Anatomical characteristic of placenta and its relationship with calf birth weight in yak

摘要

Factors that adversely affect the productive potential of yak include low reproductive rate, low calf birth weight, premature births and high calf mortality under normal grazing and management conditions. In the present study, anatomical characteristic of placenta and its relationship with calf birth weight in yak was studied to investigate causes of low calf birth weight and high calf mortality. The average calf birth weight in the study was 12.44 ± 2.96 kg, which represented 6.41 ± 1.2% of average dam weight after calving. The average post-partum body weight of yak cows was 187.00 ± 26.98 kg, which was 20% less than the average female weight in breeding season. The average placental weight was 1.58 ± 0.49 kg. Total numbers of cotyledons in pregnant and non-pregnant horns were 45.00 ± 7.11 and 27.25 ± 4.06, receptively. Total cotyledon area was 1493.94 ± 327.37 cm~2 and total cotyledon area/birth weight of calf was 123.02 ± 23.44. These results seem to suggest that malnutrition in the third trimester of pregnancy is the major cause of low calf birth weight and low placental weight.