OSOBINE RASTA HIBRIDNIH SVINJA PREDVIĐENE POMOĆU ASIMETRIČNE S-KRIVULJE

The present study was performed on 24 pigs distributed over two MHS-genotypes (NN, Nn) and two feeding regimes (intensive, restrictive). These pigs were investigated as the last of four trials in the experiment carried out by Kušec et al. (2005). The data on muscle and fatty tissue volumes were obtained by means of Magnetic Resonance Imaging (MRI). For the growth depiction and for the predictions of live weight as well as of muscle and fat tissue, four models developed by Kušec et al. (2007) were used. These models were set up on the basis of the general form of asymmetric S-function. This function seemed to fit well to the data collected in the present study; but the inaccuracy of the models appeared to increase with age. At the age of 124 days, the estimated values of live weight, muscle and fat volumes were close to the actual values measured in the group of intensively fed pigs; in the group of restrictively fed pigs live weight and muscle volume were underestimated while the volume of fat was overestimated. At the time of the last MR imaging (154 days of age), live weight and muscle volume was to some extent overestimated in the pigs fed intensively and underestimated in those fed restrictively. The volume of fatty tissue was estimated with favourable accuracy in all investigated groups of pigs. For further predictions, two approaches were used. In the first approach to predict individual live weights, at the age of 124 days, the predictions were fairly accurate for most of the pigs, falling in the range within one week; 4 of them being estimated falsely by more than ±7 days. Generally, when expressed as absolute value, the average misestimate was ~4 days in all groups, except for the restrictively fed MHS-gene carrier pigs which were estimated with 6 days difference on the average. At the age of 154 days, the predictions were to some extent less accurate; 7 pigs (in total) were incorrectly predicted by more than a week. The prediction accuracy was lower in the intensively fed pigs, ~6 days on the average; in the restrictive group of pigs, misestimates of live weight predictions were on the average ~4 and ~5 days for NN and Nn genotypes, respectively. Finally, in the second approach, the time that particular group of pigs would need to achieve a predetermined live weight of 100 kg was calculated. The closest prediction was achieved in the group of intensively fed MHS-homozygous negative pigs (4 days) while other groups were estimated with 6 days divergence from the actual age at 100 kg live weight. It was concluded that the predictions made by means of asymmetric S-function were fair enough for a pig producer to make a fattening plan or some other important decisions, e.g. in selection on growth traits.Istraživanja prikazana u ovome radu izvršena su na 24 hibridne svinje raspodijeljene prema genotipu (NN i Nn) i sustavu hranidbe (intenzivna i restriktivna). Te su svinje ispitivane u posljednjem od četiri ponavljanja u istraživanjima koje su proveli Kušec i sur. (2005). Podaci o volumenu mišićnoga i masnoga tkiva dobiveni su primjenom magnetno-rezonantne tomografije (MRT). Za opisivanje rasta i za procjenu živih masa; mišićnoga i masnoga tkiva korištena su četiri modela; koje su ustanovili Kušec i sur. (2007.) primjenom asimetrične S-funkcije. Dobivene S-krivulje nisu previše odstupale od podataka prikupljenim u ovom istraživanju; ali je uočeno da se nepreciznost modela pojačava s dobi životinja. U dobi od 124 dana; procijenjene vrijednosti žive mase; mišićnoga i masnoga tkiva bile su blizu vrijednostima izmjerenim u skupini intenzivno hranjenih svinja; u skupini restriktivne hranidbe žive su mase i volumeni mišića bili podcijenjeni; dok je volumen masnoga tkiva bio precijenjen. U trenutku posljednjega MRT mjerenja (dob od 154 dana); živa masa i mišićno tkivo bili su precijenjeni u intenzivno hranjenih svinja; a podcijenjeni u skupini restriktivne hranidbe. Volumen masnog tkiva bio je procijenjen sa zadovoljavajućom točnošću u svih istraživanih skupina svinja. Za daljnja predviđanja koristila su se dva pristupa. U prvome pristupu predviđale su se individualne žive mase u dobi od 124 dana; a prognozirane vrijednosti bile su u rasponu od tjedan dana; osim u 4 slučaja; što se može smatrati prilično točnim. Općenito; prosječna pogreška u prognozi bila je četiri dana u svim skupinama; osim u skupini restriktivno hranjenih svinja; nositelja MHS-gena (Nn); u kojih je pogreška prognoze iznosila 6 dana u prosjeku. U dobi od 154 dana; predviđanja su bila ponešto slabija; u 7 svinja (od ukupnoga broja) pogreška u prognozi iznosila je više od tjedan dana. Točnost prognoze bila je slabija u intenzivno hranjenih svinja (prosječna pogreška ~6 dana); dok je u restriktivnoj skupini prosječna pogreška za NN i Nn genotipove iznosila ~4; odnosno ~5 dana. Na kraju; primjenjujući drugi pristup; izračunalo se vrijeme koje bi skupina svinja trebala za porast do 100 kg. Najbliže predviđanje postiglo se u skupini intenzivno hranjenih MHS-homozigotno negativnih svinja (4 dana); dok je u ostalim skupinama odstupanje bilo 6 dana od dobi; pri kojoj je zaista dostignuta živa masa od 100 kg. Zaključeno je da se asimetrična S-funkcija može poslužiti u praksi za planiranje tova ili za donošenje neke druge važne odluke; na primjer u selekciji na svojstva rasta