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Food, fibre and pharmaceuticals from animals
RESEARCH ARTICLE

Performance, digestibility, nitrogen balance and ingestive behaviour of goat kids fed diets supplemented with condensed tannins from Acacia mearnsii extract

Paulo Roberto Silveira Pimentel https://orcid.org/0000-0002-0652-1160 A , Caius Barcellos de Pellegrini A , Jocasta Meira Galvão https://orcid.org/0000-0002-8761-5280 A , Lara Maria Santos Brant https://orcid.org/0000-0002-8454-8895 A , Claudio Vaz Di Mambro Ribeiro https://orcid.org/0000-0002-1729-2359 A , Thadeu Mariniello Silva https://orcid.org/0000-0002-3259-059X A , Analivia Martins Barbosa https://orcid.org/0000-0002-7336-6623 A , Jarbas Miguel da Silva Júnior https://orcid.org/0000-0002-6001-2180 A , Leilson Rocha Bezerra https://orcid.org/0000-0002-8815-3946 B and Ronaldo Lopes Oliveira orcid.org/0000-0001-5887-4753 A C
+ Author Affiliations
- Author Affiliations

A Federal University of Bahia, Department of Animal Science, Av. Adhemar de Barros, 500, Ondina, 40170-110, Salvador, Bahia, Brazil.

B Federal University of Campina Grande, Department of Animal Science, Av. Universitária, Caixa Postal 61, 58700-000, Patos, Paraíba, Brazil.

C Corresponding author. Email: ronaldooliveira@ufba.br

Animal Production Science 61(15) 1534-1545 https://doi.org/10.1071/AN19317
Submitted: 1 June 2019  Accepted: 3 May 2021   Published: 2 June 2021

Abstract

Context: Tannins are phenolic compounds derived from secondary plant metabolism that at moderate levels can limit the excessive degradation of the protein in the rumen and provide greater amino acids availability in the small intestine.

Aims: Two experiments were performed to determine the best level of inclusion of condensed tannins (CT) from Acacia mearnsii extract in the diet of goat kids. An experiment was performed with 32 castrated crossbreed Boer goat kids, with a mean age of 4 months and mean bodyweight (BW) of 19.7 ± 2.05 kg, to measure nutrient intake and performance, and another experiment was developed with 20 Boer goat kids, at 5 months of age and 29.0 ± 2.45 kg BW, in which the digestibility, nitrogen (N) balance, microbial protein synthesis, ingestive behaviour and blood urea N were determined. In both experiments, a completely randomised design was used, including CT levels at 0, 16, 32 and 48 g/kg DM.

Results: DM; crude protein; ether extract; neutral detergent fibre (NDF); non-fibrous carbohydrates and total digestible nutrients intakes, ether extract digestibility; time spent on ruminating, idling or chewing; number of chews per bolus; eating and ruminating rate of DM and NDF; N intake and retained, blood urea N and loin eye area were not affected (P > 0.05) by the addition of CT from A. mearnsii extract in the goat kid diets. However, the NDF g/kg BW and BW0.75 intakes and N faecal excretion showed a linear increase (P < 0.05). There was a linear increase trend (P < 0.1) in time spent eating, and a linear decrease on N urinary excretion by CT from A. mearnsii extract inclusion. The digestibility of DM, crude protein, NDF, non-fibrous carbohydrates and total digestible nutrients exhibited a linear decrease (P < 0.05) by CT from A. mearnsii extract inclusion. There was a quadratic increase (P < 0.05) in synthesis and microbial efficiency, final BW, average daily gain, total gain, gain:feed ratio, and hot and cold carcass weights and yields.

Conclusion: The inclusion of CT from A. mearnsii extract up to 17.7 g/kg DM is recommended, as it improves the synthesis and efficiency of microbial production, increasing the gain:feed ratio and performance of goat kids.

Implications: The use of condensed tannins from A. mearnsii does not affect the nutrient intakes on goat kids’ diet and also improves performance and carcass trait of these animals.

