Estimation of gestational age by the use of fetal parameters : placentome, femur length, and biparietal diameter : a dissertation presented in partial fulfillment of the requirements for the degree of Master of Veterinary Studies at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Date
2015
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Massey University
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Abstract
The research was conducted at (LATU) Large Animal Teaching Unit, Massey University,
New Zealand. The study involved 23 beef cows and 60 dairy cows. The aim of the study was
to test and assess the agreement between actual gestational age and that predicted using a
model developed in previous studies based on placentome length (gestational age =
placentome*2.88 - 6.11; Adeyinka et al., (2014) and to compare this agreement with that
obtained using fetal measurements of femur length and head size (biparietal diameter). The
research commenced on February 2015 and July 2015 for beef and dairy cows respectively
and ended June 2015 and September 2015 for beef and dairy cows respectively. Beef cows
were scanned transrectally every after three (3) weeks while dairy cows were scanned every
after one (1) week.. Overall there was no evidence of bias in all the parameters studied. The
strongest association (R2=0.85) was seen in dairy cattle when biparietal diameter was
measured and the weakest was placentome size in dairy cattle (R2=0.39). This is the first
study that has specifically focused on the agreement between estimates of gestational age
from fetal size and actual gestational age. This study has shown biparietal diameter to be a
better predictor of gestational age than mean placentome size across the range of gestational
ages found in this study. However, because the limits-of-agreement for biparietal diameter
increase as gestational age increases, by 120 days of gestation the difference between the
limits-of-agreement for biparietal diameter and those for mean placentome size are much
smaller than in early gestation, and the limits-of-agreement for biparietal diameter are similar
to those previously reported where data from all placentomes measured were used to predict
gestational age rather than just a single mean placentome size. At 120 days of gestation,
placentomes can be measured in a much higher proportion of cattle than biparietal diameter,
and even when the latter can be measured, placentome measurements are markedly easier to
obtain. Femur length was by far the most difficult parameter to measure and especially by
120 days was much less precise than mean placentome size or biparietal diameter. Therefore,
femur length should be restricted to use only in early gestation and then should be used
alongside other parameters like biparietal diameter.
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Keywords
Gestational age, Testing, Cattle, Foetuses, Fetuses, Measurement, Research Subject Categories::VETERINARY MEDICINE::Obstetrics and gynaecology