Productivity of cow–calf pairs grazing tall fescue pastures infected with either the wild-type endophyte or a nonergot alkaloid-producing endophyte strain, AR5421,2

Abstract

The nonergot alkaloid-producing endo-phyte, AR542, has been shown to improve the persistence and yield of tall fescue pastures without causing the animal disorders commonly associated with tall fescue toxicosis. A 3-yr grazing study was conducted to compare effects of AR542-infected tall fescue pastures with wild type endophyte-infected (E+) tall fescue pastures on cow-calf performance. Replicated 7.3-ha pastures of each treatment were grazed by cow-calf pairs (16 pairs per pasture replication) each year from March to weaning in September. The cows were exposed to breeding on their respective pasture treatments from April 1 through June 15. The treatment groups were compared for reproductive performance, ADG, BCS, calf growth rate, and weaning weight. Blood samples were also collected for serum prolactin (PRL) analysis. There were no significant differences in calving rate (P = 0.98) or calving interval (P = 0.62) between pasture treatments. Cows that grazed the AR542 pastures subsequently gave birth to calves that were heavier (P < 0.05) than calves from cows that had grazed the E+ pastures. Cows grazing the AR542 pastures had higher (P < 0.05) BCS at the end of the grazing period, and had higher ADG during the grazing period. Calves raised on the AR542 pasture had higher (P < 0.05) ADG and weaning weights than calves of the same sex raised on the E+ pastures. Serum PRL concentrations were decreased (P < 0.05) in both cows and calves on the E+ pastures compared with serum PRL concentrations in cows and calves grazing the AR542 pastures. The results indicate that grazing tall fescue pastures infected with the AR542 endophyte may give significant advantages in cow-calf growth rates and BCS over grazing E+ pastures. However, there did not seem to be any benefit in reproductive performance in this trial. There was a small, but significant increase in birth weight in cows grazing AR542 pasture.

Growth and reproductive performance of beef heifers grazing endophyte-free, endophyte-infected and novel endophyte-infected tall fescue

“…Studies evaluating the effects of E+ on pregnancy rate have been conducted with variable results. Some studies have reported cows or heifers consuming E+ have reduced pregnancy rates (Schmidt et al, 1986;Beers and Piper, 1987;Gay et al, 1988) while others have reported no difference (Fanning et al, 1992;Burke et al, 2001b;Burke and Rorie, 2002;Watson et al, 2004). The discrepancies in E+ effect on pregnancy rate may be related to differences in experimental conditions including the amount of ergot alkaloid consumed and environmental temperature during the breeding period.…”

“…However, the numbers of animals tested was low and pregnancy rates were numerically lower for E+ than E− (Table 4). Watson et al (2004) began breeding in spring and observed no difference in calving rate between E+ and EN (Table 4). Starting breeding in the spring resulted in the cows being exposed to cooler temperatures and would have reduced potential for heat stress.…”

“…Their study was conducted from November to March when alkaloid concentrations are usually low (Kallenbach et al, 2003;Drewnoski et al, 2007) and ambient temperatures are cool. Calving rate is reported for Beers and Piper (1987) and Watson et al (2004); Pregnancy rate is reported for all other studies.…”

The economic benefits of forage improvement in the United States

“…In proof of concept grazing studies (Bouton et al 2002), MaxQ was found to provide stand survival equivalent to E+ tall fescue, but markedly better than Etall fescue. Removing ergot alkaloids also showed dramatic positive effects on animal performance (Bouton et al 2002;Parish et al 2003aParish et al , 2003bWatson et al 2004). With cows and calves at weaning, cow body condition scores were higher and calves were 22.7 kg heavier on MaxQ pastures compared to toxic E+ pastures.…”

Indole-Diterpene Biosynthetic Capability ofEpichloëEndophytes as Predicted byltmGene Analysis

“…Artificially inoculated associations of these endophytes with elite tall fescue (4) and perennial ryegrass cultivars (16) have been commercially established and shown to enhance animal productivity, while alleviating the negative responses such as fescue toxicosis and ryegrass staggers (1,2,50,51,68).…”