Keywords: animal nutrition, phenolic compounds, protein, ruminants.


References

Abdullah MAM, Farghaly MM, Youssef IMI (2018) Effect of feeding Acacia nilotica pods to sheep on nutrient digestibility, nitrogen balance, ruminal protozoa and rumen enzymes activity. Journal of Animal Physiology and Animal Nutrition 102, 662–669.
Effect of feeding Acacia nilotica pods to sheep on nutrient digestibility, nitrogen balance, ruminal protozoa and rumen enzymes activity.Crossref | GoogleScholarGoogle Scholar | 29363190PubMed |

Aboagye IA, Oba M, Castillo AR, Koenig KM, Iwaasa AD, Beauchemin KA (2018) Effects of hydrolyzable tannin with or without condensed tannin on methane emissions, nitrogen use, and performance of beef cattle fed a high-forage diet. Journal of Animal Science 96, 187
Effects of hydrolyzable tannin with or without condensed tannin on methane emissions, nitrogen use, and performance of beef cattle fed a high-forage diet.Crossref | GoogleScholarGoogle Scholar |

Aguerre MJ, Capozzolo MC, Lencioni P, Cabral C, Wattiaux MA (2016) Effect of quebracho-chestnut tannin extracts at 2 dietary crude protein levels on performance, rumen fermentation, and nitrogen partitioning in dairy cows. Journal of Dairy Science 99, 4476–4486.
Effect of quebracho-chestnut tannin extracts at 2 dietary crude protein levels on performance, rumen fermentation, and nitrogen partitioning in dairy cows.Crossref | GoogleScholarGoogle Scholar | 27060814PubMed |

Alves TP, Dall-Orsoletta AC, Ribeiro-Filho HMN (2017) The effects of supplementing Acacia mearnsii tannin extract on dairy cow dry matter intake, milk production, and methane emission in a tropical pasture. Tropical Animal Health and Production 49, 1663–1668.
The effects of supplementing Acacia mearnsii tannin extract on dairy cow dry matter intake, milk production, and methane emission in a tropical pasture.Crossref | GoogleScholarGoogle Scholar | 28801856PubMed |

AOAC (2012) ‘Official Methods of Analysis of AOAC.’ 19th edn. (Association of Official Analytical Chemistry: Washington, DC)

Belenguer A, Yanez D, Balcells J, Baber NO, Ronquillo MG (2002) Urinary excretion of purine derivatives and prediction of rumen microbial outflow in goats. Livestock Science 77, 127–135.
Urinary excretion of purine derivatives and prediction of rumen microbial outflow in goats.Crossref | GoogleScholarGoogle Scholar |

Bhatta R, Uyeno Y, Tajima K, Takenaka A, Yabumoto Y, Nonaka I, Enishi O, Kurihara M (2009) Difference in the nature of tannins on in vitro ruminal methane and volatile fatty acid production and on methanogenic archaea and protozoal populations. Journal of Dairy Science 92, 5512–5522.
Difference in the nature of tannins on in vitro ruminal methane and volatile fatty acid production and on methanogenic archaea and protozoal populations.Crossref | GoogleScholarGoogle Scholar | 19841214PubMed |

Bohnert DW, Schauer CS, DelCurto T (2002) Influence of rumen protein degradability and supplementation frequency on performance and nitrogen use in ruminants consuming low-quality forage: Cow performance and efficiency of nitrogen use in wethers. Journal of Animal Science 80, 1629–1637.
Influence of rumen protein degradability and supplementation frequency on performance and nitrogen use in ruminants consuming low-quality forage: Cow performance and efficiency of nitrogen use in wethers.Crossref | GoogleScholarGoogle Scholar | 12078745PubMed |

