Abstract: In this experiment, 90 healthy and similar weight (8.89±1.02kg) piglets (big York × Landrace) weaned at 28 days of age were randomly divided into 5 treatments according to weight and gender: control group (basic diet) and 4 experimental groups (0.025%, 0.05%, 0.10% and 0.20% of highly active dry yeast were added to the basic diet respectively, and the number of viable bacteria per gram feed were 5.0×10⁶ ,1.0×10⁷, 2.0×1⁰⁷ and 4.0×10⁷. The trial lasted for 4 weeks, studying the effects of different addition levels of active dry yeast on the production performance of weaned piglets. The results show that: (1) Adding active dry yeast to the diet of weaned piglets significantly improved the average daily feed intake and average daily weight gain in the 0 to 4 weeks after weaning (P<0.05). (2) Regression analysis of the impact of different addition levels of active dry yeast on each production indicators (curve fitting) showed that the impact of supplementation level on the average daily feed intake (P<0.05), average daily weight gain (P<0.05) and average daily weight gain (P<0.05) in the 0-2 weeks after weaning and the average daily weight gain in the 0-4 weeks after weaning had a quadratic curve trend, indicating that the additive dose of treatment 4 was more effective. Based on various test indicators, active dry yeast added to the diet of weaned piglets at a concentration of 2×10⁷/g can better improve production performance.

Keywords: weaned piglets, active dry yeast, production performance, diarrhea rate

Yeast is a type of probiotic, active dry yeast refers to yeast products that are dried, maintain fermentation ability, and contain yeast viable bacteria count higher than 1.5×10⁹/g (AAFCO, Association of American Feed Control Officials, 2002). Yeast cells are very rich in proteins, B vitamins, fats, sugars, enzymes and certain synergistic factors. Its long history of use in food, medicine and feed demonstrates its safety and beneficial effects on health. Studies on pigs have shown that yeast or yeast cultures can increase feed intake and accelerate weight gain (Mathew et al., 1998; Heugten et al., 2003), improve sow milk quality and improve piglet weaning performance (Jurgens et al., 1997). It can reduce the pathogenic bacteria in feces (Heugten et al., 2003), make the fur shiny, and promote the digestion and absorption of feed and the weight gain rate of pigs in the growing and fattening periods. It is speculated that the mechanism of active dry yeast in improving the production performance of weaned piglets is ① affecting the microbial fermentation in the hindgut and increasing the supply of nutrients to the animals (Glade, 1991); ② providing beneficial ingredients such as proteins, enzymes, vitamins and growth-promoting factors. It is speculated that It can improve the growth performance of pigs (Korrengoy, 1995); ③ The mannan in the yeast cell wall can adhere to Gram-negative bacteria with type 1 pili, interfere with their binding to the surface of epithelial cells, and prevent the colonization of bacteria on the surface of the digestive tract, maintain the stability of the microflora of the digestive tract (Spring et al., 2000); ④ Zymosan (mainly mannan and β-glucan) extracted from the yeast cell wall has immunomodulatory effects. Extensive research has been done on the application effects of yeast and yeast cultures at home and abroad, but most of them are concentrated on ruminants and horses, and there are few research reports on weaned piglets. Highly active dry yeast for feeding contains more than 35 billion yeast cells/g and ≥20 billion viable yeast cells/g. This experiment aims to study the effects of different addition levels of active dry yeast on the production performance of weaned piglets, and to provide experimental basis for the application of active dry yeast in weaned piglets.

1. Materials and methods

1.1 Experimental animals

This experiment selected 90 28-day-old weaned piglets (large York × Landrace) with the same genetic background and similar weight (8.89±1.02kg) from the original breeding pig farm in Ninghe, Tianjin. They were randomly divided into 5 groups according to weight and gender, with 6 replicates in each group(three replicates of males and females), 3 pigs per replicate. The test period was from April to May 2004.

1.2 Experimental diet

There are a total of 5 dietary treatments in the test. The basic diet is mainly corn-soybean meal. It is designed with reference to the nutritional needs of piglets weighing 10 to 20 kg in NRC (1998). The powder diet is prepared according to the experimental design in Table 1.

The basic dietary formula and nutritional levels are shown in Table 2.

1.3 Experimental design

Table1 Experimental design

1.4 Feeding and management

The airtight pig house has a slotted floor, and the pen is well ventilated. Ad libitum access to food and water. The environment, temperature and immunization procedures were all carried out according to the routine feeding and management of the original breeding pig farm in Ninghe, Tianjin.

