Some Effects of Pregnancy on Body Weight and Paunch Girth

Weight of the uterus and its content was determined by Swett et al. ( 6) from over 100 cows slaughtered at varying stages of pregnancy.The best-fitting curve for growth of the fetus was log~o weight (kg) = --8.596486-b 4.152249 log~o days pregnant, after 150.The entre describing the collective increase in weight of fetal membranes, amniotic fluid, and empty uterus was log,0 weight (kg) =--2.793861+1.728121 log~0 days pregnant, after 150.Adjustment of the body weight of a pregnant cow for these extraneous factors can amount to ahnost 15% of the observed values.Gross increases in paunch girth associated with pregnancy in cattle 24 to 48 months of age varied from .075 to .080em per day, after 150 days pregnant.It was estimated from changes in nonpregnant cows that true paunch growth varied from .020 to .030em per day, between 24 and 48 months, under favorable conditions.The average net increase in paunch girth due to pregnancy alone, after 150 days, was from .047 to .057cm per day.Adjustments of paunch girth for pregnancy generally were of minor concern, and amounted to a maximum of approximately 5% of the observed values.Studies of body growth and relationship of various body measurements to lactation performance comprise a sizable segment of dairy cattle research.Of the several body measures generally included, weight and paunch girth are most subject to extraneous factors, of which two principal ones are fill and stage of pregnancy.Varianee due to fill probably can best be controlled by certain management practices, sueh as taking weight and measurements only