COBISS: 1.08 Agris category code: L01
EFFECT OF PRE-SLAUGHTER WEIGHT AND SEX ON COMMERCIAL MEAT CUT YIELDS OF IBERIAN PIGS
Javier GARCÍA-GUDIÑO 1 2, Mercedes IZQUIERDO Dolores AYUSO Ana I. del ROSARIO Juan L. DUARTE Miguel A. PÉREZ Francisco I. HERNÁNDEZ-GARCÍA 1
abstract
It is very important for the Iberian swine industry to determine the optimum slaughter weight. Therefore, predicting the weights and yields of valuable meat cuts (ham, foreleg and loin) at a given pre-slaughter live weight may be very useful for management decisions. Also, sex differences in prime-cut yields should be elucidated. For this study, 300 extensively reared Iberian pigs (castrated males and females) were slaughtered at live weight (LW) ranging from 125 to 200 kg. At the packing plant, carcass and meat cuts were weighed, and meat cut yields were recorded. Increasing LW class was associated with heavier carcass and meat cuts, but also with lower carcass and prime-cut yields. Males were heavier, but females had higher carcass yield. Nevertheless, males were superior to females in the case of foreleg weight and yield and combined prime-cut yield. Sex differences within each LW class were consistent. Results suggest that in Iberian pig weight gain during finishing in extensive systems is mostly based on fat cover deposition, and also that males, despite castration, have a greater front leg development than females.
Key words: Iberian pig / slaughter weight / carcass yield / prime cuts / sex differences
1 introduction
The weights and yields of valuable meat cuts, especially hams, forelegs and loins are of great importance for the Iberian swine industry. In traditional extensive systems, which have an acorn-based finishing phase called "montanera", at the beginning of the fattening period, Iberian pigs grow more muscle than fat, but at the end of this stage, growth is mainly based on fat tissue deposition, with high daily gains in the finishing phase (963 g/ day), compared to low gains (around 200 g/day) in the previous phase (Mayoral et al., 1999). In Iberian pigs, Barba et al. (2000) obtained a carcass yield of 83.2% for a live weight of 142 kg, with ham and foreleg mean weights of 21.6 and 14.3 kg, respectively. Mayoral et al. (1999), with acorn-fed Iberian pigs of 153 kg of live weight at 16 months of age, obtained 80.9% of carcass yield and prime
1	Agricultural Research Center of Extremadura; 06187-Guadajira, Badajoz (SPAIN)
2	Corresponding author, e-mail: javier.garcia@juntaextremadura.es
cut, ham, foreleg and loin weights of 17.3, 9.3, 6.5 and 1.4 kg, respectively. Also, the age at the beginning (Daza et al., 2007) and at the end of the fattening period are important factors for meat yield, as well as the sex, although this latter factor has not been studied in depth. The commercially optimal Iberian pig carcass composition represents an equilibrium between meat and fat deposition which is sometimes difficult to control. Determining the optimal slaughter weight (live weight at slaughter) at which finishing should be terminated for a given range of age is one of the most difficult decisions to be taken by extensive Iberian pig producers, especially if finishing is based only on natural resources, i.e. acorns. In consequence, the present study aimed to determine the effect of pre-slaughter weight and sex on yields of carcass and prime cuts of Iberian pigs.
Table 1: Body, carcass and prime cut (ham, foreleg and loin) weights (kg) per			class of live weight at slaughter	(LW)	in castrated Iberian pigs
	Class 1	Class 2	Class 3		Class 4
Weight variable	(LW < 140 kg; n = 22)	(140-155 kg LW; n =	= 82) (156-170 kg LW; n =	177)	(LW > 170 kg; n = 19)
Live weight	135.23a	150.27b	160.93c		174.14d
Carcass weight	111.60a	125.43b	133.95c		145.65d
Hams weight	24.32a	26.46b	28.19c		29.99d
Forelegs weight	16.94a	18.28b	19.03c		20.08d
Loins weight	3.60a	3.51b	3.57c		3.76d
Prime cuts weight	45.17a	48.75b	51.05c		53.92d
Values within a row having different superscripts differ (P < 0.05).
