Svetlosni program, gustina naseljenosti i sastav obroka u funkciji proizvodnih parametara,kvaliteta mesa i dobrobiti brojlerskih pilića

Abstract

Cilj istraţivanja bio je da se ispita uticaj svetlosnog programa (konstantnog – KS i opadajuĆe- rastuĆeg - ORS), gustine obroka i gustine naseljenosti i njihove interakcije na proizvodne i klaniČne osobine brojlerskih piliĆa, kvalitet mesa i ošteĆenje tabanskih jastuČiĆa. Istraţivanja su sprovedena na farmi piliĆa Donji Crnci nadomak Podgorice u tri ogleda: u prvom su ispitivani efekti svetlosnog programa i gustine obroka, u drugom programi svetla i gustina naseljenosti piliĆa, a u treĆem program svetla i gustina obroka (smeše sa standardnim i poveĆanim sadrţajem energije i proteina, pri Čemu je odnos energija : protein bio konstantan). U svakom ogledu bilo je 320 piliĆa linijskog hibrida Cobb 500, mešanih po polu, a ogledi su trajali 42 dana. U sva tri ogleda formirane su po Četiri grupe sa Četiri ponavljanja i u svakoj grupi bilo je 80 jednodnevnih piliĆa. Proizvodni parametri (telesna masa, utrošak hrane i uginuĆa) praĆeni su u svim ogledima, a izraČunati su konverzija hrane i proizvodni indeks. Telesne mase su merene u uzrastu od 1; 7; 14; 21; 28; 35 i 42 dana. Utrošak hrane utvrčivan je na kraju perioda primene pojedinih smeša, i to: 14. dana koliČina konzumirane starter smeše, 35. dana grovera i 42. dana finišer smeše. Mortalitet je odrečivan beleţenjem broja uginulih piliĆa u toku trajanja ogleda. Na osnovu telesnih masa, konverzije hrane i mortaliteta izraČunati su proizvodni indeksi. Na kraju svakog ogleda, sa 6 nedelja starosti, piliĆi su izmereni pojedinaČno, izraČunati su proseci tretmana, a zatim je od svakog tretmana izdvojeno 20 piliĆa (10 muških i 10 ţenskih) radi ispitivanja klaniČnih karakteristika. Pre klanja piliĆi su gladovali 12 sati. Nakon klanja i ČišĆenja trupovi su ohlačeni na 40C u toku 24 sata, a potom obračeni kao: „klasiČna obrada” „spremno za peČenje” i „spremno za roštilj”. Pri konfekcioniranju trupova izdvojena je abdominalna mast, izmerene mase obračenih trupova i dobijeni randmani. Radi utvrčivanja prinosa i udela osnovnih i sporednih delova trupa izvršeno je rasecanje ohlačenih trupova. Ocena konformacije trupova izvršena je na osnovu utvrčenih apsolutnih mera: duţine piska, duţina kobilice, dubina grudi i obim bataka. KorišĆen je indeks koji predstavlja odnos ţive mase pre klanja i posmatrane mere (g/mm). U ogledu II izvršeno je i fiziČko ispitivanje kostiju, na femuru nakon izdvajanja od skeleta brojlera, a u ogledu III odrečeni su sadrţaj vlage, sadrţaj ukupne masti, ukupnog pepela i ukupnih proteina belog i crvenog mesa, na uzorcima mišiĆnog tkiva grudi i karabataka od 5 muških i 5 ţenskih trupova u svakom tretmanu (ukupno 20). Rezultati ukazuju da svetlosni program nije statistiČki znaČajno uticao na završne telesne mase u ogledima I i II, dok su u ogledu III veĆe mase utvrčene kod piliĆa tovljenih pri KS. Primena ORS uticala je na usporavanje stope rasta u prvom periodu tova, a kao rezultat kompenzacionog porasta bez uticaja na završne mase, sem u treĆem ogledu. Bolju konverziju hrane u periodu ishrane finišerom postigli su piliĆi u ogledu I pri ORS nego pri KS, kao i u ishrani starterom u ogledu III. Svetlosni programi u ogledu II