Early weaning is used to minimize cow nutrient requirements in situations where feed inputs are scarce or expensive. For many years, maintenance energy requirements have been assumed to be 20% greater in lactating compared with non-lactating beef cows. While not well established, maintenance energy requirements are thought to be greatest in primiparous cows and to decline with age. Consequently, early weaning primiparous cow–calf pairs should improve overall efficiency, particularly in situations where mid-to-late lactation forage or feed nutritive value is low. The objective of this study was to determine the biological efficiency of early weaning and maintenance energy requirements of lactating versus non-lactating primiparous cows. Experiments were conducted in two consecutive years using 90 primiparous cows and their calves (48 in yr 1, 42 in yr 2). Pairs were randomly assigned to one of the six pens (8 pairs/pen yr 1, 7 pairs/pen yr 2) and pens were randomly assigned to 1 of 2 treatments; (1) early weaning (130 d ± 15.4; EW, n = 6) and (2) traditional weaning (226 d ± 13.1; TW, n = 6). Late lactation cow and calf performance and feed consumption were measured for 92 d (yr 1) and 100 d (yr 2). Cows were limit-fed to meet maintenance requirements, while calves were offered ad libitum access to the same diet in a creep-feeding area. Calves were not allowed access to the cows’ feed. Cow feed intake, body condition score, body weight (BW), milk yield and composition, and calf body weight gain and creep feed intake were recorded. After accounting for lactation and retained energy, there was a trend for greater maintenance energy requirements of lactating primiparous cows (P = 0.07). From the early weaning date to traditional weaning date, calf average daily gain (ADG) was greater (P < 0.01) for TW calves. Feed and energy efficiency of the pair was improved for the TW system (P < 0.01). Greater ADG were reported for EW calves during the stocker period (P = 0.03), but there were no differences during the finishing period (P > 0.40). At harvest, BW was greater (P = 0.02) and gain to feed ratio tended (P = 0.06) to be improved for TW calves. The increased TW calf performance offset the additional maintenance costs of their lactating dams, resulting in the TW system converting total feed energy to kilograms of calf BW gain more efficiently.
The objective of this study was to investigate the impacts of cow breed type and age on maintenance requirements, feed energy utilization, and voluntary forage intake. The main effect of breed type included Angus (ANG; n = 32) and Hereford × Angus (HA; n = 27) lactating cows. The main effect of age included 2- and 3-yr-old (YOUNG; n = 29) and 4- to 8-yr-old (MATURE; n = 30) cows. Within breed type and age class, cows were randomly assigned to 1 of 2 pens for a total of 8 pens, each housing 7 to 9 cow/calf pairs. To determine maintenance energy requirements, cows and calves were limit-fed for 105 d to body weight (BW) and body condition score (BCS) stasis. There were no differences between breeds in cow hip height, BW, average milk yield (P > 0.31), diet digestibility, or cow maintenance energy requirement (P = 0.54). Crossbred cows had greater BCS (P < 0.05) throughout the experiment. Efficiency of calf growth was not different between breeds when expressed as feed intake of the cow/calf pair nor as energy intake of the pair per unit of calf BW gain (P ≥ 0.31). Young cows produced less milk per day and per unit of BW0.75 (P < 0.01); however, there was no effect of cow age on maintenance energy requirement, diet digestibility, or efficiency of calf growth (P > 0.10). Subsequently, a 45-d experiment was conducted to determine voluntary low-quality forage intake. Cows were housed in dry-lot pens equipped with shade, windbreaks, and feed bunks with free-choice access to clean water and a chopped hay ration was provided ad libitum to determine forage intake. Daily forage intake was lower (P = 0.05) for HA compared with ANG (123 vs. 132 g/kg BW0.75, respectively) although there was no difference in BW. However, HA cows sustained greater BCS (P < 0.01). There was no difference (P = 0.60) in forage intake per unit of BW0.75 due to cow age. Results indicate similar calf growth efficiency among breed types although crossbred cows maintained greater body energy stores and consumed less low-quality forage during the voluntary intake experiment. These differences could not be attributed to lower maintenance energy requirements. Neither maintenance energy requirement nor calf growth efficiency was different between young and mature cows.
A 112 d finishing study was conducted to evaluate the effects of feeding dried distillers grains plus solubles (DDGS) from the MSC-Fiber stream of the FluidQuip post-fermentation fiber separation process compared to conventional DDGS. Yearling crossbred steers (n = 240, initial BW = 463 ± 35kg) were blocked by initial BW, stratified by BW, and assigned randomly to pen (n = 30; 8 steers/pen). Treatments were arranged as a 2×2 + 1 factorial with DDGS type (MSC DDGS [MSC]; Conventional DDGS [CONV]) and inclusion level (20 or 40% diet DM) as the factors. All treatments were compared to a corn-based control (CON). DDGS replaced a 60:40 blend of high-moisture corn and dry-rolled corn. All diets contained 7.5% alfalfa hay and supplement. Data were analyzed as a randomized block design with pen as experimental unit and block as fixed effect. Increasing concentrations of CONV or MSC resulted in a linear increase in DMI (P < 0.01). Steers fed 40% MSC had the greatest DMI (P < 0.01) while CON steers had the least (P < 0.02). Daily gains for MSC steers linearly increased (P = 0.03), while CONV steers showed a tendency for a quadratic response to ADG (P=0.08). Feed efficiency of CONV steers increased quadratically (P = 0.04) and tended to decrease linearly (P = 0.09) for steers fed MSC. Efficiency was greatest for 20% CONV but not different (P > 0.16) than CON, or 20% MSC. Steers fed 40% MSC or 40% CONV were not different in feed efficiency. Inclusion of MSC DDGS resulted in linear increases in DMI and ADG over CON, but decreased feed efficiency by 1.0 and 5.3% resulting in MSC DDGS having a relative feeding value of 95.0 and 86.7% of corn at 20 and 40% DM, respectively.
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