5 October 2012

1 minute read

In Journal of Animal Science, Manoel Sá of FMVZ-USP in Sao Paulo, Brazil and co-authors at RG Genetica Avancada, Agropecuaria Abe, Firmasa and Sexing Technologies Brazil describe three experiments designed to evaluate methods to optimise the use of sex-sorted sperm in timed AI (TAI) programmes for suckled beef cows.

In all three experiments, suckled Bos indicus cows were synchronised using an intravaginal progesterone (P4) device over eight days and a 2.0-mg injection of intramuscular oestradiol benzoate (OEB) at device insertion. The females received PG and eCG (300IU) at P4 device removal and 1.0mg of OEB 24 hours later. The cows were inseminated 60 to 64 hours after P4 device withdrawal.

All cows had their ovaries scanned by transrectal ultrasound at TAI to identify and measure the largest follicle (LF) present.

In Experiment 1, a total of 853 cows had their LF classified as <9mm or >9mm at the time of TAI; these cows were then randomly assigned to four groups according to their LF diameter (<9 mm or >9 mm) and the type of sperm used (sex-sorted or non-sex-sorted).

There was an interaction (P=0.02) between the type of sperm and LF diameter beginning at TAI:

• non-sex-sorted >9mm = 58.9% a (126/214)
• non-sex-sorted <9mm = 49.5% b (106/214)
• sex-sorted >9mm = 56.8% ab (134/236)
• sex-sorted <9 mm = 31.2% c (59/189)
• a?b?c = P<0.05.

In Experiment 2, suckled cows (n=491) were classified immediately before TAI as having displayed oestrus or not (oestrus or no oestrus) between P4 device removal and TAI. These cows were randomly assigned to four groups according to the occurrence of oestrus and the type of sperm (sex-sorted or non-sex-sorted).

• no oestrus, non-sex-sorted = 43.6% (27/62)
• oestrus, non-sex-sorted = 58.5% (107/183)
• no oestrus, sex-sorted = 33.9% (21/62), and
• oestrus, sex-sorted = 50.0% (92/184)

However, no interaction between the occurrence of oestrus and type of sperm was observed (P=0.87).

In Experiment 3, a total of 200 suckled cows presenting LF >9mm at TAI were randomly assigned to receive sex-sorted sperm deposited into the uterine body (n=100) or into the uterine horn ipsilateral to the recorded LF (n=100). No effect of deeper AI on P/AI was found (P=0.57).

LF diameter at TAI and the occurrence of oestrus can be used as selection criteria to identify cows with greater odds of pregnancy to receive sex-sorted sperm in TAI programmes, concluded the researchers. In addition, performing TAI with sex-sorted sperm deeper into the uterus did not alter the pregnancy results.

Reference

Sá Filho M.F., R. Girotto, E.K. Abe, L. Penteado, E.P. Campos Filho, J.F. Moreno, R.V. Sala, M. Nichi and P.S. Baruselli. 2012. Optimizing the use of sex-sorted sperm in timed artificial insemination programs for suckled beef cows. J. Anim. Sci., 90(6):1816-1823. doi: 10.2527/jas.2011-4523

Further Reading You can view the full report (fee payable) by clicking here.