Indirect methods for predicting the body composition of sheep of different sex classes

The aim was to evaluate the correlation and develop regression equations for the body composition of sheep of different sex classes, obtained by the comparative slaughter method, using the composition of the neck region and loin eye area (LEA). Forty-five sheep of three sex classes (15 intact males, 15 castrated males and 15 females) received three feeding levels (ad libitum or restrictions of 70 or 80% of ad libitum intake). Animals were distributed in a 3×3 factorial arrangement, with 5 repetitions. The LEA showed: positive correlation with empty body weight, fasting body weight, meat, protein, ether extract and water (p < 0.01), for all sex classes; with bones for intact males and females (p < 0.01); with ash content for intact males and a moderate correlation for castrated males (p < 0.01). The neck was correlated with empty body weight, fasting body weight, meat, protein, ether extract, water and energy in all sex classes (p < 0.01); and moderate correlation with bone (r=0.58) and ash (r=0.67) for intact males. Intact males showed higher R² values in their prediction equations in relation to the other sex classes.

Keywords:
chemical composition; loin eye area; neck. prediction equations.

Authorship

Ivonete Ferreira da Silva

Departamento de Zootecnia, Universidade Federal do Vale do São Francisco, Rod. BR-407, 12 Lote 543, s/n, 56300-000, Petrolina, Pernambuco, Brazil. Universidade Federal do Vale do São FranciscoBrazilPetrolina, Pernambuco, BrazilDepartamento de Zootecnia, Universidade Federal do Vale do São Francisco, Rod. BR-407, 12 Lote 543, s/n, 56300-000, Petrolina, Pernambuco, Brazil.

Glayciane Costa Gois

Mário Adriano Ávila Queiroz

Mario Luiz Chizzotti

Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.Universidade Federal de ViçosaBrazilViçosa, Minas Gerais, BrazilDepartamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.

Rafael Torres de Souza Rodrigues ^** Author for correspondence. E-mail: rafael.rodrigues@univasf.edu.br

https://orcid.org/0000-0002-6436-8299

* Author for correspondence. E-mail: rafael.rodrigues@univasf.edu.br

SCIMAGO INSTITUTIONS RANKINGS

Tables

Tables (7)

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Table 1
Dry matter intake (DMI), average daily gain (ADG), fasting body weight (FBW), empty body weight (EBW) and neck of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

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Table 2
Proportion of ingredients and chemical composition of experimental diet.

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Table 3
Correlation coefficients between loin eye area (LEA) and empty body weight (EBW), fasting body weight (FBW) and proximate composition of empty body (in kg) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

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Table 4
Linear regression equations to estimate the proximate composition (in kg) in empty body (y) as a function of the loin eye area (LEA, in cm²) of the carcass, (x), of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

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Table 5
Correlation coefficients between empty body weight (EBW) and fasting body weight (FBW) with neck weight and between the proximate composition of the empty body and the proximate composition of the neck of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

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Table 6
Linear regression equations to estimate empty body weight (EBW) and fasting body weight (FBW) (y) from the neck weight (x) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

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Table 7
Linear regression equations to estimate the proximate composition of the empty body (y) as a function of the proximate composition of the neck (x) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

Table 1 Dry matter intake (DMI), average daily gain (ADG), fasting body weight (FBW), empty body weight (EBW) and neck of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

Items	Sex classes			Feeding levels				P value
Items	IM	CM	F	AL	70%	80%	SEM	S	F	I
DMI, kg dia^-1	0.58	0.60	0.58	1.17	0.35	0.23	0.04	0.71	<0.01	0.82
ADG, kg dia^-1	0.05	0.05	0.06	0.19	0.01	-0.05	0.02	0.66	<0.01	0.65
FBW, kg	21.3	21.2	20.7	29.2	18.7	15.5	1.19	0.75	<0.01	0.57
EBW, kg	19.1	19.2	18.5	26.6	16.3	13.9	0.59	0.76	<0.01	0.51
Neck, kg	0.50	0.38	0.49	0.69	0.38	0.29	0.02	0.94	<0.01	0.72

IM = Intact males; CM = Castrated males; F = Females; 70% = Feed restriction of 70% of average intake ad libitum; 80% = Feed restriction of 80% of average intake ad libitum; SEM = Standard error of the means; S = Sex classes effect; F = Feeding level effect; I = Interaction effect between sex classes and feeding level. Significant at the 5% probability level

Table 2 Proportion of ingredients and chemical composition of experimental diet.

