Body weight and sex effects on digesta mean retention time in growing Saanen goats

Marcelo Gindri; Rafael Fernandes Leite; Carla Joice Härter; Simone Pedro da Silva; Normand St-Pierre; Márcia Helena Machado da Rocha Fernandes; Telma Teresinha Berchielli; Izabelle Auxiliadora Molina de Almeida Teixeira

doi:10.1093/tas/txaa028

Body weight and sex effects on digesta mean retention time in growing Saanen goats

Transl Anim Sci. 2020 Mar 18;4(2):txaa028. doi: 10.1093/tas/txaa028. eCollection 2020 Apr.

Authors

Marcelo Gindri¹, Rafael Fernandes Leite¹, Carla Joice Härter¹, Simone Pedro da Silva¹, Normand St-Pierre², Márcia Helena Machado da Rocha Fernandes¹, Telma Teresinha Berchielli¹, Izabelle Auxiliadora Molina de Almeida Teixeira¹

Affiliations

¹ Department of Animal Sciences, Universidade Estadual Paulista, Jaboticabal, SP, Brazil.
² Perdue AgriBusiness LLC, Salisbury, MD.

Abstract

Despite the important role of digesta mean retention time (MRT) on digestive efficiency of ruminants, it is poorly investigated in total gastrointestinal tract (GIT) of growing ruminants, especially in goats. The objective of this study was to evaluate the effect of body weight (BW) and sex on GIT MRT of particles and solutes in growing Saanen goats. A dataset from two studies, comprising 103 individual records of castrated males (n = 36), females (n = 34), and intact males (n = 33) Saanen goats slaughtered at 15, 22, 30, 37, and 45 kg BW, was used. Goats were fed basically with total mixed ration composed by dehydrated corn plant (Zea mays) milled to pass a 10-mm screen, cracked corn grain, and soybean (Glycine max) meal. Variables evaluated were BW, feed intake, feed intake level, composition of ingested diet, wet weight of GIT tissues, wet digesta pool size, digesta composition (dry matter and neutral detergent fiber [NDF]), indigestible NDF:NDF ratio of ingested diet and GIT digesta, MRT of particles (MRT_iNDF) and solutes (MRT_Cr), and reticulorumen selectivity factors (large particles/solutes). Reticulorumen, omasum, abomasum, small intestine, cecum, and colon-rectum segments were evaluated. The dataset was analyzed as mixed models considering sex, BW, and sex × BW interaction as fixed effects, and study and residual error as random effects. Sex did not affect MRT_iNDF in any GIT segments. Females and intact males presented similar reticulorumen MRT_Cr (5.6 h; P = 0.92) and they presented lower reticulorumen MRT_Cr than castrated males (7.0; P ≤ 0.04). Total GIT MRT_Cr was similar between castrated males and females (15.7 h; P = 0.11) and between females and intact males (14.2 h; P = 0.76). Body weight (BW) did not affect MRT_iNDF in reticulorumen and colon-rectum and total GIT MRT_Cr (P ≥ 0.11). Reticulorumen and omasum MRT_Cr increased as BW increased (P < 0.01), and abomasum MRT_Cr decreased as BW increased (P = 0.02). Feed intake, and wet tissues and wet pool size of all GIT segments increased as BW increased, except abomasum wet pool size (P ≤ 0.01). The mechanism related to sex effect on MRT has to be elucidated. Reticulorumen MRT_iNDF and total GIT MRT_Cr were modulated by intake and capacity of reticulorumen and GIT, respectively. On the other hand, reticulorumen MRT_Cr seemed to be regulated by reticulo-omasal orifice opening and saliva secretion.

Keywords: dairy goat; digesta kinetic; digesta washing; gastrointestinal tract fill; sorting mechanism.