et al (2005), Tra catfish residue meal can completely replace fish meal in fattening pig diets based on broken rice as the main ingredient and without effects on back fat thickness.
The present study was conducted in order to determine average daily gain, feed conversion ratio, back fat thickness and economic benefits among diets based on cassava root meal, with marine fish meal and different by-product meals from processing catfish as protein sources.
The experiment was carried out in the experimental station of Angiang University, in Chau Phu district, Angiang Province, from August 25 to December 26, 2009. The average annual daily temperature is 270C, with the highest temperatures of 35 to 360C from April to May and the lowest of 20 to 210C from December to January. The mean rainfall is 1400 to 1500 millimeters. The climate has two seasons, the rainy season from May to November and the dry season from December to April (Angiang Portal 2008).
The animals in the experiment were bought from a pig farm in Angiang Province. Twenty four crossbred (Landrace x Yorkshire x Duroc) castrated male pigs with a mean body weight of 22.7 kg ± 0.5 at 70 days of age were used in the experiment. All pigs were vaccinated against hog cholera and foot and mouth disease and were treated against round worms with Levamysole before starting the experiment.
The pigs were housed in individual pens (0.6 m x 1.2 m) made of bamboo with feeding troughs to allow recording of offered feed and to collect refused feed. Animals were given feed ad-libitum four times per day at 07:00, 11:00, 14:00 and 17:00 h and feed refusals were collected and weighed before the morning and afternoon feeding.
During the trial, one pig in treatment FM died due to lung problems.
The diets were based on cassava root meal, marine fish meal, broken meat by-product, oil extracted by-product and head and bone by-product, and were formulated to contain from 17 to 18 % crude protein (CP) in DM to meet requirements according to NRC (1998).
All ingredients were bought at one time at the beginning of the experiment. The bone and head, broken meat and oil extracted catfish by-product meals were bought in local processing factories, and the cassava root meal and fish meal were bought from an animal feed shop in Angiang province. Before making the dietary formula, samples of ingredients were taken and analyzed for crude protein, and then were mixed together following the formula every week.
Treatments
Control treatment (FM): cassava root meal plus marine fish meal and one percent of a premix of minerals and vitamins.
Treatment BM: cassava root meal plus broken meat catfish by-product meal and one percent of a premix of minerals and vitamins.
Treatment OE: cassava root meal plus oil extracted catfish by-product meal and one percent of a premix of minerals and vitamins.
Treatment BH: cassava root meal plus bone and head catfish by-product meal and one percent of a premix of minerals and vitamins.
The experiment was designed as a Complete Randomized Block with four treatments and six replications, and the experimental unit was one pig. The pigs were allocated to blocks based on initial live weight and at random within blocks according to treatment. The experiment was conducted over four months (finishing when the pigs reached slaughter weight, at 90 to 100 kg). The chemical composition of the ingredients is shown in Table 1 and the ingredient composition of the diets is shown in Table 2.
Table 1: Dry matter content (%) and chemical composition of ingredients (%, dry matter basis) |
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Table 2: Ingredient and chemical composition of the experimental diets |
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FM: fish meal diet; BM: broken meat meal diet; OE: oil extracted meal diet; BH: bone and head meal diet According to McDonald et al (2002): ME (MJ/kg, DM) contents of diets were estimated as: ME = %EE*25.4 + %(CP+CHO)*12.7;%(CP+CHO) = 100 - %EE - %ash -%CF*% digestibility |
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All pigs were weighed at the beginning and end of the experiment to determine daily live weight gain. Amounts of offered and refused feed in every pen were recorded every day to calculate feed intake, and then feed conversion ratio was calculated and an economic analysis performed. Back fat thickness at the last rib of all pigs was measured by an ultrasonic technique (RENCO Co., Ltd, Minneapolis, USA) at the end of the experiment.
The formula to calculate average daily weight gain (ADG), and feed conversion ratio (FCR) were:
ADG = (W2 –W1)/T
FCR = Total dry matter intake/weight gain
Where: W1 is live weight at start of experiment; W2 is live weight at the end of the experiment, and T is the number of days on experiment.
All ingredients were analyzed for dry matter (DM) ether extract (EE) and ash according to the standard methods of AOAC (1990), and crude protein (CP) was determined by the Kjeldahl procedure before making the diets. Offered and refused feed samples were analyzed for dry matter by using microwave radiation (Undersander et al 1993). One representative pig in each treatment was slaughtered, and back fat samples taken for analysis of iodine number according to the standard method of AOAC (1984).
The data for feed intake, growth rate and feed conversion ratio were analyzed as a Randomized Complete Block Design by using the General Linear Model (GLM) of the Analysis of Variance (ANOVA) procedure of the Minitab statistical software release 14 (Minitab, 2003). Sources of variation were: animals, treatments, blocks and error. The Tukey Test for pair-wise comparisons was used to separate means when the differences were significant at the five percent level.
