PSVI-7 - Effects of increasing levels of calcium on nursery pig growth performance and health

Abstract: The objective of this experiment was to determine the optimal level of total calcium (Ca) to maximize growth performance and health during the nursery period. In total, 2,473 weaned pigs (7.77 ± 2.89 kg initial body weight, 21 days old) were housed in 3 barns and allotted to 29 pens per treatment with 20-22 mixed sex pigs per pen. Experimental diets were formulated to test four levels of total Ca (0.47, 0.52, 0.57, and 0.62%) by adding calcium carbonate at the expense of corn. All experimental diets contained equal amount of total P (0.59 and 0.61%, phase 1 and 2, respectively) and 1,100 FTU/kg of microbial phytase. The experiment lasted for 43 days, and pigs were fed with experimental diets during the first two nursery phases (21 days) and received a common diet during phase 3 (22 days). All diets contained feed medication, whereas water medication and individual parenteral medications were allowed as needed and recorded. Pig and feed weights were recorded at the beginning and end of each phase, and pen scouring (yes/no) was assessed on day 3, 6, 17, and 23. All data were analyzed in R using procedures provided by the lme4, lmerTest and forestinventory packages. Performance variables were analyzed as a general linear model. Mortality, removals, injectable treatments, and scouring were analyzed as a probabilistic generalized mixed model specifying a binomial distribution with a logit link with treatment as fixed effect and location block and barn as random effect. Contrast statements were used to determine linear and quadratic effect of increased dietary inclusion of Ca. During this trial, pigs had Streptococcus suis and Escherichia coli challenges particularly during phase 3, leading to high closeout mortalities (7-10%). Results indicated that under these conditions, increasing dietary total Ca from 0.47 to 0.62% did not have an effect on growth performance (average daily feed intake, average daily gain, final body weight, and feed efficiency) for each phase and overall period (Table 1). No differences in probability of injectable treatments and probability of pen scouring were observed among treatments. However, probability of mortality and removals tended to linearly increase (P = 0.07) during phase 1 and 2 and numerically increased during the overall period as total Ca in diets increased. In conclusion, increasing levels of Ca from 0.47 to 0.62% did not affect growth performance, however, it numerically increased the probability of mortality and removals under Strep and E. coli challenge conditions.