1. Performance of Holsteins that originated from embryo transfer or twin births H.D. Norman, J.R. Wright* and R.L. Powell Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350 OBJECTIVES Compare the performance of ET Holsteins to their non-ET full sibs. Compare cows from multiple births (twins, triplets) to their single birth full sibs. INTRODUCTION Preferential management of embryo transfer (ET) animals could potentially cause bias in genetic evaluations. Previous studies have indicated that the rate of twin births may be increasing. CONCLUSIONS Numbers of ET animals peaked in 1993 and is currently declining. Numbers of cows coded twin (multiple birth) has increased during the last 25 years. PA of ET cows and bulls was superior to the population mean for milk, fat and protein. PA of bulls coded twin (multiple birth) was less than population mean while PA of cows was nearly the same. ET cows were nearly identical to their non-ET full sisters for all traits indicating no preferential treatment. Cows coded twin were out-performed by their non-twin full sibs and stayed in the herd for an average of.4 mo less. DATA ET  293,033 females and 129,394 males with pedigree records.  185,104 cows and 26,238 bulls with Parent Average (PA) records.  10,277 cows and 3,512 bulls with PTAs also having non-ET full sibs with PTAs. Twin (all multiple births; twins, triplets)  684,329 multiple birth code females with pedigree records and 11,446 multiple birth code males with pedigree records.  301,434 multiple birth code cows and 769 multiple birth code bulls with PA records.  6,514 multiple birth code cows and 57 multiple birth code bulls with PTAs also having full sibs with PTAs. RESULTS (cont.) RESULTS Abstr. W89 PA of ET cows was superior to cow population mean by an average of 133 kg for milk. PA of ET bulls was superior to cow population mean by an average of 339 kg and bull population mean by 80 kg for milk. ETFull Sisters Standardized trait: Milk (kg) 10,570 10,565 Fat (kg) 387 390 Protein (kg) 315 316 SCS 3.1 3.1 Productive Life (mo) 26.9 26.3 Yield deviation: Milk (kg) -287-277 Fat (kg) -6 -3 Protein (kg) -6 -5 PTA: Milk (kg) -106 -107 Fat (kg) -2 -1 Protein (kg) -2 -2 SCS 3.1 3.1 Productive Life (mo) 0.3 0.3 PA of cows recorded from twin births was nearly identical to the population mean with a difference of only 3 kg for milk. PA of bulls recorded from twin births was less than bull population mean by an average of 138 kg for milk. TwinsFull Sisters Standardized trait: Milk (kg) 10,050 10,161 Fat (kg) 366 371 Protein (kg) 298 301 SCS 3.1 3.1 Productive Life (mo) 26.3 26.7 Yield deviation: Milk (kg) -500-407 Fat (kg) -17 -12 Protein (kg) -14 -11 PTA: Milk (kg) -186 -170 Fat (kg) -6 -5 Protein (kg) -2 -2 SCS 3.1 3.1 Productive Life (mo) 0.0 0.0 Productive Life was.6 mo longer for ETs than for their non-ET full sib sisters. PTAs for ETs and their non-ET full sib sisters were nearly identical. Yield deviations of twin cows were lower than their non-twin full sibs by 93, 5, and 3 kg for milk, fat, and protein, respectively. Average PTAs of twin cows were lower than their non-twin full sibs for milk and fat but the same for protein, SCS, and PL. Means for Holstein ET cows with DHI milk records and their non-ET full sisters Means for Holstein twin cows with DHI milk records and their non-twin full sisters RESULTS