Reproductive performance of 50% Bos Indicus cattle grazing the Mitchell grasslands of north Queensland

[Summary]: The reproductive performance was measured in a beef breeding herd, of 50% Bos Indicus, grazing the Mitchell (Astrebla spp) grasslands of north Queensland from 1973 to 1980. The mean pregnancy rate over the eight years (1973 to 1980) was 91.4% ranging from 79.0% to 96.0%. Mean pregnancy rates and ranges for variousage groups were (i) 2 year old heifers, 93.4% (86.2 - 97.6%), (ii) wet 3 year old cows, 79.6% (41.4 - 94.4%), (iii) wet 4 year old and older cows, 92.4% (74.4 - 96.6%). Generally, dry cows had higher conception rates than wet cows. Lactation failures (cows pregnant one year but dry at the following year's pregnancy test) wer 9.3% (range 4.7 - 15.8%). Age of dam had no effect on prevalence of lactation failures. Body condition levels were dependent on seasonal conditions and the mean herd body condition varied from 4.8 (backward store-store) to 7.5 (prime-fat).