Factors affecting pregnancy rate in Holstein-Friesian cattle mated during summer in a tropical upland environment.
The relationships between some environmental factors and reproductive rates of dairy cattle during summer in a tropical upland area were studied using records for Holstein-Friesian milking cows and non-lactating growing heifers maintained at the Kairi Research Station on the Atherton Tableland in north Queensland. The Station is situated in a tropical upland environment with warm, wet summers and dry, cool winters. Data were collected over a 12-year-period (1977 to 1988) for cows grazing nitrogen (N)-fertilised grass pastures and receiving either no supplement or about 3.5 kg molasses/cow/day. Cattle were mated over a 10-week period starting from mid-January to early February, with 32 to 36 cows and 5 to 42 heifers used in each year. There was considerable variation among years in the pregnancy rate after 3 inseminations, with a low of 39% and a high of 94% pregnancy. This variation from year to year was reduced for cows grazing pastures receiving 300 kg N/ha/yr after molasses feeding commenced in 1984-85. Pregnancy rates after molasses introduction were higher for cows grazing pastures receiving 300 compared with 100 kg N/ha/yr. Pregnancy rate in cows and heifers was reduced from 80 to 55% as mean daily maximum temperature increased from 26 degrees C to 27.5 degrees C. At mean maximum temperatures above 27 degrees C for cows and 27.6 degrees C for heifers pregnancy rates to 3 inseminations were consistently below 60%. Much of the year to year variation in pregnancy rate was related to rainfall during the mating period.(ABSTRACT TRUNCATED AT 250 WORDS)
Queensland Department of Primary Industries, Mutdapilly Research Station, Ipswich.
W N
WN
Orr
R T
RT
Cowan
T M
TM
Davison
D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D005260:Female; D005298:Fertility; D005306:Fertilization; D005308:Fertilizers; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D008892:Milk / Q000378:metabolism; D008965:Molasses; D011247:Pregnancy; D011270:Pregnancy, Animal; D011793:Queensland; D011891:Rain; D012621:Seasons; D013696:Temperature; D014329:Tropical Climate
D005308:Fertilizers