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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #89965
Title: EFFECTS OF DIETARY FAT AND SIRE BREED ON AGE AT PUBERTY OF HEIFERS

Author
item LAMMOGLIA, M - BOVA GEN
item Bellows, Robert
item Grings, Elaine
item Short, Robert

Submitted to: Governors Conference on the State of the Livestock Industry
Publication Type: Other
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: F1 heifers [n=246; crossbred dams bred to either Hereford (H), Limousin (L) or Piedmontese (P) sires] were randomly allotted to receive 1.9%(LF) or 4.4% (HF) dietary fat. Safflower seeds (37% oil with 80% linoleic acid) were used as a fat source. Rations were isocaloric and isonitrogenous and were fed from 250 d of age until puberty or breeding season started. If necessary, rations were adjusted every 56 d to maintain an average daily gain of .77 kg. Epididectomized bulls were placed with the heifers to aid in estrous detection (performed twice daily). Puberty was defined when a heifer showed estrous behavior, had a CL, and serum progesterone (P4) concentrations above 1 ng/mL between d 7 to 10 following estrus. Heifers were weighed every 28 d and a 60-heifer sample representing each breed type and dietary treatment were back fat measured using ultrasonography. HF increased back fat thickness (P<.01), P4 concentrations (P<.01), and number of estrous cycling heifers before the breeding season (P<.06). HF increased (P<.06) the number of estrous cycling F1 H and P before the breeding season but had no effect on F1 L heifers. HF decreased (P<.05) age of puberty in F1 P, but not in F1 H or L heifers. F1 H and L heifers gained more weight (P<.01) than F1 P. F1 H had greater (P<.01) back fat thickness than F1 L and P heifers. Sire breed affected (P<.01) age of puberty with F1 P being the youngest, F1 H intermediate, and L heifers the oldest. In conclusion, HF has the potential to decrease age of puberty and increase the number of estrous cycling heifers before the breeding season in some breeds. The HF ration increased back fat thickness and P4 concentrations. Sire breed influenced total gain, back fat thickness, and age of puberty.

Technical Abstract: F1 heifers [n=246; crossbred dams bred to either Hereford (H), Limousin (L) or Piedmontese (P) sires] were randomly allotted to receive 1.9%(LF) or 4.4% (HF) dietary fat. Safflower seeds (37% oil with 80% linoleic acid) were used as a fat source. Rations were isocaloric and isonitrogenous and were fed from 250 d of age until puberty or breeding season started. If necessary, rations were adjusted every 56 d to maintain an average daily gain of .77 kg. Epididectomized bulls were placed with the heifers to aid in estrous detection (performed twice daily). Puberty was defined when a heifer showed estrous behavior, had a CL, and serum progesterone (P4) concentrations above 1 ng/mL between d 7 to 10 following estrus. Heifers were weighed every 28 d and a 60-heifer sample representing each breed type and dietary treatment were back fat measured using ultrasonography. HF increased back fat thickness (P<.01), P4 concentrations (P<.01), and number of estrous cycling heifers before the breeding season (P<.06). HF increased (P<.06) the number of estrous cycling F1 H and P before the breeding season but had no effect on F1 L heifers. HF decreased (P<.05) age of puberty in F1 P, but not in F1 H or L heifers. F1 H and L heifers gained more weight (P<.01) than F1 P. F1 H had greater (P<.01) back fat thickness than F1 L and P heifers. Sire breed affected (P<.01) age of puberty with F1 P being the youngest, F1 H intermediate, and L heifers the oldest. In conclusion, HF has the potential to decrease age of puberty and increase the number of estrous cycling heifers before the breeding season in some breeds. The HF ration increased back fat thickness and P4 concentrations. Sire breed influenced total gain, back fat thickness, and age of puberty.