River-sourced Cladophora glomerata macroalgal biomass as a more sustainable and functional feed raw material for growing rabbits

Figures & data

Figure 1. Protocol structure of the rabbit feeding trial.

Table 1. Ingredients in rabbit feed and chemical composition of a standard compound diet and diets supplemented with river-sourced C. glomerata biomass (52–122 days old).

	Diet
Ingredients (g/kg as fed basis)	SCD	CG4	CG8
Corn	30.00	31.30	34.40
Barley	180.00	180.00	180.00
Oats	250.00	250.00	250.00
Sunflower meal	132.20	119.70	99.70
Linseed meal	10.00	10.00	10.00
Soy meal	37.20	30.00	30.00
Vegetable oil	10.00	10.00	10.00
Beer east	20.00	20.00	20.00
Hay	292.60	271.00	247.90
C. glomerata biomass	˗	40.00	80.00
Antimycotoxin	3.00	3.00	3.00
Vitamin-mineral premix^a	35.00	35.00	35.00
Chemical composition (g/kg as fed basis, unless stated otherwise)
DE (MJ/kg)	10.49	11.13	12.16
Crude protein	175.40	175.30	175.40
Crude fibre	135.60	143.90	150.50
Ash	100.30	103.70	103.10
Ether extract	31.20	32.00	31.00
NDF	324.90	341.90	358.90
ADF	197.10	201.20	207.30
ADL	48.90	49.40	51.50

Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass.

DE: diet energy; NDF: neutral detergent fibre; ADF: acid detergent fibre; ADL: acid detergent lignin.

^aVitamin and mineral premix (per kg of feed): vitamin A 10.08 TV, vitamin D3 1.14 TV, vitamin E 50.30 mg, vitamin K3 0.99 mg, vitamin B1 3.71 mg, vitamin B2 2.80 mg, vitamin B5 9.80 mg, vitamin B12 0.01 mg, nicotinic acid 20.40 mg, folic acid 0.22 mg, choline chloride 170.00 mg, Mg 76.28 mg, Fe 317.00 mg, Zn 110.89 mg, Cu 19.16 mg, Co 0.29 mg, I 0.67 mg, Se 0.31 mg.

Table 2. Impact of river-sourced C. glomerata macroalgal biomass on rabbit growth performance.

Item	Trial period	Diet			SEM	p-value
		SCD	CG4	CG8
BWG (g)	52–122 days of age	1633.00	1560.25	1492.75	240.65	n.s.
ADG (g)		22.59	23.74	22.04	1.27	n.s.
DFI (g)		71.55^ab	73.79^a	70.31^b	1.13	0.013
FCR (kg/kg)		3.71^b	4.23^a	2.93^c	0.20	<0.001

Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass.

BWG: body weight gain; ADG: average daily gain; FCR: feed conversion ratio.

^a–cMeans with different superscript letters (a–c) in a row were significantly different (p < 0.05).

^abMeans with ab superscript letters in a row were not significantly different (p > 0.05).

SEM: standard error of the means; n.s.: not significant (p > 0.05).

Table 3. Impact of river-sourced C. glomerata macroalgal biomass on rabbit slaughter performance.

