Maternal perinatal transfer of vitamins and trace elements to piglets J. J. Matte† and I. Audet Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, 2000 College Street, Sherbrooke, QC, J1M 0C8, Canada (Received 9 November 2018; Accepted 23 May 2019; First published online 27 June 2019) Nursing piglets are entirely dependent, for their micronutrient provisions, upon in utero, colostrum and milk transfers from the dam. An adequate maternal transfer of micronutrients is all the more important during these periods which, in fact, lasts for approximately half the life cycle (conception to slaughter) of modern pigs. The present study aimed to set up a simple approach to assess the maternal perinatal transfer of vitamins and trace elements in sows. Prenatal transfer (R-u) was estimated as limited, passive or active using the ratio between pre-colostral serum concentrations of a given micronutrient in newborn piglets and corresponding pre-farrowing values in sows. Efficiency of the postnatal transfer (R-c) was estimated from the ratio between serum concentrations of post- and pre-colostral micronutrients in piglets. Data from literature (12 studies) were used for vitamins A, D, E, C, folic acid and B12, whereas vitamins B2, B3, B6 and B8 as well as Zn, Fe, Cu and Se were generated from a trial where blood sera from 20 sows, and their litter were collected during the perinatal period. In sow trial, statistical t tests were used to determine if ratios differed from 1. Prenatal transfer was active and in favour of piglets (R-u> 1, P< 0.03) for Zn and vitamins B6 and B8 (sow trial) as well as for vitamins C and B12 (literature data). This transfer was limited (R-u< 1, P< 0.01) for vitamin B2, Fe, Cu and Se (sow trial) and for vitamins A, E, D and folic acid (literature data) whereas it was passive for vitamin B3 (R-u = 1, P> 0.37). After birth, the early postnatal transfer through colostrum was active towards piglets for most micronutrients but vitamins B6 and B8 (R-c < 1, P< 0.01). Globally, the perinatal transfer (combination of R-u and R-c) was favourable to the neonatal piglets for most micronutrients except for vitamins A and D as well as Fe, Cu and Se whereas there is apparently a barrier for prenatal transfer which is not compensated by the colostrum provision to neonatal piglets. Then, post-colostral concentrations of these micronutrients in piglets remain below prenatal levels of their dam. Neonatal strategies of micronutrient provision are known for Fe (intramuscular injection) and Se (sow milk enrichment). Further studies are needed to assess the importance of the unfavourable perinatal transfer for Cu and vitamins A and D for piglet robustness later in life. Keywords: colostrum, late gestation, micronutrients, neonate, sow Implications A simple approach was set up to assess the maternal perinatal transfer of 10 vitamins and 4 trace elements from sows to pig- lets. The perinatal transfer was favourable to newborn piglets for most micronutrients except for vitamins A and D as well as Fe, Cu and Se. Neonatal strategies of micronutrient provision are known for several years in the case of Fe (intramuscular injection) and Se (sowmilk enrichment). However, for Cu, vita- min A and vitamin D, the relevance of neonatal strategies of supplementation during early lactation to compensate for this unfavourable perinatal transfer for piglets need to be explored. Introduction In spite of invaluable advantages in terms of productivity, hyperprolificity in pig species is often associated to drawbacks such as heterogeneity for birth weight and sub- sequent development (Quesnel et al., 2008a) with lasting consequences up to market age (Gondret et al., 2005). It has been suggested that the perinatal maternal transfer of some micronutrients could be suboptimal in high prolific sows (Matte and Lauridsen, 