Items	% DM
Elephant grass	40.0
Ground corn grain	28.6
Soybean meal	29.5
Sodium chloride	0.5
Commercial premix^a	1.1
Urea	0.3
Chemical composition
Dry matter, %NM	63.8
Organic matter, % DM	92.7
Mineral matter, % DM	7.3
Crude protein, % DM	17.9
Ether extract, % DM	2.9
Neutral detergent fiber, % DM	37.9
Non-fibre carbohydrates, % DM	33.9
Digestible energy, Mcal kg^-1 DM	2.4
Metabolizable energy, Mcal kg^-1 DM	1.9

^aGuaranteed levels provided by the manufacturer (per kg in active elements): 240 g kg^-1 calcium; 71 g kg^-1 phosphorus; 28.2 g kg^-1 potassium; 20 g kg^-1 sodium; 20 g kg^-1 Magnesium; 30 mg kg^-1 cobalt; 400 mg kg^-1 copper; 250 mg kg^-1 iron; 1350 mg kg^-1 manganese; 15 mg kg^-1 selenium; 1700 mg kg^-1 zinc; 40 mg kg^-1 iodine; 10 mg kg^-1 chromium; 710 mg kg^-1 fluorine; 135000 IU kg^-1 Vitamin A; 68000 IU kg^-1 Vitamin D3; 450 IU kg^-1 Vitamin E. Means of digestible energy and metabolizable energy at the ad libitum level calculated according to National Research Council (NRC, 2001National Research Council [NRC]. (2001). Nutrient requirements of dairy cattle (7th ed.). Washington, DC: National Academy Press.) and National Research Council (NRC, 2016National Research Council [NRC]. (2016). Nutrient requirements of beef cattle (8th ed.). Washington, DC: National Academy Press. ), respectively; NM = Natural matter; DM = Dry matter.

Table 3 Correlation coefficients between loin eye area (LEA) and empty body weight (EBW), fasting body weight (FBW) and proximate composition of empty body (in kg) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

	EBW	FBW	Meat	Bone	CP	EE	Ash	Water
Intact males
LEA	0.90	0.88	0.89	0.75	0.89	0.83	0.86	0.90
P value	*	*	*	*	*	*	*	*
Castrated males
LEA	0.72	0.73	0.84	0.38	0.78	0.72	0.60	0.68
P value	*	*	*	0.19	*	*	*	*
Females
LEA	0.61	0.57	0.70	0.73	0.70	0.52	0.37	0.63
P value	*	*	*	*	*	*	0.17	*

Meat = muscle + fat + sinews; CP = Crude protein; EE = Ether extract; * - Significant correlation at the 5% probability level

Table 4 Linear regression equations to estimate the proximate composition (in kg) in empty body (y) as a function of the loin eye area (LEA, in cm²) of the carcass, (x), of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

Sex classes	Parameters						R²	P value
Sex classes	Y		Intercept		Slope	X	R²	Intercept	Slope
Intact males	Meat, kg	=	-1.00	+	1.01	LEA	0.79	0.39	*
Castrated males	Meat, kg	=	-0.02	+	0.97	LEA	0.71	0.99	*
Females	Meat, kg	=	-0.17	+	0.97	LEA	0.50	0.93	*
General	Meat, kg	=	-0.27	+	0.96	LEA	0.68	0.71	*
Intact males	Bone, kg	=	1.39	+	0.13	LEA	0.58	*	*
Castrated males	Bone, kg	=	1.68	+	0.16	LEA	0.15	*	0.19
Females	Bone, kg	=	1.25	+	0.16	LEA	0.53	*	*
General	Bone, kg	=	1.55	+	0.13	LEA	0.21	*	*
Intact males	Water, kg	=	0.57	+	1.22	LEA	0.83	*	*
Castrated males	Water, kg	=	6.50	+	0.98	LEA	0.47	*	*
Females	Water, kg	=	6.11	+	0.91	LEA	0.40	*	*
General	Water, kg	=	5.37	+	1.04	LEA	0.59	*	*
Intact males	CP, kg	=	0.59	+	0.34	LEA	0.80	0.12	*
Castrated males	CP, kg	=	1.02	+	0.32	LEA	0.62	0.06	*
Females	CP, kg	=	1.12	+	0.28	LEA	0.49	0.05	*
General	CP, kg	=	0.94	+	0.31	LEA	0.65	*	*
Intact males	EE, kg	=	-2.00	+	0.63	LEA	0.69	*	*
Castrated males	EE, kg	=	-0.97	+	0.54	LEA	0.52	0.36	*
Females	EE, kg	=	-1.36	+	0.59	LEA	0.27	0.47	*
General	EE, kg	=	-1.37	+	0.58	LEA	0.49	*	*
Intact males	Ash, kg	=	0.39	+	0.07	LEA	0.75	*	*
Castrated males	Ash, kg	=	0.51	+	0.07	LEA	0.36	*	*
Females	Ash, kg	=	0.72	+	0.02	LEA	0.14	*	0.17
General	Ash, kg	=	0.52	+	0.06	LEA	0.43	*	*

Meat = muscle + fat + sinews; CP = Crude protein; EE = Ether extract; R² = coefficient of determination; * - Significant at the 5% probability level.

