The Effects of Endophyte-Infected Tall Fescue on the Production and Reproductive Performance Parameters of Beef Cattle and Calves ^†

Abstract

Records from 2012 to 2019 for two herds were analyzed to determine how tall fescue (Schedonorus arundinaceus (Schreb.) Dumont) endophyte (Epichloë coenophialum) status affected the productivity of spring-calving cows and calves. Pastures either contained tall fescue with wildtype endophyte (high levels of ergot alkaloids) or novel- or endophyte-free tall fescue (largely ergot alkaloid free). The experimental design was a randomized complete block with year as the replication unit. Forage samples from the farm with toxic endophyte-infected tall fescue contained 1136 ± 413 ppb total ergot alkaloids, while forage from the non-toxic pastures on the second farm contained 118 ± 83 ppb total ergot alkaloids. Artificial insemination pregnancy rates and calving rates were greater (p < 0.05) for cows that grazed non-toxic tall fescue (51.2 ± 2.8% and 93.5 ± 1.4%, respectively) than for cows on toxic endophyte-infected tall fescue (43.3 ± 2.8% and 88.8 ± 1.4%, respectively). Birth weights and weaning weights were greater (p < 0.05) for calves from the non-toxic tall fescue system (37 ± 1 kg and 278 ± 8 kg, respectively) than for calves from the toxic endophyte-infected tall fescue system (33 ± 1 kg and 254 ± 8 kg, respectively). Raising cattle on tall fescue without the toxic endophyte improved cow and calf productivity.

1. Introduction

Tall fescue (Schedonorus arundinaceus (Schreb.) Dumont.) (other synonyms for tall fescue are Lolium arundinaceum (Schreb.) Darbysh. and Festuca arundinacea (Schreb.)) is the predominant cool season forage for cow–calf producers in Virginia and the north–south transition zone in the continental United States. Tall fescue forms a mutualistic symbiosis with a fungus, Epichloë coenophialum [1]. The relationship between the fungal endophyte and the grass allows the forage to resist and tolerate insects, drought, low soil fertility, competition from other plants, and overgrazing [2,3].

Although the fungus benefits the grass, it also negatively affects the livestock that consume it [4,5,6]. The endophyte produces ergot alkaloids, toxic compounds that cause a syndrome in cattle collectively known as fescue toxicosis. Bovine fat necrosis, fescue foot, and summer slump are three signs presented by cattle grazing toxic tall fescue. More generally, the consumption of ergot alkaloids reduces livestock productivity as measured by birth weight, weaning weight (WW), conception and pregnancy rates, body weight, calving rate (CR), and body condition score (BCS) [2,3,7,8,9,10]. Fescue toxicosis costs the United States beef industry more than USD 2 billion each year [6,10,11]. Much of the loss can be attributed to decreased calving rates [6]. Reduced CRs and WWs alone constitute a loss of USD 609 million each year [12]. Raising cattle on tall fescue in the southeastern United States can be particularly challenging given the region’s greater temperatures and humidity. This region, which contains a significant portion of the “fescue belt,” is home to 12 million head of cattle (2015) [10].

Most available data in the literature regarding production on tall fescue systems come from university research trials, and there are few data showing the productivity of different systems from long-term farm-based studies. For this research, records from 2012 to 2019 were obtained from two spring-calving beef herds managed by the Virginia Department of Corrections (VADOC) Agribusiness program. The records were analyzed to compare the performance of cattle that primarily grazed toxic (E+) tall fescue with those that grazed primarily endophyte-free (E−) or non-toxic endophyte-infected (NE+) tall fescue. The NE+ tall fescue does not negatively impact animal performance [13].

We hypothesized that cattle consuming E+ tall fescue would have reduced reproductive and production performance compared to cattle that consumed primarily E− and NE+ tall fescue. To test this hypothesis, cattle production records were analyzed to compare differences in reproductive performance parameters, including the artificial insemination pregnancy rate (PR) and CR; birth weight; cow condition, including the BCS and pre-breeding body weight; and calf growth, including WW and ADG as a function of tall fescue endophyte status.

