Impacts of early-weaning and winter feeding strategies on cow-calf performance and forage utilization.

摘要

Early-weaning in conjunction with strategic winter feeding may improve cow performance. It may also result in forage savings that would be economically beneficial for the rancher.;The objective of this study was to evaluate the effects of early-weaning of beef calves versus normal-weaning on cow body condition score (BCS), weight, longevity and reproductive performance, evaluate calf performance under normal- and early-weaning treatments from birth to weaning, evaluate the biological effects of low input versus high input winter nutritional management of cows with calves weaned early or at the normal time, and to evaluate the effects of early weaning beef calves versus normal weaning time on pasture forage disappearance.;The cattle study was conducted at the South Dakota State University Antelope Livestock and Range Research Station near Buffalo, SD, in 2003 and 2005--2008. Treatments were applied in a two-by-two factorial arrangement with cow as the experimental unit/block. Weaning treatment was applied in either August (early-weaning, EW) or November (normal-weaning, NW) and winter feeding treatments were low-input (LI) or high-input (HI) feeding regimens. Cow BCS and cow and calf weights were recorded at calving, breeding, early-weaning and normal-weaning.;Forage disappearance was measured in pastures at the North Dakota State University, Dickinson Research Extension Center, Dickinson, ND in 2003, 2004 and 2006. Cattle from the early- and normal-weaned treatments were grazed from the period of early- to normal-weaning. The experiment was a randomized complete block design with pastures as blocks. There were three pastures per treatment and eight cows (with or without calves) per pasture. Biomass disappearance was estimated from early-weaning to normal-weaning for the two weaning treatment groups. A paired-plot method was used to estimate forage disappearance by taking biomass data before and after grazing.;Cow BCS and weights were greater in November (at normal-weaning) for the cows in the early-weaning treatment. Cow condition was consistently improved for the cows in the early-weaning and high-input winter feeding treatments in the last two years of the study, indicating a long-term effect of treatments. Cow reproductive performance and longevity were not affected by time of weaning or level of winter supplementation. There was a savings of nearly 8.5 kg˙hd -1˙d-1 (or 36 %) of forage in pastures grazed by cows with calves weaned early. The value of this amount of saved forage from a livestock producer standpoint is more days of winter grazing or more available AUM's. In this study, early-weaning beef calves resulted in 26 additional AUM's.;Economic benefits of early-weaning may be seen through fall feed savings from the period of early- to normal-weaning, as well as lower winter maintenance requirements and potential feed savings for cows with calves weaned early. Using a low-input feeding strategy had no affect on cow reproductive performance, and all cows maintained acceptable body condition so additional economic benefits may be realized by choosing to use a low-input winter feed strategy in combination with early-weaning. These practices may be useful as management practices, with an aggressive feeding and marketing strategy for early-weaned calves.