2013). Several micronutrients, specifically vitamins, have been identified as critical for ‘in utero’ physiological events in early gestation of pigs (Mahan and Vallet, 1997) where the uterine secretions have to provide the right amount and balance of nutrients, hormones and growth factors. Nursing piglets are entirely dependent upon the transfer from the sow (in utero, colostrum and milk) for their micronutrient provisions during gestation and lactation. As the combined gestation and lactation phases represent, at 135 days, approximately half the life cycle (conception to slaughter) of a market pig, an adequate maternal transfer of vitamins and trace minerals appears crucial to the micronutrient status at the time of† E-mail: Jacques.Matte2@canada.ca Animal (2020), 14:1, pp 31–38 © Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada 2019. animal doi:10.1017/S175173111900140X 31 https://orcid.org/0000-0002-0134-6148 mailto:Jacques.Matte2@canada.ca https://doi.org/10.1017/S175173111900140X weaning, a period of feeding and environmental perturba- tions. However, the information on that matter is either fragmentary or inexistent for several vitamins and trace min- erals and the increase of prolificacy during the last decades has likely accentuated the pressure for an adequate transfer of micronutrients among individual piglets within litters (Lauridsen and Matte, 2017). Therefore, the hypothesis was raised that for some micronutrients, transient nutritional deficits may nowadays occur in early life of suckling piglets. This study aimed to assess the relative importance of pre- and postnatal transfer of vitamins and trace elements in sows. Prenatal transfer was estimated as limited, passive or active by comparing pre-colostral serum concentrations of a givenmicronutrient in newborn piglets and corresponding pre-farrowing serum values in sows. Efficiency of the postnatal transfer was estimated from comparison between serum con- centrations of post- and pre-colostral micronutrients in piglets. Data from literature (12 studies) were used for vitamins A, D, E, C, folic acid and B12. As the information was not available for vitamins B2, B3, B6, and B8 as well as Zn, Fe, Cu and Se, an in vivo trial was carried out where blood sera from 20 sows and their litters were collected during the perinatal period. Material and methods The approach The prenatal transfer (R-u) was estimated from the ratio between serum concentrations of micronutrients in newborn piglets, before the first intake of colostrum and those of sows before parturition. Values of R-u smaller, equal or greater than 1 were, respectively, considered as indicators of a lim- ited, passive or active in utero transfer of a given micronu- trient. The postnatal transfer (R-c) was estimated from the ratio between post-colostral serum concentrations of micro- nutrients and those of newborn piglets before the first intake of colostrum. Values of R-c smaller, equal or greater than 1 were, respectively, considered as indicators of a limited, neu- tral or active transfer of a given micronutrient. The ratio between post-colostral serum concentrations of micronu- trients and those of sows before parturition (R-uc) was also calculated and allowed to assess if the post-colostral status of micronutrients of piglets, which combines in utero and colostral transfers, is smaller, similar or greater (R-uc< , = or> 1, respectively) than that of their dam in late gestation. Part of data used to calculate those ratios was drawn from scientific literature. The reportswere selected based on availabil- ity of information on sow plasma vitamin concentrations in late gestation and/or piglet plasma vitamin concentrations before and/or after colostrum consumption (≤ 3 days). For the other studied vitamins and trace minerals, the required information was