nisu uticali na konverziju hrane i mortalitet piliĆa. Gustina obroka nije uticala na završne mase, konverziju hrane, mortalitet i proizvodni indeks. Kod piliĆa hranjenih obrocima sa višim sadrţajem proteina i energije utvrčene su veĆe telesne mase na kraju tova (P<0.01). Gustina obroka u ogledima I i III nije imala uticaj na konverziju hrane, mortalitet i proizvodni indeks. Znatno je veĆa završna masa piliĆa tovljenih pri gustini naseljenosti od 12 grla/m2 (2667,08 g) nego pri 17 grla/m2 (2435,76 g) i razlike su bile statistiČki visoko znaČajne. Nije utvrčen uticaj gustine naseljenosti na konverziju hrane, mortalitet i proizvodni indeks. Ispitivani faktori (svetlo, gustina obroka i gustina naseljenosti) nisu uticali na randmane, ali jesu interakcije nekih od njih. U svim ogledima utvrčen je manji udeo abdominalne masti pri ORS nego pri KS, ali bez statistiČke znaČajnosti. Gustina obroka i gustina naseljenosti nisu uticali na sadrţaj abdominalne masti. VeĆi je sadrţaj abdominalne masti u svim ogledima bio kod ţenskih nego muških piliĆa. Udeo grudi veĆi je pri KS nego pri ORS, ali su razlike statistiČki znaČajne samo u treĆem ogledu. Gustina obroka i gustina naseljenosti nisu uticale na udeo grudi. Udeo bataka bio je veĆi kod piliĆa tovljenih pri ORS nego pri KS, ali su razlike statistiČki znaČajne samo u prvom ogledu. Udeo karabataka u prvom i drugom ogledu nije se znaČajno razlikovao izmeču svetlosnih programa, dok je u treĆem bio veĆi pri ORS nego pri KS (P<0.01). Nije utvrčen uticaj gustine naseljenosti i gustine obroka na udeo bataka i karabataka. Kod muških piliĆa utvrčen je veĆi udeo bataka, a kod ţenskih karabataka. Relativne vrednosti mera konformacije nisu bile pod uticajem svetlosnih programa i gustine obroka, osim što je pri manjoj gustini naseljenosti relativna vrednost dubine grudi bila veĆa (P<0.05). Na ošteĆenje tabanskih jastuČiĆa nije utvrčen uticaj svetla i gustine obroka, ali su piliĆi pri veĆim gustinama naseljenosti, poČev od 28. dana, imali znatno veĆa ošteĆenja tabanskih jastuČiĆa nego pri manjoj gustini. Svetlosni program i gustina naseljenosti nisu uticali na fiziČke osobine femura: površinu preseka, silu loma i specifiČnu silu loma. Muški piliĆi imali su veĆi površinu preseka i silu loma femura, razlike za površinu preseka su statistiČki znaČajne, ali ne i za silu loma. Procenat masti u tamnom mesu bio je veĆi, a proteina niţi pri ORS nego pri KS. Ostali parametri hemijske analize tamnog i belog mesa nisu bili pod uticajem svetlosnih programa. Gustina obroka nije imala uticaj na hemijski sastav mesa grudi i karabataka. Na osnovu svega iznesenog moţe se zakljuČiti da su sva tri faktora (svetlosni program, gustina obroka i gustina naseljenosti), kao i njihove interakcije, uticali na brojne proizvodne parametre i kvalitet mesa brojlera, pa i na njihovu dobrobit u razliČitim fazama tova. ImajuĆi u vidu ogromne razlike u efektima koji se mogu postiĆi pri razliČitim kombinacijama ovih Činilaca, rezultati ovih i sliČnih istraţivanja treba da olakšaju izbor tehnologije koja Će davati najbolje ekonomske efekte u tovu piliĆa. Takoče, tamo gde su rezultati nejasni ili kontradiktorni, treba nastaviti istraţivanja na veĆem broju jedinki i fokusirati se na ekonomski vaţnije proizvodne i klaniČne osobine piliĆa.

