Apparent diet digestibility and morphometric measurements of ruminal papillae of water buffaloes finished in feedlot

The objective of this study was to evaluate the relationship between parameters of apparent diet digestibility and morphometric measurements of ruminal papillae of water buffaloes (Bubalus bubalis) finished in feedlot. Sixty-five non-castrated males (BW and mean age of 314 ± 117 kg and 390 ± 58 d, respectively) were used. The animals were allocated in collective pen and received a diet based on corn silage (30%), milled grain (53.19%), cotton meal (12.99%), urea (0.76%) calcitic lime (0.75%) and mineral salt (2.24%). Diet was offered into automatic feeder system (Intergado®, MG, Brazil) with ad libitum access. Animal DMI and ADG were recorded. In order to estimate the apparent digestibility of nutrients (DM, CP, NDF, ADF, TDN and OM), fecal collection was used to calculate fecal excretion from the internal indigestible neutral detergent fiber marker (iNDF). A fragment (1-cm², approximately) of each rumen from cranial sac (atrium ruminis) was collected for the study of macroscopic morphological variables such as: number of papillae (NOP; n/cm² of rumen wall); papillae surface area (PSA; mm²); papillae width (W); papillae length (L); absorptive surface area (ASA; cm²/cm² of rumen wall) calculated as follows: [1 + (NOP×PSA)-(NOP×0.002)]; and, proportion of the papillae on absorptive surface (PPAS; %) calculated as follows: [(NOP×PSA/ASA)×100]. Data were obtained from captures and analysis of the images by software (Image J, National Institutes of Health, Bethesda, MD, USA). Subsequently, data were analyzed with PROC CORR (SAS, Inst. Inc., Cary, NC). There were associations among the nutrients digestibility (P < 0.05) with ASA, PPAS, and W, except to W and DigCP (P > 0.05). Relationship was observed (P< 0.05) among papillae length, ADG and DMI. The relationship between papillary morphometric characteristics and nutrients digestibility illustrates the efficiency of water buffaloes in the utilization of the feed. Supported by FAPESP #2014/05473-7 and #2016/01109-4.

 Table

	NOP	PSA	ASA	PPAS	HEIGHT	WIDTH	LENGTH
DM digestibility	-0.14	-0.24**	-0.37*	-0.29*	-0.14	-0.29*	-0.09
CP digestibility	-0.15	-0.16	-0.32*	-0.27*	-0.12	-0.20	-0.06
NDF digestibility	-0.12	-0.23**	-0.35*	-0.32*	-0.13	-0.32*	-0.04
ADF digestibility	-0.07	-0.23**	-0.35*	-0.33*	-0.16	-0.28*	0.04
TDN digestibility	-0.10	-0.23**	-0.34*	-0.24*	-0.12	-0.29*	-0.08
OM digestibility	-0.13	-0.23**	-0.35*	-0.27*	-0.13	-0.29*	-0.13
ADG	-0,13	-0.06	-0.21**	-0.20	-0.12	0.01	0.29*
DMI	-0.11	-0.002	-0.08	-0.10	0.04	-0.09	0.48*

*P < 0.05 **P < 0.10