The Effect of Dietary Nutrient Density on Growth Performance, Physiological Parameters, and Small Intestinal Type IIb Sodium Phosphate Co-transporter Expression in Broilers

A 3 × 4 factorial experiment was con- ducted to determine the effect of dietary nutrient den- sity on growth performance, physiological parame- ters, and small intestinal epithelial phosphate trans- porter expression in broiler chicks fed different dietary nutrient density （DND） and non-phytate phosphorus （NPP） levels. Dietary energy densities used had ME values of 2,850, 2,950, and 3,050 kcal/kg of diet and the NPP levels were 0.35%, 0.40%, 0.45%, and 0.50% within each ME value. Crude protein and essential amino acids levels were maintained propor- tionally to dietary ME levels. Each of the twelve diets was fed to five pens of seven male broiler chicks from 1 to 21 days of age. Broiler growth performance, ser- um physiological parameters, 1-hydroxylase activity in the kidney, type-IIb sodium phosphate co-trans- porter （NaPi-IIb）, and vitamin D receptor （VDR） expression levels in the duodenal mucosa were deter- mined. Our results showed that an increase in dietary nutrient density increased body weight and improved feed conversion. Additionally, serum parathyroid hormone concentration, 1-a-hydroxylase activity in the kidney, NaPi-IIb mRNA expression and VDR protein expression in the duodenal mucosa increased as DND increased. Feed intake and body weight in- creased as NPP levels increased. Serum parathyroid hormone, VDR and NaPi-IIb gene expression also in- creased as the level of NPP in the diet increased at the medium range level. The results of this study suggest that high DND can increase small intestinal type IIb sodium dependent phosphate co-transporter mRNA expression by up-regulating parathyroid hormone and activation of 1-ot-hydroxylase activity which might be in consistent with high growth rate of broilers. Small intestinal NaPi-IIb mRNA expression increases linear- ly only within the range of dietary NPP dosage levels close to the requirement recommended in the broilers feeding standards.

Calcium supplementation in low nutrient density diet for meat ducksimproves breast meat tenderness associated with myocyte apoptosisand proteolytic changes

To define the relationship between dietary nutrient density, calcium (Ca), and meat quality in meatducks. A total of 288 male Cherry Valley SM3 medium ducklings were fed a common standard starter dietuntil d 14. At 15 d of age, ducks were randomly divided into 2 treatment groups and fed either a conventionaldiet or a low nutrient density (LND) diet. Compared with the conventional diet, the energy wasreduced in the LND diet by 8.6% and 16.8% in grower (15 to 35 d) and finisher (36 to 56 d) phases,respectively, while other essential nutrients were kept proportionate to energy. The LND diet decreasedthe shear force (P < 0.05) and increased the lightness values of the pectoralis muscle when compared tothe conventional diet, suggesting that LND diet exerted a beneficial role in meat quality. Subsequently,the effects of grated Ca in the LND diet on meat quality of pectoralis muscle were evaluated. A total of 576male ducklings were fed a common starter diet until d 14, followed by feeding 4 LND diets with 0.5%,0.7%, 0.9%, and 1.1% Ca. The results show that LND diets with 0.7% or more Ca decreased the shear force ofpectoralis major muscle in 42-d-old meat ducks (P < 0.05). To explore the mechanism underlying Ca andtenderness, data from birds fed either 0.5% or 1.1% Ca in the LND diet indicated that birds fed 1.1% Caexhibited lower shear force, upregulated calpains 1 expression, and higher calpains activity compared tothose fed the LND diet with 0.5% Ca (P < 0.05). Moreover, the 1.1% Ca LND diet induced a higher myocyteapoptosis (P =0.06) and upregulated mRNA expression of caspase-3 (P =0.07) in breast muscle. Our datasuggest that LND diets with 0.9% or 1.1% Ca had a positive role in the tenderness of breast meat,particularly the enhancing effect of 1.1% Ca LND diet on tenderness seems to be associated with proteolyticchanges of myofibrillar proteins and myocyte apoptosis in meat ducks.

Balanced nutrient density for broiler chickens using a range of digestible lysine-to-metabolizable energy ratios and nutrient density:Growth performance,nutrient utilisation and apparent metabolizable energy

Currently,specific nutrient concentration,metabolizable energy(ME)and digestible amino acids are used as feed formulation criteria.A balanced nutrient density(BND)concept based on 2 criteria of nutrient density and balanced amino acids-to-ME ratio may offer more flexibility in optimisation of profit in formulation of diets compared with current formulation based on set values per unit of feed mass.A total of 672 one-d-old off-sex male Ross 308 broiler chickens were used across two 42-d performance trials in a 3×2 factorial arrangement of treatments with each diet replicated 8 times(14 birds per replicate).The experimental factors were 2 nutrient density levels(low[LD]and high[HD])and 3 digestible lysine-to-ME ratios(DLYS:ME;low,medium,and high).Low density diets had ME of 2,876 and 3,023 kcal/kg for starter and finisher,respectively,while values for HD diets were 3,169 and 3,315 kcal/kg with proportionally higher non-nitrogenated nutrients.Separate digestibility and apparent metaboliz-able energy(AME)assays were conducted at d 21 and 42.Digestibility assays at d 7 were conducted on birds used for performance trials.Regardless of the diet density,birds fed low DLYS:ME had a lower(P<0.01)feed intake(d 0 to 42)than medium and high DLYS:ME.Without interaction,birds fed low and medium DLYS:ME had a similar body weight gain being the heaviest while birds low DLYS:ME were the lightest.By an interaction(P<0.05),the highest overall FCR value was observed for birds fed LD×low DLYS:ME and improved linearly when DLYS:ME increased to the highest level reaching a limit for birds fed HD×medium DLYS:ME.Calorie conversion linearly decreased(P<0.001)with increments in DLYS:ME.Jejunal and ileal starch and protein digestibility were affected on d 21 and 42 but not on d 7 of age.Given the independence of response on BW and feed consumption,the use of BND as a flexible system in diet formulations has the potential to enable more accurate formulation for optimisation of growth performance of broiler chickens.

Species Richness, Diversity and Density of Understory Vegetation along Disturbance Gradients in the Himalayan Conifer Forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.