Bryszak M, Szumacher-Strabel M, El-Sherbiny M, Stochmal A, Oleszek W, Roj E, Patra AK, Cieslak A (2019) Effects of berry seed residues on ruminal fermentation, methane concentration, milk production, and fatty acid proportions in the rumen and milk of dairy cows. Journal of Dairy Science 102, 1257–1273.
Effects of berry seed residues on ruminal fermentation, methane concentration, milk production, and fatty acid proportions in the rumen and milk of dairy cows.Crossref | GoogleScholarGoogle Scholar | 30580953PubMed |

Bürger PJ, Pereira JC, Queiroz AC, Silva JFC, Valadares Filho SC, Cecon PR, Casali ADP (2000) Ingestive behavior in Holstein calves fed diets with different concentrate levels. Revista Brasileira de Zootecnia 29, 236–242.

Carulla JE, Kreuzer M, Machmüller A, Hess HD (2005) Supplementation of Acacia mearnsii tannins decreases methanogenesis and urinary nitrogen in forage-fed sheep. Australian Journal of Agricultural Research 56, 961–970.
Supplementation of Acacia mearnsii tannins decreases methanogenesis and urinary nitrogen in forage-fed sheep.Crossref | GoogleScholarGoogle Scholar |

Chen XB, Gomes MJ (1992) ‘Estimation of microbial protein supply to sheep and cattle based on urinary excretion of purine derivatives – an overview of technical details.’ (International Feed Resources Unit: Aberdeen, UK)

Costa CTC, Bevilaqua CML, Morais SM, Vieira LS (2008) Tannins and their use in small ruminants. Revista Brasileira de Plantas Medicinais 10, 108–116.

Costa M, Alves SP, Cappucci A, Cook SR, Duarte A, Caldeira RM, McAllister TA, Bessa RJB (2018) Effects of condensed and hydrolyzable tannins on rumen metabolism with emphasis on the biohydrogenation of unsaturated fatty acids. Journal of Agricultural and Food Chemistry 66, 3367–3377.
Effects of condensed and hydrolyzable tannins on rumen metabolism with emphasis on the biohydrogenation of unsaturated fatty acids.Crossref | GoogleScholarGoogle Scholar | 29494146PubMed |

da Silva CS, de Souza EJ, Pereira GF, Cavalcante EO, de Lima EI, Torres TR, da Silva JR, da Silva DC (2017) Plant extracts as phytogenic additives considering intake, digestibility, and feeding behavior of sheep. Tropical Animal Health and Production 49, 353–359.
Plant extracts as phytogenic additives considering intake, digestibility, and feeding behavior of sheep.Crossref | GoogleScholarGoogle Scholar | 27909913PubMed |

Dallastra LJH, Alves TP, Dal-Pizzol JG, Fonseca BL, Camera M, Raupp GT, Ribeiro-Filho HMN (2018) Tannin extract of Acacia mearnsii for lactating ewes. Semina. Ciências Agrárias 39, 2741–2748.
Tannin extract of Acacia mearnsii for lactating ewes.Crossref | GoogleScholarGoogle Scholar |

Detmann E, Valadares Filho SC (2010) On the estimation of non-fibrous carbohydrates in feeds and diets. Arquivo Brasileiro de Medicina Veterinária e Zootecnia 62, 980–984.
On the estimation of non-fibrous carbohydrates in feeds and diets.Crossref | GoogleScholarGoogle Scholar |

Dijkstra J, Oenema O, Van Groenigen JW, Spek JW, Van Vuuren AM, Bannink A (2013) Diet effects on urine composition of cattle and N 2 O emissions. Animal 7, 292–302.
Diet effects on urine composition of cattle and N 2 O emissions.Crossref | GoogleScholarGoogle Scholar | 23739471PubMed |

Focant M, Froidmont E, Archambeau Q, Van QD, Larondelle Y (2019) The effect of oak tannin (Quercus robur) and hops (Humulus lupulus) on dietary nitrogen efficiency, methane emission, and milk fatty acid composition of dairy cows fed a low-protein diet including linseed. Journal of Dairy Science 102, 1144–1159.
The effect of oak tannin (Quercus robur) and hops (Humulus lupulus) on dietary nitrogen efficiency, methane emission, and milk fatty acid composition of dairy cows fed a low-protein diet including linseed.Crossref | GoogleScholarGoogle Scholar | 30594358PubMed |

