Feed intake and production efficiency of beef cows

Abstract Text: The objective of this study was to determine the relationships between DMI and growth as heifers and cows and calves weaned, weight of calf weaned, and milk production.  Cows born in 1999-2001and sired by industry AI bulls (Angus, Hereford, Simmental, Limousin, Charolais, Gelbvieh, and Red Angus) and with Angus, Hereford, and MARC III (composite) dams were randomly mated to F₁ bulls from these same crosses (with the exception of MARCIII dams) resulting in heifers (F₁²) that were 2-, 3-, and 4-breed crosses.  Heifers (F₁²) born in 4 consecutive years (2004-2007) were retained and bred to produce four successive calf crops, calving first at 2 yr of age.  Individual feed intake and BW gain were measured for an 84-d period between weaning and first breeding on F₁² heifers born in years 2005-2007 (n = 220, 249, and 218, respectively).  At 5 yr of age, F₁² cows were not bred.  Twenty-one d after weaning, F₁² cows (n = 158, 179,154, and 131, respectively, for birth years 2004-2007)  were individually offered 120 kcal ME/kg BW^0.75∙d^-1in Calan gates for 112 d, and then given ad libitum access for an additional 98 d.  Milk production at approximately 100 d after calving was measured using a 16-h weigh-suckle-weigh at 2- and 5-yr of age.  Heritability and genetic correlations were estimated with MTDFREML.  The heritability estimates were Heifer DMI (0.69) Heifer ADG (0.49), Cow DMI (0.48), Cow ADG (0.46), and 5-yr-old milk production (0.41).  There were positive genetic correlations between heifer DMI and heifer ADG (0.89), cow DMI (0.65), cow ADG (0.73), average weaning weight of calves (0.52), and total calf weight weaned (0.23).  There were positive genetic correlations between cow DMI and average weaning weight of calves (0.28), and total calf weight weaned (0.21).  In conclusion, there are genetic correlations between DMI and total weight of calf weaned; also, heifer intake does offer some opportunity to select for intake in mature cows.  Selection for reduced DMI may have a negative effect on total BW of calf weaned.  USDA is an equal opportunity provider and employer.

Keywords:

Cows, feed intake, production efficiency