Monitoring of recessive defects associated with low reproductive performance in dairy cattle in Uruguay.

Background: Most dairy cattle breeds originate show an average generational inbreeding rate of 1%, which favors the occurrence of recessive defects associated with low reproductive performance. Aim: The objective of this study was to monitor recessive defects associated with low reproductive performance in dairy cattle. Methods: To monitor bulls carrying the Holstein Friesian haplotype (HH) 1, HH3, and HH4 haplotypes, we analyzed the records of 3,028 national and imported Holstein Friesian bulls from the 2021 updated sires' catalog published by "Evaluaciones Genéticas Lecheras"; and to determine the presence of these mentioned haplotypes, as well as Jersey haplotype (JH) 1 and complex vertebral malformation (CVM), were genotype with the GeneTitan® 2,500 single nucleotide polymorphism (SNP) bovine chip, estimate their frequencies and evaluate their impact on the fertility of 100 Holstein Friesian cows and 70 Holstein Friesian-Jersey crosses belonging to an experimental dairy. Results: From a total of 1,468 (48.5%) bulls with genetic information from the sires' catalog for HH1 and 1,471 (48.6%) for HH3 and HH4, we found 90 (6.1%) carriers for HH1, 60 (4.1%) for HH3, and 6 (0.4%) for HH4, respectively. By genotyping with the chip, we calculated the herd frequency of the mutant alleles and herd prevalence of carriers for HH1 and CVM as q = 0.003 and 0.022; 0.59% and 4.3% (call rate >0.99), respectively. No mutant alleles were found for HH3, HH4, and JH1 in the analyzed population. We examined reproductive data by observing the presence of CVM and HH1 mutant alleles in repeat cows with an average of four services to achieve pregnancy. Conclusion: This study demonstrated the presence of recessive defects associated with low reproductive performance in the analyzed population, which can affect the health and productivity of dairy cattle. Therefore, cows and bulls should be closely monitored through genetic testing to lower the incidence of recessive defects in dairy cattle.

Transfer of ß-lactam and tetracycline antibiotics from spiked bovine milk to Dambo-type cheese, whey, and whey powder.

The aim of this study was to investigate the transfer of residues of five ß-lactam antibiotics (ampicillin, penicillin G, cloxacillin, dicloxacillin and cephalexin) and two tetracyclines (tetracycline and oxytetracycline) in the processing of cheese and whey powder, evaluating the effect of the processes and the final concentration in each product generated. Raw milk was fortified at two concentration levels with the seven antibiotics. The first concentration level (C1) was chosen according to the maximum residue limit (MRL) of each antibiotic (ampicillin and penicillin G: 4 µg kg-1; cloxacillin and dicloxacillin: 30 µg kg-1; cephalexin, tetracycline and oxytetracycline: 100 µg kg-1). The second concentration level (C2) was spiked as follows according to each antibiotic: 0.5 MRL (cloxacillin, dicloxacillin, cephalexin), 0.1 MRL (tetracycline and oxytetracycline) and 3 MRL (ampicillin and penicillin G). The antibiotics were analyzed by LC-MS/MS. No ampicillin or penicillin G residues were found in cheese or whey powder, although they were detected in whey at concentrations similar to those added to raw milk. Cephalexin was mostly distributed in whey between 82% and 96%, being the antibiotic that presented the highest concentration in whey powder (784 ± 98 µg kg-1) when milk was spiked at the MRL. The whey distribution of cloxacillin and dicloxacillin ranged from 57% to 59% for cloxacillin and from 46% to 48% for dicloxacillin, and both concentrated in whey powder. Tetracyclines were the antibiotics that concentrated in cheese, with retentions between 75% and 80% for oxytetracycline and between 83% and 87% for tetracycline. The distribution of antibiotics in the dissimilar stages of the cheese and whey powder production processes, as well as their concentration in the final products, depend on each type of antibiotic. Knowledge of the transfer of antibiotic residues during the process and final disposal is an input for the risk assessment of their consumption.