INTRODUCTION
Research to determine the nutritional needs of most micronutrients for pigs was done mainly before the decade of 1990 and focused on avoiding nutritional deficiencies (Gaudré and Quiniou, 2009).
Nutritional reference tables represent the theoretical basis for pig feed formulations indicating minimum requirement levels of supplementation (NRC, 2012) or values for best cost to benefit in feed formulations (Rostagno et al., 2017). However, considering the significant advances made throughout the last decades by the pork industry in terms of sows’ prolificacy and growth rate of growing pigs, it can be hypothesized that reference levels for some trace minerals and vitamins may be outdated. In fact, commercial pig diets contain nutritional levels greater than those suggested by reference tables (Rostagno et al., 2017; NRC, 2012) to meet the nutritional requirements of the modern pig (Gaudré and Quiniou, 2009). However, optimum levels of trace minerals and vitamins for growth and reproduction are largely unknown.
Coelho and Cousins (1997) reported supplemental levels for vitamins and Flohr et al. (2016) described supplemental levels of trace minerals and vitamins used by North American pork producers. Both studies indicated great variations between farms for the use of these nutrients, further supporting the lack of knowledge on nutritional requirements of trace nutrients for the modern pig. To the best of our knowledge, a survey of current levels of trace minerals and vitamins used in commercial diets by the Brazilian pork industry has never been done.
This study describes the levels of trace minerals and vitamins used in commercial diets by the Brazilian pork industry for growing and breeding pigs. The present study does not intend to establish new nutritional requirements but aims to serve as a supplementary source of information to support pig nutritionists.
MATERIALS AND METHODS
This survey targeted pig feed companies (n = 19) operating in different regions of Brazil and the most important cooperatives/agro-industries (n = 19) of the pork sector in Brazil. The project was first discussed with nutritionists and/or managers of the nutrition department from those companies by telephone or e-mail between June and December of 2019. For those that showed spontaneous interest in participating (n = 15 for feed companies and n = 15 for cooperatives/agro-industries) an electronic spreadsheet was officially sent by e-mail with the requested information. Data from the participants were sent by e-mail in Microsoft Excel or PDF files.
Collected data were minimum guaranteed levels for trace minerals and vitamins, along with the indication of use, for premixes from feed companies and actual levels of trace minerals and vitamins in the feed from cooperatives/agro-industries. Companies also indicated the respective feeding phases for each premix or feed by range of age or weight. These feeding phases were nursery, growing, finishing, gestation, lactation, and boar. Some companies have also spontaneously informed values for pre-nursery (lactating piglets), developing gilts, and transition (pre-farrow) diets. Because of the wide variation in weight ranges indicated by different companies, data was pooled by range of age that allowed uniformity between companies. Therefore, this study defined the feeding phases (in days of age) as: lactating piglets (3 to 20 days), nursery I (21 to 35 days), nursery II (36 to 49 days), nursery III (50 to70 days), growing (71 to 120 days), finishing (121 days until slaughter), developing gilts, gestation, transition, lactation, and boars. Within each feeding phase, the evaluated nutrients were: vitamin A (vitA), vitamin D (vitD), vitamin E (vitE), vitamin K (vitK), thiamine (vitB1), riboflavin (vitB2), niacin (vitB3), pantothenic acid (vitB5), pyridoxine (vitB6), biotin (vitB7), folic acid (vitB9), cobalamin (vitB12), choline, ascorbic acid (vitC), cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), iodine (I), manganese (Mn), selenium (Se), and zinc (Zn). Few companies informed the respective nutrients source (e.g. inorganic vs organic minerals). The limited data was not considered representative and was not used. Therefore, supplementation levels reported in this study represent total amounts independently of source. There were companies that reported more than one premix or feed per feeding phase whereas others did not present data for all phases.
All data was compiled to determine descriptive statistics including average values, standard deviations, minimum values, percentiles 25th, medians, percentiles 75th, and maximum values. All results were determined using the Microsoft Excel 2010 functions for average (AVERAGE), standard deviations (STDEV.S), minimum values (MIN), median (MEDIAN), maximum values (MAX) and percentiles 25th and 75th (PERCENTILE.EXC). For each feeding phase, ratios between levels of trace minerals and vitamins obtained in the present study vs those from the Brazilian Tables for Poultry and Swine (Rostagno et al., 2017) were calculated. This methodology was also used to compare the present values vs those reported by the North American pork industry (Flohr et al., 2016).