Fossati P, Prencipe L, Berti G (1980) Use of 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone chromogenic system in direct enzymic assay of uric acid in serum and urine. Clinical Chemistry 26, 227–231.
Use of 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone chromogenic system in direct enzymic assay of uric acid in serum and urine.Crossref | GoogleScholarGoogle Scholar | 7353268PubMed |

Fujihara T, Ørskov ER, Reeds PJ, Kyle DJ (1987) The effect of protein infusion on urinary excretion of purine derivatives in ruminants nourished by intragastric nutrition. Journal of Agriculture Science 109, 7–12.
The effect of protein infusion on urinary excretion of purine derivatives in ruminants nourished by intragastric nutrition.Crossref | GoogleScholarGoogle Scholar |

García EM, Cherry N, Lambert BD, Muir JP, Nazareno MA, Arroquy JI (2017) Exploring the biological activity of condensed tannins and nutritional value of tree and shrub leaves from native species of the Argentinean Dry Chaco. Journal of the Science of Food and Agriculture 97, 5021–5027.
Exploring the biological activity of condensed tannins and nutritional value of tree and shrub leaves from native species of the Argentinean Dry Chaco.Crossref | GoogleScholarGoogle Scholar | 28417450PubMed |

Gerlach K, Pries M, Tholen E, Schmithausen AJ, Büscher W, Südekum KH (2018) Effect of condensed tannins in rations of lactating dairy cows on production variables and nitrogen use efficiency. Animal 12, 1847–1855.
Effect of condensed tannins in rations of lactating dairy cows on production variables and nitrogen use efficiency.Crossref | GoogleScholarGoogle Scholar | 29306350PubMed |

Getachew G, Pittroff W, Putnam DH, Dandekar A, Goyal S, DePeters EJ (2008) The influence of addition of gallic acid, tannic acid, or quebracho tannins to alfalfa hay on in vitro rumen fermentation and microbial protein synthesis. Animal Feed Science and Technology 140, 444–461.
The influence of addition of gallic acid, tannic acid, or quebracho tannins to alfalfa hay on in vitro rumen fermentation and microbial protein synthesis.Crossref | GoogleScholarGoogle Scholar |

Grainger C, Clarke T, Auldist MJ, Beauchemin KA, McGinn SM, Waghorn GC, Eckard RJ (2009) Potential use of Acacia mearnsii condensed tannins to reduce methane emissions and nitrogen excretion from grazing dairy cows. Canadian Journal of Animal Science 89, 241–251.
Potential use of Acacia mearnsii condensed tannins to reduce methane emissions and nitrogen excretion from grazing dairy cows.Crossref | GoogleScholarGoogle Scholar |

Gxasheka M, Tyasi TL, Qin N, Lyu ZC (2015) An overview of tannins rich plants as alternative supplementation on ruminant animals: A Review. International Journal of Agricultural Research and Review 3, 343–349.

Hackmann TJ, Firkins JL (2015) Maximizing efficiency of rumen microbial protein production. Frontiers in Microbiology 6, 465–471.
Maximizing efficiency of rumen microbial protein production.Crossref | GoogleScholarGoogle Scholar | 26029197PubMed |

Jennings JS, Meyer BE, Guiroy PJ, Cole NA (2018) Energy costs of feeding excess protein from corn-based by-products to finishing cattle. Journal of Animal Science 96, 653–669.
Energy costs of feeding excess protein from corn-based by-products to finishing cattle.Crossref | GoogleScholarGoogle Scholar | 29390094PubMed |