2. Materials and Methods

This project utilized cattle production data from two sites within the VADOC Agribusiness system. Due to the retrospective and observational nature of this study, protocol approval from the Virginia Tech Institutional Animal Care and Use Committee (IACUC) was not required for this project per Virginia Tech IACUC policy on protocol submission, which states that, “Observational studies (no direct contact) where the animal’s normal behavior, environment or nutrition are not altered by the research or teaching” are excluded from the requirement for approved research protocols. Cattle were managed in this production system according to typical industry standards, including appropriate veterinary care and intervention as necessary. No abnormal adverse events were reported in the data. Humane endpoints were the responsibility of the production and veterinary care team throughout the production periods. Cattle data from this system were ideal for this project because there are thousands of cattle managed on an annual basis across the state following similar protocols and veterinary programs. Due to the use of artificial insemination (AI), the animals have similar genetic backgrounds and environmental exposure. All heifers are developed at a single site for the statewide system and are stocked primarily on tall fescue-based pastures under similar management. The cattle data used for this analysis included records from both primiparous and multiparous cows.

2.1. Study Sites

The two agribusiness operations used for this study were selected based on their breeding season and the endophyte status of their tall fescue pastures. The Coffeewood Correctional Center (Coffeewood) is located at 38°21′53.2″ N, 78°1′13.08″ W. This farm has approximately 263 ha under management, with 101 ha used for permanent pasture and 162 ha used for hay production. For part of the grazing season, mature cattle (mostly over five years old) are managed at a separate location (Sky Meadows State Park; 38°59′27.6″ N, 77°57′52.56″ W). The cattle remain at the state park from April to November and are then brought back to Coffeewood to calve from December to March. Although breeding for the Sky Meadows herd is completed at the state park location, the two sites were treated as a single farm because the cattle are managed together during the calving season and are only separated seasonally. The dominant forage species utilized at these farms is E+ tall fescue.

The Greensville Correctional Center (Greensville) is located at 36°47′52.188″ N, 77°28′57.41″ W. This farm has approximately 179 total ha with 141 ha used for pasture and 38 ha used for hay production. With the exception of three E+ pastures (23 ha total), non-toxic forages are the primary forage resource available on this farm, including NE+ and E− tall fescue and bermudagrass (Cynodon dactylon Pers.). The bermudagrass is used predominantly for hay production. The NE+ tall fescue was established on 18 ha of land that had been cleared from forest in 2007. The remaining tall fescue fields were originally E−, but they were overseeded with NE+ tall fescue as stands declined in subsequent years.

2.2. Climatological Data

Weather data were gathered from the National Oceanic and Atmospheric Administration (NOAA) weather stations located the closest to the study sites. Weather data for Coffeewood were collected from the Virginia Tech Northern Piedmont Research Center weather station (Orange, VA, USA; US00446712). Weather data for Greensville were collected from National Weather Service stations in Emporia (USC00442790) and Wakefield (USC00448800). Data from two locations were used for Greensville because data from the Emporia weather station were not complete. The minimum, maximum, and average daily temperatures and precipitation totals were collected from 1 January 2012 to 31 December 2018. The minimum and maximum daily temperatures were averaged by month, and these monthly averages were used to calculate monthly average daily temperatures. Daily precipitation amounts were summed to obtain a monthly total. The weather facilities used corresponding to the Coffeewood facility are located 11 miles south (Virginia Tech Northern Piedmont Research Station). The weather facilities used corresponding to the Greensville facility are located 8 miles south (Emporia 1WNW USC00442790) and 29 miles northeast (National Weather Service, Wakefield, UK).

2.3. Cattle Performance Data

Records of interest included artificial insemination PR, CR, birth weight, WW, body weight, BCS, and average daily gain (ADG). These metrics were used to compare the effects of endophyte status on production and reproductive performance parameters.

All cattle growth and reproductive performance data were collected by veterinary students from the Virginia-Maryland College of Veterinary Medicine (VMCVM) under the supervision of DVM instructors. The data were retrieved from the recordkeeper for the VADOC and included breeding and weaning records from 2012 to 2019. Data was recorded for 818 unique cows across the two locations with 2306 cow–calf production records across the eight years of this project. The number of datapoints available from each location was 1501 at Coffeewood and 805 at Greensville.