RESULTS
Out of 38 feed companies and cooperatives/agro-industries of the Brazilian pork sector that were initially contacted, a total of 30 companies participated in this study.
Lactating piglets (3 to 20 days) diets
Supplementation levels of trace minerals and vitamins for lactating piglets (Table 1) diets were provided by 10 companies.
Considering the lack of reference values for this feeding phase in the Brazilian reference tables (Rostagno et al., 2017) and that these data were not investigated by Flohr et al. (2016), comparisons were not possible. However, trace minerals levels for lactating piglets represented 0.8 to 1.5 fold and 0.9 to 18.1 folds the respective levels in nursery I diets of the present study (Table 2) and from Rostagno et al. (2017), respectively. Levels of Cu and Zn were particularly high (growth promoter levels) and great variation between companies was observed for Cu (60.9 %), Fe (75.3 %) and Se (56.7 %).
Fat-soluble vitamins represented 1.0 to 2.6 folds and 1.4 to 3.2 folds the respective levels in nursery I diets of the present study (Table 2) and from Rostagno et al. (2017), respectively. Levels of vitK were particularly high and great variation between companies was observed for all fat-soluble vitamins (55.6 to 212.6 %).
Water-soluble vitamins represented 1.0 to 2.7 folds and 1.3 to 6.4 folds the respective levels in nursery I of the present study (Table 2) and from Rostagno et al. (2017), respectively. Levels of vitB7, vitB9, and vitC were particularly high and, except for vitB1 (37.2 %) and vitB2 (49.0 %), great variation between companies was observed for water-soluble vitamins (52.9 to 225.9 %).
Nursery I (21 to 35 days), nursery II (36 to 49 days), and nursery III (50 to70 days) diets
Supplementation levels of trace minerals and vitamins for nursery I (Table 2), nursery II (Table 3), and nursery III (Table 4) diets were provided by 25 companies.
Considering these three feeding phases, trace minerals levels represented 0.9 to 15.3 folds the respective levels from Rostagno et al. (2017) and 0.5 to 2.2 folds those from Flohr et al. (2016). Compared to Rostagno et al. (2017), Cu and Zn levels were markedly higher but not compared to Flohr et al. (2016) whereas Mn and I levels were significantly higher. Except for Cu (70.9 - 80.0 %), Zn (63.4 - 181.9 %), and Co (55.6 %; nursery II diets only), small variation between companies was observed (29.5 to 47.5 %).
Fat-soluble vitamins levels represented 0.9 to 1.7 fold the respective levels from Rostagno et al. (2017) and 0.8 to 1.3 fold those reported by Flohr et al. (2016). Except for vitK, reported levels were higher than Rostagno et al. (2017) but similar to Flohr et al. (2016). Great between-companies variation was observed for vitE (61.7 - 71.4 %) and vitK (50.0 - 53.4 %).
Water-soluble vitamins levels represented 1.0 to 5.0 folds the respective levels from Rostagno et al. (2017) and 0.4 to 2.1 folds the reported levels by Flohr et al. (2016). These levels were overall higher than Rostagno et al. (2017) but globally they were significantly lower than Flohr et al. (2016), the only exception was choline that was significantly higher. Great variation was observed between companies for vitB6, vitB7, vitB9, and choline in nursery I and nursery II (50.5 to 88.1 %) diets and for vitB3 and vitB5 in nursery III (50.9 - 51.6 %) diets.
Growing (71 to 120 days) and finishing (121 days until slaughter) diets
Supplementation levels of trace minerals and vitamins for growing (Table 5) and finishing (Table 6) diets were provided by 30 companies.
Trace minerals levels represented 1.1 to 1.3 fold the respective levels from Rostagno et al. (2017) for growing diets and 1.3 to 13.0 folds for finishing diets. Compared to Flohr et al. (2016), these levels represented 0.9 to 2.3 folds for both diets. Supplemental levels for growing diets were similar to the recommendations of Rostagno et al. (2017) but for finishing diets those levels were significantly higher (except for Se). Compared to Flohr et al. (2016), Mn and I levels were markedly higher. Except for Cu (70.3 - 70.1 %), Mn (64.1 %; growing diet only), and Co (109.4 - 136.0 %), small variation was observed (20.2 to 49.0 %) between companies.
