Utilization of macrominerals and trace elements in pregnant heifers with distinct feed efficiencies.
The objective of the study was to evaluate utilization of dietary minerals and trace elements in pregnant heifers with distinct residual feed intakes (RFI). Feed intake, body weight (BW), and body composition traits were recorded in 36 crossbred heifers over a period of 37 wk, starting shortly after weaning at 8.3 (0.10; standard deviation) mo of age with an average BW of 276 (7.8) kg. Both BW and body composition were monitored regularly throughout the study, whereas individual feed intake was assessed during the last 84 d of the trial. Data recorded were used to calculate RFI for each heifer. Heifers were ranked based on RFI and assigned to high (n=14) or low (n=10) RFI groups. After the RFI study, 24 selected heifers [age 18.2 (0.14) mo; 87.5 (4.74) d in gestation; 497 (8.5) kg of BW] were used in an indirect digestibility trial (lignin as internal marker). Heifers were fed a ration containing corn silage, haylage, and a mineral premix in which Ca, P, K, Na, Mg, S, Cu, Fe, Mn, Mo, Se, Zn, and Co were provided in the diet according to National Research Council requirements of pregnant replacement heifers. The digestibility trial lasted 1 wk, during which samples of feces were gathered twice daily, and blood and liver biopsy samples were collected on the last day. We noted no significant differences between low- and high-RFI heifers in dry matter digestibility. Apparent absorption of Cu, Zn, and Mn was increased in heifers with low RFI, and apparent absorption of Co tended to be greater for these animals. Concentrations of macrominerals and trace elements in serum of pregnant heifers were similar for both groups except for Se, which was increased in the serum of low-RFI heifers. Liver concentrations of Cu, Fe, Mn, Mo, Se, and Zn did not differ between low- and high-RFI heifers. In conclusion, whereas improved absorption of some trace elements (Cu, Zn, Mn, and Co) and increased Se serum concentration appear to be associated with superior feed efficiency in pregnant heifers, further studies are needed to investigate the causality of such relationships.
Department of Animal Biosciences, University of Guelph, Guelph N1G 2W1, ON, Canada.
R S
RS
Dias
Department of Animal Biosciences, University of Guelph, Guelph N1G 2W1, ON, Canada; Department of Plant and Animal Sciences, Dalhousie University, Truro B2N 5E3, NS, Canada.
Y R
YR
Montanholi
Instituto de Ganadería de Montaña (IGM) CSIC-Universidad de León, Departamento de Producción Animal, Universidad de León, E-24071 León, Spain. Electronic address: s.lopez@unileon.es.
S
S
Lopez
Department of Animal Biosciences, University of Guelph, Guelph N1G 2W1, ON, Canada; Monsanto, Headingley, R3T 6E3, MB, Canada.
B
B
Smith
Department of Animal Biosciences, University of Guelph, Guelph N1G 2W1, ON, Canada; Invermay Agricultural Centre, AgResearch Limited, Mosgiel, 9053 New Zealand.
S P
SP
Miller
Department of Animal Biosciences, University of Guelph, Guelph N1G 2W1, ON, Canada.
J
J
France
D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D005247:Feeding Behavior; D005260:Female; D008903:Minerals / Q000378:metabolism*; D011247:Pregnancy; D014131:Trace Elements / Q000378:metabolism*
D008903:Minerals; D014131:Trace Elements
digestibility; internal marker; mineral status; residual feed intake; trace element utilization