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United States Department of Agriculture

Agricultural Research Service

Title: Effects of restricted feeding of beef heifers during the postweaning period on growth, efficiency and ultrasound carcass characteristics

Authors
item Roberts, Andrew
item Paisley, S - UNIV OF WYOMING
item Geary, Thomas
item Grings, Elaine
item Waterman, Richard
item Macneil, Michael

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2007
Publication Date: July 3, 2007
Citation: Roberts, A.J., Paisley, S.I., Geary, T.W., Grings, E.E., Waterman, R.C., MacNeil, M.D. 2007. Effects of restricted feeding of beef heifers during the postweaning period on growth, efficiency and ultrasound carcass characteristics. Journal of Animal Science 85:2740-2745.

Interpretive Summary: Traits used for selection and feeding levels during postweaning development of replacement beef heifers can have major financial implications due to affects on maintenance requirements and level of production. The present study evaluated effects of two levels of feeding during the postweaning period on growth, efficiency and ultrasound carcass measurements of heifers. Beginning approximately 1 month after weaning when heifers averaged 8 month of age, heifers were placed in a drylot for a 140-day trial in which they were fed a diet either to appetite (control) or restricted at 80% of that consumed by controls a similar weight. Restricted feeding decreased average daily feed intake (4.1 vs. 5.6 kg of dry matter; restricted vs. control, respectively) over the course of the trial which corresponded to 27% decrease in total feed consumed. Average daily gain over the trial was less in restricted (0.52 kg/d) than control (0.65 kg/d) heifers, which resulted in restricted heifers being lighter at the end of the trial (291 vs. 314 kg). At the end of the trial restricted heifers had smaller loin eye muscle area (55 vs. 59 cm2), less intramuscular fat (3.2 vs. 3.5 %) and less subcutaneous fat (3.2 vs. 3.9 mm) than controls. Approximately one month after the trial, heifers were turned out to pasture and subjected to a 60 d breeding season. Pregnancy rate of restricted heifers tended to be less than control heifers (86 vs. 91.5%). Feed efficiency was greater in restricted heifers than control heifers when evaluated for the 140-d trial and subsequent 7 month on pasture. In summary, restricted fed heifers consumed 27% less feed, had reduced maintenance requirements, less variation in maintenance requirements, and improved efficiency of gain that continued beyond 7 month after restriction. Although a 5% depression in pregnancy rate was observed in restricted heifer, results from this study indicate a potential economic advantage of developing heifers under restricted feeding.

Technical Abstract: Traits used for selection and feeding levels during postweaning development of replacement beef heifers can have major financial implications due to affects on maintenance requirements and level of production. The present study evaluated effects of two levels of feeding during the postweaning period on growth, efficiency and ultrasound carcass measurements of heifers, and the associations among these traits. Heifers (composite gene combination : ½ Red Angus, ¼ Charolais, ¼ Tarentaise) born in 3 different years were randomly assigned to either control (fed to appetite; n=205) or restricted (fed at 80% of that consumed by controls adjusted to a common BW basis; n=192) feeding during a 140-d postweaning period. Heifers were individually fed a diet of 68% corn silage, 18% alfalfa and protein-mineral supplement (DM basis) in pens equipped with Calan gates. Ultrasound measurements of LM area, intramuscular fat (IMF), and subcutaneous fat thickness over the LM (FT) were made on d 140, at about 1 yr of age. After 140 d, restricted feeding decreased (P < 0.001) average DMI (4.1 vs. 5.6 kg/d for restricted vs. control), BW (291 vs. 314 kg), ADG (0.52 vs. 0.65 kg/d), LM area (55 vs. 59 cm2), IMF (3.2 vs. 3.5 %) and FT (3.2 vs. 3.9 mm) when compared to control. Feed restriction tended to reduce (86.3 ± 2.3 vs. 91.5 ± 2. 3; P < 0.12) pregnancy rate. Magnitude of associations of DMI with ADG (r = 0.32 vs. 0.21), 140-d BW (r = 0.78 vs. 0.36), hip ht ( r = 0.57 vs. 0.17), LMA (r = 0.30 vs. 0.18) and BCS (r = 0.17 vs. 0.11) were greater in restricted fed heifers vs. control heifers, resulting in improved (P < 0.001) efficiency of gain (0.12 vs. 0.11 kg BW/ kg DMI) in the restricted heifers. Variance of residual feed intake (RFI) calculated within each treatment, was greater (P < 0.01) in control (0.088) than restricted (0.004) fed heifers. Magnitude of association between RFI and average DMI was greater in control (r = 0.88) than restricted (r = 0.41) fed heifers, indicating that selection for RFI may be better applied on animals that are not limit fed. In summary, restricted fed heifers consumed 27% less feed, had reduced maintenance requirements, less variation in maintenance requirements, and improved efficiency of gain that persisted beyond 7 mo after restriction. Although a 5% depression in pregnancy rate was observed in restricted heifer, results from this study indicate a potential economic advantage of developing heifers under restricted feeding.

Last Modified: 7/10/2014
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