Fat-soluble vitamins levels represented 0.9 to 1.4 fold the respective levels from Rostagno et al. (2017) and 0.9 to 1.5 fold the respective levels from Flohr et al. (2016). In finishing diets, levels of vitA and vitD were higher than those recommended by Rostagno et al. (2017) whereas levels of vitD (growing and finishing diets) and vitE (growing diets only) were higher than those reported by Flohr et al. (2016). Great variation was observed only for vitE (73.7 %) in growing diets and small variation only for vitA (35.7 %) in finishing diets.
Water-soluble vitamins levels represented 0.9 to 2.2 folds the respective levels from Rostagno et al. (2017) and 0.8 to 2.0 folds those of Flohr et al. (2016). Except for vitB5 (growing diets only), vitB3, and vitB6, the observed levels were markedly higher than Rostagno et al. (2017). Levels of vitB7 were particularly higher than Flohr et al. (2016). Small variation was observed only for vitB3 (41.7 %) and vitB6 (48.8%; finishing diets only).
Developing gilts and gestation diets
Supplementation levels of trace minerals and vitamins for developing gilts (Table 7) and for gestation (Table 8) diets were provided by 10 and 29 companies, respectively.
Trace minerals levels represented 1.0 to 13.4 folds the respective levels from Rostagno et al. (2017) and 0.8 to 4.0 folds the reported levels by Flohr et al. (2016). Compared to Rostagno et al. (2017), Cu and Mn levels were significantly higher in both feeding phases whereas levels of Cu, Mn (developing gilts only), and I were considerably higher than Flohr et al. (2016). Great variation was observed only for Cu (93.0 - 117.6 %), Cr (53.2 %; gestation only), and Co (56.8 - 65.0 %) between companies.
Fat-soluble vitamins levels represented 1.3 to 3.3 folds the respective levels from Rostagno et al. (2017) and 0.7 to 2.0 folds those from Flohr et al. (2016). Supplemental levels of vitD and vitE (developing gilts only) were significantly higher than Rostagno et al. (2017) whereas vitK levels (gestation only) were particularly lower than Flohr et al. (2016). Small between-companies variation was observed (28.7 to 42.7 %) for developing gilts diets whereas great variation was observed (58.6 to 84.2 %) for gestation diets, except for vitA (28.8 %).
Water-soluble vitamins levels represented 1.1 to 2.2 folds the Rostagno et al. (2017) recommendations and 0.4 to 1.8 fold the reported levels by Flohr et al. (2016). Except for vitB3, vitB5, and vitB12 (gestation only), the present levels were higher than Rostagno et al. (2017). Vitamin B3 levels were particularly higher in developing gilts diets compared to Flohr et al. (2016) but in gestation diets the levels of vitB2, vitB3, vitB5, vitB6, vitC, and choline (developing gilts and gestation diets) were considerably lower. For developing gilts, vitB7 (80.3 %), vitB9 (67.1 %), and choline (52.8 %) had great variations between companies whereas for gestation diets small variations were observed for vitB1 (48.8 %), vitB2 (44.0 %), vitB3 (44.9 %), and vitB12 (41.8 %).
Transition
Supplementation levels of trace minerals and vitamins for transition (Table 9) diets were provided by three companies.
Considering the lack of reference values for this feeding phase in the Brazilian reference tables (Rostagno et al., 2017) and that these data were not investigated by Flohr et al. (2016), comparisons were not possible. However, trace minerals levels for transition diets represented 0.8 to 1.7 fold the respective levels in gestation (Table 8) and lactation (Table 10) diets of the present study. Supplemental levels of Cu and Cr (n = 1) were particularly high. Great variation between companies was observed only for Cu (105.3 %) and Co (70.7 %).
Fat-soluble and water-soluble vitamins levels represented 0.6 to 0.9 fold the respective levels in gestation (Table 8) and lactation (Table 10) diets of the present study. Supplemental levels of vitA, vitD, vitB2, vitB6, and vitB7 were particularly low. Great variation between companies was observed only for vitB6 (69.3 %), vitB7 (67.1 %), and vitB9 (93.9 %).
Lactation
Supplementation levels of trace minerals and vitamins for lactation (Table 10) diets were provided by 29 companies.