There were differences in the average daily gain (ADG), feed conversion ratio (FCR), back fat thickness and iodine number among diets (P<0.05), with a descending trend from BM, OE, FM and BH. Dry matter intake (DMI) was highest in BM (1955 g/day), followed by FM (1573 g/day), OE (1264 g/day) and BH (925 g/day) (P<0.001). The differences between BM and FM, and BH and OE were non-significant (P>0.05). Average daily gain was highest in BM (629 g) followed by OE (372 g), FM (365 g) and BH (182 g) (P<0.001). The difference between OE and FM was non-significant (P>0.05). The FCR in BM was lower than in FM (P<0.05), but not different from OE, and the FCR in BH was higher than in FM (P<0.05) (Table 3). Back fat thickness of the FM and OE diets did not differ, while BM had the highest value, and BH lowest (P<0.05). Iodine number of BM was higher than FM and OE (P<0.05), and was lowest in BH (P<0.05) (Table 3).
The feed cost per kg weight gain of pigs fed diet BM was the lowest, and differed from the other diets (P<0.05), while differences among diets FM, OE and BH were non-significant (P>0.05) (Table 4). There were no differences among treatments FM, OE and BH in gross income and net benefit per pig. However, they were lower than in diet BM (P<0.05) (Table 4).
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Table 3 Effect of protein source on daily feed and nutrient intake, daily live weight gain, feed conversion ratio and back fat thickness |
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Table 4: Effect of diet on economic benefits |
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Discussion
The metabolisable energy (ME) content in diet BH was very low (10.8 MJ/kg) because of the very high ash content and low content of EE. In contrast diet BM had a high content of EE and low content of ash, and therefore a high ME content (13.4 MJ/kg). Crude fibre content in all diets was very low, around 3% of DM.
The DM intake differed among diets. The low ME content of diet BH would have been expected to have increased DMI, as pigs try to adjust their feed intake to give a constant ME intake. However, that this was not the case could have been due to the lower palatability of diet BH, probably due to the very high ash content, and also due to possible rancidity. This could also explain the positive relationship between DMI and ratio of ME:CP in the diets, as diets FM and OE also had a high ash content, and DMI that were much lower than that of pigs on BM, which had an ash content of only 3 %. Furthermore, there were positive relationships between apparent digestibility of DM and CP (Tuan et al 2010) and the DMI. Pomar et al (2003) and Speedy (1997) confirmed that voluntary feed intake is limited when the feed is unbalanced in terms of the ratio between energy and protein. According to Holness (2005) the optimum ratio of ME and CP, and ME requirement of pigs in the tropics are 0.08 and 12 MJ/kg, respectively.
Average daily gains on the tested diets in descending order were BM, OE, FM and BH (Table 3), and generally reflected daily dry matter intakes. Growth rates were highest on diet BM, which also had the highest DMI. Average daily gain and DMI were very low in diet BH, but although DMI was higher in the fish meal (FM) diet than in the diet containing the oil extracted meal (OE), ADG in these two diets were similar, probably because the ME content in the diets and ratio of ME:CP between the treatments were different, and calculated ME content in diet BH was lower than the requirement of tropical pigs, as the ideal mean ME in diets for pigs in the tropics is from 20 to 120 kg is 12.0 (Holness, 2005), which is much higher than the ME content in diet BH, of 10.8 MJ/kg. There is a positive relationship between ME intake, and protein deposition in pigs (Renaudeau et al, 2006). Several authors confirmed that subsequent growth performance was reduced when pig had low energy intake in the early growing period (Chadd and Cole, 1999; Smith et al, 1999; De la Llata et al, 2001). In addition, ash content in the diet could also have negatively also affected growth rate for a different reason, because animals must excrete minerals through urine and use energy to do this function when intakes are higher than body demand. Consequently, all the above factors probably affected ADG.
The FCR among the diets were different. This can be explained by the fact that the diets had higher ME contents, and thus hiigher protein deposition in pigs, and therefore, the efficiency of feed utilization was better. These results are in agreement with Lopez et al (1997) who found that when the ME in the diets was higher, the FCR was lower, and when the ratio of ME : CP was high, the FCR was reduced (Le Bellago et al, 2002).
The back fat thickness was different among treatments, and there was a positive relationship between ME content in the diet and back fat deposition. According to Renaudeau et al (2006) the higher the ME intake, the thicker the back fat.
There were differences among the treatments in iodine number of back fat, with the BM diet having the highest value. Generally, when the catfish oil level was increased, the iodine number was higher. This can be explained by the fact that the proportion of EE in diets BM and OE was higher than in diets FM and BH and the unsaturated fatty acid content in catfish by-product meal is very high. According to Nguyen Thi Thuy et al (2007) the unsaturated fatty acid content in catfish by-product meal is higher than in other fish meals. However, our values for iodine number were lower than those reported by Le Thi Men et al (2003) in a study on the effects of catfish oil in diets for fattening pigs.
The BM diet was the best in terms of economic benefit. Although the other diets were not different from each other broken head meal should not be used in pig diets because of the very poor performance.
It can therefore be concluded that the average daily gain,
feed conversion and economic benefit of the broken meat meal diet was the best,
followed by diets OE, FM and BH.
The authors would like to express most sincere thanks to SIDA-SAREC (Swedish International Development Cooperation Agency - Department for Research Cooperation), through the regional MEKARN program for support financial of this study.
Angiang Portal 2008 article March 13, 2008
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