Based on the assumption that dietary and faecal nitrogen correlate, the number of studies using faecal samples collected in the wild to understand diet selection by wild herbivores and other ecological patterns has been growing during the last years, especially due to the recent development of cheap tools for analysis of nutrients like Near-Infrared Reflectance Spectroscopy (NIRS). Within the annual reproductive cycle, cervids (members of the family Cervidae) face strong seasonal variations in nutritional demands, different for hinds (gestation and lactation) and stags (antler growth) and reflected in differential patterns of seasonal diet selection. In this study we aimed to quantify how pasture availability, season and individual factors like sex, age, reproductive status, body mass and body condition affect faecal nutrients in captive red deer with the goal of understanding how these factors may influence the interpretation of results from samples obtained in the wild with little or no information about the animals who dropped those faeces. We used NIRS for analysing nitrogen, neutral and acid detergent fibres in faeces. The relative influence of some individual factors like pregnancy was low (around 4%), while age and weight may induce a variability up to 18%. The presence or absence of pasture contributed to a variability around 13%, while the season contributed to an average variability around 17% (and up to 21% in certain situations). This high variability in faecal nutrients was observed in a controlled setting with captive animals and controlled diets. Thus, in natural situations we suspect that there would be even greater variation. According to the results, we recommend that preliminary research with captive animals of the species of interest should be conducted before collecting samples in the wild, which should help in the interpretation of results.

Department of Animal Science and Food Processing Faculty of Tropical AgriSciences Czech University of Life Sciences Prague Czech Republic

Department of Game Management and Wildlife Biology Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Czech Republic

Department of Science and Agroforestry Technology and Genetics ETSIAM University of Castilla La Mancha Albacete Spain

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Dixon R, Coates D. Near infrared spectroscopy of faeces to evaluate the nutrition and physiology of herbivores. J. Near Infrared Spectrosc. 2009;17:1–31. doi: 10.1255/jnirs.822. DOI

Holechek JL, Vavra M, Arthun D. Relationships between performance, intake, diet nutritive quality and fecal nutritive quality of cattle on mountain range. J. Range Manag. 1982;35:741–744. doi: 10.2307/3898253. DOI

Leslie DM, Starkey EE. Fecal indices to dietary quality of cervids in old-growth forests. J. Wildl. Manag. 1985;49:142–146. doi: 10.2307/3801860. DOI

Leslie DM, Jr, Bowyer RT, Jenks JA. Facts from feces: nitrogen still measures up as a nutritional index for mammalian herbivores. J. Wildl. Manag. 2008;72:1420–1433. doi: 10.2193/2007-404. DOI

Hamel S, Garel M, Festa-Bianchet M, Gaillard JM, Côté SD. Spring normalized difference vegetation index (NDVI) predicts annual variation in timing of peak faecal crude protein in mountain ungulates. J. Appl. Ecol. 2009;46:582–589. doi: 10.1111/j.1365-2664.2009.01643.x. DOI

Van Soest PJ. Nutritional Ecology of the Ruminant. Ithaca: Cornell University Press; 2018.

Jancik F, Homolka P, Cermak B, Lád F. Determination of indigestible neutral detergent fibre contents of grasses and its prediction from chemical composition. Czech J. Anim. Sci. 2008;53:128–135. doi: 10.17221/2716-CJAS. DOI

Kay RNB, Staines BW. The nutrition of the red deer (Cervus elaphus) Nutr. Abstr. Rev. 1981;51:601–622.

Palacios F, Martínez T, Garzon-Heydt P. Data on the autumn diet of the red deer (Cervus elaphus L. 1758) in the Montes de Toledo (Central Spain) Doñana, Acta Vertebrata. 1989;16:157–163.

Alvarez G, Martínez T, Martínez E. Winter diet of red deer stag (Cervus elaphus L.) and its relationship to morphology and habitat in central Spain. Folia Zool. 1991;40:117–130.

García-González R, Cuartas P. Food habits of Capra pyrenaica, Cervus elaphus and Dama dama in the Cazorla Sierra (Spain) Mammalia. 1992;56:195–202. doi: 10.1515/mamm-1992-0203. DOI

Bugalho MN, Milne JA, Racey PA. The foraging ecology of red deer (Cervus elaphus) in a Mediterranean environment: is a larger body size advantageous? J. Zool. 2001;255:285–289. doi: 10.1017/S0952836901001376. DOI

Perea R, Girardello M, San Miguel A. Big game or big loss High deer densities are threatening woody plant diversity and vegetation dynamics. Biodivers. Conserv. 2014;23:1303–1318. doi: 10.1007/s10531-014-0666-x. DOI