Trace minerals levels represented 1.0 to 12.4 folds the respective levels from Rostagno et al. (2017) and 0.8 to 3.4 folds the reported levels by Flohr et al. (2016). Compared to Rostagno et al. (2017), levels of Cu and Mn were markedly higher whereas levels of Cu and I were significantly higher than Flohr et al. (2016). Only Cu (136.0 %) and Co (59.8 %) had high variations between companies.
Fat-soluble vitamins levels represented 1.2 to 1.6 folds the respective levels from Rostagno et al. (2017) and 0.7 to 1.1 folds those from Flohr et al. (2016). Supplemental levels of vitA and vitD were considerably higher than the Rostagno et al. (2017) recommendations whereas vitK levels were significantly lower than reported by Flohr et al. (2016). Only vitE (58.2 %) had high between-companies variation.
Water-soluble vitamins levels represented 1.1 to 2.2 folds the respective levels from Rostagno et al. (2017) and 0.6 to 1.3 folds the levels reported by Flohr et al. (2016). Except for vitB3, vitB5, and vitB12 the present levels were considerably higher than Rostagno et al. (2017) whereas levels of vitB2, vitB3, vitB5, vitB6, and vitB12 were markedly lower than those reported by Flohr et al. (2016). Small variation between companies was observed for vitB2 (37.2 %), vitB3 (41.0 %), vitB5 (42.6 %), and vitB12 (34.7 %).
Boars
Supplementation levels of trace minerals and vitamins for boars (Table 11) diets were provided by 26 companies.
Trace minerals levels represented 1.0 to 11.8 folds the Rostagno et al. (2017) recommendations and 0.6 to 2.2 folds the respective levels from Flohr et al. (2016). Compared to Rostagno et al. (2017), Cu and Mn levels were significantly higher whereas Cu and I levels were considerably higher and Co markedly lower than Flohr et al. (2016). Great between-companies variation was observed only for Cu (140.2 %) and Co (73.1 %).
Fat-soluble vitamins levels represented 1.4 to 2.0 folds the respective levels from Rostagno et al. (2017) and 0.8 to 2.4 folds those from Flohr et al. (2016). Supplemental levels for all fat-soluble vitamins were higher than those from Rostagno et al. (2017) whereas only vitD levels were higher than Flohr et al. (2016). Between-companies variation was small for vitA (28.5 %) and vitD (41.6 %) but high for vitE (81.6 %) and vitK (62.4 %).
Water-soluble vitamins levels represented 1.3 to 2.7 folds the respective levels from Rostagno et al. (2017) and 0.6 to 1.5 folds the reported levels by Flohr et al. (2016). Except for vitB3 and vitB5, the present levels were considerably higher than Rostagno et al. (2017). Levels of vitB2, vitB3, vitB5, vitB12, vitC, and choline were markedly lower and vitB9 higher than Flohr et al. (2016). Small variation between companies was observed for vitB2 (43.9 %), vitB3 (43.8 %), vitB5 (49.7 %), and vitB12 (38.6 %).
DISCUSSION
Trace minerals and vitamins levels used by the Brazilian pork industry were overall higher than the recommendations of the Brazilian Tables for Poultry and Swine (Rostagno et al., 2017), which complies with the contemporary tendencies that indicate high levels of supplementation to avoid compromising pigs’ performance (Hernández et al., 2012, Isabel et al., 2012). Average levels of supplementation were remarkably higher for trace minerals (240 %; or 210 % if disregarding supranutritional levels of Zn and Cu in nursery diets) and moderately higher for fat- and water-soluble vitamins (40 and 70 %, respectively) than those recommended by Rostagno et al. (2017).
Comparing to the North American pork industry (Flohr et al., 2016), the present results for trace minerals were 20 to 60 % higher whereas for fat-soluble vitamins they varied from slightly lower to slightly higher, and water-soluble vitamins were mostly lower. Although the effects of water-soluble vitamins on growth performance are not clearly established (Coelho and Cousins, 1997; Santos et al., 2019), the greater use these vitamins in nursery, development gilts, gestation, lactation, and boar diets by the North American pork industry compared to the Brazilian industry is justified by their actions as cofactors in reactions related to the metabolism of proteins, carbohydrates, and lipids as well as in metabolic pathways that impact the synthesis of ATP and the immune and antioxidant systems (Bender, 2003). Consequently, supplementation of water-soluble vitamins in pigs diets alleviate the oxidative burst of ovulation (Dalto et al., 2015a; 2017), positively impact early embryo development (Dalto et al., 2015b; 2016; 2018), and may optimise the transfer of these nutrients through the placenta, colostrum, and milk (Matte and Audet, 2020).