Kiran D, Mutsvangwa T (2010) Effects of partial ruminal defaunation on urea-nitrogen recycling, nitrogen metabolism, and microbial nitrogen supply in growing lambs fed low or high dietary crude protein concentrations. Journal of Animal Science 88, 1034–1047.
Effects of partial ruminal defaunation on urea-nitrogen recycling, nitrogen metabolism, and microbial nitrogen supply in growing lambs fed low or high dietary crude protein concentrations.Crossref | GoogleScholarGoogle Scholar | 19966167PubMed |

Kononoff PJ, Heinrichs AJ, Buckmaster DR (2003) Modification of the Penn State forage and total mixed ration particle separator and the effects of moisture content on its measurements. Journal of Dairy Science 86, 1858–1863.
Modification of the Penn State forage and total mixed ration particle separator and the effects of moisture content on its measurements.Crossref | GoogleScholarGoogle Scholar | 12778598PubMed |

Kozloski GV, Härter CJ, Hentz F, Ávila SC, Orlandi T, Stefanello CM (2012) Intake, digestibility and nutrients supply to wethers fed ryegrass and intraruminally infused with levels of Acacia mearnsii tannin extract. Small Ruminant Research 106, 125–130.
Intake, digestibility and nutrients supply to wethers fed ryegrass and intraruminally infused with levels of Acacia mearnsii tannin extract.Crossref | GoogleScholarGoogle Scholar |

Lammers BP, Buckmaster DR, Heinrichs AJ (1996) A simple method for the analysis of particle sizes of forage and total mixed rations. Journal of Dairy Science 79, 922–928.
A simple method for the analysis of particle sizes of forage and total mixed rations.Crossref | GoogleScholarGoogle Scholar | 8792291PubMed |

Licitra G, Hernandez TM, Van Soest PJ (1996) Standartization of procedures for nitrogen fractionation of ruminants feeds. Animal Feed Science and Technology 57, 347–358.
Standartization of procedures for nitrogen fractionation of ruminants feeds.Crossref | GoogleScholarGoogle Scholar |

Makkar HPS (2003) Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds. Small Ruminant Research 49, 241–256.
Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds.Crossref | GoogleScholarGoogle Scholar |

Martin P, Bateson P (1993) ‘Measuring behaviour.’ 2nd edn. (Cambridge University Press: Cambridge, UK)

Martin AK, Blaxter KL (1965) The energy cost of urea synthesis in sheep. In ‘Proceedings of the 3rd Symposium on Energy Metabolism’ pp. 83–91. (Academic Press, London, UK)

Mezzomo R, Paulino PVR, Detmann E, Valadares Filho SC, Paulino MF, Monnerat JPIS, Duarte MS, Silva LHP, Moura LS (2011) Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet. Livestock Science 141, 1–11.
Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet.Crossref | GoogleScholarGoogle Scholar |

Mezzomo R, Paulino PVR, Barbosa MM, da Silva Martins T, Paulino MF, Alves KS, Gomes DI, dos Santos Monnerat JPI (2016) Performance and carcass characteristics of young cattle fed with soybean meal treated with tannins. Animal Science Journal 87, 775–782.
Performance and carcass characteristics of young cattle fed with soybean meal treated with tannins.Crossref | GoogleScholarGoogle Scholar | 26355192PubMed |

Min BR, Solaiman S, Gurung N, Behrends J, Eun JS, Taha E, Rose J (2012) Effects of pine bark supplementation on performance, rumen fermentation, and carcass characteristics of Kiko crossbred male goats. Journal of Animal Science 90, 3556–3567.
Effects of pine bark supplementation on performance, rumen fermentation, and carcass characteristics of Kiko crossbred male goats.Crossref | GoogleScholarGoogle Scholar | 22851241PubMed |

Molina-Botero IC, Montoya-Flores MD, Zavala-Escalante LM, Barahona-Rosales R, Arango J, Ku-Vera JC (2019) Effects of long-term diet supplementation with Gliricidia sepium foliage mixed with Enterolobium cyclocarpum pods on enteric methane, apparent digestibility, and rumen microbial population in crossbred heifers. Journal of Animal Science 97, 1619–1633.
Effects of long-term diet supplementation with Gliricidia sepium foliage mixed with Enterolobium cyclocarpum pods on enteric methane, apparent digestibility, and rumen microbial population in crossbred heifers.Crossref | GoogleScholarGoogle Scholar | 30785622PubMed |