Ceacero F, et al. Why do cervids feed on aquatic vegetation? Behav. Proc. 2014;103:28–34. doi: 10.1016/j.beproc.2013.10.008. PubMed DOI

Gambín P, Ceacero F, Garcia AJ, Landete-Castillejos T, Gallego L. Patterns of antler consumption reveal osteophagia as a natural mineral resource in key periods for red deer (Cervus elaphus) Eur. J. Wildl. Res. 2017;63:39. doi: 10.1007/s10344-017-1095-4. DOI

García AJ, Landete-Castillejos T, Garde JJ, Gallego L. Reproductive seasonality in female Iberian red deer (Cervus elaphus hispanicus) Theriogenology. 2002;58:1553–1562. doi: 10.1016/S0093-691X(02)01048-8. PubMed DOI

Oftedal OT. Pregnancy and lactation. Bioenerget. Wild Herbivores. 1985;10:215–238.

Bronson FH. Mammalian Reproductive Biology. Chicago, IL: University of Chicago Press; 1989.

Carrión D, García AJ, Gaspar-López E, Landete-Castillejos T, Gallego L. Development of body condition in hinds of Iberian red deer during gestation and its effects on calf birth weight and milk production. J. Exp. Zool. Part A: Ecol. Genet. Physiol. 2008;309:1–10. PubMed

Landete-Castillejos T, et al. Milk production and composition in captive Iberian red deer (Cervus elaphus hispanicus): effect of birth date. J. Anim. Sci. 2000;78:2771–2777. doi: 10.2527/2000.78112771x. PubMed DOI

Dryden GM. Nutrition of antler growth in deer. Anim. Prod. Sci. 2016;56:962–970. doi: 10.1071/AN15051. DOI

Asleson MA, Hellgren EC, Varner LW. Nitrogen requirements for antler growth and maintenance in white-tailed deer. J. Wildl. Manag. 1996;60:744–752. doi: 10.2307/3802373. DOI

Ceacero F, García AJ, Landete-Castillejos T, Bartošová J, Bartoš L, Gallego L. Benefits for dominant red deer hinds under a competitive feeding system: food access behavior, diet and nutrient selection. PLoS ONE. 2012;7:e32780. doi: 10.1371/journal.pone.0032780. PubMed DOI PMC

Ceacero F, et al. Habituating to handling: factors affecting pre-orbital gland opening in red deer calves. J. Anim. Sci. 2014;92:4130–4136. doi: 10.2527/jas.2014-7716. PubMed DOI

Audigé L, Wilson PR, Morris RS. A body condition score system and its use for farmed red deer hinds. N.Z. J. Agric. Res. 1998;41:545–553. doi: 10.1080/00288233.1998.9513337. DOI

Foley WJ, et al. Ecological applications of near infrared reflectance spectroscopy—a tool for rapid, cost-effective prediction of the composition of plant and animal tissues and aspects of animal performance. Oecologia. 1998;116:293–305. doi: 10.1007/s004420050591. PubMed DOI

Kamler J, Homolka M, Čižmár D. Suitability of NIRS analysis for estimating diet quality of free-living red deer Cervus elaphus and roe deer Capreolus capreolus. Wildl. Biol. 2004;10:235–240. doi: 10.2981/wlb.2004.021. DOI

Showers SE, Tolleson DR, Stuth JW, Kroll JC, Koerth BH. Predicting diet quality of white-tailed deer via NIRS fecal profiling. Rangel. Ecol. Manag. 2006;59:300–307. doi: 10.2111/04-069.1. DOI

Dryden G. Near Infrared Spectroscopy: Applications in Deer Nutrition. Barton: RIRDC Pub (W03/007); 2003.

Norris KH, Barnes RF, Moore JE, Shenk JS. Predicting forage quality by infrared reflectance spectroscopy. J. Anim. Sci. 1976;43:889–897. doi: 10.2527/jas1976.434889x. DOI

Hruschka WR. Data analysis: wavelength selection methods. In: Williams P, Norris K, editors. Near-Infrared Technology in the Agricultural and Food Industries. St. Paul, MN: American Association of Cereal Chemist; 1987. pp. 35–55.

Holá M, Ježek M, Kušta T, Červený J. Evaluation of winter food quality and its variability for red deer in forest environment: overwintering enclosures vs. free-ranging areas. For. J. 2016;62:139–145.

Otles, S. & Ozyurt, V.H. Classical Wet Chemistry Methods 6. Handbook of Food Chemistry, 133 (2015).

ASAB. Guidelines for the treatment of animals in behavioural research and teaching. Anim. Behav. 83, 301–309 (2012).

