The influence of cross-breeding Zlotnicka Spotted native breed sows with boars of Duroc (D) and Polish Large White (PLW) breeds on meat quality

The aim of the study was to investigate the influence of cross-breeding of Zlotnicka Spotted sows with Duroc and Polish Large White boars on the quality of meat of crossbred fatteners. The investigation was done on 50 carcasses of fatteners from four genetic groups: Zlotnicka Spotted x Zlotnicka Spotted (n = 20), Zlotnicka Spotted x Polish Large White (n = 10), Zlotnicka Spotted x Duroc (n = 10) and Zlotnicka Spotted x (Zlotnicka Spotted x Duroc, n = 10). The analysis of pH in the longissimus and semimembranosus muscles in all the genetic groups revealed typical values of meat without qualitative deviations. No statistically significant differences between the groups were observed. Pale, soft and exudative (PSE) meat was found in one carcass of Zlotnicka Spotted x Zlotnicka Spotted group and two carcasses of Zlotnicka Spotted x Polish Large White group. The results of evaluation of physiochemical characteristics indicate very good quality of meat in all the groups of animals. The highest content of intramuscular fat, that is, 3.80%, was observed in the carcasses of the Zlotnicka Spotted x (Zlotnicka Spotted x Duroc) group. Statistical differences were found between this group and Zlotnicka Spotted x Polish Large White, in which the intramuscular fat content was 2.95%. The meat of all the genetic groups of pigs was characterised by desirable and the same colour in the profile of the longissimus muscle. However, similarly to many native breeds, this muscle was characterised by lesser lightness than breeds with high meat content. Also, the results of evaluation of sensory quality determinants, that is, flavour, juiciness, tenderness and palatability, which were higher than four points on average (one to five scale), confirmed perfect quality of the meat. To sum up, it is possible to say that the raw meat of Zlotnicka Spotted pigs and their cross-breeds with Duroc and Polish Large White breeds is characterised by good quality and because of its considerable intramuscular fat content, it has a high culinary and processing value, especially for ripening products

Stand tests of a powered roof support after a long time of operation : case study

The process and results of stand tests on the powered support manufactured in 1996 are discussed. The tests were conducted at the KOMAG’s accredited testing laboratory, implementing an author’s testing program. After completion of the static strength, load bearing capacity and fatigue strength tests, the roof support was inspected and no mechanical damage to the basic components of the tested roof support was found. The recorded permanent deformations of the basic components of the roof support tested in 2020 were compared with the results of tests of the same roof support, conducted in 1996 (prototype tests) and 2009 (tests after modernisation), also at the KOMAG laboratory. Based on the results of tests conducted in 2020, it was shown that the current properties of the roof support meet the normative requirements. Therefore, the customer may decide to continue using them in other longwall panels.Omówiono przebieg i wyniki badań stanowiskowych sekcji obudowy zmechanizowanej wyprodukowanej 1996r. Badania wykonano w akredytowanym laboratorium badawczym ITG KOMAG, realizując autorski program badawczy. Po zakończeniu badań wytrzymałości statycznej, podporności i wytrzymałości zmęczeniowej, przeprowadzono oględziny sekcji i nie stwierdzono uszkodzeń mechanicznych elementów podstawowych badanej sekcji. Zarejestrowane odkształcenia trwałe elementów podstawowych sekcji badanej w 2020 r. porównano z wynikami badań tej samej sekcji, wykonanych w 1996 r. (badania prototypu) oraz 2009 r. (badanie po modernizacji), również w laboratorium ITG KOMAG. Na podstawie wyników badań wykonanych w 2020 r. wykazano, że aktualne właściwości funkcjonalne sekcji spełniają wymagania normatywne. Zleceniodawca może więc podjąć decyzję o dalszym użytkowaniu w kolejnych ścianach