Rumen morphometry and sorting behavior of fattening male goat fed pelleted and unpelleted TMR with two levels of wheat straw

•Goats showed preference for short and medium particles.•Sorting behavior was influenced by straw level, higher straw level provided greater opportunities for feed selection.•Pelleted TMR with 15 % wheat straw increased rumen papillae length, width and surface area.•Pelleted TMR could be a feeding intervention to prevent feed sorting and to improve rumen papillae length, density and surface area.•Thickness of stratum corneum was higher and color of rumen and reticulum mucosa was darker in those fed pelleted TMR. The physical form of the diet and level of straw in fattening total mixed rations (TMR) can influence sorting behavior and rumen morphometry. Therefore, the objectives of this experiment were to evaluate two levels of wheat straw (WS) in conventional and pelleted TMR on feed sorting behavior, rumen morphometry, the thickness of stratum corneum (SC), and color of reticulorumen mucosa. Thirty-two Beetle male goats (8 goats/treatment) were assigned to one of the four treatments in a 2 × 2 factorial arrangement: CTMR15 and CTMR 25 (conventional TMR containing 15 and 25 % WS, respectively), the PTMR15 and PTMR25 (pelleted TMR containing 15 and 25 % WS, respectively). In PTMR, the WS was ground to 8 mm and then pelleted. Feed sorting behavior of goats fed conventional TMR was evaluated twice weekly using Penn State Particle Separator (PSPS). At the end of the experiment, goats (n = 8/treatment) were slaughtered and rumen tissues preserved for further rumen morphometric examination. The CTMR25 fed goats consumed more medium (< 19,> 8 mm) and short (> 1.18) particles. There was a significant interaction (P < 0.05) between physical form (PF) of the diet and straw level (SL) for papillae length (PL), papillae density (PD), and surface area. The PL was greater (P < 0.05) in PTMR15 and PTMR25 compared with CTMR15 and CTMR25. Additionally, PD and surface area were higher (P < 0.05) in PTMR15 than the rest of the treatments. However, the papillae width (PW) was not affected (P> 0.05) by the PF or the SL in the diet. The thickness of stratum corneum (SC) (18.55 μm) was highest (P < 0.05) in the PTMR15 compared with the PTMR25, CTMR15, and CTMR25. Lightness (L*), redness (a*), and yellowness (b*) values for reticulorumen mucosa color were greater (P < 0.05) in CTMR15 and CTMR25 than PTMR25 and PTMR15. In conclusion, fattening goats fed on conventional TMR selected for medium and short fiber particles. Feeding PTMR15 resulted in a greater PL, PD; however, a thicken