Determination of the Optimal Level of Dietary Zinc for Newly Weaned Pigs: A Dose-Response Study

Abstract

One hundred and eighty individually housed piglets with an initial body weight of 7.63 ± 0.98 kg (at 28 days of age) were fed a diet containing either 153, 493, 1022, 1601, 2052 or 2407 mg zinc/kg (added Zn as zinc oxide; ZnO) from day 0–21 post weaning to determine the optimal level of Zn for weaned piglets. Body weight, feed intake and faecal scores were recorded, and blood and faecal samples were collected. Dietary Zn content quadratically affected both feed intake and gain in the first two weeks, with an approximately 1400 mg Zn/kg diet and a Zn intake of 400 mg/day as the optimal levels. The relative risk of diarrhoea increased up to 60% at day 7 and 14 if serum Zn status dropped below the weaning level (767 µg/L), and maintain the weaning serum Zn status required approximately 1100 mg Zn/kg (166 mg Zn/day) during week 1. Blood markers of intestinal integrity (D-lactate and diamine oxidase) were unaffected by dietary Zn, and dietary Zn levels of 1022 and 1601 mg/kg did not affect the faecal numbers of total bacteria, Lactobacilli and E. Coli bacteria compared to 153 mg Zn/kg. These results indicate that the requirement for Zn in newly weaned piglets may be substantially higher than currently assumed.

Bioavailability of Different Zinc Sources in Pigs 0–3 Weeks Post-Weaning

“…The negative or close to zero ATTD of Zn when supplied at 100 mg added/kg irrespective of Zn source in the present study therefore indicates that on day 14 PW, pigs were under supplied with Zn. This result is well in line with recent results by Hansen et al [ 25 ]. They showed that 150 mg total Zn/kg feed was far from enough to provide weaned pigs the NRC recommended 46.8 mg Zn per day [ 27 ] and also not enough to ensure optimal feed intake, growth and serum Zn status during the first two weeks PW.…”

“…The average daily feed intake across treatments during the first week PW was slightly lower (118 g/day) than what we have previously observed in individually housed piglets fed similar types of diets (approximately 150 g/day) [ 25 ]. This is most likely caused by the lower initial weight at weaning (average 6.8 kg) compared to pigs in the study by Hansen et al [ 25 ] (7.6 kg).…”

“…The average daily feed intake across treatments during the first week PW was slightly lower (118 g/day) than what we have previously observed in individually housed piglets fed similar types of diets (approximately 150 g/day) [ 25 ]. This is most likely caused by the lower initial weight at weaning (average 6.8 kg) compared to pigs in the study by Hansen et al [ 25 ] (7.6 kg). Bruininx et al [ 28 ] reported that individually fed group-housed pigs weaned at an average of 27 days of age with a BW of 6.7 kg had an average daily feed intake from d 0–13 PW of 168 g, which is well in line with feed intake results from another study in individually fed group-housed weaned pigs [ 29 ].…”

“…Studies of bioavailability of Zn from different Zn sources in broilers have also shown that differences in Zn digestibility are not necessarily translated into differences in the serum Zn status [ 35 , 36 , 37 ]. Serum or plasma Zn concentration is recognized as a reliable measurement for estimating Zn status in humans [ 38 , 39 ] and is also used to assess Zn status in weaned pigs [ 25 , 40 , 41 ]. None of the Zn sources, when included at 100 mg Zn/kg, were able to maintain the serum Zn level at weaning (852 μg/L), at d 7, d 14 or d 21 post-weaning.…”

“…Prior to Zn analysis, feed, faeces and serum samples were digested with concentrated HNO 3 (67–69%), followed by destruction using a microwave system (Ultra wave, single reaction chamber, Milestone Inc, Shelton, CT, USA). The Zn content was measured on an iCAP TQ ICP-MS (Inductively Coupled Plasma-Mass Spectrometer; Thermo Scientific, Bremen, Germany) as described in detail by Hansen et al [ 25 ]. Titanium oxide was analysed by the digestion of samples with sulphuric acid and by measuring the absorbance after the addition of hydrogen peroxide [ 26 ] with the modification that 15 mL of 30% hydrogen peroxide was added instead of 10 mL, and before measuring the absorbance, five additional drops of hydrogen peroxide were added.…”