Mueller‐Harvey I (2006) Unravelling the conundrum of tannins in animal nutrition and health. Journal of the Science of Food and Agriculture 86, 2010–2037.
Unravelling the conundrum of tannins in animal nutrition and health.Crossref | GoogleScholarGoogle Scholar |

Muscher AS, Schröder B, Breves G, Huber K (2010) Dietary nitrogen reduction enhances urea transport across goat rumen epithelium. Journal of Animal Science 88, 3390–3398.
Dietary nitrogen reduction enhances urea transport across goat rumen epithelium.Crossref | GoogleScholarGoogle Scholar | 20581287PubMed |

Naumann HD, Tedeschi LO, Zeller WE, Huntley NF (2017) The role of condensed tannins in ruminant animal production: advances, limitations and future directions. Revista Brasileira de Zootecnia 46, 929–949.
The role of condensed tannins in ruminant animal production: advances, limitations and future directions.Crossref | GoogleScholarGoogle Scholar |

NRC (2007) ‘Nutrient Requirements of Small Ruminants: Sheep, Goats, Cervids and New World Camelids.’ (National Academic Press: Washington, DC)

Orlandi T, Kozloski GV, Alves TP, Mesquita FR, Ávila SC (2015) Digestibility, ruminal fermentation and duodenal flux of amino acids in steers fed grass forage plus concentrate containing increasing levels of Acacia mearnsii tannin extract. Animal Feed Science and Technology 210, 37–45.
Digestibility, ruminal fermentation and duodenal flux of amino acids in steers fed grass forage plus concentrate containing increasing levels of Acacia mearnsii tannin extract.Crossref | GoogleScholarGoogle Scholar |

Patra AK, Saxena J (2011) Exploitation of dietary tannins to improve rumen metabolism and ruminant nutrition. Journal of the Science of Food and Agriculture 91, 24–37.
Exploitation of dietary tannins to improve rumen metabolism and ruminant nutrition.Crossref | GoogleScholarGoogle Scholar | 20815041PubMed |

Patra AK, Dutta N, Pattanaik AK, Chaturvedi VB, Sharma K (2017) Effect of condensed tannins from Ficus infectoria and Psidium guajava leaf meal mixture on nutrient metabolism, methane emission and performance of lambs. Asian-Australasian Journal of Animal Science 30, 1702–1710.

Perna F, Cassiano ECO, Martins MF, Romero LA, Zapata DCV, Pinedo LA, Marino CT, Rodrigues PHM (2017) Effect of tannins-rich extract from Acacia mearnsii or monensin as feed additives on ruminal fermentation efficiency in cattle. Livestock Science 203, 21–29.
Effect of tannins-rich extract from Acacia mearnsii or monensin as feed additives on ruminal fermentation efficiency in cattle.Crossref | GoogleScholarGoogle Scholar |

Recktenwald EB, Ross DA, Fessenden SW, Wall CJ, Van Amburgh ME (2014) Urea-N recycling in lactating dairy cows fed diets with 2 different levels of dietary crude protein and starch with or without monensin. Journal of Dairy Science 97, 1611–1622.
Urea-N recycling in lactating dairy cows fed diets with 2 different levels of dietary crude protein and starch with or without monensin.Crossref | GoogleScholarGoogle Scholar | 24377801PubMed |

Røjen BA, Theil PK, Kristensen NB (2011) Effects of nitrogen supply on inter-organ fluxes of urea-N and renal urea-N kinetics in lactating Holstein cows. Journal of Dairy Science 94, 2532–2544.
Effects of nitrogen supply on inter-organ fluxes of urea-N and renal urea-N kinetics in lactating Holstein cows.Crossref | GoogleScholarGoogle Scholar | 21524545PubMed |

