Author
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Jenkins, Thomas |
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Ferrell, Calvin |
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Submitted to: American Society of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/24/2007 Publication Date: 7/2/2007 Citation: Jenkins, T.G., Ferrell, C.L. 2007. Daily dry matter intake to sustain body weight of mature, nonlactating, nonpregnant cows. Journal of Animal Science. 85(7):1787-1792. Interpretive Summary: The annual production cycle of beef cows typically is based on forage environment that can vary in the availability of DM and quality that can be readily consumed which may affect the ability of cows to convert feed resources to weight of calf at weaning on a herd basis. Limitations in DM availability may result in reduced expression of genetic potential for production traits such as pregnancy rate or total milk yield which contributes to the reduction of total calf weight for sale. Results from the present study suggest maintenance requirements respond to DM availability and the response varies across breeds. Characterization of such a dynamic mechanism for maintenance requirements may create an opportunity for cattle producers to utilize variation among breeds of beef cattle to better match the genetic potential for production to the forage environment. With over 65% of annual energy budget of a cow/calf production system used to meet the maintenance requirements of the cows in the herd, genetic improvement in the efficiency of feed use of mature cows would seem to be desirable. However, if feed allowance influences energy requirement for maintenance, basing improvement in cow feed efficiency upon selection criteria in the post weaning growing period in which the typical protocol for the evaluation period is ad libitum feeding of high energy diets may not be the appropriate venue to identify replacement females. Technical Abstract: To quantify the relationship between DM consumption, the ability to sustain weight per unit of DMI and days to reach weight equilibrium among diverse cattle breeds, weight and DM intake data were recorded for mature, non-pregnant and non-lactating cows sampled from Angus, Braunvieh, Charolais, Hereford, Gelbvieh, Limousin, Pinzgauer, Red Poll and Simmental cows. Within each breed cows received one of four daily DM allowances (56, 76, 92, or 110 g/wt**-0.75) of a ground alfalfa hay/corn based diet. During the first 60 d of the trial, weights were record every 28 d, after which weights were recorded on a weekly basis until the cows were determined to have attained weight equilibrium. Individual cows were determined to be at weight equilibrium when the rate of weekly weight change did not differ from zero over an 8 wk period. Days to reach weight equilibrium were not affected (P > 0.05) by either breed or daily DM allowance. Within breed linear and quadratic regressions were significant for weight maintained per kg of DM intake (weight stasis). Weight stasis estimates for Red Poll cows did not differ across DM allowance while Angus and Charolais exhibited a negative linear relationship (P < 0.05) between weight equilibrium and DM allowance. The relationship between weight stasis and DM allowance was curvilinear for the remainder of the breeds in the study with the lowest estimates of weight maintained observed at 76 and 93 g/wt**-0.75 feeding allowance. Ranking among breeds for weight stasis varied dependent on feeding allowance with Red Poll (64.1 +/- 7.4) exhibiting lower (P < 0.05) estimates than all breeds with the exception of Limousin (72.3 +/- 4.4), Braunvieh (75.5 +/- 3.8) and Simmental (79.4 +/- 3.8) (P > 0.05) at the 56 g/wt**-0.75 rate and the Gelbvieh (81.1 +/- 5.0) differed from the Limousin (P < 0.05) but not from the remaining breeds of the study (P > 0.05). At ad libitum feeding, weight stasis of Red Poll, Angus, and the Charolais (66.2 +/- 4.1, and 64.6 +/- 4.2) differed from all breeds except Braunvieh (P < 0.05) which did not differ from the remaining breeds (P > 0.05). These findings provide evidence of a genotype X nutrition interaction for weight stasis. |
