RELATIONSHIPS BETWEEN THE FATTENING TRAITS AND THE SLAUGHTER TRAITS AND MEAT CHEMICAL COMPOSITION IN PIGS

Eugenia Jacyno, Arkadiusz Pietruszka, Roman Czarnecki, Czesław Elzanowski

ABSTRACT

The objective of the study was to determine relationships between the fattening traits and the slaughter traits and chemical composition of meat in fatteners, hybrids after boars of high-meat breeds. The study was carried out on 80 fatteners (40 gilts and 40 barrows) fed with rationed mixture.

Key words: fatteners, fattening value, slaughter value, chemical composition of meat..

INTRODUCTION

Daily gains of body weight in pigs fed with standardized feeding system depend in the first place on protein daily deposition [4, 5, 7]. There are high correlations (r>0.9) between the quantity of protein deposited in pig organisms and the meat content in carcass [10].

Ad libitum feeding of young pigs (to 70 kg body weight) increases the gains of body weight without excessive fatness [8, 18]. On the other hand, in older pigs, even in those with high genetic potential, the increased gains are accompanied by deterioration of carcass quality [8, 15].

Feed intake per 1 kg body weight gain is the smaller, the greater is the amount of lean meat in the carcass of fattener [5, 13, 20, 21]. According to Fandrejewski [7] the rate of protein daily deposition in growing pigs influences the feed conversion the most of all factors.

It was found [2, 14], that the increase of body weight gains and pig meatiness affects the decrease of intramuscular fat in meat, whereas it is of no effect on the content of water, protein and mineral components. It has negative effect on meat sensory properties, as savoriness, tenderness and juciness are positively correlated with the amount of intramuscular fat [3, 6, 16, 23].

The aim of the present study was to determine the relationships between the daily gains and feed conversion and the slaughter traits as well as between the daily gains and the chemical composition of m. longissimus dorsi in meat type fatteners fed with standardized feeding system.

MATERIALS AND METHODS

Study material consisted of 80 fatteners, hybrids after boars of meat breeds: Belgian Landrace, Hampshire x Pietrain, Pietrain and Polish Large White. The experimental group had equal numbers of fatteners in respect of origin and sex. The fatteners were kept in individual pens without straw and fed with a standardized food ration. During the whole fattening period (23-100 kg body weight), one type of granulated feed mixture was used. Chemical composition of the mixture and its feeding value are given in Table 1. The growth rate in pigs and the feed intake per 1 kg body weight gain were controlled individually as well.

The experiment was closed by the slaughtering, when the animals reached 100 kg body weight. Carcass slaughter evaluation was performed according to the methods used at Polish Pig Testing Stations [17]. During the slaughter, samples of m. longissimus dorsi were collected for chemical analysis from the region between lumbar verterbrae 1 and 4.

The content of nutrients in mixture and meat samples was determined with standard methods [1], and the amino acids with AAA-400 amino acid automatic analyzer of Czech production.

Relationships between the traits of fattening value and those of slaughter value and the content of meet nutrients were determined basing on the calculated coefficients of rectilinear correlation of first degree.

RESULTS AND DISCUSSION

Production results (Table 2) point to the high rate of growth in the examined pigs. Mean daily gain of body weight amounted to 778 g, and the maximum value of it exceeded even 920 g. The basic measure of fattening performance is feed conversion per 1 kg body weight gain. In this respect, the fatteners used in the study also obtained very good results. They intake 2.69 kg feed, 363 g digestible protein and 32.3 MJ metabolic energy per 1 kg body weight gain, and these were considerably smaller than those obtained in other studies for meat type pigs fed with rationed way [11, 19].

Meatiness indices (eye muscle area, basic cuts meat weight, ham and loin weights) and backfat thickness (average of 5 measurements and in point C₁) point to well-developed musculature and not very large fatness of carcasses in experimental pigs. Mean meat content in carcass amounted to approximately 51%, and the maximum value even to 61%.

The content of nutrients in m. longissimus dorsi in the examined fatteners was similar to the values found by Barowicz et al. [2] in the meat of 990 line fatteners.

Significant (p≤0.01) positive correlation was found (Table 3) in the examined pigs between daily gains of body weight and the area of eye muscle (r=0.31), the weight of basic cuts (r=0.29), the weight of ham (r=0.33), and the meat percentage in carcass (r=0.32). On the other hand, the backfat thickness decreased slightly with the increase of body weight gains, significant coefficient of correlation (r=-0.23) being found only for the backfat thickness over loin III. More direct negative correlation (r=-0.35*) occurred between daily gains and the backfat thickness over eye muscle region in point C₁.

The correlations obtained in the present study corroborate the findings of other authors [5, 13], who also found significant correlations (p≤0.01) in high-meat pigs between carcass meat percentage and body weight daily gains, whereas low and negative correlations between the backfat thickness and the gains.

According Fandrejewski and Skiba [9], the daily gain of body weight is more influenced by daily protein deposition in pig organisms than by fat deposition. These authors found, that deposition of 1 g protein in pig organisms increased their body weight gain by 4.6 g, whereas deposition of 1 g fat was an equivalent to 1 g only.

The coefficients of correlation determined between the feed intake, and that of digestible protein and metabolic energy per 1 kg gain and the meatiness traits and the backfat thickness (Table 3) indicate, that fatteners with better musculature and smaller fatness were of significantly better feed conversion (p≤0.01) per 1 kg body weight gain. Thus, the results of other authors [12, 22] has been confirmed, that pigs intake much less feed for production of muscle tissue than for that of fat tissue.

Positive coefficients of correlation between the amount of meat in carcass of meat type pigs and the feed intake per 1 kg gain were found as well by Demo et al. [5]. Correlations given by these authors were higher than those showed in the present study.

It should be stressed, that proportional meat content and also the value of particular meatiness traits in the examined pigs were more correlated with feed conversion than with daily gain of body weight. Fandrejewski [7] found, that feed conversion is influenced the most by the amount of protein deposited in pig organisms.

The coefficients of correlation presented in Table 4 show no significant relationships between daily body weight gains and the content of nutrients in meat. Negative and low correlation between daily gains and intramuscular fat content (r=-0.094) indicate, that the increase of growth rate in pigs will not have negative effect on sensory properties of meat. Cameron [3] and Meyer [16] obtained the other results.

CONCLUSIONS

1. Fatteners, that are characterised by thinner backfat and better carcass musculature, obtain higher daily gains of body weight and have better feed conversion.

2. Meatiness traits in pigs are more correlated with feed conversion than with daily gains of body weight.

3. The increase of growth rate and meatiness in pigs not decreased essentially the intramuscular fat content, responsible for sensory properties of meat.

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