Smith AH, Zoetendal E, Mackie RI (2005) Bacterial mechanisms to overcome inhibitory effects of dietary tannins. Microbial Ecology 50, 197–205.
Bacterial mechanisms to overcome inhibitory effects of dietary tannins.Crossref | GoogleScholarGoogle Scholar | 16222487PubMed |

Sniffen CJ, O’ Connor JD, Van Soest PJ (1992) A net carbohydrate and protein system for evaluating cattle diets: II, Carbohydrate and protein availability. Journal of Animal Science 70, 3562–3577.
A net carbohydrate and protein system for evaluating cattle diets: II, Carbohydrate and protein availability.Crossref | GoogleScholarGoogle Scholar | 1459919PubMed |

Souza CM, Oliveira RL, Voltolini TV, Menezes DR, dos Santos NJA, Barbosa AM, Silva TM, Pereira ES, Bezerra LR (2018) Lambs fed cassava silage with added tamarind residue: Silage quality, intake, digestibility, nitrogen balance, growth performance and carcass quality. Animal Feed Science and Technology 235, 50–59.
Lambs fed cassava silage with added tamarind residue: Silage quality, intake, digestibility, nitrogen balance, growth performance and carcass quality.Crossref | GoogleScholarGoogle Scholar |

Starke S, Muscher AS, Hirschhausen N, Pfeffer E, Breves G, Huber K (2012) Expression of urea transporters is affected by dietary nitrogen restriction in goat kidney. Journal of Animal Science 90, 3889–3897.
Expression of urea transporters is affected by dietary nitrogen restriction in goat kidney.Crossref | GoogleScholarGoogle Scholar | 22665662PubMed |

Statistical Analysis Software ‘SAS/STAT (2003) User’s Guide: Basics.’ (SAS Institute: Cary, NC)

Theodoridou K, Aufrère J, Andueza D, Pourrat J, Le Morvan A, Stringano E, Mueller-Harvey I, Baumont R (2010) Effects of condensed tannins in fresh sainfoin (Onobrychis viciifolia) on in vivo and in situ digestion in sheep. Animal Feed Science and Technology 160, 23–38.
Effects of condensed tannins in fresh sainfoin (Onobrychis viciifolia) on in vivo and in situ digestion in sheep.Crossref | GoogleScholarGoogle Scholar |

Van Soest PJ, Robertson JB, Lewis BA (1991) Method for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74, 3583–3597.
Method for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition.Crossref | GoogleScholarGoogle Scholar | 1660498PubMed |

Ventura-Cordero J, Sandoval-Castro CA, Torres-Acosta JFJ, Capetillo-Leal CM (2017) Do goats have a salivary constitutive response to tannins? Journal of Applied Animal Research 45, 29–34.
Do goats have a salivary constitutive response to tannins?Crossref | GoogleScholarGoogle Scholar |

Waghorn G (2008) Beneficial and detrimental effects of dietary condensed tannins for sustainable sheep and goat production—Progress and challenges. Animal Feed Science and Technology 147, 116–139.
Beneficial and detrimental effects of dietary condensed tannins for sustainable sheep and goat production—Progress and challenges.Crossref | GoogleScholarGoogle Scholar |

Yang WZ, Beauchemin KA (2007) Altering physically effective fiber intake through forage proportion and particle length: Chewing and ruminal pH. Journal of Dairy Science 90, 2826–2838.
Altering physically effective fiber intake through forage proportion and particle length: Chewing and ruminal pH.Crossref | GoogleScholarGoogle Scholar | 17517723PubMed |

Zhao XH, Zhang T, Xu M, Yao JH (2011) Effects of physically effective fiber on chewing activity, ruminal fermentation, and digestibility in goats. Journal of Animal Science 89, 501–509.
Effects of physically effective fiber on chewing activity, ruminal fermentation, and digestibility in goats.Crossref | GoogleScholarGoogle Scholar | 20935139PubMed |