title: Effect of increasing energy and protein intake on body growth and carcass composition of heifer calves.
abstract: The objective was to determine whether increased energy and protein intake between 2 and 14 wk of age would increase growth rates of heifer calves without fattening. At 2 wk of age, Holstein heifer calves were assigned to 1 of 4 treatments in a 2 x 2 factorial arrangement with 2 levels of protein and energy intake (moderate [M]; high [H]) in period 1 (2 to 8 wk of age) by 2 levels of protein and energy intake (low [L]; high [H]) in period 2 (8 to 14 wk of age) to produce similar initial BW for all 4 treatments. Treatments were ML, MH, HL, and HH, indicating moderate or high energy and protein intake during the first period and low or high intake during the second period. The M diet consisted of a standard milk replacer (21.3% CP, 21.3% fat) fed at 1.1% of BW on a DM basis and a 16.5% CP grain mix fed at restricted intake to promote 400 g of average daily gain (ADG), whereas the L diet consisted only of the grain mix. The H diet consisted of a high-protein milk replacer (30.3% CP, 15.9% fat) fed at 2% of BW on a DM basis and a 21.3% CP grain mix available ad libitum. Calves were weaned gradually from milk replacer by 7 wk and slaughtered at 8 (n = 11) or 14 wk of age (n = 41). In periods 1 and 2, ADG and the gain:feed ratio were greater for calves fed the H diet. Calves fed the H diet were taller after both periods 1 and 2. No difference was observed in carcass composition at 8 wk, but at 14 wk calves fed MH and HH had less water and more fat than calves fed ML and HL. Plasma IGF-I concentrations were greatest for calves fed the H diet during either period. Plasma leptin concentrations were increased in calves fed the H diet during period 1 from 4 to 6 wk of age. Increasing energy and protein intake from 2 to 8 wk and 8 to 14 wk of age increased BW, withers height, and gain:feed ratio. Calves fed the H diet from 8 to 14 wk of age had more body fat than calves fed the L diet. Increased energy and protein intake can increase the rate of body growth of heifer calves and potentially reduce rearing costs.
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing 48824, USA.
authors.forename: E G
authors.initials: EG
authors.lastname: Brown
authors.forename: M J
authors.initials: MJ
authors.lastname: Vandehaar
authors.forename: K M
authors.initials: KM
authors.lastname: Daniels
authors.forename: J S
authors.initials: JS
authors.lastname: Liesman
authors.forename: L T
authors.initials: LT
authors.lastname: Chapin
authors.forename: D H
authors.initials: DH
authors.lastname: Keisler
authors.forename: M S Weber
authors.initials: MS
authors.lastname: Nielsen
mesh_terms: D000273:Adipose Tissue; D000821:Animal Feed / Q000191:economics; D000818:Animals; D001699:Biometry; D001823:Body Composition; D001835:Body Weight; D002417:Cattle / Q000254:growth & development* / Q000502:physiology*; D003365:Costs and Cost Analysis; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005260:Female; D006304:Health Status; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D020738:Leptin / Q000097:blood; D015430:Weight Gain
chemical_list: D004044:Dietary Proteins; D020738:Leptin; D007334:Insulin-Like Growth Factor I