Evaluation of chromium oxide and titanium dioxide as inert markers for calculating apparent digestibility in sheep

Figures & data

Table 1. Ingredients and chemical composition (g/kg DM) in the diet using Cr₂O₃, TiO₂ and their interaction used in growing lambs.

Ingredients (g/kg DM)	Cr2O3	TiO2	Cr2O3 + TiO2
Sorghum grain	720.0	720.0	720.0
Alfalfa hay	61.8	61.8	61.8
Oat hay	123.5	123.5	123.5
Molasses	54.6	54.6	54.6
Urea	10.0	10.0	10.0
Calcium, 38%	11.5	11.5	11.5
Phosphate 18/20	2.0	2.0	2.0
Magnesium oxide	2.1	2.1	2.1
Na Bicarbonate	5.0	5.0	5.0
NaCl	5.0	5.0	5.0
Minerals mix^a	0.5	0.5	0.5
Cr2O3	4.0	ND^b	4.0
TiO2^b	ND	4.0	4.0
Chemical composition
DM	917	921	919
OM	871	870	871
NDF	166	163	164
N	15	15	15

^aMinerals mix: Ca 15.0%, P 8.0%, Mg 0.5%, K 0.035%, S 0.2%, Fe 450 mg/kg, Zn 1900 mg/kg, Mn 1800 mg/kg, Se 15 mg/kg, I 30 mg/kg, Co 25 mg/kg.

^bND, no data; the marker is not part of the diet.

Table 2. Markers recovery percentage in faeces, using Cr₂O₃, TiO₂ and Cr₂O₃+TiO₂, estimated by PS and AAS.

Markers^a	CrPS^b	CrAAS^c	TiPS^d	TiAAS^e
Cr2O3	140.8	138.3	ND^h	ND
TiO2	ND	ND	148.7	121.1
Cr2O3 + TiO2	148.2	162.9	143.5	128.4
SEM^f	8.0	6.5	8.3	10.8
p value^g	.388

^aMarkers, 0.4% Cr₂O₃, 0.4% TiO₂, 0.4% + 0.4% TiO₂ Cr₂O₃.

^bCr-PS: Cr₂O₃ determined by PS.

^cCr-AAS: Cr₂O₃ determined by AAS.

^dTi-PS: TiO₂ determined by PS.

^eTi-AAS: TiO₂ determined by atomic absorption spectrophotometry.

^fSEM, standard error of the mean.

^gp value: value of general significance.

^hND, no data; the marker is not part of the mixture.

Table 3. Intake (g DM/d), digestibility (g/g) and digestibility marker/TFC¹ ratio, obtained by Cr₂O₃, TiO₂ or combined determined by PS and AAS.

Item	Markers (M)^2				Technique (T)		SEM^5	p value
	Cr2O3	TiO2	Cr2O3 + TiO2^3	TiO2 + Cr2O3^4	PS	AAS		M	T	M × T
Intake, g/d
DM	909	909	909	909
OM	863	860	862	862
Digestibility, g/d
DM	746^a	751^a	752^ab	774^b	749	763	3.8	.041	.062	.625
OM	727	731	729	748	729	739	3.3	.087	.115	.569
Digestibility, g/g
DM	0.83	0.81	0.84	0.83	0.83	0.84	0.004	.070	.258	.264
OM	0.85	0.83	0.86	0.85	0.85	0.85	0.004	.101	.290	.243
Digestibility, marker/TFC ratio
DM	1.00	0.99	1.02	1.02	1.01	1.01	0.007	.367	.927	.271
OM	1.00	0.99	1.02	1.02	1.00	1.01	0.006	.360	.913	.204

Note: Means with the different letter in the same row are significantly (p < 0.05) different.

¹TFC: total faecal collection.

²Markers, 0.4% de Cr₂O₃, 0.4% TiO₂, 0.4% Cr₂O₃ + 0.4% TiO₂.

³Estimated digestion based on chromium.

⁴Estimated digestion based on titanium.

⁵SEM, standard error of mean.