Background and Objective: Demand for high energy poultry feed ingredients has increased with increased competition. Hence in this study we aimed to examine the effect of high oleic peanuts (HOPN) and sweet potato by-products (SWP) on hen production and egg quality. Materials and Methods: Seven hundred twenty hens were fed one of 5 treatments for 6 weeks, a conventional control (C1), a soy protein-isolate control (C2), 4% SWP diet, an 8% HOPN diet and a 4% HOPN+4% SWP diet. Eggs, body and feed weights were collected bi-weekly. Eggs were analyzed for quality and chemistry. All data were analyzed using an ANOVA at p<0.05 significance level. Results: Hens fed the C2 and HOPN diets produced significantly more eggs (p<0.01), relative to the other treatments. There were no treatment differences in body or egg weights. Feed conversion was similar between the HOPN, SWP and SWP+HOPN diets. At week 4 and 6, SWP eggs had increased egg yolk color relative to the HOPN and SWP+HOPN treatments (p<0.01). Stearic fatty acid levels were lowest in eggs produced from hens fed the HOPN and SWP+HOPN diets (p<0.0001). Conclusion: Egg yolk color may be enhanced with feeding laying hens a SWP supplemented diet relative to a HOPN-containing diet.
PDF Abstract XML References Citation
How to cite this article
As the poultry industry continues to grow, competition for high energy feed ingredients, like corn, has caused an increase in feed costs1. Corn is used in many ways including high levels of human consumption, livestock consumption and ethanol production in the United States2. The increase in feed costs can cause a decrease in poultry production as well as an increase in cost for the consumer. Some countries that do not have food security have shut down some of their broiler facilities because of the increased feed costs3. Because of the shortage of high energy grains, such as corn, it has become imperative to find alternative feed ingredients that can replace these grains without reducing the performance or production or increasing costs. Past research has looked at sweet potato (Ipomoea batatas) and how it effects the performance and production of broilers and layers. Sweet potato is thought to be a good candidate because it has similar metabolizable energy levels as corn4. Sweet potato storage roots were found to be good sources of carbohydrates, vitamins and β-carotene5,6. Research conducted with layers determined that peeled sweet potato meal can replace 75% of corn in the diet without adversely affecting hen performance7. Another study demonstrated that 100% replacement of corn in diet with sun dried sweet potato meal did not adversely affect egg production, egg weight, feed intake or eggshell thickness, Haugh unit, or total feed consumed/dozen eggs in a 12-week layer trial8. A trial conducted by Hassan and Abd-El Galil9 looked at different levels of sun-dried sweet potato peel waste (0, 15, 20, 25, 30%) in another 12-week layer trial and they determined that up to 25% of the sweet potato peel waste could replace corn in the diet without negatively affecting layer performance or egg quality. However, final body weights declined with increasing levels of sweet potato peel waste.
North Carolina has ranked as the number 1 sweet potato producing state in the U.S. since 1971, providing nearly 60% of the U.S. annual supply10. Sweet potato waste by-products are generated annually in the form of culled whole sweet potatoes or remnants from food manufacture processing. Culled whole sweet potatoes are rejected due to damage during harvest, transportation or storage, inferior size or weight, or damage from insects, or mold, while sweet potato peels and/or chunks from whole sweet potato flesh are generated during processing11, producing approximately 7,000 metric tons of sweet potato waste by-products12 annually worldwide.
North Carolina also ranks within the top 6 peanut producing states within the United States: Georgia, Florida, Alabama, Texas, North Carolina and South Carolina13. In our previous layer feeding trials, we demonstrated the efficacious use of unblanched high-oleic peanuts as a suitable alternate layer feed ingredient to enrich the eggs produced with unsaturated fats, β-carotene and enhanced yolk color14,15. Nevertheless, while body weights and feed consumption of hens fed a 24% unblanched high-oleic peanut-containing diet was similar to that of hens fed a control diet containing soy protein isolate, hens fed the high-oleic peanut diet produced significantly less eggs16. Therefore, in this study we aimed to compare layer performance (body weights, feed intake and egg production) between a conventional control layer diet of defatted soybean meal and yellow corn to a control diet containing defatted soybean meal, yellow corn and soy protein isolate. Also, we aimed to determine the effect of sweet potato by-products on layer performance and the quality and chemistry of the eggs produced. Moreover, we aimed to determine the effects of feeding one-third of the previous inclusion level of unblanched high-oleic peanuts in the diet (8%) of layers to determine the effects on layer production performance, egg chemistry and quality.
MATERIALS AND METHODS
The procedures used in these studies were approved by the North Carolina State University Institutional Animal Care and Use Committee (IACUC No. 17-001A) following an accredited internal research animal protocol review in accordance with the standards within the “Guide for the Care of Use of Agricultural Animals in Research and Teaching” set forth by the American Dairy Science Association, the American Society of Animal Science and the Poultry Science Association.
