The response of zinc transporter gene expression of selected tissues in a pig model of subclinical zinc deficiency.

This study compared the relative mRNA expression of all mammal zinc (Zn) transporter genes in selected tissues of weaned piglets challenged with short-term subclinical Zn deficiency (SZD). The dietary model involved restrictive feeding (450 g/animal*day-1) of a high-phytate diet (9 g/kg) supplemented with varying amounts of zinc from ZnSO4*7H2O ranging from deficient to sufficient supply levels (total diet Zn: 28.1, 33.6, 38.8, 42.7, 47.5, 58.2, 67.8, 88.0 mg Zn/kg). Total RNA preparations comprised jejunal and colonic mucosa as well as hepatic and nephric tissue. Statistical modelling involved broken-line regression (P≤.05). ZIP10 and ZIP12 mRNAs were not detected in any tissue and ZnT3 mRNA was only identified in the kidney. All other genes were expressed in all tissues but only a few gene expression patterns allowed a significant (P<.0001) fitting of broken-line regression models, indicating homeostatic regulation under the present experimental conditions. Interestingly, these genes could be subcategorized by showing significant turnarounds in their response patterns, either at ~40 or ~60 mg Zn/kg diet (P<.0001). In conclusion, the present study showed clear differences in Zn transporter gene expression in response to SZD compared to the present literature on clinical models. We recognized that certain Zn transporter genes were regulated under the present experimental conditions by two distinct homeostatic networks. For the best of our knowledge, this represents the first comprehensive screening of Zn transporter gene expression in a highly translational model to human physiology.

Effects of whole plant brown algae (Laminaria japonica) on zootechnical performance, apparent total tract digestibility, faecal characteristics and blood plasma urea in weaned piglets.

Two trials were conducted with 48 newly weaned piglets (28 d old) each 8.6 ± 0.05 kg to study how Laminaria japonica plants (LJ) affect zootechnical performance, feed conversion and the apparent total tract digestibility (ATTD) of crude nutrients. All basal diets consisted of cereals, soybean meal, skim milk powder and premixes according to recommendations (no growth promoters or enzymes). For Trial 1, piglets from 16 litters (50% male-castrated, 50% female) were assigned to three treatment groups (n = 16) in a completely randomised block design. Groups received either 2.5% supplementation with sun dried (SD) or drum dried (DD) LJ powder or 2.5% of diatomaceous earth (control). For Trial 2, piglets from 12 litters received either 5% of diatomaceous earth (control) or one of three mixtures of diatomaceous earth + DD LJ powder (3.3%+1.7%, 1.7%+3.3% or 0.0%+5%; n = 12). Data collection included zootechnical performance, faecal consistency, blood plasma urea (Trial 1 and 2) and ATTD (Trial 2). Metabolisable energy (ME) of DD LJ and diets in Trial 2 was estimated using digestible nutrients. Statistical analysis included two-way ANOVA (treatment, block) and mixed linear regression. During both trials, LJ at dosages ≥2.5% significantly reduced feed:gain ratio compared to control (p ≤ 0.0001, = 0.01 for Trial 1, Trial 2) irrespective of the drying method. ATTD from Trial 2 significantly increased digestibilities of dry matter (DM) and crude ash (CA) (p ≤ 0.01) and significantly decreased digestibilities of organic matter and crude fibre in animals fed ≥3.33% DD LJ (p = 0.01). Fractional digestibility of the DD LJ resulted in limited ME of ~9.3 ± 2.5 MJ/kg DM. Dietary conversion ratios of ME and digestible DM of DD LJ diets from Trial 2 decreased linearly with increasing algal supplementation (R2 = 0.93, 0.94 and pslope = 0.002, 0.002 for MCR, DCR). In conclusion, dried LJ powder was included up to 5% into diets without impairing zootechnical performance. The improved feed conversion in the presence of LJ was partly due to slightly higher ME within the algae diets compared to control. However, piglets receiving LJ during Trial 2 needed significantly lower dietary ME and digestible DM to maintain growth performance. Thus, LJ exerted a performance enhancing effect on weaned piglets. The precise mode-of-action is yet unclear.

Adaption of body zinc pools in weaned piglets challenged with subclinical zinc deficiency.

