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Title: QUANTITATIVE ANALYSIS OF BIRTH, WEANING AND YEARLING WEIGHTS, AND CALVING DIFFICULTY IN PIEDMONTESE CROSSBREDS SEGREGATING AN INACTIVE MYOSTATIN ALLELE

Author
item Casas, Eduardo
item Keele, John
item Fahrenkrug, Scott
item Smith, Timothy - Tim
item Cundiff, Larry
item Stone, Roger

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Piedmontese breed has a high frequency of double-muscling. Double- muscling appears to result from two copies of the mutation (C313Y) in the myostatin gene. The objective was to determine the effect of zero, one and two copies of this mutation on the proportion of assisted calving and weights at birth, weaning and one year of age. A total of 301 animals born nfrom 1995 through 1997 were studied. A single copy of C313Y increased birth weight 3 kg compared to zero copies. Double-muscled animals with two copies of C313Y had more difficulty at birth than the other animals. Animals with a single copy were 9 kg heavier at weaning than animals with zero copies and were 20 kg heavier than animals with two copies at one year of age. The detection of the mutation that causes double-muscling in Piedmontese allows early life identification of animals with one copy of C313Y, improving the production system by selecting individuals with better rperformance and higher market value. Production systems that utilize mature cows to produce calves with a single copy of C313Y at the myostatin gene will benefit from heavier weights at weaning and at one year of age and higher yield of lean meat compared to normal cattle, while avoiding calving problems observed for double-muscled animals.

Technical Abstract: Piedmontese animals tested are homozygous for a guanine to adenine transition in exon 3 (C313Y) of the myostatin (MSTN) gene, responsible for double-muscling. The objective was to utilize a population segregating C313Y to determine its effect on proportion of assisted calving and weights at birth, weaning, and one year of age. Calves resulting from reciprocal backcrosses and F2 matings out of Piedmontese-Angus (PA) and Piedmontese- Hereford (PH) dams, born in 1995 (n=82), 1996 (n=75), and 1997 (n=144) were evaluated for birth weight (BWT, kg), adjusted weaning (W200, kg) and yearling (W365, kg) weight, and calving difficulty expressed as a proportion of assisted calving (CD). The number of copies of C313Y was assessed in each calf. The number of copies of C313Y was a significant source of variation for all traits (P<.01). For BWT, heterozygous animals were 3.2+/-.8 kg heavier than homozygous normal animals. Homozygous double-muscled animals had .19+/-.06 increase in proportion of CD, compare within heterozygous animals. A difference between homozygous animals (normal and double-muscled) was observed for BWT (5.2+/-1 kg) and CD (.21+/-.06). Heterozygous animals were heavier at W200 than homozygous normal animals (difference of 9.1+/-4 kg). Homozygous normal and heterozygous animals were heavier at W365 compared with homozygous double- muscled animals (difference of 20+/-8 and 24.5+/-8 kg, respectively). A difference was also estimated between the heterozygous and the mean of both homozygous for W200 and W365 (8.8+/-3 and 18+/-5 kg, respectively). Production of heterozygous animals, to take advantage of the positive impact of one copy of C313Y on carcass traits, is a viable production option since large increases in BWT or CD are not observed.