Table 5 Correlation coefficients between empty body weight (EBW) and fasting body weight (FBW) with neck weight and between the proximate composition of the empty body and the proximate composition of the neck of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80% of ad libitum intake.

	EBW	FBW	Meat	Bone	CP	EE	Ash	Water	Energy Mcal kg^-1
Intact males
Neck	0.86	0.85	0.89	0.58	0.74	0.88	0.67	0.91	0.90
P value	*	*	*	*	*	*	*	*	*
Castrated males
Neck	0.88	0.92	0.90	0.83	0.86	0.90	0.82	0.86	0.87
P value	*	*		*	*	*	*	*	*
Females
Neck	0.91	0.87	0.89	0.41	0.90	0.94	0.49	0.87	0.95
P value	*	*	*	0.13	*	*	0.06	*	*

Meat = muscle + fat + sinews; CP = Crude protein; EE = Ether extract. * - Significant at the 5% probability level.

Table 6 Linear regression equations to estimate empty body weight (EBW) and fasting body weight (FBW) (y) from the neck weight (x) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

	Parameters							P value
Sex classes	Y		Intercept		Slope	X	R²	Intercept	Slope
Intact males	EBW, kg	=	3.07	+	36.50	kg	0.73	0.30	*
Castrated males	EBW, kg	=	8.64	+	23.64	kg	0.78	*	*
Females	EBW, kg	=	6.95	+	27.10	kg	0.82	*	*
General	EBW, kg	=	6.71	+	27.92	kg	0.75	*	*
Intact males	FBW, kg	=	4.91	+	37.41	kg	0.73	0.12	*
Castrated males	FBW, kg	=	9.40	+	26.60	kg	0.84	*	*
Females	FBW, kg	=	8.81	+	27.92	kg	0.75	*	*
General	FBW, kg	=	8.09	+	29.79	kg	0.75	*	*

R² = coefficient of determination; * - Significant at the 5% probability level.

Table 7 Linear regression equations to estimate the proximate composition of the empty body (y) as a function of the proximate composition of the neck (x) of sheep of different sex classes, fed ad libitum (AL) or restricted at 70 or 80 % of ad libitum intake.

Sex classes		Parameters					R²	P value
	Y		Intercept		Slope	X	R²	Intercept	Slope
Intact males	Meat, kg	=	0.05	+	20.13	Meat, kg	0.78	0.96	*
Castrated males	Meat, kg	=	2.17	+	12.11	Meat, kg	0.70	*	*
Females	Meat, kg	=	1.69	+	14.44	Meat, kg	0.78	*	*
General	Meat, kg	=	1.50	+	14.98	Meat, kg	0.72	*	*
Intact males	Bone, kg	=	0.95	+	12.65	Bone, kg	0.33	*	*
Castrated males	Bone, kg	=	0.65	+	19.14	Bone, kg	0.69	0.55	*
Females	Bone, kg	=	1.75	+	5.34	Bone, kg	0.16	*	0.13
General	Bone, kg	=	2.41	+	14.02	Bone, kg	0.44	*	*
Intact males	Water, kg	=	2.13	+	35.19	Water, kg	0.84	0.13	*
Castrated males	Water, kg	=	6.63	+	21.68	Water, kg	0.75	*	*
Females	Water, kg	=	6.42	+	20.32	Water, kg	0.75	*	*
General	Water, kg	=	5.40	+	24.65	Water, kg	0.74	*	*
Intact males	CP, kg	=	0.96	+	31.30	CP, kg	0.51	0.11	*
Castrated males	CP, kg	=	1.47	+	19.22	CP, kg	0.74	*	*
Females	CP, kg	=	1.43	+	22.64	CP, kg	0.81	*	*
General	CP, kg	=	1.49	+	22.68	CP, kg	0.61	*	*
Intact males	EE, kg	=	-0.08	+	42.11	EE, kg	0.77	0.87	*
Castrated males	EE, kg	=	0.35	+	32.99	EE, kg	0.80	0.36	*
Females	EE, kg	=	-0.50	+	46.90	EE, kg	0.89	0.17	*
General	EE, kg	=	-0.04	+	40.30	EE, kg	0.80	0.86	*
Intact males	Ash, kg	=	0.53	+	21.70	Ash, kg	0.45	*	*
Castrated males	Ash, kg	=	0.61	+	15.90	Ash, kg	0.67	*	*
Females	Ash, kg	=	0.75	+	6.64	Ash, kg	0.24	*	0.06
General	Ash, kg	=	0.63	+	14.55	Ash, kg	0.47	*	*

Meat = muscle + fat + sinews; CP = Crude protein; EE = Ether extract; R² = coefficient of determination; * - Significant at the 5% probability level.

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Indirect methods for predicting the body composition of sheep of different sex classes

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[1] * Author for correspondence. E-mail: rafael.rodrigues@univasf.edu.br