Interpretive Summary: Effects of added dietary salt on pig growth performance
By: Megan LaFollette
In October 2018, Translational Animal Science published an article that investigated the effects of added dietary salt on growth performance of pigs. Dietary salt contains ions (sodium and chloride) that are important for cellular processes, movement and digestion. Optimizing the levels of these ions in the diet can improve growth performance. Previous work to determine optimum sodium and chloride levels have used sources such as sodium bicarbonate, sodium tripolyphoshate, ammonium chloride, and HCl. However, the most common source of these ions is through dietary salt. Therefore, the purpose of this study was to assess the effects of added dietary salt on the growth performance of nursery and grower pigs via three experiments.
In all three experiments, several methods were used consistently. All pigs were weaned at 21 days of age. Phase-appropriate standard diets were fed before pigs were randomly assigned to experimental diets. Experimental diets were all corn-soybean meal-based with different amounts of added salt. In terms of housing, the nursery pigs were housed with 5 pigs per pen, 13 pens per treatment and the grower pigs were housed with 27 pigs per pen, 11 pens per treatment. Growth performance was measured via average daily gain and gain to feed ratio. Finally, statistical models were run to identify when growth performance reached maximum values or breakpoints after which increases were minimal.
The first experiment focused on nursery pigs weighing 7-10 kg. In this experiment, 325 pigs were fed 1 of 5 diets with added salt at 0%, 0.2%, 0.4%, 0.6%, or 0.8%. These diets were fed from day 7 to 21 after weaning. Results showed that increasing dietary salt increased growth performance (linear model). For average daily gain, a breakpoint was found at 0.59% added salt for all models (linear, quadratic polynomial, and broken-line linear models). For gain to feed ratio, a breakpoint was found at 0.33% added salt using a broken-line linear model, while a maximum was found at 0.67% added salt using a quadratic polynomial model.
The second experiment focused on nursery pigs weighing 11-30 kg. In this experiment, 300 pigs were also fed 1 of 5 diets with added salt at 0.2%, 0.35%, 0.5%, 0.65%, or 0.8%. These diets were fed from day 25 to 59 after weaning. Results showed that increasing dietary salt increased growth performance (quadratic model). For average daily gain, a breakpoint was found at 0.51% added salt for quadratic polynomial and broken-line linear models. For gain to feed ratio, a breakpoint was predicted at 0.35% for the broken-line linear model.
The third experiment focused on grower pigs weighing 27-65 kg. In this experiment, 1,188 pigs were fed 1 of 4 diets with added salt at 0.1%, 0.33%, 0.55%, or 0.75%. These diets were fed for 44 days in pigs that initially weighed 27.1 ± 0.95 kg. Results from this experiment did not show that increasing dietary salt increased growth performance. Rather, growth performance from all diets was similar.
Overall, this study shows that added dietary salt can effectively improve growth performance in nursery pigs. It is important to note that diets formulated with dietary salt will be limited by sodium concentration since dietary salt is composed of 39% sodium and 61% chloride. Specifically, the models from this study suggested nursery pigs weighing 7-10 and 11-30 kilograms benefit from 0.59% and 0.51% added salt, respectively, to maximize growth performance, particularly average daily gain. Conversely, there was no evidence that grower pigs weighing 27-65 kilograms benefit from over 0.10% added salt in terms of growth performance.
To view the full article, visit Translational Animal Science.