Uticaj Energetskog Bilansa na Endokrini i Metabolički Status Krava

Abstract

Cilj ove doktorske disertacije je bio da se ispita uticaj energetskog dodatka na bazi glicerola na metabolički i endokrini status krava u kasnom graviditetu i ranoj laktaciji. Ispitivanja su izvršena na 60 krava odabranih u zasušenju podeljenih u dve jednake grupe. Obe grupe su dobijale potpuno izmešan obrok dva puta dnevno koji je bio usklađen sa potrebama jedinki u odnosu na fazu proizvodno reproduktivnog ciklusa. Dodatno, krave ogledne grupe su u jutarnjem obroku dobijale energetski dodatak u količini od 250 ml u periodu zasušenja, odnosno od 15. dana pre očekivanog termina teljenja do momenta teljenja, i u količini od 300 ml u periodu rane laktacije, odnosno prvih 60 dana posle teljenja, čime im je obezbeđeno dodatnih 9,30 MJ NEL tokom zasušenja, odnosno 13,95 MJ NEL tokom rane laktacije. Kontrolna grupa krava nije primala energetski dodatak. Telesna kondicija krava određena je 15. dana pre i 7., 30. i 60. dana posle teljenja. Sedmog, tridesetog i šezdesetog. dana nakon teljenja zabeležena je dnevna proizvodnja mleka. Od reproduktivnih pokazatelja registrovani su servis period i indeks osemenjavanja. Uzorci krvi za analizu uzimani su od krava punkcijom vene jugularis 15. dana pre , kao i 7. 30 i 60. dana nakon teljenja. U uzorcima krvi određivani su koncentracije glukoze, beta-hidroksi buterne kiseline (BHBA), neesterifikovanih masnih kiselina (NEFA), ukupnih proteina, albumina, uree, ukupnog bilirubina, kalcijuma, fosfora, insulina, trijodtironina, tiroksina, IGF-I i zastupljenost IGFBP-2, -3 i -4. Uzorci tkiva jetre su uzeti 7., 30. i 60. dana laktacije i u njima je određivan sadržaj ukupnih lipida.Računski su dobijeni HOMA (homeostatic model assessment) indeks i odnos T₃ i T₄.

Krave ogledne grupe su u odnosu na kontrolnu imale značajno višu vrednost ocene telesne kondicije 7 dana nakon teljenja. Proizvodnja mleka kod krava ogledne grupe je bila značajno viša 60. dana laktacije. Krave koje su primale energetski dodatak su imale značajno kraći servis period u odnosu na kontrolnu grupu. Prosečni stepen zamašćenja jetre je 7. dana laktacije kod kontrolne grupe bio srednji a kod ogledne nizak. Tridesetog dana laktacije stepen zamašćenja jetre je bio značajno niži kod ogledne u odnosu na kontrolnu grupu, dok 60. dana ni kod jedne grupe nisu utvrđene masne kapljice u jetri.Vrednosti biohemijskih parametara i ispitivanih hormona se nisu značajno razlikovalie između grupa pre početka ogleda odnosno u zasušenju. Koncentracije glukoze i insulina je bila značajno viša kod ogledne u odnosu na kontrolnu grupu 30. i 60. dana laktacije. Koncentracije BHBA i NEFA su bile značajno niže kod krava ogledne grupe u odnosu na kontrolnu grupu u sva tri postpartalna perioda ispitivanja. Koncentracija ukupnog bilirubina je bila značajno viša kod kontrolne u odnosu na oglednu grupu 7. dana posle teljenja. Koncentracija ukupnih proteina, albumina, IGF-I, kao i zastupljenost IGFBP-3 je bila značajno viša kod ogledne u odnosu na kontrolnu grupu u sva tri perioda postpartalnog ispitivanja dok razlika u koncentraciji uree između dve grupe nije utvrđena. Zastupljenost IGFBP-2 je bila značajno viša u oglednoj u odnosu na kontrolnu grupu 60. dana laktacije dok nije utvrđena značajna razlika u zastupljenosti IGFBP-4 između grupa. Nije bilo razlike u koncentraciji fosfora između grupa dok je kalcemija bila značajno viša kod ogledne u odnosu na kontrolnu grupu 60. dana laktacije. Koncentracije T₃ i T₄ su bile značajno više kod ogledne u odnosu na kontrolnu grupu 7. dana laktacije. Tridesetog dana laktacije krave ogledne grupe su i dalje imale značajno višu koncentraciju T₄ u odnosu na kontrolnu grupu. HOMA indeks je bio značajno viši 30. i 60. dana laktacije, a indeks konverzije T₄ u T₃značajno niži u puerperijumu i 30. dana laktacije kod krava ogledne grupe u odnosu na kontrolu. Na osnovu dobijenih rezultata se može zaključiti da je energetski dodatak povoljno uticao na smanjenje izraženosti postpartalnog NEBa kod krava što je za posledicu imalo manji stepen zamašćenja jetre, veću mlečnost i kraći servis period kod ovih jedinki.