Both the Coffeewood and Greensville farms have a spring-calving season that extends from late January to March, and the breeding season extends from late April to early May. Cows at each farm are enrolled in estrous synchronization and fixed-time AI programs, followed by a 70-day breeding season with natural service. Pregnancy status is determined at approximately 60 days post AI and again at approximately 45 days following the end of the breeding season. Cows are weighed, and BCSs are estimated prior to breeding (approximately 20 days prior to insemination). During each pregnancy check, BCSs are estimated for all cows. Weaning is completed early to mid-October, totaling approximately 230 days from birth to weaning, and calves are weighed at weaning.

Some datapoints were removed from the dataset based on the following criteria which were established a priori (11 datapoints were excluded from the Coffeewood dataset, and 20 datapoints were excluded from the Greensville dataset based on these criteria):

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No identification or data entry present in the dataset.

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The cow was brought to the farm mid-season as already bred.

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The cow was not exposed via artificial insemination or natural service.

The calving rate was not provided in the original records but was calculated for each farm based on the number of live calves born divided by the number of cows exposed to breeding.

2.4. Weaning Weight Data Analysis

Some calf production datapoints had to be removed from the dataset based on the following criteria which were established a priori (121 datapoints were excluded from the Coffeewood dataset, and 58 datapoints were excluded from the Greensville dataset based on these criteria):

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Died prior to weaning.

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No identification or data entry present.

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Sold prior to weaning.

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Bottle-fed.

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No weaning weight available.

The average daily gain was calculated by subtracting weaning weight from birth weight then dividing by 230 days.

2.5. Forage Sample Analysis

To verify and determine alkaloid levels in the fescue pastures, tall fescue leaf samples (n ≥ 30) were collected from each grazing field at each farm in April 2019. Leaf samples were collected (rather than whole tillers) to provide an estimate and comparison of the alkaloid levels in the forage from each site. Samples were randomly collected from multiple locations throughout the fields. The samples were placed on ice in the field, then frozen and lyophilized before grinding through a 1 mm screen. Total ergot alkaloid analysis was conducted by a commercial lab (Agrinostics Ltd., Watkinsville, GA, USA) using an ELISA-based system.

2.6. Statistical Analysis

A mixed-model ANOVA was used to test the effects of tall fescue endophyte status on birth weight, BCS, pre-breeding body weight, CR, AI PR, WW, and ADG with farm as the experimental unit. The analysis was conducted using the PROC MIXED procedure in SAS Studio, v. 3.81 (SAS Inst., Cary, NC, USA). This study was treated as a randomized complete block design with farm (tall fescue endophyte status, n = 2) as the experimental unit and year as the replication unit. Arcsine transformation was used to normalize data reported as proportions (CR and AI PR). A Shapiro–Wilk test was completed to ensure the normal distribution of the data. Differences between treatments were considered significant when p < 0.05 and as trends when 0.05 ≤ p < 0.10.

3. Results

3.1. Climatological Data

The mean maximum monthly temperatures, mean minimum monthly temperatures, and mean monthly temperatures are provided in Figure 1. Temperatures each year were similar across locations, although Greensville was generally warmer than Coffeewood. Monthly precipitation for each location is presented in Figure 2.

3.2. Total Ergot Alkaloid Concentrations

Total ergot alkaloid concentrations in the four forage samples collected from Coffeewood averaged 1136 ± 413 ppb. Of the two E− and NE+ tall fescue pastures sampled at Greensville, the total ergot alkaloid concentrations were 236 ppb and 0 ppb. The E+ pasture sampled at Greensville contained 2187 ppb total ergot alkaloids.

3.3. Cow Weight and Condition and Calf Performance

Cows that grazed E+ had lower (p < 0.05) body condition scores than cows on primarily non-ergot alkaloid-producing (non-toxic) tall fescue in the pre-breeding period (

Table 1. Cow body weight at pre-breeding and body condition score (BCS) at pre-breeding, first pregnancy check, and second pregnancy check and calf birth weight, weaning weight (WW), and average daily gain (ADG) from grazing systems with either toxic endophyte-infected (E+) or primarily endophyte-free (E−) and non-toxic, novel endophyte-infected (NE+) tall fescue for 2012–2019. N: total number of unique cow or calf records analyzed from 2012 to 2019. SE: standard error of mean (calculated as standard deviation/N).

