Southern Section Interdisciplinary Beef Cattle Symposium: Forage and co-product systems for stockers in the South: have fundamental shifts in markets changed the optimal system?

Stockering calves in the southern United States has been an economically viable enterprise for decades. Historically, the system that yielded the best opportunity for profitability was to purchase lightweight calves (130 kg to 220 kg) in autumn, add 100 to 200 kg of BW gain, and sell them in the spring. In most years, the value of the BW gain was worth more than the cost of BW gain in this system. With the exponential price increases in feed, fuel, and fertilizer during 2008 and the significant increase in cattle prices, it is prudent to assess the potential for continued profitability in this segment of the beef industry. Evaluation of 37 grazing experiments indicated that the forage systems most likely to result in inexpensive costs of BW gain for stocker calves involve tall fescue with legumes or ryegrass with small grains. Even with increased input prices, these systems still yield economical BW gain for stocker calves. Likewise, many diets can be blended to produce ADG of 1 kg using co-products that are abundant across the South. With many of these co-products, the most important performance factor in determining their value is G:F. In several experiments, DMI has exceeded 3% of BW in stocker calves, and the resulting G:F has been less than desirable. Several experiments have reported G:F of 0.13 to 0.16, resulting in economical BW gain, whereas some experiments have reported G:F as low as 0.09, which could result in BW gain that costs more to produce than it is worth. From 1979, the value of BW gain for stocker calves in Alabama has averaged US$1.05/kg. However, in the last 3 yr, the value of BW gain has risen to $2.32/kg. Fundamental shifts in feed, fuel, and fertilizer prices experienced in the United States between 2005 and 2010 have markedly changed the amount of capital needed to purchase several hundred stocker calves and to provide adequate feedstuffs for BW gain. However, the value of BW gain associated with producing feeder calves from those stockers has experienced a concomitant increase. The optimal system still uses high-quality cool-season forages and supplementation with co-product feeds. With this system, a significant margin of profit still exists for the Southeastern stocker cattle production system.

Reproductive and economic impact following controlled introduction of cattle persistently infected with bovine viral diarrhea virus into a naive group of heifers.

The reproductive impact following controlled introduction of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) was evaluated in BVDV-naive heifers. Heifers were randomly allocated into two groups: an unexposed control herd (n = 34) and a herd exposed to five persistently infected (PI) animals for 7 mo, beginning 50 days before the breeding season (n = 34). Initiation of the BVDV-challenge was timed to mimic either direct contact with PI calves born in the previous calving season or accidental introduction of PI herd additions prior to the breeding season. The PI animals represented BVDV Types 1a (n = 3), 1b (n = 1) and 2 (n = 1). Two BVDV-free, seropositive bulls were used in each group for 78 days breeding seasons. In both groups, 33 of 34 heifers became pregnant, with similar distribution of fetal ages. Two heifers in each group aborted (etiology undetermined). In addition, one calf was born dead and one calf died 3 days post-partum in the BVDV-exposed group. One calf in the unexposed group died 4 mo post-partum. No calves, including the stillborn calf and the two calves that died prior to weaning, were persistently infected with BVDV. In summary, introduction of PI cattle to a group of BVDV-naive heifers 50 days prior to the breeding season did not negatively impact reproductive performance. To the contrary, the active immunity that developed following field exposure to BVDV provided effective reproductive and fetal protection during the breeding season and subsequent gestations, despite continuous exposure to PI animals until approximately midgestation. Although BVDV can have potentially devastating reproductive effects, timing of infection is a critical determinant in the outcome of a BVDV infection. A controlled breeding season with introduction of herd additions at less critical reproductive time points can mitigate the negative reproductive health consequences of BVDV.

Finishing steers on winter annual ryegrass (Lolium multiflorum Lam.) with varied levels of corn supplementation I: effects on animal performance, carcass traits, and forage quality.

Crossbred steers (n = 72) were selected to study forage-based finishing systems using winter annual ryegrass (Lolium multiflorum Lam.) with varying levels of grain supplementation. In December, cattle were allotted to 1 of 6 treatments consisting of ryegrass pasture (1 ha) with whole shell corn supplemented at 0.0% (0.0), 0.5% (0.5), 1.0% (1.0), 1.5% (1.5), and 2.0% (2.0) of BW, or an ad libitum mixed-ration grain diet in a drylot. Steers were randomly assigned to pens of 4 with pen serving as the experimental unit. Cattle were slaughtered by pen when average pen backfat thickness (as measured by real-time ultrasound) reached approximately 0.64 cm. Forage samples and disk meter height were taken from ryegrass paddocks on a monthly basis to determine forage quality and mass. Live animal performance, carcass traits, proximate analysis, Warner-Bratzler shear force, and sensory characteristics from the LM of the rib section were analyzed. Increasing the amount of grain in the diet of finishing cattle resulted in a linear decrease (P < 0.05) in days on feed and a linear increase (P < 0.05) in ADG, preliminary yield grade, final yield grade, flavor intensity, and beef flavor. Forage DM mass increased with each incremental increase in grain added to the grazing diets. Quality of forage was not (P > 0.05) affected by adding grain to the diet. Adding corn to the diet of cattle being finished on forage improved animal performance and decreased forage utilization characteristics in addition to improving the flavor characteristics of beef.