Experimental design, animal husbandry and dietary treatments: This study was conducted at the North Carolina Department of Agriculture and Consumer Services Piedmont Research Station facility in Salisbury, NC (USA) for the routine rearing breeding of egg laying hens and egg production. Prior to the onset of this study, all experimental protocols and procedures were approved by the North Carolina State University Institutional Animal Care and Use Committee (IACUC No.19-761-A, approved 11/27/2019, expires 11/27/2022). Seven hundred and twenty Shaver laying hens (28 to 34 weeks of age) were randomly assigned to one of the five dietary treatments (144 hens per treatment), with four replicates of thirty-six birds each. Hens were housed in two Conventional Tri-Deck Stacked Layer Cage Systems with 66.04×121.92 cm2 (26×48 in2) per cage, with 18 birds per cage allowing a space of 447.31 cm2 per hen. Each cage unit consisted of two rows, with 2 cages per upper and lower row with a treatment replicate of 36 hens on each row, for a total of 4 replicates per treatment. Each row had a feeding trough measuring 48 inches (122 cm) in length and 21 inches (53.34 cm) in height. The study was conducted in a standard height, windowless enclosed ventilated house.
Throughout the feeding trial, birds were provided 14 L:10 D and feed and water ad libitum for 6 weeks. Pen body and feed weights were recorded once every two weeks. Shell eggs were collected and enumerated daily from each pen and replicate and totaled each week. Total number of eggs produced per replicate for each treatment was calculated for the total 6 week feeding trial. The average feed conversion ratio (FCR) was calculated as:
Five experimental diets were formulated in Concept 5 (level 2, version 10.0) to be isocaloric (2,922 kcal kg1) and isonitrogenous (19.5% crude protein) with an estimated particle size between 800 and 1000 μm (Table 1). All experimental diets were prepared with yellow corn and solvent extracted defatted soybean meal. For comparison two experimental control diets were prepared with (Control-2) and without (Control-1) Soy Protein Isolate (ADM, Chicago, Illinois, USA). The sweet potato by-product containing diet (SWP) was prepared using 4% dried Covington sweet potato by-products+solvent extracted defatted soybean meal+yellow corn. Covington sweet potato peelings, skins and small tubers were donated from Yamco, LLC. (Snow Hill, NC). These sweet potato by-products were thawed at 4°C and ground using a Buffalo meat grinder and dried to a moisture level below 10% using blowers at ambient temperatures during the summer months. The nutritional content for dehydrated ground Covington sweet potato by-products was analyzed by ATC Scientific (Little Rock, AR, USA) prior to formulation and preparation of the experimental diets (0.96% crude fat, 11.0% crude protein, 10.4% ash, 66.8% carbohydrates, 102 ppm β-carotene, gross energy 3447 kcal kg1).
A high oleic peanut experimental diet (HOPN) was prepared using 8% unblanched (skin intact) high-oleic peanuts+solvent extracted defatted soybean meal+yellow corn. An additional experimental diet was prepared using 4% SWP+4% HOPN diet for comparison. Aflatoxin-free unblanched peanuts were used in all peanut-containing experimental diets and crushed using a Roller Mill to form crumbles, prior to inclusion in the finished diets. Each experimental diets were supplemented with vitamin, mineral and selenium premixes manufactured at the NC State University Feed Mill (Raleigh, NC, USA) to meet and/or exceed poultry requirements for vitamins, minerals and selenium. All experimental diets were analyzed by the North Carolina Department of Agriculture and Consumer Services and the Food and Drug Protection Division Laboratory (Raleigh, NC, USA) for aflatoxin and microbiological contaminants. All feed ingredients and feed samples were verified to be free of microbiological contaminants.
Association of Official Analytical Chemists (AOAC)17-approved methods for nuts and seeds with crude fat determination using Gravimetric methods for nuts-AOAC17 948.22, protein was determined using Kjeldahl method for nuts-AOAC17 950.48, mineral was determined by elemental analysis of mineral by atomic absorption spectroscopy, carbohydrates were determined using standard colorimetric assay determination and spectroscopy, enzymatic-gravimetric methods were used for carbohydrate determination (AOAC 991.4317), standard bomb calorimetry methods were used to determine gross energy and β-carotene was determined using standard high-performance liquid chromatography and spectrophotometry methods.
