Effects of high environmental temperatures on feeding behavior of cows and milk production

Abstract

The effects of high air temperatures and high relative air humidity (from the beginning of May till the end of September) on feeding behavior of cows, milk production and milk fat, were observed in black-pied breed on seven farms in the vicinity of Belgrade during three summers (1997-1999). Green mass (produced in conveyer) in the amount of 20-25 kg a day per cow was a base for the cow feeding ratio. The other part of the ratio consisted of whole maize plant silage (30-35% DM, 10-12 kg), alfalfa hay (1-2 kg), dry beet pulp (2 kg) and concentrate (15% crude protein, 0.25 kg kg-1 milk). Cows were kept in open stables, while water was given at libitum. High environmental temperatures (above 21oC, especially those higher than 26oC) and high air humidity lowered daily intakes of feeds and reduced milk production. The poorer isolation of stables from the direct exposure to sun was, the higher negative effects were.

Tokom tri letnje sezone (1997-1999) na sedam farmi Korporacije PKB u Pančevačkom Ritu, na kojima se gaje krave crno-bele rase, praćen je uticaj visokih temperatura i relativne vlažnosti vazduha (od početka maja do kraja septembra) na hranidbeno ponašanje krava, proizvodnju i masnoću mleka. Osnovu ishrane krava činio je zeleni konvejer: uljana repica (maj), ozima mešavina (maj i juni), jara mešavina (juni), zelena lucerka i sirak (juli-septembar) i to u količini od 20-25 kg zelene mase po kravi dnevno. Ostali deo obroka sačinjavali su: silaža cele biljke kukuruza (30-35% SM) 10-12 kg, seno lucerke 1-2 kg, suvi rezanci šećerne repe 2 kg, sirovi pivski trop 4 kg i koncentrat (sa 15% sirovih proteina) u količini od 0,25 kg/kg namuženog mleka. Krave su držane vezane u otvorenim stajama, a vodom su napajane po volji iz pojilica. Držanje krava u otvorenim objektima pokazalo se pogodnim u sprečavanju toplotnog stresa. Takođe, ishrana krava zelenom hranom i koncentratima povoljno je uticala na konzumiranje i proizvodnju mleka. Međutim, povremene visoke temperature spoljne sredine (preko 21oC, a naročito one iznad 26oC) i visoka vlažnost vazduha snižavale su konzumiranje hrane i proizvodnju mleka.