2 MATERIALS AND METHODS
Carcass data came from 300 castrated Iberian pigs (146 females and 154 males) raised in years 2009 to 2012 in extensive conditions on a research farm. Pigs were slaughtered at a live weight (LW) of 125 to 200 kg. Weight of carcass, ham, foreleg, loin (cw, hw, fw and lw, respectively), as well as prime cuts weight (pcw = hw + fw + lw) were recorded. The yields (y) of carcass (cy), hams (hy), forelegs (fy), loin (ly) and prime cuts (pcy) were calculated as follows:
cy = (cw / LW) x 100 hy = (hw / cw) x 100 fy = (fw / cw) x 100 ly = (lw / cw) x 100 pcy = (pcw / cw) x 100
Male (M) and female (F) castrated pigs were ranked into 4 live weight (LW) classes (with similar numbers of both sexes for each class) according to the body weight at slaughter:
Class 1: LW < 140 kg (n = 22) Class 2: 140-155 kg LW (n = 82) Class 3: 156-170 kg LW (n = 177) Class 4: LW > 170 kg (n = 19)
Data were analyzed with statistical package SAS using GLM procedure with model that included the effects of LW class (Class), Sex and the interaction Class x Sex. Least-squared means were calculated to adjust for unbalanced data.
3 results and discussion
Table 1 shows mean values of live, carcass and prime cut weights for the pigs in each LW class. All weight variables increased significantly as LW increased. In contrast, with respect to carcass and prime cut yields for each live weight class (Table 2), carcass yield did not increase along with LW, and, on the contrary, combined or separated prime cuts decreased in yield as LW increased, with 2 to 4 significantly different levels depending on the particular yield variable. This is consistent with results from Mayoral et al. (1999), because data from Table 1 and 2 suggest that carcass weight increased mostly in fat cover during finishing and to a lesser extent in muscular contents, which are the main constituents of prime cuts.
In relation to sex differences for weight variables (Table 3) and for yield variables (Table 4), when all LW classes were pooled, LW was significantly greater for males (155.8 kg) than for females (154.4 kg), but female carcasses appeared to be heavier (although not significantly) than those of males (Table 3). This is consistent
Table 2: Carcass and pi	-ime cut (ham, foreleg and loin) yields (%) per class of live		weight at slaughter	(LW) in castrated Iberian pigs
	Class 1	Class 2	Class 3	Class 4
Yield variable	(LW < 140 kg; n = 22)	(140-155 kg LW; n = 82)	(156-170 kg LW;	n = 177) (LW > 170 kg; n = 19)
Carcass yield	82.54a	83.47a	83.23a	83.63a
Hams yield	21.79a	21.09b	21.04b	20.60b
Forelegs yield	15.18a	14.59b	14.22c	13.79c
Loins yield	3.22a	2.77b	2.66c	2.58c
Prime cuts yield	40.36a	38.44b	37.89c	36.89d
Values within a row having different superscripts differ (P < 0.05). 102 Acta agriculturae Slovenica, Supplement 4 - 2013
Table 3: Body, carcass and prime cut (ham, foreleg and loin) weights (kg) per class of live weight at slaughter (LW) and sex (M: male, n = 154; F: female, n = 146) in castrated Iberian pigs
Weight variable	Sex	Class 1 (LW < 140 kg; n = 22)	Class 2 (140-155 kg LW; n = 82)	Class 3 (156-170 kg LW; n = 177)	Class 4 (LW > 170 kg; n = 19)	All classes (n = 300)
Live weight	M	135.75a	150.41a	161.94a	175.29a	155.84a
	F	134.70a	150.13a	159.93b	173.00a	154.44b
Carcass weight	M	110.77a	124.72a	134.34a	145.41a	128.81a
	F	112.43a	126.14a	133.56a	145.88a	129.50a
Hams weight	M	24.25a	26.45a	28.11a	29.58a	27.10a
	F	24.39a	26.47a	28.27a	30.40a	27.38a
Forelegs weight	M	17.04a	18.72a	19.39a	21.08a	19.06a
	F	16.84a	17.82b	18.66b	19.08b	18.10b
Loins weight	M	3.59a	3.52a	3.65a	3.59a	3.59a
	F	3.61a	3.50a	3.50b	3.92a	3.63a
Prime cuts weight	M	45.16a	48.95a	51.45a	54.44a	50.00a
	F	45.18a	48.54a	50.65b	53.40a	49.44a
Values within a LW class and a weight variable having different superscripts differ (P < 0.05; M vs. F)
with a significantly greater carcass yield for the pooled group of females (Table 4; 83.8 vs. 82.6%).
