Integrating the Use of Spring- and Fall-Calving Beef Cows in a Year-round Grazing System (A Progress Report)

Animal production, hay production and feeding, and the yields and composition of forage from summer and winter grass-legume pastures and winter corn crop residue fields from a year-round grazing system were compared with those of a conventional system. The year-round grazing system utilized 1.67 acres of smooth bromegrass-orchardgrass-birdsfoot trefoil pasture per cow in the summer, and 1.25 acres of stockpiled tall fescue-red clover pasture per cow, 1.25 acres of stockpiled smooth bromegrass-red clover pasture per cow, and 1.25 acres of corn crop residues per cow during winter for spring- and fall-calving cows and stockers. First-cutting hay was harvested from the tall fescue-red clover and smooth bromegrass-red clover pastures to meet supplemental needs of cows and calves during winter. In the conventional system (called the minimal land system), spring-calving cows grazed smooth bromegrass-orchardgrass-birdsfoot trefoil pastures at 3.33 acres/cow during summer with first cutting hay removed from one-half of these acres. This hay was fed to these cows in a drylot during winter. All summer grazing was done by rotational stocking for both systems, and winter grazing of the corn crop residues and stockpiled forages for pregnant spring-calving cows and lactating fall-calving cows in the year-round system was managed by strip-stocking. Hay was fed to springcalving cows in both systems to maintain a mean body condition score of 5 on a 9-point scale, but was fed to fall-calving cows to maintain a mean body condition score of greater than 3. Over winter, fall-calving cows lost more body weight and condition than spring calving cows, but there were no differences in body weight or condition score change between spring-calving cows in either system. Fall- and spring-calving cows in the yearround grazing system required 934 and 1,395 lb. hay dry matter/cow for maintenance during the winter whereas spring-calving cows in drylot required 4,776 lb. hay dry matter/cow. Rebreeding rates were not affected by management system. Average daily gains of spring-born calves did not differ between systems, but were greater than fall calves. Because of differences in land areas for the two systems, weight production of calves per acre of cows in the minimal land system was greater than those of the year-round grazing system, but when the additional weight gains of the stocker cattle were considered, production of total growing animals did not differ between the two systems.

The Influence of MGA and PG600 on the Out of Season Reproductive Performance of Ewes

Seasonal lamb supply has been established as one of the major hindrances to the American sheep industry. The ability to consistently lamb ewes on an accelerated production system offers additional benefits of reduced maintenance costs, more uniform cash flow along with reduced labor and facility demands. Previous work at McNay with spring breeding indicated that light priming rams regardless of genetic base improved conception rates, however, MGA feeding postweaning gave inconsistent and sometimes depressed reproductive activity in ewes. This study was conducted to evaluate the use of MGA in late lactation and a single PG600 injection at weaning, either individually or in combination.

Pasture Conditions at the Initiation of Grazing to Optimize Forage Productivity: A Progress Report

To determine environmental, soil, and sward effects at the initiation of cattle grazing in the spring on seasonal (forage accumulated during the grazing season) and cumulative (seasonal + initial forage mass) forage accumulation (FA), 15 commercial cow-calf producers from southern Iowa were selected by historical initial grazing date. At grazing initiation, twelve .25-m2 samples were hand-clipped from each pasture and sward heights (SH) measured with a falling plane meter (4.8 kg/m2) to determine initial forage mass. At each location, soil temperature and load bearing capacity (LBC) were measured and a soil sample was collected to measure pH and moisture, P, and K concentrations. Cumulative degree-days (base=3.85°C) and precipitation at grazing initiation were calculated from NOAA records. At the beginning of each month, at least three grazing exclosures were placed on each grazed pasture to determine monthly FA. SH in each exclosure was recorded, and a .25-m2 forage sample was hand-clipped proximate to each exclosure. At the end of each month, SH was recorded and .25-m2 hand-clipped forage samples from inside exclosures were obtained. In linear regressions, cumulative and seasonal SH increased with greater soil P (r2=.5049 and .5417), soil K (r2=.4675 and .4397), and initial forage mass (r2=.1984 and .2801). Seasonal SH increased with earlier initial grazing dates (r2=.1996) and less accumulated degree-days (r2=.2364). Cumulative and seasonal FA increased with earlier initial grazing dates (r2=.2106 and .3744), lower soil temperatures (r2=.2617 and.2874), and greater soil P (r2=.3489 and .2598). Cumulative FA increased with greater soil K (r2=.4675). In quadratic regressions, cumulative and seasonal SH were correlated to soil P (r2=.6310 and .5310) and soil K (r2=.5095 and.4401). Cumulative and seasonal FA were correlated to degree days (r2=.3630 and.4013) and initial grazing date (r2=.3425 and .4088). Cumulative FA was correlated to soil P (r2=.3539), and seasonal FA was correlated to soil moisture (r2=.3688).