not available in the scientific literature and data had to be generated from a trial with 20 sows during the perinatal period. Trial with sows during the perinatal period Animal management. Twenty multiparous (3rd parity) Yorkshire-Landrace sows were selected within a group of sows used for another study (Audet et al., 2015) where the animal care procedure before early gestation was detailed. From approximately 4 days before insemination, all sows received 2.7 kg/day of a gestation diet described in Table 1. Ten sows were chosen from each of the two treat- ments reported by Audet et al. (2015), complementing the daily allowance with an equivalent of either 1 mg of folic acid and 20 μg of B12 per kg of diet or 10 mg of folic acid and 200 μg of B12 per kg of diet. Pregnancy was confirmed by ultrasonic examination on day 30 post-mating. At day 100 of gestation, the daily feed allowance of the gestation diet was increased to 3.7 kg/day. At day 110 of gestation, sows were placed in individual farrowing crates (1.5 × 2.2 m) and blood samples were taken by venepuncture from the jugular vein of fasted sows (16 h). Samples were collected in trace mineral- free Vacutainer® tubes (6 ml; Becton Dickinson and Co., Franklin Lakes, NJ, USA). On day 114 of gestation, all sows received an i.m. (neck) injection of 1.5 ml of cloprostenol (Planate, Schering-Plough Animal Health, Pointe Claire, Canada) to induce farrowing, which usually occurred within 20–30 h after the injection. The gestation diet was replaced by the lactation diet (Table 1) on day 1 after farrowing with the same levels of supplements in folic acid and B12 as during Table 1 Composition of experimental basal diet (as-fed basis) offered to sows Ingredients (%) Gestation diet1 Lactation diet1 Corn 62.8 63.0 Wheat shorts 12.0 – Soybean hulls 10.6 – Canola meal 9.0 6.0 Soybean meal (48% CP) 2.6 23.8 Biscuit waste meal – 2.5 Limestone 1.3 1.9 Salt 0.67 0.44 Monocalcium phosphate 0.45 1.11 Fat – 0.50 Mineral2 and Vitamin3 Premix 0.30 0.30 L-Lysine 0.12 0.21 Choline chloride 0.10 0.10 Anti-mould 0.05 0.05 L-Threonine 0.03 0.05 Methionine – 0.04 Calculated nutrients composition Metabolizable energy (MJ/Kg) 11.3 12.5 CP(%) 11.8 17.9 Lysine (%) 0.62 1.09 Ca (%) 0.73 1.02 P (%) 0.47 0.59 1For another study purpose, 10 sows received during gestation a supplement containing 1 mg/kg of folic acid and 20 μg/kg of vitamin B12 while 10 other sows received 10 mg/kg of folic acid and 200 μg/kg of vitamin B12. 2Provided per kg of diet: Mn as manganous oxide, 44 mg; Zn as zinc oxide, 167mg; Fe as ferrous sulphate, 142 mg; Cu as copper sulphate, 17mg; I as calcium iodate, 2.27 mg and Se as selenite, 333 μg. 3Provided per kg of diet: vitamin A, 11 100 IU; vitamin D3, 1666 IU; vitamin E, 67 IU; vitamin K (menadione), 2.76 mg; vitamin B1 (thiamin), 2.27 mg; vitamin B2 (riboflavin), 6.67 mg; vitamin B3 (niacin), 44 mg; vitamin B5 (pantothenic acid), 22 mg; vitamin B6 (pyridoxine), 2.79 mg and vitamin B8 (biotin), 445 μg. Matte and Audet 32 gestation. After farrowing, the daily allowance of 3.7 kg of lactation diet on day 1 was increased by 1.0 kg/day until it reached ad libitum intake before the end of the first week of lactation. Feed intake of all sows was 6.2 ± 0.3 kg/day during the lactation period. Colostrum samples were taken on each sow at the beginning of the farrowing. At birth, piglets were identified individually, weighed and moved in comfort boxes to be dried. Blood samples (day 0) were collected in trace mineral-free Vacutainer® tubes (6 ml; Becton Dickinson and Co., Franklin Lakes, NJ, USA) after ven- epuncture at the jugular vein on at least eight piglets per litter (≥ 1.0 kg of body weight) within 20 min following birth. Thereafter, piglets were returned to their mother. Litters were standardized to a maximum of 12 piglets per sow. At 3 days of