Holechek JL, Vavra M, Pieper RD. Botanical composition determination of range herbivore diets: a Review. J. Rangel. Manag. 1982;35:309–315. doi: 10.2307/3898308. DOI

Robbins CT. Wildlife Feeding and Nutrition. 2. San Diego, CA: Academic Press; 1993.

Hodgman TP, Davitt BB, Nelson JR. Monitoring mule deer diet quality and intake with fecal indices. J. Rangel. Manag. 1996;49:215–222. doi: 10.2307/4002881. DOI

Kamler J, Homolka M, Kracmar S. Nitrogen characteristics of ungulates faeces: effect of time of exposure and storage. Folia Zool. 2003;52:31–38.

Hobbs NT. Fecal indices to dietary quality: a critique. J. Wildl. Manag. 1987;51:317–320. doi: 10.2307/3801008. DOI

Barbehenn RV, Constabel CP. Tannins in plant–herbivore interactions. Phytochemistry. 2011;72:1551–1565. doi: 10.1016/j.phytochem.2011.01.040. PubMed DOI

Staines BW, Crisp JM, Parish T. Differences in the quality of food eaten by red deer (Cervus elaphus) stags and hinds in winter. J. Appl. Ecol. 1982;19:65–77. doi: 10.2307/2402991. DOI

Dryden GM. Quantitative nutrition of deer: energy, protein and water. Anim. Prod. Sci. 2011;51:292–302. doi: 10.1071/AN10176. DOI

Thompson DP, Barboza PS. Seasonal energy and protein requirements for Siberian reindeer (Rangifer tarandus) J. Mammal. 2017;98:1558–1567. doi: 10.1093/jmammal/gyx132. DOI

Hungate RE. The Rumen and Its Microbes. New York: Academic Press; 1966.

Timmons GR, Hewitt DG, Deyoung CA, Fulbright TE, Draeger DA. Does supplemental feed increase selective foraging in a browsing ungulate? J. Wildl. Manag. 2010;74:995–1002. doi: 10.2193/2009-250. DOI

Gaspar-López E, Landete-Castillejos T, Estevez JA, Ceacero F, Gallego L. Biometrics, testosterone, cortisol and antler growth cycle in Iberian red deer stags (Cervus elaphus hispanicus) Reprod. Domest. Anim. 2010;45:243–249. doi: 10.1111/j.1439-0531.2008.01271.x. PubMed DOI

Bruinderink GG, Hazebroek E. Ingestion and diet composition of red deer (Cervus elaphus L.) in the Netherlands from 1954 till 1992. Mammalia. 1995;59:187–196.

Moen AN. Wildlife Ecology: An Analytical Approach. San Francisco, CA: WH Freeman; 1973.

Jenks JA, Leslie DM, Jr, Lochmiller RL, Melchiors MA. Variation in gastrointestinal characteristics of male and female white-tailed deer: implications for resource partitioning. J. Mammal. 1994;75:1045–1053. doi: 10.2307/1382488. DOI

Zimmerman TJ, Jenks JA, Leslie DM., Jr Gastrointestinal morphology of female white-tailed and mule deer: effects of fire, reproduction, and feeding type. J. Mammal. 2006;87:598–605. doi: 10.1644/05-mamm-A-356R1.1. DOI

Monteith KB, Monteith KL, Bowyer RT, Leslie DM, Jr, Jenks JA. Reproductive effects on fecal nitrogen as an index of diet quality: an experimental assessment. J. Mammal. 2014;95:301–310. doi: 10.1644/12-MAMM-A-306.1. DOI

Barboza PS, Parker KL. Allocating protein to reproduction in arctic reindeer and caribou. Physiol. Biochem. Zool. 2008;81:835–855. doi: 10.1086/590414. PubMed DOI

Schwarm A, et al. No easy solution for the fractionation of faecal nitrogen in captive wild herbivores: results of a pilot study. J. Anim. Physiol. Anim. Nutr. 2009;93:596–605. doi: 10.1111/j.1439-0396.2008.00842.x. PubMed DOI

Gross JE, Alkon PU, Demment MW. Nutritional ecology of dimorphic herbivores: digestion and passage rates in Nubian ibex. Oecologia. 1996;107:170–178. doi: 10.1007/BF00327900. PubMed DOI

Gómez JA, et al. Factors affecting antler investment in yearlings, subadults and adults of Iberian deer. Anim. Prod. Sci. 2012;52:867–873. doi: 10.1071/AN11316. DOI

Villamuelas M, et al. Predicting herbivore faecal nitrogen using a multispecies near-infrared reflectance spectroscopy calibration. PLoS ONE. 2017;12:e0176635. doi: 10.1371/journal.pone.0176635. PubMed DOI PMC

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