Uticaj toplotnog stresa na hormonalni status krava u periodu laktacije
Effect of heat stress on cows's hormonal status in the lactation period
Doktorand
Horvat, Jožef A.Mentor
Šamanc, HoreaČlanovi komisije
Šamanc, HoreaStojić, Velibor
Joksimović-Todorović, Mirjana
Metapodaci
Prikaz svih podataka o disertacijiSažetak
Cilj ovog rada bijo je da se ispita uticaj toplotnog stresa na metabolički i
endokrini status krava.
Ogled je izveden na 20 krava Holštajn – frizijske rase od 18. do 45. dana
laktacije tokom letnjeg perioda u trajanju od 37 dana. Tokom perioda izvođenja ogleda
određivana je vrednost „satnih“ toplotnih indeksa (THI) a zatim izračunata vrednost
prosečnih jutarnjih (od 22 h prethodnog do 9 h tekućeg dana), popodnevnih (od 10 h do 21
h tekućeg dana) i celodnevnih THI. Uzorkovanje krvi i određivanje trijasa izvršeno je 1.,
2., 8., 11., 14., 18., 25., 29. i 37. dana ogleda, u jutarnjem i popodnevnom periodu. Na
osnovu vrednosti satnih THI ceo ogledni period je podeljen na tri perioda: period A u
kome su krave bile izložene izrazitom toplotnom stresu (THI ≥ 78) najmanje 7 sati u
toku 24 sata (1., 8., 14., i 37. dan ogleda); period B u kome su krave bile izložene
umerenom toplotnom stresu (72 ≥ THI ≤ 78) najmanje 7 sati u toku 24 sata (2., 18., i 29.
dan ogleda); period C u kome krave nisu bil...e izložene toplotnom stresu (THI ≤ 72) u
toku 24 sata (11. i 25. dana ogleda). Prosečni dnevni THI u periodu A (73,25 ± 0,89) je
bio značajno veći (p<0,01, pojedinačno) u odnosu na period B (71,45 ± 0,96) i period C
(65,41±2,09). THI u periodu B je bio značajno viši nego u periodu C (p<0,01).
Dnevni unos hrane je bio manji kod krava tokom perioda izloženosti toplotnom
stresu za 2,9 odnosno 1,74 kg SM obroka u odnosu na period kada su bile u optimalnim
ambijentalnim uslovima držanja. U periodu optimalnih ambijentalnih uslova
temperature prosečna dnevna mlečnost je bila značajno viša (43,08 ± 5,15 L), nego u
uslovima umerenog (41,96 ± 5,51 L) odnosno izrazitog toplotnog stresa (39,47 ± 5,15
L) ali ovo smanjenje mlečnosti nije bilo u skladu sa količinom nepojedene hrane.
Hipertermija (39,72 ± 0,47 °C) i tahipnoja (86,60±6,39 n/minut) kod krava su
ustanovljene samo u popodnevnim časovima i mogu da posluže kao pouzdani klinički
poklazatelj toplotnog stresa. Pokazatelji razvoja toplotnog stresa su i promene vrednosti
elektrohemijske reakcije krvi (alkaloza).
Koncentracija koritzola je bila povišena u uslovima umerenog (10,44±3,07
nmol/L) i izrazitog topolotnog stresa (8,74±2,49 nmol/L) u odnosu na period sa
optimalnim ambijentalnim temperaturnim uslovima (6,41±2,11 nmol/L), pri čemu su razlike u koncentracijama ovog hormona bile značajne između svih ispitivanih perioda
(p<0,01, pojedinačno)...
The aim of this study was to evaluate the effects of heat stress on the metabolic
and endocrine status in cows.
The experiment was performed on 20 Holstein Friesian cows from lactation day
18 to 45 during the summer period for a duration of 37 days. During the experiment the
„hourly“ heat indices (THI) and thereon the values of the average morning (from 10PM
the previous day to 9AM of the current day), afternoon (10AM to 9PM of the current
day) and overall daily THI were determined. Blood sampling and trias readings were
recorded on the 1st, 2nd, 8th, 11th, 14th, 18th, 25th, 29th and 37th day of the
experiment, in the morning and afternoon periods. According to the values for hourly
THI the entire experimental period was divided into three periods: period A in which
the cows were exposed to a severe heat stress (THI ≥ 78) at least for 7 hours during a
24h period (1st, 8th, 14th and 37th day of the experiment); period B during which the
cows were exposed to moderate heat stress (72 ≥ TH...I ≤ 78) at least for 7 hours during a
24h period (2nd, 18th, and 29th day of the experiment), period C during which the cows
were exposed to heat stress (THI ≤ 72) during 24h (11th and 25th experimental
day).The average daily THI for period A (73,25 ± 0,89) was significantly higher
(p<0.01, individually) compared with period B (71.45 ± 0.96) and period C
(65.41±2.09), during period B THI was significantly higher compared with period C
(p<0.01).
The daily feed intake was by 2.9 and 1.74 kg DM feed less in cows exposed to
heat stress compared with the period in which the cows were kept under optimal
ambient conditions. In the period with optimal environmental temperature conditions
the average milk yield was significantly higher (43.08 ± 5.15 l), than in conditions of
moderate (41.96 ± 5.51) and severe heat stress (39.47 ± 5.15). However, this decrease
was not in unison with the quantity of not eaten feed.
Hyperthermia (39.72 ± 0.47 °C) and tahipnoa (86.60±6.39 n/min) were recorded
only during the afternoon hours in the cows exposed to severe heat stress and can be used as reliable clinical indicators of heat stress. Indicators of arising heat stress are the
changes in blood electrochemical reaction (alkalosis), also...