age, blood samples were taken on the same piglets as for day 0 as described above after a fasting period of 1 h. Analytical measurements. All blood samples tubes were centri- fuged for 10 min (1800× g) after 3 h and serum was frozen at −20°C for vitamins and minerals measurements. Concentrations of vitamins B2, B3, B6, B8 as well as Fe, Se, Zn and Cu were determined in serum of sows and piglets as well as in colostrum. For piglets, individual sera were pooled within litter. Measurements of vitamin B2 (sum of flavin mono- nucleotide, flavin adenine dinucleotide and riboflavin) were done by HPLC using a method described and validated in pig species by Giguère et al. (2002). For vitamin B3, concentra- tions of nicotinamide were measured by HPLC using a method adapted and validated by Santschi et al. (2005). For vitamin B6, concentrations of pyridoxal-5-phosphate were determined using a fluorimetric method described and validated by Matte et al. (1997). Vitamin B8 concentrations were measured in serum using commercial kits (Vitamin H, biotin ELISA, VITH. 96, MD Biosciences Inc., St. Paul, MN, USA) as described and validated in pig species by Castellano et al. (2010). Regarding trace elements, Cu and Fe concentrations were measured with commercial kits (QuantichromTM Fe Assay kit DIFE-250 et QuantichromTM Cu Assay kit DICU-250, BioAssay systems, Hayward, CA, USA). Validation for Cu was reported by Matte et al. (2017b). For Fe, average intra- and inter-assay coef- ficients of variation were 5.4% and 5.9%, respectively. Concentrations of Zn were measured by atomic absorption using a method described and validated by Matte et al. (2017b) whereas Se concentrations were obtained after wet ashing and fluorometric detection according to the method described and validated by Giguère et al. (2005). Statistical analysis. Statistical analysis was done on data generated by the trial with 20 sows using the SAS procedure (SAS Institute, Inc., Cary, NC, USA). The sow and her litter (mean for piglets per litter) are considered as experimental unit. Ratios R-u, R-c and R-uc were calculated for each litter and a t test was calculated to verify if ratios were different (lower or higher) or not from 1. Differences were assumed to be signifi- cant at P≤ 0.05 and as tendencies at P≤ 0.10. Values from the in vivo trial with sows are expressed as adjusted means ± SEM. For literature data, the different ratios were calculated with the reported average concentrations, and no statistical analysis could be performed on these values. Results In vivo trial: body condition and reproductive performance of sows Sow’s weight and backfat thickness at 110 days of gestation were 295.6 ± 4.6 kg and 20.3 ± 0.9 mm, respectively. At par- turition, litter size and weight (total born) were 14.9 ± 0.9 piglets and 19.4 ± 0.8 kg, respectively, while intra-litter mean weight for piglets born alive was 1.38 ± 0.06 kg. As mentioned before, sows were equally selected from two dietary treatments used in another experiment (Audet et al., 2015). No treatment effect (P< 0.05) was observed for any variables measured in the present trial and data cor- respond to pooled values of these two dietary treatments. Prenatal transfer The prenatal transfer was active and in favour of piglets for vitamins C and B12 (Table 2) as well as for Zn and vitamins B6 and B8 (R-u> 1, P< 0.03, Table 3) whereas it was passive for vitamin B3 (R-u = 1, P> 0.37, Table 3). For the remaining eight studied micronutrients, R-u ratios indicated that the prenatal transfer was limited for vitamins A, E, D and folic acid (Table 2) as well as for vitamin B2, Fe, Cu and Se (R-u< 1, P< 0.01, Table 3). Postnatal transfer For vitamins C and D, no R-c ratio is presented as pre- and post-colostral values were not simultaneously available within the same report (Table 2). For the