Plant ingredients used in animal feed contain low Ca levels. Therefore, Ca has to be supplemented with animal or mineral sources, such as limestone or calcium phosphates. However, increasing dietary Ca has been reported to decrease linearly growth performance and feed intake. To better understand the possible mechanisms underlying the detrimental effect of including limestone in weanling diets, two experimental trials were performed to evaluate its impact on growth performance, colonic microbiota and jejunal gene expression. A total of 240 piglets (26±2 d old, average body weight (BW) = 7.7 ± 1.04 kg) were selected for Trial 1 and randomly allotted to 3 diets: 0% limestone (NL), 0.8% limestone (ML), and 1.6% limestone (HL) to provide 0.6, 0.9 and 1.2% total Ca, respectively. Feed intake and individual BW were registered during the pre-starter phase (14 d). Pigs fed the HL diet (1.2% of total Ca) had lower BW, average daily gain (ADG), and gain to feed ratio (G:F) compared with pigs fed NL and ML diets (0.6 and 0.9% total Ca, respectively).
For Trial 2, a total of 18 pigs (28 ± 0 d old, average BW = 7.2 ± 0.24 kg) were randomly allocated individually in cages and allotted to 2 dietary treatments: 0% limestone and 1.4% limestone to provide 0.6 and 1.2% total Ca, respectively. Piglets were fed during the pre-starter phase and then euthanized to obtain jejunum tissue for gene expression and colon digesta for 16SRNA gene microbiota analyses. Pigs fed 1.4% limestone (1.2% of total Ca) showed a higher beta-diversity (higher dissimilarity between pigs) and an increase on the Bacteroides genera in colon than pigs fed 0% limestone. These animals also showed an up regulation of gene sets related to the cell cycle regulation, DNA and RNA transcription and inflammatory response in the jejunum.
In conclusion, high levels of limestone inclusion in pre-starter diets decrease growth performance without affecting feed intake in weaned pigs. However, addition of limestone to diets for 14 d after weaning can upregulate the expression of genes related to the inflammatory response, and enlarge colonic beta-diversity with an increased Bacteroides genera.
Blavi, L., Perez, J. F., Villodre, C., López, P., Martín-Orúe, S. M., Motta, V., Luise, D., Trevisi, P., and Sola-Oriol, D. Effects of limestone inclusion on growth performance, intestinal microbiota, and the jejunal transcriptomic profile when fed to weaning pigs. Animal Feed Science and Technology 242 (2018): 8-20. https://doi.org/10.1016/j.anifeedsci.2018.05.008