Egg quality and grading: Egg quality was conducted at weeks 0, 2, 4 and 6 using a 120 sub-sample of eggs randomly selected from each treatment (6 eggs/replicate) in the Egg Quality Lab, Prestage Department Poultry Science, NC State University (Raleigh, NC, USA). Egg quality parameters measured included shell strength, vitelline membrane elasticity (VME), vitelline membrane hardness (VMH), vitelline membrane work of penetration (VMW), egg weight, albumen height, Haugh unit (HU), yolk color, shell color and shell thickness. Eggshell strength was determined using a texture analyzer (TA-HDplus) with a 250 kg load cell measuring in grams of force. The TA-HDplus has a trigger force of 0.02 kg and a testing speed of 1 mm sec1. Vitelline membrane strength was determined using the TA.XTplus Texture Analyzer (Stable Micro Systems, Surrey, United Kingdom) with a 1 mm blunt probe with a 5 kg load cell per the manufacturer’s instructions. The trigger force was 0.0001 kg with a 3.2 mm sec1 testing speed. Haugh Unit and albumen height were analyzed using the TSS QCD System (Technical Services and Supplies, Dunnington, York, UK). HU is calculated using the following calculation = 100Log (h-1.7w+7.6), with h = egg albumen height and w = weight of egg, with values ranging from 0-130 and HU scores below 60 for un-fresh eggs18 Yolk color was also determined using the TSS QCD System yolk color scan. Yolk color scan was calibrated using the DSM Yolk Color Fan that determines the color density from lightest to darkest with a range of 1-1519. Shell color was determined using refractometry of black, blue and red wavelengths combined to provide a score from 83.3% (white) to 0% (black). USDA shell egg grading and sizing were conducted on a 120 sub-sample of eggs randomly selected from each treatment group (30 eggs/replicate) once every two weeks.
β-carotene, lipid and fatty acid analysis: At week 0 and week 6, a total of 144 eggs were randomly selected, with 16 eggs per treatment (4 eggs randomly selected per replicate) for lipid content (total cholesterol, crude fat and fatty acid profile) and β-carotene analysis by ATC Scientific using AOAC17 approved methods. Each egg sample was mixed for homogeneity in a Whirl-pak® (Millipore Sigma, St. Louis, MO, USA) bag for 30 sec in a Smasher™ Lab Blender (Weber Scientific, Hamilton, NJ, USA), the homogenous egg sample was pipetted into a 50ml conical tube and frozen at -20°C and stored until analysis within 2 weeks of collection. Frozen homogenous egg samples were shipped on dry ice overnight to vendor for analysis. Total cholesterol, crude fat and fatty acid analysis was conducted using direct methylation methods, as described by Toomer et al.14. Total cholesterol was measured as mg cholesterol/100 g sample weight (feed or egg), while crude fat was measured as a percentage of gram crude fat/gram sample weight (feed or egg). Fatty acid content was measured as a percentage of gram of fatty acid/gram total lipid content of a sample (feed or egg). Methods used to determine β-carotene content in eggs are detailed in the AOAC17 958.05 color of egg yolk method. Egg fat hydrolysis methods were determined using the AOAC17 method 954.02.
Animal welfare statement: The authors confirm that the ethical policies of the journal have been adhered too and the North Carolina State University’s Institutional Animal Care and Use Committee: (#19-761-A) reviewed and approved the policies of the trial.
Statistical analysis: Each treatment replicate (36 hens) served as the experimental unit for all variables (body weights, egg weights, feed intake, total dozens of eggs produced, feed conversion ratio). All performance data were evaluated for significance by one-way analysis of variance (ANOVA) at a significance level of p<0.05 using JMP statistical software (version 15.2.1, SAS, Cary, NC, USA). If ANOVA results were significant (p<0.05), a Tukey’s multiple comparisons t-test was conducted to compare the mean of each treatment group with the mean of every other treatment at p<0.05 significance level. Each egg was used as an experimental unit for analyzing all egg quality measurements (120 eggs per treatment, 30 eggs/replicate at each time point) and egg chemistry data (16 eggs per treatment, 4 eggs/replicate at each time point of collection) including crude fat, total cholesterol, fatty acid profile and β-carotene content.
Dietary treatments and hen performance: Chemical analysis of the experimental diets revealed that diets containing the high-oleic peanuts (HOPN, SWP+HOPN) had higher levels of oleic fatty acid and crude fat relative to the other dietary treatments (Table 2). Dietary levels of calcium and phosphorus of all experimental diets were adequate, meeting the National Research Council20 nutrient requirements for laying hens for calcium (≈2.0% of 2900 kcal kg1 diet) and phosphorus (≈0.35% of 2900 kcal kg1 diet). Moreover, the high-oleic peanut containing diets (HOPN, SWP+HOPN) had the lowest levels of palmitic and stearic saturated fatty acids relative to the other treatment groups. As expected, the experimental diets containing high-oleic peanuts (HOPN, SWP+HOPN) had the highest levels of oleic fatty acids relative to the other diets.
There were no significant treatment differences in body weights at any of the two-week time points measured (Table 3). Hens fed the control-2 (containing soy-protein isolate) and HOPN diets produced significantly more eggs (p<0.01), relative to the other treatment groups over the 6-week feeding trial (Table 4). Interestingly, in this study egg production was not similar between the control groups, with control-1 group producing less eggs than those of the control-2 treatment. Hens fed the SWP+HOPN experimental diet produced the least number of eggs over the 6-week feeding trial.