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

• Published in: Journal of animal science Vol. 85; no. 10; pp. 2740 - 2745
• Main Authors: Roberts, A.J, Paisley, S.I, Geary, T.W, Grings, E.E, Waterman, R.C, MacNeil, M.D
• Format: Journal Article
• Language: English
• Published: Savoy, IL American Society of Animal Science 01.10.2007; Am Soc Animal Sci
• Subjects: adipose tissue; Adipose Tissue - diagnostic imaging; Animal Feed; animal growth; Animal Nutritional Physiological Phenomena; Animal productions; Animals; beef cows; Biological and medical sciences; Body Composition - physiology; carcass characteristics; Cattle - growth & development; Cattle - physiology; Cost-Benefit Analysis; cow feeding; Dairying - economics; Dairying - methods; Diet, Reducing - economics; feed conversion; feed intake; feeding level; Female; Food industries; Fundamental and applied biological sciences. Psychology; heifers; intramuscular fat; liveweight gain; longissimus dorsi; Meat and meat product industries; Muscle, Skeletal - diagnostic imaging; muscles; nutrient use efficiency; Pregnancy; Pregnancy Rate; Random Allocation; residual feed intake; restricted feeding; subcutaneous fat; Terrestrial animal productions; thickness; Ultrasonography; Vertebrates; Weaning; Weight Gain; Farming animal; Bovine; Growth; gain:feed; feed level; Meat product; Ox; cattle; Carcass; Feeding; Vertebrata; heifer development; Mammalia; Efficiency; Development; Livestock; Heifer; Artiodactyla; Beef; Ultrasound; Ungulata; Feed
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2007-0141

Traits used for identification of replacement beef heifers and feeding levels provided during postweaning development may have major financial implications due to effects on maintenance requirements and level of lifetime production. The current study evaluated the effects of 2 levels of feeding during the postweaning period on growth, G:F, and ultrasound carcass measurements of heifers, and the associations among these traits. Heifers ([fraction one-half] Red Angus, [fraction one-quarter] Charolais, and [fraction one-quarter] Tarentaise) born in 3 yr were randomly assigned to a 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, and subcutaneous fat thickness over the LM were made on d 140 (382 ± 0.8 d of age). Average daily DMI was 4.1 and 5.6 kg/d for restricted and control heifers, respectively (P < 0.001). Feed restriction decreased (P < 0.001) BW (292 vs. 314 kg), ADG (0.52 vs. 0.65 kg/d), LM area (55 vs. 59 cm²), intramuscular fat (3.2 vs. 3.5%), and subcutaneous fat thickness over the LM (3.2 vs. 3.9 mm), but increased G:F (0.12 vs. 0.11) when compared with control at the end of the 140-d study. The magnitude of the associations of DMI with ADG (r = 0.32 vs. 0.21), 140-d BW (r = 0.78 vs. 0.36), hip height (r = 0.57 vs. 0.17), LMA (r = 0.30 vs. 0.18), and BCS (r = 0.17 vs. 0.11) was greater in restricted-than control-fed heifers. Variance of residual feed intake, calculated within each treatment, was greater (P < 0.01) in control (0.088) than restricted (0.004) heifers, and magnitude of association between residual feed intake and average DMI was greater in control (r = 0.88) than restricted (r = 0.41) heifers. Pregnancy rate tended (P = 0.11) to be reduced in heifers that had been developed on restricted feeding (86.3 ± 2.3 vs. 91.5 ± 2.3%). However, ADG was greater (P < 0.001) in restricted than control heifers (0.51 vs. 0.46 kg/d) while grazing native range in the 7 mo after restriction. In summary, restricted heifers consumed 22% less feed on a per-pregnant-heifer basis during the development period and had a greater magnitude of association between DMI and several growth-related traits at the end of the 140-d postweaning feeding period, which is indicative of improved efficiency.