Chromosome abnormalities as a cause of reproductive inefficiency in heifers

Chromosome evaluations were made of 71 heifers previously diagnosed as not pregnant at the end of their first two breeding seasons. For comparison, evaluations also were made of 71 fertile contemporary females. Motaphase cells used in these analyses were obtained through 72-hour cultures of heparinized peripheral whole blood. Processed cells were affixed to slides by rapid air drying and subsequently stained with Giemsa. Karyotypes were constructed from enlarged (5 × 7 or 8 × 10) photomicrographs. Eleven breeds and various crossbreeds from the U.S. Meat Animal Research Center in Clay Center, Nebraska were used in this study. Of the 71 nulliparous heifers analyzed, 13(18.3 percent) had a varlety of chromosomal abnormalities. Abnormalities observed include one tetraplold/diploid mosaic, five presumptive 1/29 translocations, two trlsomy-X, two 59,X0/60,XX mosaics, one 60,XX/60,XY chimeric and two mixoplold mosaics with karyotype designations of 59,X0/60,XX/61,XXX and 59,X0/60,XX/61,X0. No chromosome defects were observed among the 71 contemporary fertile females.