Calcium carbonate is the main form of calcium (Ca) in pig diets and has cationic properties that would increase the pH in the pig's stomach. A low stomach pH (< 4) improves protein digestion and intestinal health, whereas a high gastric pH has been observed to result in negative gastrointestinal challenges including increased intestinal microflora. Ingredients that are higher in buffering capacity, such as calcium carbonate, increase dietary acid binding capacity (ABC). 

One method to characterize ABC is the use of ABC – 4, which is the amount of acid in milliequivalents (mEq) required to lower the pH of 1 kilogram (kg) of feed to a pH of 4. It is hypothesized that decreasing the diet ABC by decreasing calcium carbonate levels or adding an organic acid to lower the diet ABC would improve growth performance of nursery pigs.

Organic acids can decrease gastric pH and improve protein digestion. Benzoic acid has been shown to decrease the gastric population of lactic acid bacteria and cecal bacteria while improving ileal digestibility and growth performance. Therefore, the objective of these experiments was to investigate the effects of added calcium carbonate with or without benzoic acid on the growth performance, fecal dry matter and blood Ca and phosphorus (P) concentrations of nursery pigs. 

In Experiment 1, 695 barrows (DNA Line 200 × 400; initially 12.9 ± 0.05 lb) were used in a 28-day (d) study to evaluate the effects of added dietary calcium carbonate on phase 1 nursery pig growth performance and fecal dry matter. Upon arrival to the nursery research facility, pigs were randomly assigned to pens (five pigs per pen) and pens were allotted to one of five dietary treatments with 27 or 28 pens per treatment.

Dietary treatments were formulated to provide 0, 0.45, 0.90, 1.35 and 1.80% calcium carbonate added at the expense of corn. Analyzed Ca for treatment diets were 0.61, 0.80, 0.99, 1.15 and 1.37%, respectively. Standardized total tract P concentration was formulated to 0.58% in all diets. Diets were fed in two phases with treatment diets fed from weaning (d 0) to d 14 and a common phase 2 diet fed from d 14 to 28. Treatment diets were fed in both meal (group 1) and pellet (group 2) form.

From d 0 to 14 (treatment period), average daily gain (ADG), d 14 body weight and feed-to-gain (F/G) worsened (linear, P = 0.010) as calcium carbonate increased. There was no evidence for difference for average daily feed intake (ADFI) (P > 0.10). From d 14 to 28 (common period) and for the overall experiment (d 0 to 28), there was no evidence (P > 0.10) for differences observed for any growth performance criteria. For fecal dry matter, there was a tendency (quadratic, P = 0.091) with the highest and lowest calcium carbonate diets having the highest dry matter.

These data suggest increasing dietary calcium carbonate from 0 to 1.80% decreases ADG and worsens feed efficiency in phase 1 nursery diets. Despite the linear response, the largest decrease was observed when calcium carbonate increased from 0.45 to 0.90% with no difference in performance thereafter.

In Experiment 2, 360 barrows (DNA Line 200 × 400; initially 13.6 ± 0.07 lb) were used in a 38-d study to evaluate the interactive effects of added dietary calcium carbonate and benzoic acid on nursery pig growth performance, fecal dry matter and blood Ca and P concentration. Upon arrival to the nursery research facility pigs were randomly assigned to pens (five pigs per pen) and pens were allotted to one of six dietary treatments with 12 pens per treatment.

Dietary treatments were formulated to provide 0.45, 0.90 or 1.35% calcium carbonate with or without 0.5% benzoic acid (VevoVitall, DSM Nutritional Products, Parsippany, NJ). Diets were fed in three phases with phase 1 treatment diets (0.66, 0.83 or 1.00% Ca) fed from weaning (d 0) to d 10, phase 2 treatment diets (0.54, 0.72 or 0.89% Ca) fed from d 10 to 24, and a common phase 3 diet from d 24 to 38 (0.68% Ca). Standardized total tract P concentrations were formulated to 0.58, 0.51 and 0.47 in phase 1, 2 and 3, respectively.

There was no calcium carbonate × benzoic acid interactions observed for any response criteria (P > 0.10). From d 0 to 10 (phase 1), there was evidence for benzoic acid to marginally increase (P = 0.092) ADG and significantly increase (P = 0.042) ADFI. From d 10 to 24 (phase 2), F/G improved (P = 0.022) as the level of calcium carbonate decreased. For the overall experimental period (d 0 to 24), there was a tendency for benzoic acid to improve (P = 0.056) ADG and (P = 0.071) ADFI, as well as an improvement (linear, P = 0.014) in F/G as calcium carbonate in the diet decreased. During the common period (d 24 to 38), pigs previously fed benzoic acid had increased (P = 0.045) ADG and marginally increased (P = 0.091) ADFI. 

For the overall study, pigs fed benzoic acid had increased (P = 0.011) ADG and (P = 0.030) ADFI and marginally improved (P = 0.096) F/G. For fecal DM, there was no observed evidence (P > 0.10) for differences among treatments. For serum analysis, serum Ca decreased (P < 0.001) as the level of dietary calcium carbonate decreased. This data suggests that lower levels of calcium carbonate may improve feed efficiency in early nursery period. Also, nursery pigs fed benzoic acid had increased ADG and ADFI, and tended to have improved F/G.

To conclude, lower levels of calcium carbonate improved growth performance in the early nursery. This data also suggests that including benzoic acid for the first 21 days post-weaning improves ADG and ADFI, and tends to improve F/G. More research is needed to determine if the improvements in growth performance are attributed to the dietary ABC–4 concentration or a change in nutrient utilization from altered diet Ca and benzoic acid inclusion.

The full data is available with the 2021 K-State Swine Industry Day Reports. 

Source: Alan J. Warner, Joel M. DeRouchey, Mike D. Tokach, Jason C. Woodworth, Robert D. Goodband and Jordan T. Gebhardt, Kansas State University, who are solely responsible for the information provided, and wholly owns the information. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset. The opinions of this writer are not necessarily those of Farm Progress/Informa.