Changes in conception rate, calving performance, and calf health and survival from the use of crossbred Jersey x Holstein sires as mates for Holstein dams.

Differences in conception rates in matings of Holstein sires or F1 Jersey x Holstein sires to Holstein dams in the University of Wisconsin-Madison experimental herd were evaluated, as were differences in birth weight, dystocia, serum protein, serum IgG, fecal consistency, respiratory disease, and perinatal and pre-weaning mortality among the resulting calves. When mated to randomly chosen, lactating Holstein cows, Holstein sires (n = 74) and crossbred sires (n = 7) did not differ in male fertility. Calves from Holstein sires and multiparous Holstein dams (n = 99) were 1.9 kg heavier than calves from crossbred sires and multiparous Holstein dams (n = 211), leading to greater likelihood (odds ratio of 1.24) of dystocia. Furthermore, calves from crossbred sires and multiparous Holstein dams had higher serum protein and serum IgG levels between 24 and 72 h of age, as well as lower rates of perinatal and preweaning morality than calves from Holstein sires and multiparous or primiparous Holstein dams. Mean fecal consistency scores from birth to 7 d of age and number of days with scours also tended to be lower among calves from crossbred sires, compared with calves from Holstein sires. No differences were observed in the incidence or severity of respiratory disease. Results of this study suggest that introduction of Jersey genes via crossbreeding may lead to a reduction in dystocia and improvements in calf health and survival in Holstein herds. Future studies should address other traits related to dairy farm profitability, including milk composition, female fertility, longevity, feed efficiency, and resistance to infectious and metabolic diseases.

In vitro production of Holstein embryos using sex-sorted sperm and oocytes from selected cull cows.

The objective of this study was to explore potential synergies between sex-sorted sperm and in vitro embryo production for generating replacement heifers on commercial dairy farms. Selected involuntary cull cows (i.e., genetically suitable cows that were culled due to injury, illness, or infertility) from 7 Wisconsin farms were used as donors, and ovaries were collected via colpotomy or at the time of slaughter. Oocytes were aspirated, fertilized in vitro with sex-sorted sperm 22 +/- 0.2 h later, cultured, matured for 7 to 8 d, and transferred into recipient cows and heifers on the farms from which the cull cows originated. From August 2002 to June 2003, ovaries were recovered from 104 Holstein donors. Sex-sorted sperm from 3 Holstein sires (obtained via fluorescence-activated cell sorting) were used. A total of 365 transferable embryos were produced, an average of 3.6 +/- 0.3 per donor. However, due to limited availability of recipient animals, only 272 (fresh) embryos were transferred, an average of 2.6 +/- 0.3 per donor. A random subset of recipients received an injection (i.m.) of GnRH (100 microg) at the time of embryo transfer. When lactating cows were used as recipients, mean conception rates were 16.3% for recipients identified based on standing estrus and 20.0% for recipients synchronized using a timed breeding program (Ovsynch). Conception rates for in vitro-produced embryos were lower than corresponding conception rates for control cows inseminated using unsorted semen. When virgin heifers were used as embryo recipients (all standing estrus), the mean conception rate was 34.2%. The following effects significantly impacted conception rate: farm, season, recipient group (cow vs. heifer), sire of embryo, and GnRH injection. Of 40 full-term calves generated using sex-sorted semen, 37 were female. These results suggest that "low-cost" in vitro embryo production using cull cows as donors, in conjunction with sex-sorted sperm, could be an effective tool in dairy cattle breeding programs, but only if conception rates can be improved.