Hello, my name is Carly Rundle and today I will be presenting research conducted at the University of Illinois in collaboration with DuPont Animal Nutrition investigating the effects of including Buttiocella phytase to diets based on corn, soybean meal, and canola meal on the growth performance of weanling pigs.

Phytate is the main form of Phosphorous (P) found in plant feed ingredients including seeds, nuts, legumes, and grains, with about 50 to 60% of phosphorous bound to phytate. This phytate can form complexes with minerals including zinc, copper, manganese, calcium, and iron and therefore reduces the digestibility and absorption of many minerals. As phosphorous is a required nutrient for bone formation, acid base balance, and general metabolic function, it is crucial that pigs obtain optimum levels of phosphorous through the diet.    

Phytase is an enzyme that catalyzes the release of phytate complexes. However, the intrinsic concentration of phytase is very low in corn and legumes – common ingredients in diets fed to pigs in the United States. There is also some phytase expressed in the gastrointestinal tract of pigs which results in additional cleaving of the phytate, yielding available phosphorous and calcium for absorption by the pig. However, this is not enough for optimal utilization of feed ingredients.

As a result, exogenous microbial phytase produced on a large scale through cellulosic biomass fermentation is added to diets fed to pigs to maximize digestion and absorption of phosphorous in order to reduce feed costs associated with including high levels of inorganic sources of P. Additionally, phasing out of high inorganic mineral concentrations reduces mineral deposition in manure, which reduces the impact of livestock production on the environment. 

This increase in digestion and absorption of phosphorous has been shown to improve the growth performance of pigs including increases in average daily gain and G:F, and it has also been shown to improve bone strength and bone density, resulting in an improvement in overall health of the animal. Including phytase in diets fed to pigs may then result in a reduction in feed cost as improvements to growth efficiency are made and organic sources of phosphorous including corn and legumes are utilized more efficiently, enabling producers to reduce amounts of inorganic calcium and phosphorous in the diet formulation. 

Previous research conducted in the Hans Stein Monogastric Nutrition Laboratory investigated the effects of phytase inclusion on the apparent total tract digestibility in fecal excretion of Ca and P by weanling pigs. It was observed that inclusion of 250, 500 or 1000 pytase unites or FTU/kg of Buttiocella phytase increase the apparent total digestibility of both Ca and P when feed to weanling pigs, compared with the negative control diets that was formulated without a source of inorganic P. Apparent total tract digestibility of Ca and P was also quadratically increase as phytase inclusion in the diet increase, but the greatest digestibility observed in a 1000 FTU phytase diet. In addition, this phytase inclusion improves de absorption and utilization of feed ingredients evidence by reducing de fecal excretion of Ca and P letting the conclusion the Buttiocella phytase were reduce mineral deposition in manure.

Therefore the next step in testing this source on phytase was to ensure that this product not only increase digestibility of Ca and P and reduce fecal excretion of minerals, but also increase growth performances in indices including average daily gain and G:F ratio. We speculated that due to the increase in digestibility of minerals we may reduce the inclusion level of inorganic sources of Ca and P including limestone and monocalcuim phosphate in the diet, and still obtain ideal growth performance compared with conventional formulated nursery diet.

Inclusion of phytase in diets fed to growing pigs improves the digestibility of Ca and P, and consequently may improve growth performance of pigs fed diets with reduced nutrient composition.

Therefore, it was the hypothesis of this study that Buttiocella phytase from T. reesei would ameliorate the effects of reducing concentrations of nutrients in the diet on growth performance compared with a conventionally formulated diet when fed to weanling pigs.

There were 5 experimental diets in total. A positive control or PC diet based on corn, canola meal, and soybean meal was formulated with monocalcium phosphate and limestone to contain 0.33% digestible Phosphorous and 0.60% total Ca. The negative control or NC diet was then based on corn, canola meal, and soybean meal and formulated to contain 0.18% digestible Phosphorous and 0.45% total Ca with limestone and monocalcium phosphate included in the diet in reduce concentrations. Standardized ileal digestible amino acids were decreased by between 0.01 and 0.02 % in the diet, and digestible energy concentration was reduced by around 43 kilocalories per kilogram between the positive control and the negative control. Three additional diets were formulated by adding either 250, 500, or 1000 phytase units per kilogram or FTU of Buttiocella phytase obtained from T. reesei to the negative control diet. 

The experiment was conducted for 21 days. Pigs were weighed at the beginning and conclusion of the experiment. Daily feed allotments were recorded and feeders were weighed at the end of the experimental period to calculate feed intake.  Average daily gain, average daily feed intake, and gain to feed ratio were calculated for each treatment. Data were analyzed using contrast statements to compare the positive control and negative control diets, positive control and phytase diets, and to determine the linear and quadratic effects of phytase inclusion. 

Now we will move on to the results of this experiment. 

Setting up the graphs, we have phytase inclusion on the x axis, with PC indicating the positive control diet, NC as the negative control diet, and 250, 500, and 1000 indicating the inclusion level of Buttiocella phytase in the diet in FTU or phytase units per kg. First, at all looking at final body weight we did not observe an effect of phytase inclusion on final body weight of the pigs compared with the pigs fed the control diets. While there does appear to be a slight numerical reduction in the final body weight of the pigs fed the negative control diet, this difference was not significant compared with the phytase diets or with the positive control diet.

Next, looking at the average daily feed intake of the pigs, there was no difference between the pigs fed the positive and negative control treatments. Average daily feed intake linearly increased as phytase was added to the diet with the greatest feed intake by the pigs fed the 1,000 FTU phytase diet.

The pigs fed the negative control diet had reduced average daily gain compared with the pigs fed the positive control diet. However, this reduction in gain in the negative control was ameliorated when phytase was included at 250, 500, or 1000 FTU per kg. Additionally, average daily gain quadratically increased as phytase increased in the diet, with the greatest gain observed in the pigs fed the 1000 FTU phytase diet. 

Gain to feed was reduced in the negative control treatment group compared with the positive control group. Addition of phytase resulted in a quadratic increase in the gain to feed ratio with the greatest gain to feed observed in the 500 FTU treatment group. Overall, these data suggest that inclusion of phytase to diets with reduced nutrient composition such as the negative control will increase growth performance indices so that there is no difference between the phytase supplemented diets and the positive control diet.

From this work, we conclude that buttiocella phytase may be included in diets with reduced nutrient composition and energy for weanling pigs without compromising pig growth performance compared with a conventionally formulated nursery diet.

The data from this study indicated the producers may formulate diets slightly lower in inorganic Ca and P, reduce feed cost and still maintain the growth performance of their pigs.

I would like to thank DuPont animal nutrition for their financial support of this research, and with that, I would like to thank you for listening to my presentation. My email is rundle2@illinois.edu and if you would like to know more about the research conducted in the Hans Stein Monogastric Nutrition Laboratory, feel free to visit our website at nutrition.ansci.illinois.edu.