Advances in research on determination of pig nutrient digestibility by moving nylon bag method

Abstract: Accurate assessment of the nutritional value of feed ingredients is the premise and basis for studying the nutritional needs of animals and formulating dietary formulas. The modified nylon bag method has the advantages of fast measurement speed, low measurement cost, small sample amount to be tested, and the like, and is a new method for determining nutrient digestibility of pig feed ingredients. This method was originally applied to ruminants and was introduced into monogastric animals. It has been modified repeatedly to achieve good results. The review shows that the active nylon bag method can be applied to the apparent digestibility of dry matter, energy and crude protein of each raw material in pig feed.

introduction

Accurate assessment of the nutritional value of pig feed ingredients is a very important part of the pig's nutritional requirements. The current widely used methods include the full-fee method and indicator method (Dai Wei et al., 2008; Meng Jingmao et al., 2008; Thacker and Qiao, 2001; Sauer et al., 1989), but time-consuming, costly, and overworked are common shortcomings of these traditional methods (Yin et al., 2002; Sauer et al., 1989). As early as 1978, Petty and Handlos tried to use nylon bags to determine the digestibility of pig feed ingredients. In 1983, Sauer et al., based on their combination with ruminant nutrition methods, established a mobile nylon bag method. , MNBT), which has the advantages of fast measurement speed, low measurement cost, small sample amount to be tested, etc., and after more than ten years of improvement, the technology is continuously improved and has the value of popularization and application.

1 Basic procedure for the active nylon bag method

The earliest application of nylon bag technology to the determination of digestibility of pig feed ingredients was Petty and Handlos. In 1978, they directly sent nylon bags containing feed samples from the mouth into the pigs until they were discharged and collected nylon bags. As a result, it was found that since the nylon bag stayed in the stomach for too long, the measurement data was always higher than that obtained by the conventional method.

Sauer et al. (1983) created a movable nylon bag method based on them and explained their own operating procedure: a small nylon bag of 25 x 40 mm was made from a single filament nylon with a mesh aperture of 48 μm. 1 g of the test sample with a particle size of 0.8 mm was placed in a nylon bag, first placed in a beaker containing 500 mL of 0.01 N hydrochloric acid and pepsin solution, and the beaker was shaken in a 37 ° C water bath for 2.5 h. The pH of the solution was 2.0, pepsin content was 377.4 IU / L. Then remove the nylon bag from the beaker and introduce it into the healthy pig with a body weight of about 40 kg through the duodenal fistula. After the nylon bag passes through the digestive tract, recover the nylon bag from the feces, and gently wipe the surface of the bag with a dry tissue. , freeze-drying, determine the content of nutrients to be tested in the remaining material in the bag, and calculate the nutrient digestibility of the feed to be tested.

However, the digestibility values ​​measured with the original active nylon bag technique vary widely compared to conventional methods (Sauer et al., 1983). In order to find out the source of the variation, Graham et al. (1985) and Cherian et al. (1988, 1989) conducted further studies using growth-finishing pigs, indicating pH, pepsin concentration and time in vitro digestion, and the size of the feed to be tested. The pore size and nylon bag size have a significant effect on the apparent digestibility of the protein, with the most affected by the crushing size of the feed. Lin et al. (1995) observed in vitro simulated digestion conditions, including solution pH, pepsin, in a comparative study of total chyme extraction and MNBT determination of crude protein (CP), dry matter (DM) and amino acid ileal apparent digestibility. The activity and time of simulated digestion had no effect on the results of the assay.

There are many controversies regarding the method of MNBT for determining pig feed nutrients, such as the pore size of the nylon bag is too small, the particle size of the feed sample and the in vitro digestion time. The size of the pore size directly affects the exchange of substances in the digestive juice and the bag, and underestimates the digestibility of protein and amino acids in the feed (Sauer and de Lange. 1989). If it is too low, it will be overestimated. Graham et al. (1985) showed that when the mesh pore size is 20 m, some bacteria can enter and exit the nylon bag. In just a few years, some scholars have said that whether the washed manure on the nylon bag with water has a significant effect on the accuracy of the MNBT method (Qiao and Thacker, 2001). According to the latest research by Qiao and Thacker, the perfect MNBT measurement procedure is: firstly, 1 g of feed material with a crushing size of 1.0 mm is placed in a nylon bag with a mesh opening diameter of 48 μm and a size of 25×40 mm2. It was sealed on all sides; then it was digested in vitro for 4 h in a solution with a pH of 2.0 and a pepsin concentration of 377.41 IU/L, and then introduced through a common T-shaped fistula of the duodenum; finally, the nylon bag was recovered through the collecting bag, and the water could not be used. Rinse and measure separately. Yan Shiyan et al. (2002) used the improved MNBT to determine the dry matter, energy and crude protein as digestibility. Compared with the traditional method, the correlation distribution reached 93%, 94% and 76%, which is more obvious than the unmodified MNBT. improve.

2 Activity nylon bag method to determine the nutrient digestibility of feeding

2.1 Feed dry matter digestibility

The main idea is to summarize the results of all the studies, find out the correlation, and then lead to the improved nylon bag method to improve the accuracy of the measurement.

2.2 Determination of feed energy digestibility by moving nylon bag method

(The same as before) The main idea is to summarize the results of all the studies, find out the correlation, and then lead to the improved nylon bag method to improve the accuracy of the measurement.

2.3 Determination of crude protein digestibility by active nylon bag method

(The same as before) The main idea is to summarize the results of all the studies, find out the correlation, and then lead to the improved nylon bag method to improve the accuracy of the measurement.

2.4 Determination of digestibility of other components in feed by the active nylon bag method

The main idea is to summarize the previous experiments and explain the infeasibility of combining rectal anastomosis with MNBT.

3 Conclusion