Effects of different dietary vitamin D combinations during the grower phase and the feed restriction phase on growth performance and sternal morphology, mineralization, and related genes expression of bone metabolism in Pekin ducks.

Our study aimed to investigate the effects of different dietary vitamin D (VD) combinations during the grower (1-32 d of age) and feed restriction (33-52 d of age) phases on growth performance. We also evaluated sternal morphology, mineralization, and related genes expression of bone metabolism as well as absorption of calcium and phosphorous in duodenal mucosa and kidney in Pekin ducks. During the grower phase, we used 2 VD regimes (Group A: 3,160 IU/kg VD3; Group B: 400 IU/kg VD3 + 69 µg/kg 25-OH-D3). Each dietary treatment had 50 replicate pens of 10 ducks per pen. During the feed restriction phase, 30 replicate pens selected from Group A and Group B, repetitively, were redivided into 5 different dietary VD regimes to form a 2 × 5 experimental design. Each group consisted of 6 replicates, each with 10 ducks. During the feed restriction phase, we evaluated 5 different dietary VD combinations were as follows: T1: 2,000 IU/kg VD3 ; T2: 5,000 IU/kg VD3; T3: 3,620 IU/kg VD3 + 34.5 µg/kg 25-OH-D3; T4: 2,240 IU/kg VD3 + 69 µg/kg 25-OH-D3; T5: 1,800 IU/kg VD3 + 80 µg/kg 25-OH-D3). Results showed that Group B combinations with T5 had a better growth performance and breast meat deposition (P < 0.1). Regardless of 5 dietary VD regimes during the feed restriction phase, Group B significantly increased (P < 0.05) 52 d sternal depth and tended to increase (P < 0.1) 52 d sternal defatted weight, ash content, and phosphate (P) content of ducks. A significant interactive effect (P < 0.05) was observed on the mRNA abundance of DMP1 and Sost1 as well as RANKL/OPG in sternum and of VDR in duodenal mucosa of ducks at 52 d of age between dietary VD combinations during 2 phases. These results indicated that dietary VD regimes during the grower phase could affect the effectiveness of dietary VD regimes during the feed restriction phases; Dietary VD combinations of both phases could affect the genes expression of bone formation and the absorption as well as reabsorption of calcium and phosphorus in duodenum and kidney.

Effect of dietary 25-hydroxycholecalciferol on the sternal mass of meat ducks under different vitamin regimens.

Genetic selection and intensive nutrition for increased growth rate in meat-type ducks has resulted in an imbalance between pectorales increment and sternal mass, which is detrimental to productivity and welfare. Reducing body weight and increasing sternal mass probably reverses these adverse effects. Therefore, 2 experiments (Expt.) were conducted to investigate the effects of 25-hydroxycholecalciferol (25-OH-D3), a vitamin D3 metabolites, on sternal mass. In Expt. 1, 512 1-day-old male ducks were randomly assigned to 4 low-nutrient density diets and received following treatments in a 2 × 2 factorial arrangement: (i) NRC or China Agricultural industry standards (NY/T) vitamin premixes and (ii) 0.069 mg/kg 25-HyD in feed or not. At 49 D of age, regardless of 25-OH-D3, NY/T vitamin regimen inhibited bone turnover and consequently increased sternal trabecular bone volume and mineral deposition compared with NRC vitamin premix. Supplementing 25-OH-D3 to NRC but not NY/T vitamin regimen significantly improved sternal microarchitecture and mineral content, which companied by decreased serum bone resorption markers concentration, as well as downregulation of the gene expressions of osteoclast differentiation and activity. In Expt. 2, 256 1-day-old male ducks were fed a standard nutrient density diet contained NRC vitamin premix with 0 or 0.069 mg/kg of 25-OH-D3. Results also showed that 25-OH-D3 treatment significantly improved sternal mineral accumulation and microarchitecture, along with decreasing osteoblast and osteoclast numbers in bone surface, declining serum bone turnover markers levels, and increasing serum Ca concentration. Collectively, these findings indicated that the dietary administration of 25-OH-D3 increased sternal mass in NRC vitamin diet by suppressing bone resorption in 49-day-old meat duck.

High vitamin levels ameliorate negative effect of rapeseed meal in meat ducks by improving antioxidant activity.

The purpose of this study was to test the hypothesis that a high level of a vitamin premix would prevent the deleterious effects of rapeseed meal (RSM) when added to the diet of Pekin meat ducks. A total of 674 fifteen-day-old ducks were randomly allocated to 6 treatments with 7 cages of 16 ducks each. Three diets were formulated that contained 5, 10, or 20% RSM to compensate for reducing levels of soybean meal. Each RSM level diet was then supplemented with either a low level (low) or a high level (high) of a vitamin premix providing a total of 6 experimental diets. Ducks were fed one of the 6 experimental diets (N = 7 pens per diet) from days 15 to 35 at which time they were euthanized. Ducks were analyzed for antioxidant activity, liver biochemistry, thyroid hormone levels, and liver and thyroid histopathology. Addition of the high vitamin premixes to the 5 or 10% RSM diets improved BW (P < 0.05), BW gain (BWG; P < 0.05), and feed to gain ratio (F/G; P < 0.05) compared to the low vitamin premix; however, neither vitamin premix level had effects on production variables of ducks fed the 20% RSM diet. The high vitamin premix level also improved antioxidant capacity as evidenced by increased (P < 0.05) serum and liver superoxide dismutase activities over that of the low vitamin premix diets. Furthermore, the high level of vitamin premix prevented liver and thyroid pathologies in diets that contain RSM compared to diets with the low vitamin premix. These results suggested that high vitamin premix could prevent the negative effects of a 5 or 10% RSM diet in ducks by improving antioxidative capacities and alleviating liver and thyroid damage.