Year	Forage Type		SE	p Value
	E+	E−/NE+
Cows (n = 2306)
Body weight, kg	514	560	13	0.0374
BCS at pre-breeding	5.1	5.5	0.1	0.0153
BCS at first pregnancy check	5.4	5.5	0.1	0.5287
BCS at second pregnancy check	5.4	5.7	0.2	0.3292
Calves (n = 1976)
Birth weight, kg	33	37	1	0.0223
WW, kg	254	278	8	0.0216
ADG, kg day−1	0.96	1.03	0.03	0.0689

). No differences in the BCS (p ≥ 0.33) were observed in subsequent measurement periods. Cows on E+ tall fescue weighed less (p < 0.05) at pre-breeding than cows that grazed primarily non-toxic tall fescue.

The average calf birth weights were 4 kg greater (p < 0.05) for animals from non-toxic tall fescue systems. Calves whose dams grazed E+ tall fescue weighed less (p < 0.05) at weaning than those whose mothers grazed non-toxic tall fescue. However, calves on E+ only tended (p = 0.0689) to have a lower ADG than calves from non-toxic tall fescue systems.

3.4. Calving and Pregnancy Rates

Cattle grazing primarily E−/NE+ pastures had greater (p = 0.0156) CRs (93.5 ± 1.4%) than cattle grazing E+ (88.8 ± 1.4%; Figure 3). Cows grazing primarily E− and NE+ tall fescue had 18% greater (p = 0.0015) artificial insemination PRs (51.2 ± 2.8%) than those on E+ tall fescue (43.3 ± 2.8%; Figure 4).

4. Discussion

The goal of this study was to determine whether cattle and calves grazing non-toxic tall fescue had improved reproductive and weight gain performance compared to cattle and calves grazing E+ tall fescue. This study is unique in that data from 818 unique head of cattle were analyzed over the course of eight years. Other research-based studies have a smaller number of cattle, and the trials are completed over a one- to three-year period. The cattle used for this study were of similar genetic background as they were all managed as a part of the same agribusiness system within Virginia. In addition, the same livestock health, breeding, and data collection protocols and personnel were used each year at both farms.

The total ergot alkaloids measured in one of the Greensville E− and NE+ samples may be due to sampling noise and some contamination of E+ plants within the stand, but the concentration (236 ppb) was below the threshold levels considered to cause clinical signs of fescue toxicosis [14]. Although the Greensville farm had fields with E+ tall fescue, the proportion was less than 13% of the whole farm area.

Birth weight, BCS, body weight, CR, PR, weaning weights, climate data, and ergot alkaloid concentrations were compared for each forage type. Cows and calves managed on primarily E− and non-toxic NE+ tall fescue pastures had greater reproductive and growth performance than cows and calves on toxic E+ tall fescue. Despite the presence of some E+ at the Greensville farm, cattle stocked on these pastures still performed better than cattle on entirely E+ tall fescue, even though the Greensville site was likely more stressful due to greater daily temperatures. Similar results were reported by Caldwell et al. [6], who compared differences within spring- and fall-calving systems following a 25% pasture conversion to NE+ tall fescue. By stocking cattle on NE+ several weeks prior to breeding, calving rates increased by 36% compared to calving rates from cows stocked year-round on E+ pastures [6].

4.1. Birth Weight

Calves from cows grazing E+ tall fescue had lower average birth weights than calves born to cows consuming non-toxic tall fescue. Dyer [15] studied the vasoconstriction of uterine and umbilical arteries in ewes and found that ergovaline (the most common ergopeptide in E+) constricted uterine and umbilical arteries. This constriction caused reduced fetal growth in livestock. Watson et al. [9] similarly found that cows grazing the wildtype tall fescue had calves with reduced birth weights when compared to other fescue types. While excessively large calves are problematic and may result in dystocia and reduced survivability, excessively small calves also have reduced survivability and liveweight gains due to poor vigor [16].

