Supplementing diets of lactating sows with catfish (Pangasius hypophthalmus) by-product oil; effects on milk production and fatty acid composition, and performance of sows and piglets

Nguyen Thi Thuy and T R Preston*

College of Agriculture, CanTho University, CanTho, Vietnam
nthithuycn@ctu.edu.vn
* Finca Ecologica, TOSOLY, AA #48, Socorro, Santander, Colombia

Abstract

Twenty-four sows were allocated to 4 dietary treatments (levels of catfish by-product oil [CBO] of 0, 3, 6 and 9%) in a randomized block design. The experiment began when the sows were withion one week of farrowing, nad lasted until one week after weaning which was at 28 days. Performance of  sows and piglets was monitored. Milk production was measured by weighing piglets before and after suckling.

Increasing the level of catfish by-product oil up to 9 % in the sow diets: decreased sow feed intake but increased lipid and ME intake; reduced the lactation weight loss and the interval from weaning to first estrus; increased fat content of the sow's milk and tended to increase yield; and increased piglet weight gain to weaning and piglet survival (for the 9% catfish oil treatment. It was concluded that addition of 9% catfish oil to the sow diet improved the performance of sows and progeny by increasing the ouput of fat, especialy unsaturated fatty acids, into the sow’s  milk.  

Key words: Energy, estrus, fatty acids, growth, suckling, survival

Introduction

In the Mekong Delta, pig production not only plays an important role to provide meat for human consumption, but also to generate income for householders. In reality, raising sows to produce piglets has higher benefits than raising fattening pigs for meat production. However, in order to improve piglet performance, the farmers need to consider sow diets, which give higher milk production and quality. Commercial feeds improve sow performance, but are of  higher price than local feed resources. In order to reduce feed costs, producers tend to use whatever feedstuffs are available and reasonably palatable, which are very variable geographically. On the other hand, if diets are of low nutritional value, the performance of piglets may be effected by poor milk production of the sows, which leads to economic losses for producers.

Catfish by-product oil is prevalent in the Mekong Delta, where catfish production is increasing. According to Da et al  (2010), Tra catfish production in the DElta was over 1 million tonnes in 2009, and increased up to 1.5 million tonnes in 2010. A large number of factories produce catfish fillet for export, therefore, considerable amounts of processing by-products are available, accounting for 60-65% of the weight of the whole fish. Of the abundant residues, about 34% as crude fat (wet weight basis) can be recovered from the by-products (Thuy and Loc 2007). Another important feature of catfish oil is that unsaturated fatty acids account for 67.7% of the total fatty acid content (Sathivel et al 2003). In small-scale factories, a lot of catfish by-product oil is released in the processing of catfish by-product meal.

In view of the above, the main objective of this research was to determine the optimal level of catfish by-product oil in lactating sow diets, with the aim of improving milk production and milk fatty acids and performance of the sows and their progeny.

Materials and methods

Experimental design

Animals

Twenty-four pregnant sows (Landrace x Yorkshire) at 1 week before farrowing were selected from the herd of the experimental farm.All sows were in the second pregnancy. The sows were arranged in a block design (block is time of starting on the experimental diets, with six blocks of four sows, corresponding to 4 treatments per block. The treatments were levels of catfish byproduct oil (CBO) of 0, 3, 6 and 9% of the diet.

Within each block the sows were selected based on initial body weight and previous litter size. The experiment lasted 6 weeks, including 1 week before farrowing, 4 weeks of lactation and time from weaning to the first estrus.  Sows were individually penned in 2.2 x 2.4 m farrowing cages. They were weighed at 108 days of gestation, after farrowing and at weaning. At weaning, the sows were moved to individual gestation pens and feeding with experimental diets continued until display of estrus. The piglets were weighed at birth and each week until weaning. 

Experimental diets

Catfish by-product oil was collected every week from small catfish by-product meal processing factories in Can Tho City. Before feeding, the CBO was mixed with the control diet of broken rice, rice bran, maize meal and fish meal..All diets were formulated to balance contents of crude protein, calcium, and total phosphorus  (Table 1). The diets were provided from 108 days of gestation until 1 week after weaning. The sows were fed twice daily and had free access to water. During the suckling period, all piglets were offered the same creep feed from 7 days of age. 

Milk production 

Milk production was estimated by the weigh-suckle-weigh (WSW) technique (Theil and Nielsen 2002), and  took place on  days 4, 11 and 18 of lactation. The procedure for WSW involves isolation of the piglets 70 minutes before the first suckling, before re-union piglets were weighed on a whole litter basis. Then they were allowed to nurse for 15 minutes, and after nursing the piglets were weighed and isolated again. The sequence of isolation followed by weight measurement before and after each nursing period was repeated for 6 consecutive suckling bouts, each cycle lasting 70 minutes. The milk production using the WSW technique was calculated as average milk intake by the litter in all suckling bouts, multiplied by 24h day ^-1 and by 60 minutes h^-1 and divided by 70 minutes per suckling. Milk samples were collected from each teat and pooled by sow and day. Milk samples were taken after the sequences of WSW measurements had been completed.  At the end, 3 milk samples per sow were pooled and stored for analysis for the concentration of dry matter, crude protein, fat, lactose and fatty acid composition.

Estimated total milk energy was calculated using an adaptation of the equation described by Klaver  et al (1981):

Total energy (MJ/kg) = 0.0042 x (92.2 x fat %)+(61.3 x CP %)+ (35.6 x lactose %).