Item (%, unless stated otherwise)	Diet			SEM	p-value
	SCD	CG4	CG8
Pre-slaughter weight (g)	2765.67	2753.00	2745.33	60.25	n.s.
Warm carcass	49.55	48.33	48.12	1.19	n.s.
Chilled carcass	47.67	46.49	46.33	1.30	n.s.
Carcass without muscles	11.10	11.49	11.40	0.79	n.s.
Head	8.12	8.12	7.91	0.33	n.s.
Intestine weight with chymus	13.41	12.18	12.45	1.75	n.s.
Stomach with content	4.31	4.48	5.20	0.97	n.s.
Stomach without content	1.63	1.45	1.38	0.14	n.s.
Heart	0.35	0.24	0.23	0.05	n.s.
Liver	4.51	6.16	4.42	0.89	n.s.
Pancreas	0.04	0.04	0.04	0.01	n.s.
Lungs	0.57^a	0.43^b	0.43^b	0.04	0.017
Kidneys	0.76	0.65	0.62	0.06	n.s.
Perirenal fat	0.94	0.98	0.93	0.10	n.s.
Abdominal fat	4.13	4.19	4.22	0.33	n.s.
Fore part (without longissimus dorsi and legs)	5.25	4.84	5.12	0.23	n.s.
Hind part	19.33	19.17	19.03	0.80	n.s.
Longissimus dorsi muscle	7.28	7.31	7.27	0.31	n.s.
Thighs with bone	13.37	13.31	13.04	1.18	n.s.
Thighs without bone	11.14	11.28	11.07	1.24	n.s.
Shin with bone	4.60	4.63	4.31	0.37	n.s.
Shin without bone	3.50	3.54	3.47	0.33	n.s.
Longissimus dorsi yield	15.30	15.72	15.69	0.47	n.s.
Leg muscle yield	30.89	31.91	31.37	1.19	n.s.
Carcass yield	60.64	59.95	59.33	1.39	n.s.
Dressing-out percentage	49.55	48.33	48.12	3.36	n.s.
Drip loss	3.83	3.79	3.73	0.47	n.s.

Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass.

^a,bMeans with different superscript letters (a,b) in a row were significantly different (p < 0.05).

SEM: standard error of the means; n.s.: not significant (p > 0.05).

Figure 2. Impact of river-sourced C. glomerata macroalgal biomass on distinct intestinal segments content: (a) pH; (b) dry matter (DM). Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass. Diet-number, means diet sample replicate number; Diet-M, represents the means of replicate samples. ^a,bMeans with different superscript letters (a,b) in a row were significantly different (p < 0.05).

Table 4. Impact of river-sourced C. glomerata macroalgal biomass short-chain fatty acids (SCFA) contents in rabbits’ duodenum.

SCFA (%)	Segment	Diet			SEM	p-value
		SCD	CG4	CG8
Acetic	Duodenum	83.23^c	89.04^a	87.53^b	2.70	0.048
Propionic		6.18^b	7.19^ab	10.82^a	1.76	0.019
Butyric		1.78	1.03	n.d.	1.28	n.s.
Lactic		8.81^a	2.75^b	1.65^b	1.29	<0.001

Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass.

^a–cMeans with different superscript letters (a–c) in a row were significantly different (p < 0.05).

^abMeans with ab superscript letters in a row were not significantly different (p > 0.05).

SEM: standard error of the means; n.d.: not defined; n.s.: not significant (p > 0.05).

Table 5. Impact of river-sourced C. glomerata macroalgal biomass on rabbits’ duodenum and ileum histomorphometric measurements.

Item	Segment	Diet			SEM	p-value
		SCD	CG4	CG8
Villus height (V; μm)
	Duodenum	664.21	606.40	623.74	48.89	n.s.
	Ileum	1215.36^b	1526.09^a	1079.12^c	57.11	<0.001
Crypt depth (C; μm)
	Duodenum	117.57^b	153.56^ab	191.97^a	18.41	0.002
	Ileum	217.29^a	142.42^ab	90.82^b	38.70	0.007
V/C ratio
	Duodenum	5.73^a	4.16^b	3.37^b	0.69	0.005
	Ileum	6.60^a	11.31^b	12.15^b	1.67	0.006

Diets: SCD, standard compound diet; CG4, SCD enriched with 4% macroalgal biomass; CG8, SCD enriched with 8% macroalgal biomass.

^a–cMeans with different superscript letters (a–c) in a row were significantly different (p < 0.05).

^abMeans with ab superscript letters in a row were not significantly different (p > 0.05).

SEM: standard error of the means; n.s.: not significant (p > 0.05).

Data availability statement

The data that supports the findings of this study are available on request from the corresponding author.