Nutritional strategies to improve the carcass and meat fatness of pigs intended for the production of Teruel dry-cured ham
- Autores: Jesús Suárez Belloch
- Directores de la Tesis: María Ángeles Latorre Górriz (dir. tes.), José Antonio Guada Vallepuga (dir. tes.)
- Lectura: En la Universidad de Zaragoza ( España ) en 2016
- Idioma: español
- Tribunal Calificador de la Tesis: Gonzalo González Mateos (presid.), José Alberto Conde Aguilera (secret.), Jaume Coma Subirá (voc.)
- Programa de doctorado: Programa Oficial de Doctorado en Producción Animal
- Materias:
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- Resumen
Systems of commercial production of heavy pigs have been conventionally based on the use of early maturing genotypes. However, consumer preferences for lean meat and pressure on improving growth performances have led to a gradual replacement of these genotypes by late maturing breeds, which has collaterally affected body fat deposition with the consequent reduction of end cured products quality. In the case of the Protected Designation of Origin “Jamón de Teruel” (PDO Teruel ham), a decreased carcass acceptability, according to tender specifications, has been detected in association with a reduction of backfat thickness at the level of Gluteus Medius muscle (m. GM).
In order to increase the fat content and therefore the acceptability of carcasses of pigs for the PDO Teruel ham, the present work aimed to analyse nutritional strategies that could improve the carcass and pork quality with a minimal impact on production performances. Then, four nutritional strategies were tested on heavy pigs intended to PDO Teruel ham (Duroc x (Landrace x Large White)). In three of them the ratio of Lys to dietary energy was modified either by increasing the energy content of isoprotein finisher diets through the inclusion of fat (2.28, 2.35 and 2.42 Mcal NE / kg, Experiment 1), or either by reducing the Lys content of isocaloric diets, balanced for essential amino acids, during the grower (11, 9.1, 7.8 and 5.2 g total Lys/kg, Experiment 2) and finisher periods (6.3, 5.6, 4.2 and 3.2 g standardised ileal digestible Lys/kg, Experiment 3). In a further trial (Experiment 4), a commercial finisher diet was provided at younger ages than conventionally recommended (80 and 90 vs 100 kg BW) in order to stimulate fat deposition. The effect of each nutritional strategy was evaluated by studying the response to treatments of growth performances, (average daily gain, average daily feed intake and feed conversion ratio), carcass characteristics (carcass yield, carcass lengths, lean trimmed lean cuts and backfat depths), meat quality (color, water holding capacity, hardness and chemical composition of Longissimus Thoracis muscle) and fatty acid profile of subcutaneous fat.
The strategy of dietary fat inclusion up to 3.9 % led to a linear increase of backfat thickness at level of the m. GM (from 19.4 to 21.7 mm; P < 0.05) without affecting the intramuscular fat (IMF) content and growth performances (P > 0.10), resulting in an increased acceptability of carcasses for PDO Teruel ham. On the other hand, the restriction of Lys during the grower or the finisher phase increased linearly the IMF (from 2.65 to 3.37; P < 0.10 and 3.25 to 4.18%; P < 0.01) but backfat depth was improved only when the restrictionwas implemented during the grower phase (from 15.8 to 18.6 mm at m. GM; P < 0.05), probably as a response to the increased feed intake during the refeeding phase. However, a linear impairment of the feed conversion ratio was recorded as consequence of the Lys restriction during the grower (2.66 to 2.83 from 20 to 120 kg BW; P < 0.001) and finisher periods (3.53 to 4.27 from 60 to 130 kg BW; P < 0.001), limiting the economic benefit of these strategies. Even so, this constraint could be more than offset by the increased carcass acceptance for PDO Teruel ham as a result of Lys restriction during the grower phase. Finally, changing the grower diet by the finisher diet at earlier age did not affect either growth performance or carcass fat, suggesting the possibility of advancing to 80 kg BW the switch to a finisher diet, which is usually cheaper, without negative consequences on production performance or carcass quality.
According to these results, it can be concluded that manipulation of growth by nutritional means has proved to be an effective way of increasing the content of IMF and subcutaneous fat of heavy pigs intended for PDO Teruel ham, but at the cost of reducing growth performance to a degree dependent on the feeding strategy implemented. To this respect, the strategy that seems to offer best results was the increase in energy content of the finisher diet by addition of fat which increased carcass fat without impairment of growth performances. However, the potential benefit of restricting Lys during the grower phase will depend on the return, in terms of carcass acceptance and meat quality, considering the higher cost of a worst feed conversion ratio which increases by 0.066 per mm of increase in carcass fat coverage in association with 0.25 percentage units of greater IMF content.