other micronu- trients, the postnatal transfer was active for 10 of the 12 rated micronutrients (Tables 2 and 3). Vitamins B6 and B8 were the only two micronutrients with limited postnatal transfer (R-c< 1, P< 0.01, Table 3). Perinatal transfer Globally, the perinatal transfer (combination of R-u and R-c) was favourable to newborn piglets for 9 of the 14 studied micronutrients (Tables 2 and 3). Ratios R-uc were lower than 1 for vitamins A and D (Table 2) as well as for Fe, Cu and Se (R-uc< 1, P< 0.01, Table 3). Discussion The principle of using ratios of serum or plasma concentra- tions allows to make reliable comparison among animals of different sizes. This is true if serum or plasma volumes per unit of BW are constant. From the scarce information avail- able on that matter, some variations of serum or plasma vol- umes per unit of BW are reported among the metabolic stages studied in the present study. For sows at the end of gestation and piglets at birth, values of 44.7 and 44.5 ml/ kg BW were estimated from Linderkamp et al. (1981) and Matte and Girard (1996). After colostrum intake and up to Micronutrient transfer from sows to piglets 33 Table 2 Serum concentrations of vitamins in pre-farrowing sow and her piglets at birth before and shortly after colostrum intake Vitamin (citation) Dietary vitamin (per kg) Serum concentrations (mg/l) R-u3 R-c4 R-uc5 Colostrum (mg/l)1Sow (day of gestation)1 Piglets, pre-colostral (day of age)2 Piglets, post-colostral (day of age)2 A (Håkansson et al., 2001) 8 000 IU 0.27 ± 0.02 (108) 0.07 ± 0.01 (0) 0.19 ± 0.01 (3) 0.26 2.7 0.70 2.5 ± 0.32 E (Håkansson et al., 2001) 135 IU 2.3 ± 0.33 (108) 1.8 ± 0.07 (0) 5.3 ± 0.13 (3) 0.79 3.0 2.4 17.9 ± 3.8 E (Loudenslager et al., 1986) 50 IU 2.4 ± 0.19 (105) 0.27 ± 0.19 (0) 4.4 ± 7.9 (2) 0.11 16.2 1.9 8.7 ± 0.50 E (Pinelli-Saavedra and Scaife 2005) 22 IU 1.1 ± 0.25 (103) 0.35 ± 0.02 (0) – 0.32 – – 9.8 ± 0.11 E (Pinelli-Saavedra et al., 2008) 36 IU 2.5 ± 0.15 (103) < 0.17 (0) – < 0.07 – – 16.5 ± 1.0 C (Pinelli Saavedra and Scaife, 2005) 0 g/kg 4.5 ± 0.08 (103) 13.1 ± 0.07 (0) – 2.9 – – 24.7 ± 0.36 C (Yen and Pond, 1983) 0 g/kg 16.6 ± 1.1 (108) – 53.5 ± 4.1 (0.5) – – 3.2 – Serum concentrations (μg/l) Colostrum (μg/l)1 D (Goff et al., 1984) 2 200 IU 42.2 ± 1.5 (115) 4.7 ± 0.20 (0) – 0.11 – – – D (Amundson et al., 2017) 1 750 IU 22.9 ± 0.93 (115) 2.2 ± 0.05 (0) – 0.09 – – 0.53 ± 0.05 D (Matte et al., 2017a) 1 440 IU 29.0 ± 4.0 (110) – 1.0 ± 0.3 (2) – – 0.03 – Folic acid (Barkow et al., 2001) 0.6 mg/kg 45.8 ± 3.36 (100) 24.7 ± 1.52 (0) 77.0 ± 4.6 (2) 0.54 3.1 1.7 44.6 ± 10.0 Folic acid (Matte and Girard, 1989) 1.1 mg/kg 32.0 ± 2.0 (110) – 55.0 ± 3.0 (2) – – 1.7 – Vitamin B12 (Simard et al., 2007) 20 μg/kg 0.12 ± 0.01 (110) 0.74 ± 0.18 (0) 1.2 ± 0.13 (1) 6.3 1.6 9.9 6.1 ± 0.37 Vitamin B12 (Audet et al., 2015) 20 μg/kg 200 μg/kg 0.23 ±0.02 (110) 0.26 ± 0.02 (110) – 1.0 ± 0.04 (1) 2.6 ± 0.04 (1) – – 4.3 9.8 – 1Means ± SEM. 2Intra-litter means ± SEM. 3Prenatal transfer. Within study ratio assessed with mean serum concentrations of micronutrients in newborn piglets before colostrum intake divided by mean serum concentrations of micronutrients of sows before parturition (days in parentheses). 4Postnatal transfer. Within study ratio assessed with mean post-colostral (days in parentheses) divided by mean pre-colostral serum concentrations of micronutrients in piglets. 