24 Grazing Novel or Endophyte-Infected Tall Fescue during Mid-Gestation Impacts Cow Performance.

Newsome, McKayla A; Monn, Ruby; Mayberry, Kyle; Poole, Rebecca K; Young, Zachary R; Poore, M. H.; Poole, Daniel

doi:10.1093/jas/sky027.025

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“…We observed weak associations between T-Snip and performance in the environment with lower percentage of toxic fescue (i.e., BBCFL), whereas much stronger associations were found at the other location (UPRS), which had greater amount of endophyte-infected fescue. While a defined control group (i.e., cattle consuming nontoxic fescue) was not included in the experimental design of this study, another study was conducted at the same time and location with mature multiparous Black Angus cows consuming novel or toxic endophyte-infected tall fescue ( Newsome, 2018 ), provides additional support that cattle reported in this study experienced the symptoms of FT. Hence, the evaluation of a genetic test for FT tolerance must be performed in a toxic-fescue environment.…”

Section: Discussionmentioning

confidence: 98%

Evaluation of a commercial genetic test for fescue toxicosis in pregnant Angus beef cattle1

Galliou

Khanal

Mayberry

et al. 2020

Translational Animal Science

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Most tall fescue [Lolium arundinaceum (Schreb.) Darbysh] in the Southeastern United States contains an endophyte that causes fescue toxicosis in grazing animals, a serious disease that causes approximately $1 billion in economic losses to the animal industries in the US. Recently, a genetic test called T-Snip (AgBotanica, LCC, Columbia, MO), was developed with the objective of identifying animals with genetic variation for fescue toxicosis tolerance. The aim of this study was to validate the use of this genetic test in mature, pregnant cows. Over 13 weeks, weekly phenotypic data, including body weight, rectal temperatures, hair coat scores, hair shedding scores, and body condition scores, were collected on 148 pregnant purebred Angus cows at 2 locations in NC where infected fescue was the primary source of feed. Birth weights (cBW) and 205-d adjusted weaning weights (adjWW) from these cow’s calves were recorded. All cows were genotyped for T-Snip. At the end of the trial, each phenotypic trait was calculated as the slope of the linear regression of performance on weeks. The effect of T-Snip rating genotypes (4 levels) on slope traits was tested using a linear model also including the fixed effects of location, parity, and the initial measurement for each trait (covariate). For cBW and adjWW, the model also included the sex of the calf and the month of birth as categorical effects. Associations of T-Snip genotypes were observed for body weight gain (aBWd) of pregnant cows (P = 0.15; interaction with location), change in body condition score (aBCSd; P = 0.13), and adjWW (P = 0.06; interaction with location). For aBWd and adjWW, associations were found just within one location (P = 0.017 and 0.047, respectively), which was the location with higher endophyte infection rate. For all associations, the direction of the T-Snip genotypes was the same and as expected: the greater the genotype score, the better performance. No associations were found for the other traits (P > 0.10). These results indicate that the T-Snip test may be predictive of cow performance (aBWd, aBCSd, and adjWW) in an endophyte-infected tall fescue environment.

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Section: Discussionmentioning

confidence: 98%