The effect of systematical factors on quantity and quality of sheep milk

Abstract

Quantity and quality of sheep milk represent framework of any research and development projects which have as an objective creation of prerequisites for production of highly valued dairy products, primarily cheeses. It is a known fact that milk production in sheep varies depending on many factors of hereditary nature, but also numerous environmental factors. The major factors are: breed, condition, breeding value, order of lactation, stage/phase of lactation, number of lambed offspring, nutrition, housing and health condition. Objective of this paper was to investigate the influence of major systematical factors on milk yield and quality of milk in populations reared in the region of Stara Planina mountain. Research is main component of the project carried out in the region of Stara Planina mountain - Visok. Sheep included in the research are representatives of Pirot Pramenka and Pirot improved population. Investigation included three herds of 100-300 sheep, control of milk yield was carried out using standard method once a month, and quality of milk was determined on apparatus of the milk-test type. For processing of data in analysis of systematical influences we applied procedure of linear model, observing the effects of the year, order of lactation, type of lambing of dam and size of litter. Based on the performed research, processed and presented results we can conclude that the milk yield of investigated sheep of both genotypes varied depending on the year and lactation. The highest milk quantity was registered in the third year and third lactation, which was statistically significant in case of both genotypes. In the first and second year of research, as well as order of lactation, milk yield was different, or in other words we could observe considerable increase in the second year and second lactation, also significant. In both genotypes, values of mutual differences are neglect able and statistically insignificant. Content of fat and proteins in sheep milk from both observed populations decreased slightly from the first to third year, as well as from the first to third lactation, and observed differences were statistically significant. Sheep born as singles had slightly higher milk yield, and determined difference wasn’t statistically significant. Deviations in regard to the content of fat and proteins weren’t great, which indicated that type of lambing had no significant effect on these sheep milk traits. Breeding sheep which have lambed and reared two lambs had higher milk yield, and determined differences were statistically significant. Size of litter had no significant effect on content of fat and protein considering that established differences weren’t statistically significant.

Količina i kvalitet mleka ovaca variraju u zavisnosti od mnogih faktora nasledne prirode ali i uticaja mnogobrojnih spoljnih činilaca. Među najznačajnijim faktorima spadaju: rasa, kondicija, odgajivačka vrednost, laktacija po redu, faza laktacije, broj ojagnjenih mladunčadi, ishrana, držanje i zdravlje. Cilj ovoga rada je da se ispita kakav je uticaj najvažnijih sistematskih faktora na mlečnost i kvalitet mleka ovaca u populacijama koje se gaje na području Stare planine. Na osnovu sprovedenih istraživanja, možemo konstatovati da mlečnost ispitivanih ovaca varira u zavisnosti od godine i laktacije. Sadržaj masti i proteina u mleku ovaca obe posmatrane populacije beleži blagi opadajući trend od prve do treće godine, kao i od prve do treće laktacije, a uočene razlike su i statistički signifikantne. Ovce po tipu rođenja jedinci imale su nešto veću mlečnost, a utvrđena razlika nije i statistički signifikantna. Odstupanja u pogledu sadržaja masti i proteina nisu velika, što ukazuje da tip rođenja nema značajan uticaj na ove osobine mleka ovaca. Plotkinje koje su ojagnjile i odgajile po dva jagnjeta imaju veću mlečnost , a postojeće razlike su i statistički signifikantne. Veličina legla nema značajan uticaj na sadržaj masti i proteina obzirom da uočene razlike nisu statistički značajne.