Supplementation levels reported for some specific nutrients in the present study were particularly noteworthy. The use of supranutritional levels of Zn during the nursery phase was not surprising because of its known growth promoter effect (Heo et al., 2013). However, the present results suggest the use of supranutritional levels of Zn for piglets potentially from three to 70 days of age. Besides restrictions to the use of supranutritional levels of Zn by several countries (Record, 2017) due to its association to antibiotic-resistant bacteria (Jondreville et al., 2002) and environmental concerns (Feng et al., 2018), recent results (Dalto et al., 2020) showed that such high levels of Zn during the first two to three weeks after weaning impairs Zn homeostasis and negatively impact Cu and Fe metabolism.
Supranutritional levels of Cu from nursery to finishing phase were observed in the present study and by Flohr et al. (2016) and are explained by their known growth promoter effect (Revy et al., 2003). However, maximum levels (500 mg/Kg) of Cu observed in the present study for the nursery phase were remarkable. Besides the potential toxic effects to pigs (NRC, 2012), there is no evidence that Cu levels higher than 250 mg/Kg promote additional growth promoting effects. Curiously, the present study identified the use of growth promoter levels of Cu in reproductive diets. Feeding gestation sows with 60 or 250 mg/kg of Cu improved total pigs born and piglets’ birth weight (Lillie and Frobish, 1978; Cromwell et al., 1993) but reduced farrowing rate (Cromwell et al., 1993). No effect of high maternal Cu supplementation was observed on piglets’ performance (Roos e Easter, 1986; Dove, 1993). For boars, to the authors’ knowledge, there is no scientific study on this matter. Considering the inconsistent reproductive results and the recent above-mentioned concerns, the use of supranutritional levels of Cu in reproduction diets for pigs is discouraged.
The present reported levels of Mn were similar to those from Flohr et al. (2016) for breeding diets and considerably higher than Rostagno et al. (2017) for some feeding phases. For I, the present observed levels were widely higher than those reported by Flohr et al. (2016). Although toxicity is unlikely (Newton and Clawson, 1974; Grummer et al., 1950) by supplementing pigs with such levels of Mn and I, their effectiveness is yet to be validated. Using Mn levels lower than the presently observed, Kerkaert et al. (2020) reported conflicting results on growth performance but litter birthweight was improved by supplementing sows with levels of Mn (Rheaume and Chavez, 1989) greater than the ones reported in the present study.
Supplementation levels of Se reported by Flohr et al. (2016) agree with the legal limit of 0.3 mg/Kg allowed in North America. Although there is no such precise regulation in Brazil, the present reported levels are only marginally higher than those of Flohr et al. (2016). Greater Se supplemental levels are potentially beneficial for the antioxidant and immune systems (Surai, 2006). Considering the wide variability in endogenous levels of Se in feedstuffs (Mahan et al., 2005) and the intense pig metabolism (Lauridsen and Matte, 2017), it can be hypothesized that under certain conditions the supplementation of 0.3 mg/Kg may be suboptimal, as demonstrated by Dalto et al. (2016) in gilts in early gestation.
The present study showed that the Brazilian pork industry supplements pigs’ diets with Co, Cr, choline, and vitC more widely than the North American industry (Flohr et al., 2016). Additionally, the Brazilian industry indicated the use of all water-soluble vitamins in the various feeding phases whereas Flohr et al. (2016) reported that most producers did not use vitB1, vitB6, vitB7, vitB9 and/or choline during the growing and finishing phases.
CONCLUSIONS
Adding margins of safety for the supplementation of trace nutrients in commercial pig diets is a common practice in the Brazilian pork industry. Overall, supplementation levels of trace minerals by the Brazilian industry were higher than those from the North American industry whereas for water-soluble vitamins levels were markedly lower.
The wide variability in the indication of trace minerals and vitamins for pigs’ diets between companies, especially for water-soluble vitamins, indicates the insufficient scientific data on nutritional requirements for these nutrients in the modern pig.