4.2. Weaning Weight

Weaning weight followed the same pattern as birth weight, with calves raised on non-toxic tall fescue weighing more at weaning than calves grazing ergot alkaloid-producing tall fescue. During gestation, the effects of fescue toxicosis can be passed from the cow to the calf as evidenced by decreased birth weights and WWs [17]. Decreased prolactin production leads to decreased milk production in cattle grazing E+ tall fescue, effectively reducing milk availability to suckling calves [7,18,19]. The combined effect is lower calf WWs when compared to calves raised by cows grazing non-toxic forages, such as NE+ tall fescue.

Differences in calf weaning weights may also be a function of forage consumption. Steers grazing E+ tall fescue often have lower ADGs than those grazing E− tall fescue or non-toxic forage [3], and ADGs are also reduced in calves due to a reduction in feed intake [20]. In addition to these responses, cattle that graze E+ tall fescue present increased toxicity signs when exposed to stressful environmental conditions (extreme heat or cold) [7]. The present study only indicated a trend for reduced ADGs in calves stocked on E+ tall fescue, and this may be explained in part due to reduced PRs and thus later-born calves in this treatment group.

4.3. Body Condition Score and Body Weight

Cattle that grazed non-toxic tall fescue had greater BCSs at pre-breeding compared to cattle that grazed E+ tall fescue. Decreased body weight and lower BCSs occur in cows consuming E+ tall fescue [18]. Assessing the BCS of first-calf heifers at calving is also a reliable indicator of the reproductive performance at breeding [21]. In our analysis, the BCS was not parsed by cow parity but was lower for all age classes, and this had ramifications for breeding success (discussed below). Pre-partum nutritional deficiencies may lead to a lower post-partum BCS in cows [22]. In addition, restricted pre-partum nutrition may reduce calf birth weight and preweaning growth [22,23].

4.4. Pregnancy Rate

Decreased PRs have been observed in multiple studies of cattle grazing E+ tall fescue [18,24], and for heifers, reductions in CRs and reductions in pregnancy maintenance (i.e., successfully carrying a fetus to term) increase with increasing ergot alkaloid intake [18]. Decreases in conception and PRs with E+-based diets can be attributed partially to a decrease in feed intake and the corresponding lower weight gains and body condition [3]. Cows with a BCS of 5–6 generally have greater pregnancy rates and lower post-partum intervals than cows with lower BCSs (4–5) [22]. The reduction in PRs could also be due to inhibited blood flow to the reproductive system in cattle consuming E+ tall fescue [25].

4.5. Calving Rate

A larger percentage of open cows was recorded for cows grazing E+ tall fescue when compared to cattle grazing non-toxic tall fescue. Other studies have reported decreases in CRs due to E+ tall fescue consumption [26,27]. Cows consuming E+ tall fescue have lower CRs than cows consuming E− tall fescue [28]. An increase in the CR is possible when utilizing a fall-calving system or by converting a percentage of the pasture to NE+ tall fescue [6]. In a fall-calving system, cattle are not simultaneously subjected to elevated ergot alkaloid concentrations and heat stress while breeding, even though fall alkaloid concentrations can be high [29]. By converting a portion of the pastures to NE+ tall fescue, cattle are not consuming solely E+ tall fescue, which helps to mitigate the effects of the ergot alkaloids.

4.6. Climatological Data

The goal of analyzing climatological data was to determine a correlation between extreme temperatures and decreased reproductive performance. Environmental conditions, and particularly heat stress, play a role in the severity of fescue toxicosis and are linked to decreased production [30]. However, given the limited number of farms and the similar weather patterns across each year, no relationship between climate and herd performance was apparent from these data. In general, Greensville experienced warmer temperatures than Coffeewood, which would be expected to have a greater detrimental effect for cattle in that environment. The fact that animals from that site performed better on an array of growth and reproductive metrics despite being in a warmer production environment gives further support to the value of non-toxic tall fescue.

5. Conclusions

Increased birth weights occurred for calves produced from cows that grazed non-toxic tall fescue. Lactating cows had greater body weights and BCSs when grazing non-toxic tall fescue. Artificial insemination PRs and CRs were also increased when cattle grazed non-toxic tall fescue. Growth performance in calves, measured as WW, was increased when they were raised on non-toxic tall fescue. Samples and data were not available to document changes in endophyte status over time in the farm at Greensville, and further research on ergot concentrations and pasture infection rates is warranted to understand their relationships with and the implications of long-term management practices for E+ and NE+ tall fescue pastures.