Alternate abstract:

The aim of this PhD thesis was to examine the effect of glycerol based energy supplementation on metabolic and endocrine status of cows in late pregnancy and early lactation. The study was conducted on a total of 60 cows, selected in dry period and divided into two groups. Both groups of cows were fed with a total mix ratio adjusted to the nutritive needs for pregnancy and lactation. Additionally, each cow in the experimental group was given energy supplement dispersed in the morning feed by sprayer for the period of the experiment in the quantity of 250 mL during last 15 days of pregnancy and 300 mL during first 60 days of lactation. Added glycerol provided additional 9.30 MJ NEL during dry period and additional 13.95 MJ NEL during early lactation period. Control animals did not receive energy supplement. Body condition score was performed at day 15 before and days 7, 30 and 60 after calving. Milking was measured at days 7, 30 and 60 of lactation. Service period and insemination index were determined. Four blood samples were taken by jugular venipuncture from each animal at day 15 before and days 7, 30 and 60 after calving. The blood glucose, beta-hydroxi butirate (BHBA), non-esterified fatty acid (NEFA), total protein, albumin, urea, total bilirubin, Ca, P, insulin, triiodothyroinine, thyroxine, IGF-I as well as relative abundance of IGFBP-2, -3 and - were measured. Liver percutaneous biopsies were obtained at days 7, 30 and 60 after calving and total lipid content in hepatocites was measured.

At day 7 after calving, cows from experimental group had significantlly higher values for body condition scores than cows from control group. Experimental group of cows had significantlly higher milk production than control group at day 60 of lactation. Energy supplemented cows had significantlly shorter service period than control group. At day 7 of lactation, average degree of fatty liver was moderate in cows of control group and mild in cows from experimental group. At day 30 of lactation exerimental group of cows had significantlly lower fatty liver digree then control group. At day 60 of lactation there was no fat droplets in hepatocites of cows from both groups. Concentrations of blood measured biochemical and hormone parameters did not significantlly differ between two groups at dry period, meanining before the biggining of experiment.Glucose and insulin concentrations were significantly higher in experimental compared to control group of cows. Concentrations of BHBA and NEFA were significantly lower in experimental compared to control group of cows at all three examined postpartal periods. Total bilirubin concentration was significantly higher in control comapred to experimental group at day 7 after calving. Total protein, albumin, IGF-I copncentrations as well as relative abundancy of IGFBP-3 were significantly higher in experimental than in control group of cows at all three examined postpartal periods, while there was no significant difference in urea concentrations between groups. Relative abundancy of IGFBP-2 was significantly higher in experimental than in control group at day 60 of lactation, while there was no significant difference in IGFBP-4 abundancy between groups. There was no significant difference in P concentrations between groups, while calcemia was significantlly higher in experimental compared to control group at day 60 of lactation. T₃ and T₄ concentrations were significantly higher in experimental than in control group at day 7 of lactation. At day 30 of lactation, experimental group of cows had still higher T₄ concentartion than control group. HOMA index was significantly higher at days 30 and 60 of lactation, and index of T₄ to T₃conversion was significantly lower at days 7 and 30 of lactation in experimental compared to control group of cows.

In conclusion, dietary energy supplementation in peripartal dairy cows improved energy of cows, implicating that these cows probably did not suffer from severe negative energy balance. Consequently, fatty liver degree was depressed, milk production was enhanced and reproductive performance is improved in cows that received dietary energy supplement.