5Perinatal transfer. Within study ratio assessed with mean post-colostral (days in parentheses) serum concentrations of micronutrients in piglets divided by mean serum concentrations of micronutrients of sows before parturition (days in parentheses). M atte and Audet 34 3 days of age, numeric increases between 10% (statistically non-significant) and 25% of plasma volume per unit of BW have been reported by Ramirez et al. (1963) and Pownall and Dalton (1973), respectively. Therefore, all R-c and R-uc values might be slightly underestimated but, likely, without conse- quences for the global interpretation of results. Prenatal transfer The present results on prenatal transfer corroborate the hypothesis from Mahan and Vallet (1997), who suggest that for most micronutrients, the in utero transfer is not a passive mechanism in pregnant sows. For fat-soluble vitamins, the transfer from sow to foetuses appears restrained during gestation. This might be related to the epitheliochorial nature of porcine placenta which limits the overall transfer of fatty acids from sows to foetuses (Ramsay et al., 1991; Père, 2003). However, the placental transfer appears active for vitamin C and for most water-soluble vitamins, with the exception of vitamins B2 and folic acid. For vitamin B2, the present results in pigs contrast with the situation in humans where riboflavin is found in much lower concentrations in maternal plasma than in cord plasma (ratio of 1 : 4.7), suggesting that the transport mechanism of this vitamin is efficient in haemochorial placenta (Combs and McClung, 2017). To the best of our knowledge, the present estimated ratio for riboflavin has never been reported for pig species. For folic acid, the expression of the gene coding for placental folate binding proteins has been reported in pigs (Kim and Vallet, 2007) but, from the present results, it appears that the capacity of the binding proteins derived from this gene transcription does not allow folates to concentrate on the foetal side of the placenta. For trace minerals, no equivalent is available in the literature in terms of ratios using serum concentrations. Peters et al. (2010) reported concentrations of trace minerals in other metabolic pools such as whole body and liver from sows and stillborn piglets according to parity and source of dietary trace minerals. Unfortunately, as sow measurements were made at weaning (17 days of lactation), estimates of ratios comparable to actual R-u cannot be assessed. In a study on foetal mineral accretion in pigs, Mahan et al. (2009) mentioned that high prolificy in sows may jeopardize the adequate transfer of minerals to the foetus during the latter part of gestation. Postnatal transfer The present estimations of R-c ratios indicate that, globally, sow colostrum is a major source of micronutrients for the newborn piglets (Tables 2 and 3). The importance of colos- trum for providing micronutrients to the newborn piglets was already reported for some individual micronutrients (Csapò et al., 1995; Mahan and Vallet, 1997; Simard et al., 2007; Peters et al., 2010). Nevertheless, the present results also showed that three vitamins (D, B6 and B8) diverged from this general pattern. For vitamin D, the apparent lack of postnatal transfer is in line with small concentrations of this vitamin in colostrum which are, in fact, 43 times smaller than concen- trations in sow blood plasma. Assuming a colostrum intake of approximately 430 g/day for a piglet of 1.4 kg (Devillers et al., 2004), the daily ingestion of the newborn pigs represents a maximum of 6.5 IU/kg of BW. In comparison, the daily requirement for piglets of 5 kg (NRC, 2012), expressed also per kg of BW, are almost two times greater at 11.8 IU/kg of BW. Thus, sow colostrum is apparently not an adequate source of vitamin D for newborn piglets. For vitamins B6 and B8, the situation is more ambiguous although serum con- centrations represent, at 3 days of age, respectively, 34% and Table 3 Serum concentrations of vitamins and trace elements in pre-farrowing sow and her piglets (intra-litter mean) at birth before colostrum intake (day 0) and at 3 days of age (day 3). Data were measured in the animal trial with 20 sows described in the ‘Materials and methods’ section Micronutrients Serum concentrations (mg/l) R-u3 R-c4 R-uc5 Colostrum (mg/l)1Sow (day 110)1 Piglets (day 0)2 Piglets (day 3)2 Vitamin B2 0.09 ± 0.01 0.06 ± 0.01 0.19 ± 0.01 0.68 ± 0.03 3.1 ± 0.12 2.0 ± 0.06 4.4 ± 0.59 Vitamin B3 0.21 ± 0.01 0.21 ± 0.01 0.83 ± 0.12 1.0 ± 0.06 4.1 ± 0.60 2.8 ± 0.43 0.56 ± 0.04 Vitamin B6 0.15 ± 0.01 0.78 ± 0.03 0.26 ± 0.01 5.0 ± 0.19 0.34 ± 0.01 1.7 ± 0.05 4.4 ± 0.50 Fe 2.1 ± 0.11 1.3 ± 0.05 1.7 ± 0.11 0.60 ± 0.04 1.3 ± 0.09 0.77 ± 0.05 1.7 ± 0.04 Zn 0.60 ± 0.01 0.78 ± 0.04 1.2 ± 0.05 1.2 ± 0.11 1.7 ± 0.15 2.0 ± 0.11 13.1 ± 0.61 Cu 2.0 ± 0.05 0.60 ± 0.02 0.96 ± 0.04 0.29 ± 0.07 1.6 ± 0.07 0.46 ± 0.02 3.8 ± 0.16 Serum concentrations (μg/l) Colostrum (μg/l)1 Vitamin B8 2.7 ± 0.12 21.2 ± 1.1 4.8 ± 0.5 7.5 ± 0.55 0.23 ± 0.02 1.46 ± 0.17 23.5 ± 3.2 Se 159.6 ± 5.0 56.1 ± 1.8 77.4 ± 3.0 0.34 ± 0.02 1.4 ± 0.06 0.47 ± 0.02 250 ± 8.0 1Means ± SEM. 2Intra-litter means ± SEM. 3Prenatal transfer. Means ± SEM of within litter ratio between pooled serum concentrations of micronutrients from eight newborn piglets (day 0) before colostrum intake and the serum concentration of micronutrients of the sow before parturition (day 110). All ratios are different from 1 at P< 0.01 except for Zn (P< 0.03) and vitamin B3 (P> 0.37). 4Postnatal transfer. Means ± SEM of within litter ratio between post-colostral (day 3) and pre-colostral (day 0) pooled serum concentrations of micronutrients from eight piglets. All ratios are different from 1 at P< 0.01. 5Perinatal transfer. Means ± SEM of within litter ratio between post-colostral (day 3) pooled serum concentrations of micronutrients from eight piglets and the serum concentration of micronutrients of the sow before parturition (day 110). All ratios are different from 1 at P< 0.01. Micronutrient transfer from sows to piglets 35 22% of values at birth. It appears that the maternal transfer of these vitamins through colostrum has not provided enough B6 and B8 to sustain blood serum homoeostasis in piglets during early life. According to the present results and using the same approach as above for vitamin D, daily colostral supplies of both vitamins B6 and B8, expressed per kg of BW, can be estimated at a maximum of 1.36 mg and 7.2 μg, assuming a colostrum intake of approximately 430 g/day for a piglet of 1.4 kg (Devillers et al., 2004). In com- parison, daily requirements for piglets of 5 kg (NRC, 2012), expressed also per kg of BW, are estimated at 0.37 mg and 4 μg, respectively. Therefore, colostrum could be considered as a valuable source of vitamins B6 and B8 but it cannot be ruled out that the present postnatal period of 3 days include the gradual transformation of mammary glands secretion towards milk. Nonetheless, the drop of both vitamins in blood serum between birth and 3 days of age of piglets sug- gested a metabolic utilization that was intensive enough to generate a negative balance for vitamins B6 and B8 during the early life of piglets. Perinatal transfer The perinatal transfer of the micronutrients studied was calculated (R-uc) with the data presented in Tables 2 and 3. As mentioned before, this ratio allows estimating the micronutrient’s status of piglets at 3 days of age relative to that of their mother at the end of the gestation. For some micronutrients, the limited prenatal transfer was compen- sated by the postnatal transfer (vitamins E and B2) whereas for others, the prenatal transfer, active or passive, was added up (vitamins C, B12, B3 and Zn) or was not affected (vitamins B6 and B8) by the postnatal transfer. However, for 5 of the 14 micronutrients studied (vitamin A, vitamin D, Cu, Fe and Se), the limited prenatal transfer was not compen- sated by the postnatal transfer. For Fe and Se, the present R- uc values were not unexpected as an inadequate perinatal transfer has been reported before (Mahan and Vallet, 1997). Supplementation strategies