Chemical analysis

The chemical composition of feeds and milk were determined using the standard AOAC (1990). Dry matter was determined by drying the fresh samples at 105^oC until dry. Crude protein was determined by the Kjeldahl method. Total ash was the residue after ashing the sample at 550^oC; NFE and OM were calculated by difference. Lactose content was analyzed by Spectrophotometer. Fatty acid composition of milk was analyzed by Gas Chromatography (GC/FID- ISO/CD 5509:94).

Statistical analyses

Data collected were analyzed by the General Linear Model (GLM) option of the ANOVA progran in the Minitab Software Version 15. Tukey pair-wise comparisons were used to determine differences between treatment means at P<0.05.

Results and discussion

Analyses of feed

The ingredients and chemical composition of the experimental diets are shown in Table1. As expected, the ether extract and calculated ME values increased with the level of CBO in the diet.   

 Sow performance

There were no differences in initial body weight (day 108 of gestation) of sows (Table 2). Howerver, there were higher body live weight at weaning from sows fed CBO6 and CBO9  compared with CBO3 and CBO0. Differences in daily feed intake before farrowing and during lacation were observed between treatments. Sows fed CBO3, CBO6 and CBO9 diets consumed less feed  than sows fed the control diet.  In contrast, estimated ME intake was increased by supplementation with catfish oil. Similar findings were reported by Tilton and Miller (1999). There were close relationships between level of catfish oil and loss of live weight during lactation and days to first estrus (Figures 1 and 2). Feeding the catfish oil reduced the weight loss during lactatiuon and decreased the interval from weaning to first estrus.  Sows that lost less weight in lactation  had shorter interval to first estrrus after weaning (Figure 3). During lactation it is normal for sows to lose weight as their body reserves are moblized for milk production (Trottier and Johnston 2001). According to Hardy (2003), sows often lose 10-12 kg in a 21 day lactation with no detriment to subsequent performance. In contrast with our findings, Schoenherr  et al (1989) showed that subsequent estrus activity of the sow was not altered by dietary energy source as no difference was observed in the number of days from weaning to first estrus.

Figure 1. Relationship between level of dietary catfish oil and weight loss of sows during lactation	Figure 2. Relationship between level of dietary catfish oil and interval from weaning to first estrus

Figure 3. Relationship between loss of live weight during lactation and interval from weaning to first estrus

 Milk production, chemical and fatty acid compositions

Milk yield increased linearly with stage of lactation (Table 3; Figure 4). and tended (P=0.02) to be higher for all diets containing catfish oil, compared with the control, but with no apparent differences among levels. This contrasts with the findings of Lauridsen and Danielsen (2004) who found no effect of dietary fat level on sow milk yield. The increased yield could have been the result of the fat level in the diet and also the greater number of piglets on the diets with added catfish oil.  Hardy (2003).showed that the number of piglets suckled affects milk yield. The fat content of the milk was increased linearly with increased level of catfish oil (Figure 5). This is in agreement with the findings of Shurson and Irvin (1992) and Jones and Edwards (2002), who showed that fat suplementation of the sow diet increased fat in the milk. Lactose in milk tended to be higher (P=0.06) for diets supplemented with catfish oil but crude protein level was not affected. .

Supplementation with catfish oil increased the concentration of the unsaturated fatty acids (C18:1; C18:2, C18:3: EPA, DPA and DHA) in the sow milk but not the saturated fatty acids. The fatty acid profile of milk is known to alter with fat supplementation of sow diets. The increase in unsaturated fatty acids in the milk is probably a direct response to increase dietary intake of these fatty acids as they are in high concentratioon in catfish by-product oil (Sathivel et al 2003).

Figure 4. Relationship between milk yield and stage of lactation	Figure 5. Relationship between level of catfish oil and fat content of the sow's milk

 Performance of progeny

The dietary treatments had no influence on the litter size at birth. At weaning the litter size was greater for the 9% catoil treatment than for the control with no differences among oillevels of 0, 3 and 6%. Correcting by covariance the litter numbers at weaning according to litter numbers at birth confirmed the increase at weaning for the CBO9 treatment, which can be interpreted as an increase in piglet survival rate.  The increase in the litter size at weaning, after correction for the litter size at birth, was probably a response to the increased fat in the milk (Table 4). Live weights at birth were not affected by dietary treatments, but at weaning were increased liunearly by oil suplementation of the sow diet (Figure 6). Piglet weight gain to weaning showed the same trend (Figure 7). The intake of creep feed by the piglets was not affected by dietary catfish oil level in the sow diets.  The beneficial effect on piglet survival resulting from supplementation of the sow diet with 9% catfish oil is important and may reflect both the higher milk yield of supplemented sows and the increased concentrations of fat, and especially the unsaturated fatty acids, in their milk.

Figure 6. Relationship between level of catfish oil and piglet live weight at weaning	Figure 7. Relationship between level of catfish oil and piglet live weight gain to weaning

Conclusions

Increasing the level of catfish by-product oil up to 9 % in the diets of lactating sows:

• decreased sow feed intake but increased lipid and ME intake,

• reduced the lactation weight loss and the interval from weaning to first estrus

• increased milk fat content and tended to increase sow milk production

• increased piglet weight gain to weaning and piglet survival.

References

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Received 28 November 2011; Accepted 1 December 2011; Published 2 December 2011

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