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.

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.

Inflammation neither increases hepatic hepcidin nor affects intestinal (59)Fe-absorption in two murine models of bowel inflammation, hemizygous TNF(ΔARE/+) and homozygous IL-10(-/-) mice

Hepcidin-synthesis was reported to be stimulated by inflammation. In contrast, hepcidin synthesis was inhibited by TNFα and serum hepcidin was low. To elucidate these contradictions, we compare data on hepcidin expression, on iron absorption and homoeostasis and markers of inflammation between two murine models of intestinal inflammation and corresponding wild-types as determined by standard methods. In TNF(ΔARE/+) and IL-10(-/-)-mice hepatic hepcidin expression and protein content was significantly lower than in corresponding wild-types. However, (59)Fe whole-body retention showed no difference between knock-outs and corresponding wild-types 7d after gavage, in neither strain. Compared to wild-types, body weight, hepatic non-haem iron content, hemoglobin and hematocrit were significantly decreased in TNF(ΔARE/+) mice, while erythropoiesis increased. These differences were not seen in IL-10(-/-) mice. Duodenal IL-6 and TNFα content increased significantly in TNF(ΔARE/+) mice, while ferritin-H decreased along with hepatic hepcidin expression, ferritin L, and non-haem iron. In IL-10(-/-) mice, these changes were less marked or missing for non-haem iron. Duodenal ferritin-L and ferroportin increased significantly, while HFE decreased. Our results corroborate the conflicting combination of low hepcidin with inflammation and without increased intestinal iron absorption. Speculating on underlying mechanism, decreased hepcidin may result from stimulated erythropoiesis. Unaltered intestinal iron-absorption may compromise between the stimulation by increased erythropoiesis and inhibition by local and systemic inflammation. The findings suggest intense interaction between counterproductive mechanisms and ask for further research.

Development of an experimental model to assess the bioavailability of zinc in practical piglet diets

Sufficient zinc (Zn) supply is a key element of successful animal husbandry. Proper use of dietary Zn sources, however, demands knowledge of Zn requirement and bioavailability, reflecting practical feeding systems. In this study, an experimental model is presented where 48 fully weaned and individually housed piglets received a fine differentiated alimentary Zn supply. The basal diet consisted mainly of corn and soybean meal (native Zn: 28.1 mg/kg feed) and was fortified with Zn from Zn sulphate at eight levels (0, 5, 10, 15, 20, 30, 40 and 60 mg Zn/kg). All animals were pretreated uniformly with the highest Zn supply (88 mg total Zn/kg feed) for two weeks (feeding ad libitum). Subsequently, animals were switched to the eight experimental diets (six animals per group, restricted feeding at 450 g/d). This period was limited to 8 d in order to avoid clinical Zn-deficiency symptoms. Measurements included amounts of apparently digested Zn, final levels of plasma Zn, plasma Zn-binding capacity, plasma alkaline phosphatase activity, femur Zn, liver Zn as well as hepatic metallothionein (Mt) 1a and Mt2b gene expression and hepatic Mt protein abundance. Clinical signs of Zn deficiency were completely absent through the entire study. All the analysed parameters except for Mt protein abundance responded sensitively to graduations in dietary Zn contents and indicated the presence of Zn deficiency at lower dietary Zn additions. Amounts of apparently digested Zn, liver Zn as well as hepatic Mt1a and Mt2b gene expression indicated transition from deficient to sufficient Zn supply between 47.5 and 58.2 mg of total Zn per kg of diet as assessed by broken-line response techniques. Analysed blood and bone parameters responded linearly to graduations in dietary Zn supply even within sufficient Zn supply levels. Taken together, the results indicate the suitability of our experimental model to determine Zn requirement in piglets and hence to also assess bioavailability of dietary Zn sources. The latter may be done by comparing the slope of the amounts of apparently digested Zn as well as by determining the response of blood and bone parameters to graduations in dietary Zn at insufficient Zn supply.