Effects of supplementation with different rapeseed oil sources and levels on production performance, egg quality, and serum parameters in laying hens.

This study was to determine the effects of rapeseed oil on production performance, egg quality, and serum parameters in laying hens. A total of 1,080 hens (33-wk-old) were randomly divided into a 1 plus 4 × 2 factorial design including four different rapeseed oil sources [high erucic acid of Mianyang city (MH); high erucic acid of Deyang city (DH); low erucic acid of Mianyang (ML); low erucic acid of Deyang (DL)] at two levels (2% and 4%) for 12 wk. The egg production and egg weight were decreased (P < 0.05) during 9 to 12 wk and 1 to 12 wk, while the average daily feed intake (ADFI) and feed conversion ratio were decreased (P < 0.01) in all phases compared to the control group. Adding ML as oil source had higher (P < 0.05) egg weight compared to DH in all periods in spite of levels. Meanwhile, layers fed 4% rapeseed oil decreased (P < 0.01) egg production compared with 2% in all phases except 1 to 4 wk. Regardless of rapeseed oil sources, hens fed 4% oil decreased (P < 0.05) egg weight in contrast to 2% during the whole experiment except 5 to 8 wk. The ADFI was lower (P < 0.01) in 4% oil inclusion groups compared with 2% during overall phase. Rapeseed oil decreased the yolk color (P < 0.01) and yolk ratio (P = 0.02) and increased (P < 0.01) the albumen height and Haugh unit at 12 wk. Dietary rapeseed oil supplementation resulted in a decreased total triglyceride (TG; P < 0.01) and increased high-density lipoprotein cholesterol (P = 0.02). Regardless of rapeseed oil levels, layers fed MH had higher TG (P < 0.01), TC (P < 0.05), low-density lipoprotein cholesterol (P < 0.05), alanine transaminase (P < 0.01) than those fed other sources. Taken together, the addition of rapeseed oil decreased laying performance, reduced TC and TG in the serum, and increased Haugh unit, with low erucic acid or 2% group showed more pronounced results among all treatments.

Hypothalamic galanin-like peptide rescues the onset of puberty in food-restricted weanling rats.

Galanin-like peptide (GALP) is a known mediator of metabolism and reproduction; however, the role that GALP plays in the onset of puberty is unknown. First, we tested the hypothesis that central GALP administration could rescue puberty in food-restricted weanling rats. GALP treatment in food-restricted rats of both sexes rescued the timing of the onset of puberty to that seen in ad lib. fed controls. Second, we tested whether GALP translation knocked-down in ad lib. fed, prepubertal rats would alter the timing of puberty. Knock-down females, but not males, showed a significant (P < 0.01) delay in the onset of puberty compared to controls. Third, we sought evidence that the role of GALP in pubertal onset is mediated by the kisspeptin system. In situ hybridisation analyses showed a significant (P < 0.01) reduction in Kiss1 mRNA within the hypothalamic arcuate nucleus in food-restricted rats compared to ad lib. fed controls and this reduction was prevented with i.c.v. GALP administration. Furthermore, analyses of Fos-immunoreactivity (-IR) after i.c.v. GALP treatment did not elicit Fos-IR within any kisspeptin neurones, nor are GALP and kisspeptin peptides or mRNA colocalised. These data demonstrate that hypothalamic GALP infusion maintained the onset of puberty in food-restricted weanling rats, although probably not via direct innervation of kisspeptin neurones.

Immunotoxic catecholamine lesions attenuate 2DG-induced increase of AGRP mRNA.

Injections of the immunotoxin, saporin conjugated to anti-dopamine-beta-hydroxylase (DSAP), into the hypothalamic paraventricular nucleus (PVH) selectively destroy norepinephrine (NE) and epinephrine (E) terminals in the medial hypothalamus and abolish glucoprivic feeding. We utilized PVH DSAP injections to examine the role of NE/E neurons in the previously reported 2-deoxy-D-glucose (2DG)-induced increases in mRNA levels for the orexigenic peptides, AGRP and NPY. Northern blot analysis revealed that DSAP lesions elevated basal but blocked 2DG-induced increases in AGRP mRNA levels. Changes in NPY mRNA were not detectable. AGRP neurons may contribute to circuitry activated by NE/E neurons for elicitation of glucoregulatory responses.