The purpose of the research was to investigate the effect of the lighting program (constant – KS and intermittent – ORS), feed density and stocking density and their interaction with production and slaughterhouse characteristics of broiler chicken, meat quality and feet pad damage. The research was conducted on a chicken farm Donji Crnci in the vicinity of Podgorica, in three trials: the first trial focused on effects of the lighting program and feed density, the second on the lighting program and stocking density and the third on the lighting program and the feed density (mixes with standard and increased content of energy and protein, with a constant energy:protein ratio). Each of the trials included 320 chicken of the Cobb 500 hybrid line, mixed sexes; trials lasted for 42 days. In all three trials, four groups were formed with four repetitions and each group included 80 one-day chickens. Production parameters (weight, feed consumption and deaths) were monitored in all trials and feed conversion ratio and production index were calculated. Weight was measured when broilers were 1; 7; 14; 21; 28; 35 and 42 days old. Feed consumption was determined at the end of the use of specific mixes, as follows: 14th day the quantity of starter mix consumed, 35th day the quantity of grower mix consumed and 42nd day quantity of the finisher mix. Mortality rate was determined by recording the number of chicken that died during the trial. Production indices were calculated based on weight, food conversion ratio and mortality. At the end of all trials, at 6 weeks of age, the chickens were measured individually, group averages were calculated and then by random sampling, 20 chicken were taken from each group (10 males and 10 females) in order to analyse slaughter characteristics. Pre-slaughter fasting lasted for 12 hours. After slaughter and cleaning, the carcasses were cooled to 40C over 24 hours and then processed as: “classical processing”, “ready to grill” and “barbecue ready”. In carcass processing, abdominal fat was taken out, weight of processed carcases measured and carcass yield values were obtained. In order to determine the yield and share of the main and secondary parts of the carcass, cooled carcasses were cut out. Evaluation of carcass conformation was done on the basis of absolute measures of the following: metatarsus length, keel length, breast depth and drumsticks circumference. Index representing the ratio of live weight before slaughter and measure observed was used (g/mm). In Trial II, physical examination of bones was done, on femur, upon separation from the broiler skeleton, and in Trial III moisture content, total fat content, total ash content and total protein of white and red meat was determined on samples of muscle tissue of breasts and thighs of 5 male and 5 female carcasses in each of the treatments (20 in total). The results show that lighting program had no statistically significant effect on final body weight in Trials I and II, while in Trial III, higher weights were recorded in chicken fattened under KS. ORS resulted in slowing down of the growth rate in the first fattening period, and as a result of compensatory growth it had no effect on final weights, except in the third trial. Better food conversion ratio in the period of finisher mix diet was achieved by chicken in Trial I under ORS than those under KS, as well as in starter mix diet in Trial III. Lighting program in Trial II had no effect on food conversion ratio and mortality of chicken. Feed density did not have an effect on final weights, feed conversion, mortality and production index. In chicken fed with meals with higher protein and energy content, higher weight was recorded at the end of the fattening period (P<0.01). Feed density in Trials I and III did not have an effect on feed conversion ratio, mortality and production index. Significantly higher weight was recorded in chicken fattened at the stocking density of 12 animals/m2 (2667.08 g) than at the density of 17 animals/m2 (2435.76 8 g) and differences had statistically high significance. No effect of stocking density was identified in terms of feed conversion, mortality and production index. Factors analysed (light, feed density and stocking population) did not have an effect on carcass yield, but interactions of some of them did. In all the trials, a smaller share of abdominal fat was established under ORS than under KS, but it was not statistically significant. Feed density and stocking density had no effect on abdominal fat content. Higher abdominal fat content in all trials was found in female than in male chicken. The share of breasts is larger under KS than under ORS, but differences are statistically significant only in the Trial III. Feed density and stocking density had no effect on the share of breasts in the carcass. The share of drumsticks was higher in chicken fattened under ORS than those under KS, but differences were statistically significant only in the Trial I. The share of thighs in Trials I and II did not differ significantly between lighting programs, while in the Trial III it was higher under ORS than under KS (P<0.01). Effect of stocking density and feed density on the share of drumsticks and thighs was not determined. Higher share of drumsticks was determined in male chicken while in female, the share of thighs was higher. Relative values of conformation measures were not influenced by the light programs and feed density, except that in lower stocking density the relative value of the breast depth was higher (P<0.05). Effect of light and feed density on feet pads damage was not determined, but chicken in higher stocking density, as of 28th day, had significantly higher feet pad damage than those in lower stocking density. Light program and stocking density did not have an effect on physical properties of femur: cross-sectional area, breaking force and specific breaking force. Male chicken had larger cross-sectional area and femur breaking force, differences in cross-sectional area were statistically significant, but this was not the case with the breaking force. Percentage of fat in dark meat was higher and that of proteins lower under ORS than under KS. Other parameters of the chemical analysis of dark and white meat were not under the influence of the light programs. Feed density had no effect on chemical composition of breasts and thighs meat. Based on all stated above, it can be concluded that all three factors (light program, feed density and stocking density) as well as their interactions had effect on numerous production parameters and quality of broiler meat, including on their welfare in different fattening phases. Taking into account enormous differences in effects that may be achieved in different combinations of these factors, the results of these and similar researches should make easier the selection of the technology that would yield the best economic effects in chicken fattening. Furthermore, where results are unclear or contradictory, further research should be conducted on a larger number of animals and focus on economically more significant production and slaughterhouse characteristics of chicken.