are well known for these two trace elements with parenteral administrations of Fe to piglets (Braude et al., 1962) or organic Se supplementation given to sows during gestation and lactation (Mahan, 2000; Quesnel et al., 2008b; Fortier et al., 2012). In the present study, gestation and lactation diets were supplemented with selenite (Table 1), a form of Se which is less efficient than organic Se for transferring Se in utero (Fortier et al., 2012) or through colostrum and milk (Mahan, 2000; Quesnel et al., 2008b). For vitamin A, vitamin D and Cu, concentrations of the three micronutrients were 30%, 80% and 52% lower in neonatal piglets as compared to their mother before parturition. These results might indi- cate that evolution of the swine species has not favoured the perinatal transfer of these micronutrients from dams to piglets possibly because these micronutrients were avail- able in abundance in natural conditions, that is, outside buildings. For vitamin D, the presence of UV rays in sunlight allows the conversion of vitamin D in its active metabolites, a metabolism recognized as very efficient in pigs (Cooper et al., 1997; Kolp et al., 2017). For vitamin A, its precursor β-carotene which is accessible from plants can be absorbed and stocked efficiently by piglets (Schweigert et al., 1995). Finally, for Cu, it can be linked to a direct access to soil as a source of trace elements in line to what was proposed for Fe (Pond et Maner, 1984). Nevertheless, for Cu, it appears that serum concentrations continue to increase after 3 days of age along with de novo synthesis of ceruloplasmin and val- ues could reach adult levels at 2 weeks of age in suckling piglets reared in conventional conditions (Gomez-Garcia and Matrone, 1967). In summary, the indicators used in the present study showed that, among studied micronutrients, perinatal trans- fers in vitamin A, vitamin D and Cu are the least favoured during the first half week of life in piglets. These three micro- nutrients are recognized for their role in several metabolic functions, among them antioxidative capacity and develop- ment of bone and immune systems (Combs and McClung 2017). Further studies are needed to assess the importance of these micronutrients not only during the suckling period but also later in life of pigs. The latter is in line with the recent concept of ‘lactocrine’ or ‘neonatal’ programming in young piglets (Bartol and Bagnell, 2012) where the first few days of age is a crucial period. Such studies are actually in progress in our laboratories. Acknowledgements This study was made possible through the financial support provided by Swine Innovation Porc and, for this project, their associated partnership with Shur-Gain-Nutreco and Lallemand Animal Nutrition. The authors are grateful to M. Guillette and V. Noël for technical assistance, and to the animal care team under supervision of M. Turcotte and to S. Méthot for advice related to statistical analyses. Preliminary results have been published in an abstract form at the Midwestern 2014 annual meeting of American Society of Animal Science (Matte et al., 2014). Jacques J. Matte, 0000-0002-0134-6148 Declaration of interest None of the authors had a financial or personal conflict of interest in relation to the present study. 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Matte and Audet 38 Maternal perinatal transfer of vitamins and trace elements to piglets Implications Introduction Material and methods The approach Trial with sows during the perinatal period Results In vivo trial: body condition and reproductive performance of sows Prenatal transfer Postnatal transfer Perinatal transfer Discussion Prenatal transfer Postnatal transfer Perinatal transfer Acknowledgements Declaration of interest Ethics statement Software and data repository resources References