J.W. Prevatt’s research while affiliated with Auburn University and other places

Stockering calves in the southern U.S. has been an economically viable enterprise for decades. Historically, the system that yielded the best opportunity for profitability was to purchase light-weight 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 gain was worth more than the cost of 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 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 utilizing 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. Since 1979, the value of gain for stocker calves in Alabama has averaged $1.05/kg. However, in the last 3 yr, the value of gain has risen to$2.32/kg. Fundamental shifts in feed, fuel, and fertilizer prices experienced in the U.S. 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 gain associated with producing feeder calves from those stockers has experienced a concomitant increase. The optimal system still utilizes 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.

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.

The reproductive impact following controlled introduction of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) was evaluated in BVDV-naïve heifers.

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.

  Twenty-six crossbred steers were finished either on ryegrass (Lolium multiflorum Lam.) forage (FOR, n= 13) or a primarily grain diet containing 85% corn, 7.5% cotton-seed hulls, and 7.5% vitamin/mineral/urea supplement (GRAIN, n= 13) to determine the consumer acceptance of forage- and grain-finished beef in 3 southeastern states. Shear force values were not affected by finishing treatment (P= 0.62), and both total and heat-labile collagen content means of the FOR and GRAIN steaks were similar (P= 0.88 and 0.14, respectively). Ribeye steaks were cut from wholesale roasts after 14 d of aging and were evaluated by 1250 consumers in a retail study and 87 consumers in a take-home study across Alabama, Tennessee, and Kentucky. Retail consumers rated GRAIN steaks higher for flavor (P= 0.001), overall palatability (P= 0.001), and price per kg (P= 0.001) compared to FOR steaks, but consumers in the take-home study found no differences in any of the 3 traits. Consumers that preferred FOR steaks were willing to pay an average of $2.38/kg and$5.61/kg more for FOR steaks than for GRAIN steaks in the retail and take-home studies, respectively (P= 0.001). Among consumers surveyed across all 3 states, 34.1% of retail consumers and 54.0% of take-home consumers preferred FOR steaks. At least one-third of the consumers surveyed preferred the taste of forage-finished beef and were willing to pay a premium.

Temperature of alfalfa silage was monitored for 28 d at three depths following ensiling in a vacuum bag system. For this silo system, silage was piled on one sheet of plastic and covered by another; the plastic sheets were connected on all sides by rolling and clamping around a polyvinylchloride pipe. The silo was evacuated with a vacuum pump attached to a perforated pipe placed on the bottom sheet of plastic prior to filling. Temperatures increased linearly as depths increased (0.3 to 0.6 and 0.9 m), but temperature measurements were <35.9oC at all depths. Storage cost per ton of silage ensiled was very sensitive to the quantity ensiled and marginally sensitive to DM losses. For a vacuum silo with 40 metric ton (mT) (DM) capacity, storage cost estimates per mT (DM) were 8.90, 9.50, $9.95, and$10.44 for 5, 11, 15 or 19% DM losses, respectively. Temperature differences attributable to post-ensiling days were detected. The performance of 48 midlactation (187+ 45 din milk) cows fed diets based on forages (45.8 to 61.4% DM) of corn (CS), alfalfa, or ryegrass silages (RS) with or without 7.0% cottonseed hulls (CSH) was compared in a 75-d lactation trial. Corn silage was ensiled in an upright silo; alfalfa silage was ensiled in both an Ag-Bag® (Ag-Bag International, Warrenton, OR) and vacuum bag system (BAL and VAL, respectively); RS was ensiled in an Ag-Bag® system. Cows fed CS without CSH produced more milk (21.1 kg/d) than did cows fed the other three silages (17.1 to 19.1 kg/d). No differences in milk production were detected for cows consuming silage from the different ensiling systems, indicating that the vacuum ensiling process can be a satisfactory method of making silage. Cows fed RS consumed less DM (11.0 to 12.1 kg/d) than did cows fed the other three silages (14.4 to 20.4 kg/d). Inclusion of CSH in the alfalfa silage-based diet increased DMI, milk production, and BW gain but had no effect on milk fat or protein percentage. A vacuum silo system may be a satisfactory method of ensiling crops, especially during emergency situations, for short-term ensiling, and for small herds. Systems, Silage, Dairy Cows, Milk Production.)