Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2004
Publication Date: 2/1/2005
Citation: Schultz, C.L., Ely, D.G., Aaron, D.K., Burden, B.T., Wyles, J. 2005. Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures. Journal of Animal Science. 83:478-485.
Interpretive Summary: Performance between early and normal weaned calves was similar throughtout the trial. Once milk is removed from a calf's diet, losses in protein and energy provided from milk must then be made available from forage or a supplement. However, a small ruminant can only consume so much before gut fill allows for a decrease in intake.Early weaned calves were able to consume enough total dry matter to meet their nutrient requirements and maintain a level of performance similar to normal weaned calves. However, if allowed to consume a diet that is primarily concentrate, as seen with finishing cattle, performance of early weaned calves may have been superior to that of normal weaned calves. This has already been shown with calves early weaned, placed in drylot, and provided a high concentrate ration. On the other hand, if a producer wants to early wean to pasture and utilize available forage, the cost of additional supplementation to try and produce superior gains, may not be economical.
Technical Abstract: : Sixty-two Angus x Beefmaster, spring-calving cows (yr 1) or first-calf heifers (yr 2 and 3) and their calves were used in a completely randomized design with a one-way treatment structure. Cow and calf pairs were randomly assigned to one of two management systems: 1) an early weaning system (EW) in which steer and heifer calves were weaned at 108 d of age and supplemented with a post-weaning growing diet or 2) a normal weaning system (NW) in which calves were weaned at 205 d without supplementation. Prior to early weaning and within each management system, calves and their dams were maintained in two, 1.4 ha endophyte infected tall fescue pastures. Early-weaned calves and cow/calf pairs were then randomly allotted to 1.4 ha endophyte infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow/calf pairs per pasture (four pastures per management system). Cow weights and body condition score (BCS) changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG's from early to normal weaning were not significantly different. Resultant weights of calves at normal weaning were similar. Forage intake was greater (P < 0.01) for NW calves during periods 2 and 3 of yr 1 and periods 1 and 2 of yr 2 and 3. However, total DM and CP intakes were higher (P < 0.01) for EW calves in periods 2 and 3 of each year. Intakes of NDF tended to be numerically greater for EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2, however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05). These results show condition of cows with EW calves is improved by early weaning and gains of calves weaned at 108 d to pasture plus supplementation is comparable to those continuing to nurse dams until weaned at 205 d.