The effects of subclinical Zn deficiency on depletion and redistribution of body Zn were studied in weaned piglets. Forty-eight weaned piglets (German-Large-White×Land-Race×Piétrain; 50 % female, 50 % male-castrated; body weight 8·5 (sd 0·27) kg) were fed restrictively (450 g/d) a basal maize-soyabean meal-based diet supplemented with varying amounts of ZnSO4.7H2O (analysed dietary Zn: 28·1, 33·6, 38·8, 42·7, 47·5, 58·2, 67·8, 88·0 mg/kg diet) for an experimental period of 8 d. Analyses comprised Zn concentrations in soft tissues. Statistical analyses included regression models and k-means cluster analysis. Jejunum and kidney Zn correlated positively with dietary Zn (P<0·05). Other Zn pools responded in a non-linear fashion by declining (colon, epidermis, spleen) or increasing (mesenteric lymph follicles, thymus, skeletal muscle) below 63·6, 48·0, 47·5, 68·0, 43·0 and 53·1 mg Zn/kg diet, respectively (P<0·01). Above these thresholds, Zn concentrations in epidermis, mesenteric lymph follicles and skeletal muscle plateaued (P<0·0001), whereas they exhibited a decrease in colon and thymus (P<0·01) as well as a numerical increase in spleen. Clustering by dietary Zn concentration indicated clusters of varying Zn supply status and pathophysiological status. Clustering by biological matrices revealed a discrimination between storage, transport and excretion media as well as soft tissues. Taken together, novel response patterns indicated compensation reactions in tissues that are essential for the acute survival of growing animals (heart, skeletal muscle, immune tissues). Furthermore, this is to our knowledge the first study that mapped the gross Zn requirement by clustering tissue Zn concentrations between treatment groups.

Effects of different iron supply to pregnant sows (Sus scrofa domestica L.) on reproductive performance as well as iron status of new-born piglets.

The present study aimed to investigate the effects of different iron (Fe) supply to sows during gestation on their reproductive performance and placental Fe load. Additionally, the Fe status of the corresponding offspring was assessed. Twenty multiparous sows were fed from insemination to farrowing with isoenergetic and isonitrogenic balanced diets differing in Fe content. The diet low in Fe (Group -Fe) was mainly composed of soybean meal and maize meal and had a Fe content of 114 mg/kg DM. For the diet high in Fe (Group +Fe), the diet was supplemented with Fe(II)SO4 · 7H2O to a total Fe content of 256 mg/kg. Blood characteristics (haemoglobin, haematocrit, mean corpuscular haem concentration, total Fe-binding capacity, transferrin saturation) of all sows were measured at the beginning and at the end of gestation. Daily Fe retention was calculated at the day of farrowing. After birth, reproductive performance (litter size, piglet weight, litter weight), placental Fe content and Fe blood characteristics of the piglets were determined. Apparent daily Fe retention tended to be greater in Group +Fe (p < 0.1). Blood parameters of the sows did not show any variations between feeding groups, neither at the beginning nor at the end of pregnancy, whereas placental Fe content was lower in Group -Fe (p < 0.05). In addition, Fe supply during gestation improved litter size (p < 0.01) and litter weight (p < 0.05). Although all sows were supplied according to the current Fe recommendations, a significant decline in reproductive performance of Group -Fe was recognised. Therefore, it was concluded that the re-evaluation of the gross Fe requirements of pregnant sows is inevitable to accommodate the current feeding recommendations.

Strategies and challenges to increase the precision in feeding zinc to monogastric livestock.

Practical diets for monogastric livestock must be supplemented with zinc (Zn) due to their high contents of antagonistic substances like phytates. Current feeding recommendations include quite generous safety margins because of uncertainties regarding the gross Zn requirements under varying rearing conditions. Furthermore, the use of pharmacological Zn doses to stabilise animal performance and wellbeing is widespread. Taken together, modern diets for pigs and poultry contain considerably more Zn than necessary to meet animal requirements, which is associated with concerns related to the environment as well as animal and consumer safety. Therefore, European authorities most recently reduced the allowed upper limits for Zn in complete feed. To maintain animal productivity and wellbeing while reducing the Zn load in complete feed, all measures that stabilize feed Zn bioavailability must be applied. Most importantly, reliable information on the gross Zn requirement under practical conditions must be provided, considering the bioavailability of native or supplemented feed Zn, antagonisms with dietary factors as well as the physiological status of the animal.

Environmental responsibilities of livestock feeding using trace mineral supplements.

Trace elements are essential dietary components for livestock species. However, they also exhibit a strong toxic potential. Therefore, their fluxes through the animal organism are tightly regulated by a complex molecular machinery that controls the rate of absorption from the gut lumen as well as the amount of excretion via faeces, urine and products (e.g., milk) in order to maintain an internal equilibrium. When supplemented in doses above the gross requirement trace elements accumulate in urine and faeces and, hence, manure. Thereby, trace element emissions represent a potential threat to the environment. This fact is of particular importance in regard to the widely distributed feeding practice of pharmacological zinc and copper doses for the purpose of performance enhancement. Adverse environmental effects have been described, like impairment of plant production, accumulation in edible animal products and the water supply chain as well as the correlation between increased trace element loads and antimicrobial resistance. In the light of discussions about reducing the allowed upper limits for trace element loads in feed and manure from livestock production in the European Union excessive dosing needs to be critically reconsidered. Moreover, the precision in trace element feeding has to be increased in order to avoid unnecessary supplementation and, thereby, heavy metal emissions from livestock production.