Growth of piglets during the suckling period is determined by both genetic and environmental factors. In addition to breed composition, one of the most important endogenous factors is the body weight at birth. This factor also significantly affects the losses to weaning, since it is known that light piglets are more susceptible to diseases and stress factors. In this paper we wanted to present trends of growth of Yorkshire piglets during the suckling period, with respect to the birth weight, as well as mortalities in each group. To lessen the effects of mother genetics and sex of individuals, as well as the influence of external factors, in the litter in which we observed the piglet of birth weight less than 1000 grams, the same-sex offspring heavier than 1000 g was taken as a control. Piglets were weighed at birth, on 7th, 14th and 21st day. Obtained results indicate that a statistically significant difference in body weight between the two groups maintained until weaning at the same level (P<0.01), where the piglets in the control group consistently progressed, while the lighter piglets were of very uneven growth and final weight at weaning. Average daily gain during the entire period was significantly higher (P<0.01) in heavier animals by 66.7 grams per day. Correlation of birth weight with body mass at weaning was positive and strong (r = 0.61, P<0.05). Furthermore, higher losses were recorded in the experimental group of piglets (29.2% compared to 8.3% in the control group), where they were the highest during the first 7 days.Prirast odojaka tijekom razdoblja sisanja određen je kako genetskim, tako i okolišnim čimbenicima. Pored pasminskog sastava, jedan od važnijih endogenih čimbenika je tjelesna masa pri porodu. Taj čimbenik također u značajnoj mjeri utječe i na gubitke do odbića, s obzirom da je poznata činjenica da su lakši odojci podložniji bolestima i stresu. U ovom smo radu željeli prikazati utjecaj porodne mase na prirast odojaka velikog jorkšira tijekom razdoblja sisanja te ukupna uginuća po skupinama. Kako bismo što više umanjili genetski utjecaj krmača te spola jedinki, kao i utjecaje vanjskih čimbenika, iz svakog legla u kojem smo promatrali odojka porodne mase manje od 1000 grama, kao kontrola promatran je istospolni potomak teži od 1000 g. Odojci su vagani po porodu, te 7., 14. i 21. dana. Dobiveni rezultati pokazuju da se statistički značajna razlika u tjelesnoj masi između dvije skupine zadržala do odbića na istoj razini (p<0,01), pri čemu su odojci kontrolne skupine ujednačeno napredovali, dok su lakši odojci bili vrlo neujednačenog prirasta i završne težine kod odbića. Nadalje, odojci kontrolne skupine tijekom promatranog razdoblja imali su značajno veći (p<0,01) prosječni dnevni prirast u odnosu na pokusnu skupinu za 66,7 grama/dan. Povezanost porodne mase s tjelesnom masom kod odbića bila je pozitivna i jaka (0,61; p<0,05). U pokusnoj skupini odojaka zabilježeni su veći gubici (29.2% u odnosu na 8.3% u kontrolnoj skupini), posebice tijekom prvih 7 dana
