Effects of ionophore feeding and anthelmintic administration on age and weight at puberty in spring-born beef heifers.

Abstract

Two hundred eighty-eight heifer calves in two 1-yr replications were used to test the hypothesis that ionophore (ION) feeding, anthelmintic (ANT) administration, or the combination (COMB) would cause heifers to express pubertal estrus at a younger age than control (CONT) heifers. Heifers were assigned randomly within three weight blocks in a randomized complete block design with a 2 x 2 factorial arrangement of treatments. A high-fiber diet was fed for 172 d during yr 1 (Y1) and 199 d during yr 2 (Y2). Monensin sodium (200mg.animal-1.d-1) was fed to ION and COMB treatments and ivermectin (200 micrograms/kg of BW) was given to ANT and COMB groups at weaning and 84 d later. Rate of gain was monitored every 21 d and diet intake was adjusted to obtain equal rates of gain across treatments. Fecal samples were collected from one-third of the heifers in each group and analyzed for internal parasite egg counts every 21 d. Serum progesterone samples taken twice weekly were used to estimate onset of puberty. There was no treatment x year interaction in any parameter measured and the data were pooled across both years. Total weight gain was similar (P > .10) for all treatments. Fecal egg output decreased (P < .01) after initial application of anthelmintic. The ANT, ION, and COMB heifers had greater (P < .05) gain:feed ratios than did CONT (.132, .142, and .148 vs .125 kg for ANT, ION, COMB, and CONT, respectively). Age and weight at puberty were different (P < .05) for ION (425 d, 351.8 kg), COMB (425 d, 349.5 kg), and ANT (424 d, 348.8 kg) compared with CONT (433 d, 362.5 kg). There was no difference (P > .10) in age and weight at puberty between COMB, ION, or ANT heifers. During Y1, but not Y2, there were a greater (P < .05) number of COMB, ION, and ANT heifers pubertal before the breeding season. Additionally, there was a tendency (P = .12) for higher first-service conception in the COMB, ION, and ANT heifers than in the CONT heifers. Final pregnancy rates among treatments were similar (P > .10).

Adoption of Technology, Management Practices, and Production Systems by U.S. Beef Cow-Calf Producers

“…Ionophore use in the cow-calf segment has not been determined, but in 1999, ionophores were used in 93% of U.S. feedlots (U.S. Department of Agriculture, Animal and Plant Health Inspection Service [USDA-APHIS], 2000). Use of ionophores by cow-calf producers assists in replacement heifers reaching puberty earlier (Purvis and Whittier, 1996;Sprott et al, 1988). Growth-promoting implants were used on 12% of cow-calf operations in , down from 27% in 1992-1993(USDA-APHIS, 2009b.…”

Short- and long-term association between individual levels of milk antibody against Ostertagia ostertagi and first-lactation heifer’s production performances

“…However, such an approach does not take into account the effect of different helminths and exposure levels on production losses. In addition, evidence suggests that anthelmintic drugs could directly stimulate cow milk production (Purvis and Whittier, 1996). In other studies, high levels of bulk tank milk antibody against O. ostertagi were associated with an annual drop of cow milk production (Sanchez and Dohoo, 2002;Charlier et al, 2005).…”

Prevalence, fecal egg counts, and species identification of gastrointestinal nematodes in replacement dairy heifers in Canada

“…Dairy replacement heifers represent the future of a dairy farm; they account for a substantial amount of the enterprise costs but are also more susceptible to GIN infection compared with adult cows (Zwald et al, 2007;Lang, 2012;Bellet et al, 2018). Although some studies report earlier onset of puberty, a reduced culling rate during first lactation and increased mammary tissue development in heifers treated with anthelmintic products, suggesting that overall lifetime productivity may be reduced in untreated heifers, ambiguity remains whether these effects are because of reduced GIN levels or from other pharmacological drug effects on the metabolism or immune system of the treated animal (Purvis and Whittier, 1996;Mejía et al, 1999Mejía et al, , 2009Perri et al, 2013). Furthermore, the long-term effects of GIN infection as a heifer on productivity as an adult cow have not been assessed well and the actual economic effects of GIN infection on cattle farms are more challenging to establish because multiple management factors, sociopsychological values, and local input and output costs affect farm-level economics and cattle health (Corwin, 1997;Charlier et al, 2014Charlier et al, , 2016Bellet et al, 2018;Rushton and Bruce, 2019).…”