Effect of incorporating biogas slurry (BGS) on the growth performance and carcass traits of growing pigs

S S Sikka

Department of Animal Nutrition, Punjab Agricultural University, Ludhiana, India
sssikka04@rediffmail.com

Abstract

An experiment on growing large white Yorkshire pigs was conducted to study the effect of incorporating biogas slurry on the growth performance and carcass traits. Eighteen piglets of 3 months age with similar body weight were procured and grouped in three groups containing three male and three female piglets. All the animals were housed in individual pens. One standard pig grower ration was formulated. Ten and 20 percent of biogas slurry was incorporated in the control diet replacing maize and rice bran on nitrogen equivalent basis. The experimental diets were randomly allocated to three groups. Ad libitum feeding was done individually for a period of 95 days.

Both the final body weight and average daily body weight gain reduced linearly (P£ 0.05) with the increase in the level of biogas slurry in diet. Addition of BGS deteriorated (P£ 0.05) FCR . Both the protein and energy consumption per unit gain increased (P £ 0.05) with each replacement of maize and rice bran with slurry. Incorporation of BGS significantly (P £ 0.05) affected the digestibility of various nutrients. Significant (P £ 0.05) effects of incorporating the biogas slurry in the control diet were observed on the G-1-fat and bacon. The data revealed that the BGS may be limited to 10 percent in growing pig diets.

Key words: Biogas slurry, digestibility, growth, pigs

Introduction

Intensive animal rearing, due to high demands of animal products, have resulted in two major problems viz handling and storage of excreta secondly threat to the environment w.r.t pollution due to the un degradable compounds present in it. In India cow/ buffaloe dung is conventionally used as manure in the fields and dried cakes as fuel in kitchens. Dung is also being exploited to produce gas for use in kitchens leaving behind a huge amount of waste/slurry (BGS). During the fermentation process in the bio gas digester there may be the production of microbial proteins, and several simple molecules in the useable form.

The pigs being monogastric animals directly compete with human beings for cereal grains and their use in pig diets increase the cost of pig production. To formulate economical rations it is, therefore imperative to tap alternative feed sources. Keeping in view the high cost of conventional feeds and competition for grains, an experiment was conducted to study the effect of incorporating biogas slurry (BGS) in the rations on the growth performance and digestibility of nutrients in growing pigs.

Materials and methods

Animals and their management

Eighteen growing piglets of Large White York shire (LWY) breed of approximately of 3 month age were procured from three litters. The weight of all the piglets ranged between 18-21 kg. These piglets were randomly allotted to three groups of six pigs (three males and three females) in each. The grouping was done in a way that all the groups had similar weight. All the groups contained equal number of littermates. Experimental pigs were housed in individual pens with concrete floor provided with separate feeders and waterers.

Diets and feeding

Biogas slurry (BGS) was procured from the biogas complex of the University and sun dried. A standard pig grower ration (R₁) and two experimental rations (R₂) and (R₃) containing 10 and 20 percent dried BGS respectively were formulated. The BGS partially replaced both maize and rice bran of the control diet on protien equivalent basis (Table 1). All the diets were iso-nitrogenous. Experimental diets were randomly allocated to the three groups. Each diet was offered ad libitum as two meals a day. Feeding was done for a period of 95 days. Daily feed consumption of each pig was recorded.

Metabolic studies

At the end of feeding trial three animals from each treatment were selected and shifted in specially designed metabolic cages. A known quantity of feed was offered in 4 to 5 meals per day in order to avoid wastage. During the last three consecutive days daily feed offered to each pig was recorded and the faecal material of each pig was collected manually as and when voided. Twenty four hour faeces of each pig were mixed thoroughly and dried. The urine automatically collected in the plastic canes fitted beneath the cages was measured daily. Known volume of urine was preserved daily for estimation of nitrogen. The three day dried feaces of each pig was pooled and ground. BGS, dung, experimental diets and feaces were analyzed for proximate principles (AOAC 1990).

Carcass evaluation

After the completion of feeding trial three animals from each treatment were sacrificed (USDA 1970) to study organ development and carcass traits. All the data collected were subjected to analysis of variance (Snedecor and Cochran 1968)

Results and discussion

The chemical composition of the dried cow dung, BGS and the diets is depicted in Table 1.The data indicated that fermentation of the dung in the digester reduced its organic matter (OM), crude fibre (CF) and nitrogen free extract (NFE) contents but increased crude protein (CP) content. The probable reason may be the use of both the CF and NFE by the microbes for their propagation. It was further observed that partial replacement of both maize and rice polish of the control diet with BGS increased the CF and total ash (TA) but decreased OM, ether extract (EE) and NFE contents of the experimental diets (Table 1).

Growth performance

The data of growth performance of pigs fed control and BGS containing diets (Table 2) revealed that the body weight of the pigs fed 10 percent BGS containing diet (R₂₎ was significantly (P£0.05) less than the pigs fed control diet (R₁) but was significantly (P£0.05) more than the pigs fed 20 percent BGS containing diet (R₂).

Average daily gain (ADG) also decreased linearly with each increment in the BGS in the diet. Pigs fed control as well as 10 percent BGS containing diet gained significantly (P£0.05) more than the pigs maintained on 20 per cent BGS containing diet. The decrease in ADG can be attributed to increase in CF content of the diet. Our results are in agreement with those of Sikka and Chawla (1986) and Sikka and Mehta (1986) who reported that the growth performance of growing and finishing pigs had inverse relation with the dietary crude fibre contents.

