Recipient Organization
LOUISIANA STATE UNIVERSITY
202 HIMES HALL
BATON ROUGE,LA 70803-0100
Performing Department
Dean Lee Research Station
Non Technical Summary
In much of the southeastern United States, beef cattle production is a major enterprise. In Louisiana, the beef cattle industry had a value of $463.8 million in 2017, with 559,000 head and 11,500 farms and ranches. Cow calf operation ranks second only to poultry, which is the largest animal industry in the state. In the Southeast (Texas, Oklahoma, Kentucky, Florida, Tennessee, Arkansas, Alabama, Georgia, Mississippi, Louisiana, North Carolina, and South Carolina) there are over 14 million beef cows. In 2017, this represents 48.5% of the total beef cows that have calved in the US. The majority of cattle operations in the southeast are cow-calf producers and their production and calf-marketing strategies (e.g., age at weaning, calf size, and target market) vary tremendously. Stocker operations represent an important enterprise in the southeast that varies in size and scope depending on market conditions and geography. According to the most recent report from the USDA on major land uses in the US there are approximately 144.78 million acres of grassland pasture and range in the 12 southern states; this represents 23.6% of the total 612.26 million acres in the US. A holistic approach to the beef cattle industry should encompass the soil-plant-animal relationship, understanding their close interaction and dependency. Drought, age of producers, and competing land uses have reduced the number of beef cows in production; however, drought and/or excessive rainfall (flooding), changing land use in other parts of the country, and sustainability interests have provided some opportunities for cow-calf production in the Southeast. Renewed interest in grazing systems, strategic supplementation and the understanding of a changing climate (extreme heat and flooding) has enhanced the importance of economic performance of these alternatives. This project will evaluate feeding and management practices on cow-calf and stocker production systems that may increase the productivity of the Southeastern beef cattle industry.
Animal Health Component
90%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
0%
Goals / Objectives
1. To enhance sustainability of beef cattle systems through appropriate nutrient delivery during gestation and post-natal development periods.2. To document thermotolerance and evaluate factors aiming at mitigation of heat stress in beef cattle.
Project Methods
Objective 1. Appropriate nutrition through grazing management.A) Through the evaluation of different cover crop combinations, there will be a reduction of hay feeding during the fall transition period as well as an increase in the diet nutritive value at this time. Similar impact will be tested using a complex sward of grasses and legumes during the summer monthsto reduce the summer slump normally observed in animal performance. B) In an attempt to evaluate extending the grazing season we will 1) use mix swards (oats, annual ryegrass, red and white clover) that will (through appropriate rest periods) allow to start grazing earlier and ended later than using a monoculture of annual ryegrass; 2) evaluate the establishment and management of perennial ryegrass; little is known of this grass in our conditions. If succesful, this experiment may provide a new grazing optiionfor beef cattle producers during the spring transition period.C) There is a constant need for the evaluation of new cultivars of forages. Their adaptation to our conditions and animal response to them is a major drive in the economics of the beef cattle industry. D) The forage-supplementrelationship is key to improve nutrient (protein, energy, minerals) efficiency of use.All cattle will be weighed, hip height determined (heifer calves) and managed according to pre-established LSU AgCenter health protocols, will be dewormed on d 0 of the experiment and 30 to 45 d into the experiment. Mineral mixand water will be available at all times. In all experiments, soil analyses will be conducted and soil will be fertilized accordingly. Forage mass will be determined at the beginning and every time the animals are weighed using the double sampling technique. Samples of forage for nutritive value analyses will be hand-plucked from every paddock every 28 d, walking the pasture in zig-zag pattern and taking a sample every 10 steps. Samples for nutritive value analyses will be dried for DM determination. Forage and supplement (taken every 15 d and composited by month) samples will be submitted to a commercial laboratory for nutritive value analyses using NIRS. Depending on the size of the paddock, 2-4 cages (1 x 1 m) will be placed in each paddock in order to measure the growth rate of monoculture pastures (annual ryegrass). The area under a cage will be clipped diagonally every 14 d, weighed, and dried for DM determination. The difference between pre- and post-cage placement will be considered as the total growth.Objective 1. Fetal programming.Different strategies of feeding or grazing and supplementation will be evaluated during the middle and last third of gestation in Brangus and crossbred cows. Impact of these management on animal productivity as well as of its progeny will be evaluated over 4 years. Blood samples will be obtained at the beginning of the experiment and every 30 d thereafter. At each sampling time, blood samples will be collected into 4 collection tubes [2 Vacutainer serum collection tubes containing no additives, or 0.10 mL of 15% K3 EDTA, or 15 mg of sodium fluoride and 12 mg of potassium oxalate. Plasma tubes will be placed on ice immediately following collection, and serum tubes will be allowed to clot prior to placing on ice. Samples will then be centrifuged within 6 h of collection at 1,500 × g at 4 °C for 30 min. Serum or plasma will be pipetted into 2 mL microcentrifuge tubes and stored at −20 °C until analysis. Serum samples collected on all sampling days will be analyzed for urea N using a commercially available urea N kit. Glucose concentration will be determined in plasma samples. Serum concentrations of nonesterified fatty acids (NEFA) from all sampling days will be measured using a modified procedure of the NEFA C kit. Serum total triiodothyronine (T3), thyroxine (T4), and cortisol concentrations will be determined in day 0, mid-sample and last sampling date in duplicate using commercially available kits.Objective 2. Thermo-tolerance and mitigation of heat stress. A) We will first validate a model of heat stress for our conditions which will later used for more in depth work.Cow calf pairs (Brangus) will be held in pens with cows having access to bermudagrass hay through an electronic feeding system and calves to ad linbitum hay and supplement. Some of these pens are equipped with a sprinkler system and fans allowing comparisons to pens with no such cooling systems.These model will allow us to collect data not previously recorded. B) Using the same setting previously described, heifers will be used to evaluate the effect of %NDF in the diet (high vs. low) with and without the addition of an ionophore. In these experiments, blood samples will be taken from each animal on d 0, mid, and end of the experimental period. Concentrations of triiodothyronine (T3), prolactin, and cortisol will be used as hormonal indicators of stress. Serum concentrations of the metabolites creatinine, heat shock proteins will be determined by approrpiateassays.Core body temperature will be measured for 96-hr periods during each trimester of pregnancy and during the postpartum period, prior to re-breeding. Temperature data loggers attached to blank CIDR devices will be used to measure vaginal temperature. Ambient conditions (temperature, relative humidity, solar radiation and wind speed) will be monitored using a weather station. Temperature humidity index will be calculated using the formula THI = (0.8 x T) + [(RH/100) x (T − 14.4)] + 46.4, where T is the temperature (C) and RH is the relative humidity (NOAA, 1976). Heat load index (HLI) will be calculated asHLI = 8.62 + 0.38 × RH + 1.55 × BG - 0.5 × WS + e((2.4- WS)), with BG as the black globe temperature, WS = wind speed (m/s) and e = base of the natural logarithm. Sweating rate (SR) will be evaluated using a VapoMeter (Delfin Technologies Ltd. Kuopio, Finland). On d 3 during each 96-h evaluation period cows will be monitored for SR in the sun and shade and in the morning and afternoon. Cows will be allowed to adapt to the sun or shade conditions for 20 minutes prior to having SR measured. Measurements will be taken over the shoulder, the ribs and the flank on the left side of the animal. Respiration ratewill be evaluated at these times by counting flank movements for 15 seconds and adjusting to breaths/minute.