1.5 Detection indicators

Growth performance indicators: weigh on days 0, 7, 14, 21, and 28 of the test, and calculate the average daily gain (ADG), average daily feed intake (ADFI), and feed gain ratio (F /G), while observing and recording the diarrhea and death of test pigs.

1.6 Statistical analysis

SPSS10.0 statistical software was used to conduct variance analysis and LSD multiple comparison on the data, and regression analysis (curve fitting) was performed on the impact of different addition levels of active dry yeast on each indicator.

Table 2 Basic diet formula and nutritional level (%)

Note: 1% premix ​​provides per kg complete feed: Cu, 250mg; Fe, 165mg; Zn, 175mg; Mn, 48mg; Se, 0.5mg; I, 0.4mg; VA, 9000IU; VD3, 2500IU; VE, 20IU; VK3, 3mg; VB1, 1.5mg; VB2, 4mg; VB6, 3mg; VB12, 0.012mg; Niacin, 30mg; Pantothenic acid, 15mg; Folic acid, 0.75mg; Biotin, 0.05mg; Choline chloride , 350mg; Nobida, 300mg; Colistin sulfate, 30mg; Chlortetracycline, 105mg. High-activity dry yeast is added according to the design requirements in Table 1, and the deficiency is made up by corn.

2. Results and discussion

The growth performance of test pigs is shown in Table 3 and Figures 1 to 4.

2.1 0 to 2 weeks after weaning

The average body weight of treatment 3, treatment 4 and treatment 5 groups increased to varying degrees compared with the control group, but the difference in the average weight of each treatment was not significant. The average daily weight gain and average daily feed intake of treatment 3, 4 and 5 were higher than those of the control group. The average daily weight gain and average daily feed intake of treatment 4 were the highest, which were 35.81% and 29.83% higher than those of the control group respectively, the difference was extremely significant (P< 0.01). Rregression analysis (curve fitting) showed that the impact of active dry yeast addition level on average daily feed intake (P<0.05) and average daily weight gain (P<0.05) showed a quadratic curve trend.

Table 3 Effects of active dry yeast on production performance and diarrhea rate of weaned piglets

Note: Those with different capital letters on the shoulders of peer data indicate extremely significant differences (P<0.01), and those with different lowercase letters on peer data indicate significant differences (p<0.05).
ADG: Daily weight gain, ADFI: Daily feed intake,FCR: Feed conversion ratio.

2.2 3 to 4 weeks after weaning 

The average daily weight gain of treatment 3, treatment 4 and treatment 5 were all increased compared with the control group, but the difference between the treatments was not significant.

2.3 0 to 4 weeks after weaning

The average body weight of treatments 3, 4 and 5 all increased compared with the control group, but the statstical difference was not significant. The average daily weight gain of treatments 3, 4 and 5 were all higher than that of the control group with a significant difference (P<0.05), the highest treatment 4 was 29.30% higher than the control group. The feed intake of treatment 4 is significantly diffirent compared with the control group (p<0.10). Regression analysis (curve fitting) showed that the impact of active dry yeast addition level on average daily weight gain followed a quadratic curve trend (p<0.10). There was no significant difference in diarrhea rates among treatment groups, and there were no deaths in any group during the entire trial.

The results of this test show that adding active dry yeast to the diet of weaned piglets improves production performance, and the effect is more obvious in the first 2 weeks than in the last 2 weeks. The production performance indicators of each stage of treatment 4 are better than those of other treatment groups. Therefore, a dose of 2×10⁷ viable yeast counts/g of complete feed has a better effect when added to the diet of weaned piglets. This is basically consistent with the research results of Heugten et al. (2003). From the test results, the addition of active dry yeast to the diet of piglets after weaning increased the daily feed intake, and the increase in daily feed intake led to an increase in daily weight gain. Jurgens et al. (1997) believed that active dry yeast can improve the average daily weight gain of weaned piglets. Mathewnet et al. (1998) reported that adding yeast culture to the diet of weaned piglets has a tendency to promote feed intake and increase average daily weight gain.

3. Summary

The results of this trial showed that adding active dry yeast to the diet of weaned piglets significantly improved the average daily feed intake and average daily weight gain between 0 and 2 weeks after weaning (P<0.01), and significantly improved the average daily feed intake(P<0.01) and the average daily weight gain(P<0.05) between 0 and 4 weeks after weaning. Based on the results of various test indicators and regression analysis, active dry yeast added to the diet of weaned piglets at a dose of 2×10⁷/g complete feed can better improve the production performance. The effect of active dry yeast on the intestinal microflora, nutrient digestibility and immune function of weaned piglets needs further study.

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