Effects of dietary fat level on laying hens fed various concentrations of calcium

Effects of dietary free fatty acid content and degree of fat saturation on tibia bone properties of laying hens

Acid oils and fatty acid distillates are fat by-products of the refining process of edible oils and are characterized by their high proportion of free fatty acids (FFA). While lipids are essential in poultry diets, their chemical structure may interfere with calcium absorption. Therefore, this study investigated the effects of dietary FFA content and the degree of fat saturation on bone metabolism in commercial layers. For 15-wk, a total of 144 laying hens (19-wk-old) were randomly assigned to 8 treatments (6 replicates with 3 birds each), which were obtained by gradually replacing crude soybean oil (rich in unsaturated fatty acids [UFA]) with soybean acid oil (rich in UFA and FFA), or crude palm oil (rich in saturated fatty acids [SFA]) with palm fatty acid distillate (rich in SFA and FFA). Following a 2 × 4 factorial design, 4 UFA-rich and 4 SFA-rich diets were created with varying FFA content: 10, 20, 30, and 45%. Tibiae (6 birds/treatment) were collected at the end of the trial for the assessment of mineral composition, morphological properties, and mechanical characteristics. The data were analyzed using a 2-way ANOVA with the GLM procedure. Orthogonal polynomial contrasts were employed to determine the linear effect of increasing %FFA, with statistical significance set at P < 0.05. The degree of saturation was found to negatively impact on calcium and phosphorus bone content, with higher levels found in soybean-based diets (P < 0.001). A significant interaction was observed for medullary bone mineral content, showing a linear decrease as the dietary %FFA increased (P < 0.05) in palm diets. In contrast, morphological and mechanical bone traits, total ash content, and cortical bone mineral composition remained unaffected (P > 0.05). These results suggest that the degree of fat saturation exerts a greater impact than FFA content on bone mineral metabolism, supporting the commercial use of fat by-products rich in FFA in laying hen diets, at least during the early stages of the laying cycle.

Dietary supplementation with calcitriol or quercetin improved eggshell and bone quality by modulating calcium metabolism

This study was aimed to investigate the effects of dietary calcitriol or quercetin supplementation on eggshell and bone quality of laying hens. In trial 1, 72 Hy-Line Brown layers (80-week-old) with weak-shelled strength (25 to 30 N) were assigned into 4 dietary treatments with 6 replicates of 3 birds and fed a basal diet (4% calcium level) or basal diets supplemented with 0.5% calcium, 5 μg/kg calcitriol or 500 mg/kg quercetin for 4 weeks. In trial 2, 360 Hy-Line Brown layers (60-week-old) were divided into 3 groups with 8 replicates of 15 birds: control group (basal diet), calcitriol group (basal diet + 5 μg/kg calcitriol), and quercetin group (basal diet + 500 mg/kg quercetin). This trial lasted for 12 weeks. The results showed that dietary calcitriol or quercetin improved eggshell quality in both trials (P < 0.05). In trial 2, compared with the control group, both calcitriol and quercetin supplementations improved femoral bone quality, calcium retention of hens and calcium content in uterine fluid at 18.5 h post-oviposition (PO) (P < 0.05), along with enhancing uterine morphology. Compared to the control group, supplemental calcitriol or quercetin up-regulated the relative mRNA expression levels of uterine transient receptor potential cation channel, subfamily V, member 6 (TRPV6) at 8.5 h PO and plasma membrane calcium-ATPase (PMCA), vitamin D receptor (VDR), estrogen receptor alpha (ERα) at 18.5 h PO (P < 0.05), but down-regulated the uterine caspase 3 (CASP3) relative mRNA expression level at 8.5 h PO (P < 0.05). Meanwhile, the femoral relative mRNA expression levels of tartrate-resistant acid phosphatase (TRAP) (up-regulated at 8.5 and 18.5 h PO) and alkaline phosphatase (ALP) (up-regulated at 8.5 h PO but down-regulated at 18.5 h PO) were also affected by calcitriol or quercetin supplementation (P < 0.05). Compared to the calcitriol, quercetin increased hen-day egg production and femoral medullary bone volume/bone tissue volume but reduced femoral stiffness (P < 0.05), which were accompanied by increased relative mRNA expression levels of uterine TRPV6, estrogen receptor beta (ERβ) at 18.5 h PO (P < 0.05). Overall, both dietary calcitriol and quercetin could improve eggshell and bone quality by modulating calcium metabolism of aged layers. Compared to calcitriol, dietary quercetin up-regulated the expression of uterine calcium transporters, without affecting eggshell quality.

Calcium Nutrition of Broilers: Current Perspectives and Challenges

Calcium (Ca) plays an essential role in poultry nutrition as 99% of Ca is located in birds' skeletal system. However, oversupply of Ca rather than deficiency of Ca is the current concern in commercial broiler diets. Calcium is an inexpensive dietary nutrient due to the cheap and abundant availability of limestone, the major Ca source; therefore, little attention was given to the oversupply of Ca in the past. The recent shift in the use of digestible P in broiler feed formulations has necessitated a closer look at digestible Ca, as Ca and P are interrelated in their absorption and postabsorptive utilisation. In this context, data on ileal digestibility of Ca and P in ingredients has been determined. Preliminary data on the digestible Ca and digestible P requirements for the different growth stages of broilers have also recently become available. The present review focusses on these recent advances in Ca nutrition. In addition, aspects of homeostatic control mechanisms, different Ca sources and factors influencing Ca digestibility in poultry are covered.

Effect of dietary calcium levels near the time of sexual maturity on water intake and excreta moisture content

Three trials were conducted to investigate the effect of dietary calcium on water balance of leghorn pullets. Trial 1 involved introduction of a 4% calcium layer diet at 112, 123, 134, or 144 days of age. Introducing the layer diet early had an early but transitory effect on water intake (P less than .05) and absolute quantity of excreta moisture, although the pattern of percentage excreta moisture was not clearly defined. In a second trial, birds were moved to laying cages at 105 days, with diet change from 1 to 4% calcium occurring at 112 or 142 days. When the layer diet was offered at 112 days, percentage excreta moisture was higher from 113 to 142 days, although no difference was seen after this time. In a final experiment, introduction of a 4% calcium layer diet at either 112 or 133 days of age resulted in higher percentage excreta moisture at four measurement periods to 245 days of age, although this effect was significant only at 147 days (P less than .05). These results suggest there is a transitory effect of dietary calcium on water intake and excreta moisture content. This affect may be of concern within controlled environment buildings and with certain manure-handling systems. In commercial situations, such dietary changes are often confounded with increased dietary protein concentration, another factor known to influence water balance in pullets.