With respect to the prime cut weights and yields for the pooled LW classes, the combined prime cut yield (for the 3 pieces together) was significantly greater for the males than females (38.7 vs. 38.1%; Table 4). However, the ham weight and yield were slightly (but not significantly) greater for the females, and the foreleg weight (19.1 vs. 18.1 kg) and yield (14.8 vs. 14.1%) were significantly greater for the males. In contrast, loin weights and yields were similar between sexes for the pooled LW classes
(Tables 3 and 4). Thus, females had greater carcass yield but males had heavier and greater-yielding front legs and greater combined prime-cut yield, hence suggesting that the increased female yield comes mainly, again, from an increased fat cover deposition.
When analyzing sex differences within each LW class for weight and yield variables (Tables 3 and 4), sex differences reached significance for LW in the LW-Class 3 (M > F), and for carcass yield in Class 2 (F > M). Also, two sexes differed significantly in foreleg weight for the LW-Classes 2, 3 and 4 (M > F) and in foreleg yield also
Table 4: Carcass and prime cut (ham, foreleg and loin) yields (%) per class of live weight at slaughter (LW) and sex (M: male, n = 154; F: female, n = 146) in castrated Iberian pigs
Yield variable	Sex	Class 1 (LW < 140 kg; n = 22)	Class 2 (140-155 kg LW; n = 82)	Class 3 (156-170 kg LW; n = 177)	Class 4 (LW > 170 kg; n = 19)	All classes (n = 300)
Carcass yield	M	81.58a	82.93b	82.96a	82.95a	82.60b
	F	83.51a	84.01a	83.51a	84.32a	83.84a
Hams yield	M	21.89a	21.21a	20.92a	20.36a	21.09a
	F	21.69a	20.98a	21.16a	20.83a	21.17a
Forelegs yield	M	15.39a	15.01a	14.44a	14.50a	14.84a
	F	14.98a	14.16b	13.99b	13.09b	14.05b
Loins yield	M	3.23a	2.80a	2.70a	2.46a	2.80a
	F	3.21a	2.74a	2.61a	2.69a	2.81a
Prime cuts yield	M	40.66a	38.94a	38.06a	37.16a	38.70a
	F	40.07a	37.94b	37.71a	36.62a	38.09b
Values within a LW class and a yield variable having different superscripts differ (P < 0.05; M vs. F)
for Classes 2, 3 and 4 (M > F). The combined prime-cuts were significantly different between sexes in LW-Class 3 for weight (M > F) and in LW-Class 2 for yield (M > F). Finally, in relation to the loins, there were significant sex differences only for loin weight in LW-Class 3 (M > F). Therefore, these comparisons of sexes within LW-Class provide some detail to the above stated conclusions.
4 conclusions
All weight variables (LW and carcass, prime-cut and combined prime-cut weights) were significantly affected by LW-Class and increased along with the body weight at slaughter. In contrast, carcass and prime cut yields decreased with the increasing slaughter weight, thus suggesting that weight gain during finishing in Iberian pig extensive systems is mostly based on fat cover deposition. Males were heavier, but females had greater carcass yield. However, males had greater foreleg weight and yield and a greater combined prime-cut yield, hence suggesting that the increased female yield comes mainly, again, from an increased fat cover deposition. In addition, this also shows that castrated males still exhibit superior front leg development, which constitutes a sexual dimorphic trait
for the intact animals. Finally, sex differences in weights and yields of studied variables within each LW-Class support these conclusions.
5	acknowledgements
We thank the INIA, Gobierno de Extremadura and Fondos FEDER for financial support.
6	references
Barba C., Delgado J.V., Diéguez E., Cañuelo P. 2000. Caracterización productiva de las variedades del cerdo Ibérico basada en el comportamiento en matadero. Archivos de Zootecnia, 50: 125-132 Daza A., López-Bote C., Olivares A., Menoyo D., Ruiz J. 2007. Age at the beginning of the fattening period of Iberian pigs under free-range conditions affects growth, carcass characteristics and the fatty acid profile of lipids. Animal Feed Science and Technology, 139: 81-91 Mayoral A.I., Dorado M., Guillén M.T., Robina A., Vivo J.M., Vázquez C., Ruiz J. 1999. Development of meat and carcass quality characteristics in Iberian pigs reared outdoors. Meat Science, 52: 315-324