The daily feed consumption per animal per day was similar in all the groups. The treatment means of feed conversion ratio (FCR) significantly (P£0.05) differed in all groups. The poor FCR and lower ADG due to the incorporation of BGS in the diets can be attributed to limited availability of energy (table 1) and high fibre content of the diets (Sikka and Chawla 1984) which had a negative relationship with the ME content of the diets (Sikka 1990). The protein required per unit gain in weight increased significantly (P£0.05) with each increment of the BGS in the diet. Similar to the more feed and protein required per unit gain, the pigs consumed significantly (P£0.05) more energy per g gain in weight with increase in dietary BGS level. The maximum ME consumption was in pigs fed 20 per cent BGS containing diet followed by 10 percent BGS containing diet.

Nutrient digestibility

Addition of BGS in the diet significantly (P£0.05) affected the digestibility of all the nutrients (Table 3). The digestibility coefficients of DM, OM, EE and NFE of pigs fed control diet were significantly (P£0.05) higher than the BGS containing diets. The CP digestibility in pigs fed 10 % BGS diet was significantly (P£0.05) less than the pigs fed 20 % BGS containing diet but comparable to the pigs fed control diet. The treatment means for OM and as well as of CF digestibilities significantly (P£0.05) differed from each other.

The data further suggested that though the numerical differences in the DM, EE and NFE digestibilities of the pigs fed either 10 or 20 percent BGS containing diet existed but statistically comparable to each other (Table 3). Our results are in agreement with the earlier reports of our own laboratory (Sikka and Chawla 1984, 1986; Sikka and Mehta 1986, Sikka 1990) that the high CF had negative effect on the digestibility of nutrients. Poor digestibility of the nutrients in BGS containing diets can be attributed to the high crude fibre content which might had increased passage rate of the digesta through the gastro- intestinal tract or due to the gel forming properties of fibre which might have entrapped the nutrients and reduced their exposure to the enzymic digestion.

Nitrogen retention (NR) g/h/d in the pigs fed experimental diets significantly (P£0.05) reduced when the BGS level was increased to 20 percent in the diet (Table 4). NR (% of intake) in pigs fed 10 percent BGS diet was non significantly less than the control diet but significantly (P£0.05) more than 20 percent BGS containing diet. The apparent biological value (BV) i.e. NR expressed as percent of absorbed N was significantly (P£0.05) less in pigs fed 20 percent BGS containing diet than the other dietary regimes.

Carcass parameters

The percent drift i.e. the loss in weight due to 24 hours fasting before sacrificing the pigs was found to be similar with slight increase in the dressing percentage in all the groups. Treatment means for carcass length and longisimus dorsi (LD) muscle area of the experimental groups were comparable to each other. However increase in the average back fat thickness of pigs increased non-significantly (P£0.05) with the addition of BGS in the diet (table 5).

Among the various commercial cuts (percentage of hot carcass weight), shoulder weight decreased non significant (P£0.05) with each addition of BGS in the diet. However the treatment means for total lean cuts though decreased but were statistically comparable to each other with the addition of BGS in the diet. Replacement of maize and rice bran of control diet with BGS significantly (P£0.05) increased bacon weight and the gastro-intestinal fat content in the pigs. However the weights of G-1-tract, kidney, lungs and bronchi decreased non-significantly (P£0.05) with the increase in the BGS in the diet.

The reduction in the average daily gain and the deterioration in the efficiency of each feed, protein and energy utilization in BGS containing the diets seemed to be due to the lower content of both EE and NFE contents and higher concentration of CF in these diets. High CF of these diets resulted in the poor digestibility of nutrients (Table 3) and it also has negative relationship with DE/ME contents of the diet (Sikka 1990) which have had limited the availability of energy for the muscular growth besides the similar ptotein consumption. The data of body weight gain, feed, protein and energy conversion ratio digestibility of nutrients and the carcass traits suggested that the growing pigs can not utilize more than 10% BGS in the diets partially replacing both the maize and rice bran of the diet.

References

AOAC 1990 Official methods of analysis (15^th Edition) Association of Official Analytical Chemists, Arlington, Virginia.

Sikka S S 1990 Comparative utilization of nutrients in poultry and swine. Ph.D. Dissertation submitted to Punjab Agricultural University, Ludhiana.

Sikka S S and Chawla J S 1984 Effect of quality of rice bran on performance of growing pigs.  Journal of Research of Punjab Agricultural University 21: (3): 457-59.

Sikka S S and Chawla J S 1986 Effect of feeding spent coffee grounds on the feedlot performance and carcass quality of fattening pigs. Agricultural Wastes 18: 305-308.

Sikka S S and Mehta R K 1986 Effect of feeding systems on the performance of growing pigs. Journal of Research of Punjab Agricultural University 23: (2) 312-15.

Snedecor G W and W G Cochran 1968 Statistical Methods, 6^th Edition. Oxford and IBH Pub. Co., Calcutta.

USDA 1970 Slaughtering cutting and processing of pork on the farm. Farmers' Bulletin No.2138 United States Department of Agriculture.

Received 15 September 2005; Accepted 17 April 2006; Published 11 May 2006

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