Pregnancy in slaughtered cows in North-Eastern Australia: incidence and relationship to pregnancy diagnosis, season, age and carcase weight.
A total of 7495 postpuberal beef cows from herds in north Queensland and the Northern Territory were examined at abattoirs to define the extent of wastage due to the slaughter of pregnant cows. On the basis of examination of teeth most cows (57%) were considered mature (approximately 3.5 to 7 years) at slaughter; 14% were young (9 months to 3.5 years) and 29% were old (over 7 years). In herds where pregnancy diagnosis by rectal examination had not been used at time of culling, 71.6% of slaughtered cows were pregnant and 42% of these cows were in the second trimester. This high pregnancy rate was considered an important source of herd wastage. Pregnancy rate varied little with season, but the highest percentages of cows pregnant in the first and third trimesters were recorded in autumn and spring, respectively. Most cows found non-pregnant had active ovaries at time of slaughter. Anoestrus was observed to be most common in winter and in old cows. Lactational status was not recorded. Mean cold carcase weight of 4229 cows was 161 +/- 40 kg. Maximum carcase weight was observed in cows slaughtered at 4 to 6 years of age; old cows had the lowest carcase weight (147 +/- 31 kg)  of the age groups considered. Highest (170 +/- 43 kg) and lowest (135 +/- 41 kg) carcase weights in relation to pregnancy or ovarian status were observed in non-pregnant/ovary-active and non-pregnant/anoestrus cows respectively. Carcase weight of cows in the third trimester (165 +/- 35 kg) was greater than in the second (161 +/- 35 kg) or first (157 +/- 36 kg) trimesters; difference between the first and third trimesters was significant (P less than 0.01).
D000003:Abattoirs; D000367:Age Factors; D000818:Animals; D001315:Australia; D001835:Body Weight; D002417:Cattle; D005260:Female; D007774:Lactation; D011247:Pregnancy; D011258:Pregnancy Tests; D011270:Pregnancy, Animal; D012621:Seasons