J. D. Tucker

Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue1

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.

Automated collection of heat stress data in livestock: new technologies and opportunities

© The Author(s) 2018. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com Transl. Anim. Sci. 2018.2:319–323 doi: 10.1093/tas/txy061

Performance-enhancing technologies for steers grazing tall fescue pastures with varying levels of toxicity1

The objective of this study was to evaluate a combination of best management practices strategy for steer calves grazing tall fescue pastures with a range of toxicity. The experiment was conducted over two grazing seasons (fall 2015 for 91 days and spring 2016 for 84 days). Steers (n = 80 within season, BW = 197.0 ± 15.43 kg [fall] and 116.9 ± 4.88 [spring]) were stocked at 2.45 and 4.1 calves/hectare in fall and spring, respectively, to 16 pastures with varying levels of toxicity based on interim ergovaline (EV) concentration within season. Pastures were assigned to either mineral (MIN, n = 8) only management (MGMT) or a cumulative MGMT (CM, n = 8). The CM treatment included an implant containing 40 mg trenbolone acetate, 8 mg estradiol, and 29 mg tylosin tartrate (Component TE-G with Tylan, Elanco Animal Health, Greenfield, IN), 150 mg/calf daily monensin (Elanco Animal Health), and 1% body weight (BW) of a 50:50 corn gluten feed:soybean hull supplement (as-is basis). Data were analyzed within season using pasture as the experimental unit. For fall and spring, the EV concentration was 1,476 ± 883.2 ppb and 1,173 ± 620.6 ppb, respectively, and ranged from 90 ppb to 2,180 ppb. During the fall, forage allowance did not differ (P = 0.76) between CM and MIN. In the spring, however, forage allowance only differed for the month of June (P ≤ 0.05, 2.55 versus 3.22 ± 0.177 kg DM/kg BW, for MIN and CM, respectively). In the fall, average daily gain (ADG) responded to the simple effects of EV (P = 0.01) and MGMT (P < 0.001), and ADG for MIN steers was explained by ADG = 0.41 - 0.000064 × EV; whereas, ADG for CM was explained by ADG = 1.05 - 0.000064 × EV. In the spring, there was an EV × MGMT interaction (P = 0.03) for ADG. For MIN, ADG = 0.80 - 0.000278 × EV; whereas for CM, ADG = 0.94 + 0.000001835 × EV. In spring, the ADG response to CM relative to MIN increased as EV increased. The CM strategy resulted in lower blood urea nitrogen than MIN in fall and spring (P < 0.01), but prolactin and serum Cu were not affected by MGMT in either season. In conclusion, performance was improved within the fescue belt by implementing feeding strategies using implants, ionophores and supplementation, but a detailed economic analysis is warranted. Further research is needed to evaluate CM programs under varied stocking rates and in combination with dilution of endophyte-infected fescue pastures with non-toxic grasses or legumes.