{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T04:19:44Z","timestamp":1784693984038,"version":"3.55.0"},"reference-count":89,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T00:00:00Z","timestamp":1780012800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000976","name":"Australia Eggs","doi-asserted-by":"publisher","award":["INNO020"],"award-info":[{"award-number":["INNO020"]}],"id":[{"id":"10.13039\/501100000976","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>This study evaluated the effects of arginine (Arg), guanidinoacetic acid (GAA), and citrulline (Cit) supplementation in reduced protein (RP) diets on the production performance, serum uric acid level and bone quality of aged laying hens. A total of 208 Hy-Line Brown laying hens from 60 to 75 weeks of age were assigned to eight dietary treatments, with 13 replicate cages per treatment and two hens per cage. Experimental diets comprised two protein levels (standard protein at 15.8% crude protein versus RP at 13.8% crude protein), and six RP diets supplemented with two inclusion levels (0.06% and 0.12%) of Arg, GAA, or Cit. Overall, increasing Cit supplementation improved productive performance compared with Arg and GAA, particularly by increasing egg weight (p = 0.048), egg mass (p = 0.019), and feed intake (p = 0.014) over the entire experimental period. In addition, Cit increased egg weight during 60\u201367 weeks (p = 0.049) and improved egg mass during 68\u201375 weeks (p = 0.014). Furthermore, supplementation of 0.12% Cit in RP diets significantly increased feed intake compared with standard protein (SP) and RP diets from 60 to 67 weeks (p &lt; 0.001; one-way ANOVA). Both Cit and Arg supplementation increased yolk weight compared to GAA (p = 0.018). Further, Arg supplementation to the RP diet at 0.06% significantly increased energy digestibility compared to the SP and RP diets (p = 0.037). Increasing Arg and GAA levels reduced bone breaking strength compared with their respective low levels, whereas increasing Cit level enhanced tibia (p = 0.014) and femur (p = 0.006) bone breaking strength. Low-level GAA supplementation also increased tibia breaking strength. Thus, a moderate reduction in dietary protein level by two percentage points, combined with Cit supplementation at the high level (0.12%), was effective in enhancing egg mass, egg weight, yolk weight, and bone breaking strength in aged laying hens. These findings suggest that RP feeding strategies supplemented with functional Arg precursors may support productive efficiency, skeletal health, and nutrient utilization in late-lay hens.<\/jats:p>","DOI":"10.3390\/ani16111664","type":"journal-article","created":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T15:57:18Z","timestamp":1780070238000},"page":"1664","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["The Effects of Arginine, Guanidinoacetic Acid and Citrulline Supplementation to Reduced Protein Diets for Aged Laying Hens"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-4769-381X","authenticated-orcid":false,"given":"Aamir","family":"Nawab","sequence":"first","affiliation":[{"name":"School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, NSW 2351, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3093-1207","authenticated-orcid":false,"given":"Thi Hiep","family":"Dao","sequence":"additional","affiliation":[{"name":"School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, NSW 2351, Australia"},{"name":"Faculty of Animal Science, Vietnam National University of Agriculture, Gia Lam District, Trau Quy Town, Hanoi 100000, Vietnam"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sukirno","family":"Sukirno","sequence":"additional","affiliation":[{"name":"School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, NSW 2351, Australia"},{"name":"Faculty of Animal Science, University of Mataram, Jl. Majapahit 62, Mataram 83125, Lombok, Nusa Tenggara Barat, Indonesia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8264-3012","authenticated-orcid":false,"given":"Nasima","family":"Akter","sequence":"additional","affiliation":[{"name":"School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, NSW 2351, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eunjoo","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia"},{"name":"Poultry Research Foundation, The University of Sydney, Camden, NSW 2570, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3698-8917","authenticated-orcid":false,"given":"Tamsyn M.","family":"Crowley","sequence":"additional","affiliation":[{"name":"Poultry Hub Australia, University of New England, Armidale, NSW 2351, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8647-8448","authenticated-orcid":false,"given":"Amy F.","family":"Moss","sequence":"additional","affiliation":[{"name":"School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, NSW 2351, Australia"},{"name":"Poultry Hub Australia, University of New England, Armidale, NSW 2351, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"104852","DOI":"10.1016\/j.psj.2025.104852","article-title":"Recent advances in protein and amino acid nutritional dynamics in relation to performance, health, welfare, and cost of production","volume":"104","author":"Adhikari","year":"2025","journal-title":"Poult. 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