Growth rates and patterns of organs and tissues in the bovine fetus

Slaughter of Pregnant Cattle at an Austrian Abattoir: Prevalence and Gestational Age

Simple Summary

Cattle constitute a major part of the livestock in Austria. Dairy cows are sent to slaughter at the end of their production cycle, whereas heifers are admitted to slaughter either after a fattening period or because of reproductive disorders. In several countries, evidence has been presented that pregnant female cattle are admitted to slaughter, with implications for animal welfare and meat quality. Until today, no data are available on the frequency of pregnant cattle slaughtered in Austria. Over a one-year period, we examined 1633 female cattle in one abattoir, and pregnancy was detected in 104 animals (6.4%). Sixteen cattle were in the last third of gestation. Percentages of pregnant cattle sent to slaughter were higher in beef and dual-purpose breeds than in dairy cattle, but this was not statistically significant. Measures to minimize the number of pregnant cattle sent to slaughter should be implemented at farm-level.

Abstract

The slaughter of pregnant cattle raises ethical–moral questions with regard to animal welfare, but also concerns of consumers because of higher levels of sex steroids in the meat from pregnant cattle. Since no data on the slaughter of pregnant cattle in Austria were available, we examined uteri of slaughtered female cattle in one Austrian mid-size abattoir. Sample size was calculated for an assumed prevalence of 2.5% (±1%; 95% confidence interval) of cows or heifers slaughtered in the last trimester of pregnancy and amounted to 870 cows and 744 heifers. 1633 female cattle of domestic origin were examined, most of them of dual-purpose type. Pregnancy was detected in 30/759 heifers and in 74/874 cows (an overall prevalence of 6.4%). The number of cattle in the last trimester of pregnancy was 16 to 26, depending on the evaluation scheme. We found no significant differences in percentages of pregnant cattle sent to slaughter for beef, dual-purpose and dairy breeds, although the latter group demonstrated the lowest percentage. Our results are comparable with those from previously conducted studies in other member states of the European Union. Measures to avoid sending pregnant cattle to slaughter should be implemented at farm-level.

Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis, and RNA expression in Holstein heifer calves

The objective of this study was to analyze the mammary gland transcriptome to determine how preweaning nutrient supply alters the molecular mechanisms that regulate preweaning mammary development. Holstein heifers were fed via milk replacer (MR) either an elevated level of nutrient intake (ELE; on average, 5.9 ± 0.2 Mcal of ME in 8.4 L of MR/d, n = 6) or a restricted amount of nutrients (RES; 2.8 ± 0.2 Mcal of ME in 4 L of MR/d, n = 5) for 54 d after birth, at which point they were slaughtered and samples of mammary parenchyma tissue were obtained. Parenchymal mRNA was analyzed, and the fold change (FC) of 18,111 genes (ELE relative to RES) was uploaded to Ingenuity Pathway Analysis (IPA) software (Qiagen Bioinformatics, Redwood City, CA) for transcriptomic analysis. Using a threshold of P < 0.05, IPA identified that the FC of 1,931 of 18,811 differentially expressed genes (DEG) could be used for the analysis. A total of 18 molecular and cellular functions were relevant to DEG arising from the treatments; the 5 functions most associated with DEG were cell death and survival, cellular movement, cellular development, cellular growth and proliferation, and lipid metabolism. Based on the directional FC of DEG, the mammary gland of ELE heifers was predicted to have increased epithelial-mesenchymal transition (Z = 2.685) and accumulation of lipid (Z = 2.322), whereas the synthesis of DNA (Z = -2.137), transactivation of RNA (Z = -2.254), expression of RNA (Z = -2.405), transcription (Z = -2.482), and transactivation (Z = -2.611) were all predicted to be decreased. Additionally, IPA predicted the activation status of 13 upstream regulators with direct influence on DEG as affected by ELE feeding that were ligand-dependent nuclear receptors (n = 2), enzymes (n = 1), or transcription regulators (n = 10). Of these, 6 were activated (Z > 2) and 7 were inhibited (Z < -2). In summary, feeding ELE preweaning altered the mammary transcriptome of Holstein heifers, affecting cell functions involved in the morphological and physiological development of the mammary gland.

Inclusion of bovine lipoproteins and the vitamin E analogue, Trolox, during in vitro culture of bovine embryos changes both embryo and fetal development

This experiment investigated effects of lipoproteins and Trolox (vitamin E analogue) on bovine embryo and fetal development. The treatments were: in vitro culture (IVC) in synthetic oviducal fluid alone (SOF); with bovine lipoproteins (2% v/v; SOFLP); with Trolox (100 μM; SOFT); and with lipoproteins and Trolox (SOFLPT). In vitro culture with lipoproteins increased fatty acid content of blastocysts (P < 0.001) whereas inclusion of Trolox had no effect (P > 0.05). Whereas lipoproteins reduced zygote development to blastocysts (P = 0.03), Trolox facilitated increased development (P < 0.001) and counteracted the reduction observed with lipoproteins (interaction, P = 0.009). Lipoproteins also compromised (P < 0.001) but presence of Trolox (P > 0.05) had no effect on blastocyst morphological grade. Pregnancy rates resulting from synchronous transfer of IVP embryos were not affected by IVC treatment. At Day 70 of pregnancy, compared with SOF, fetal weight was lower in SOFLP but not SOFLPT (interaction, P < 0.001). Liver weight (g kg–1 fetal weight) was greater (P = 0.03) in treatments containing Trolox. Placentome numbers were greater in SOF and SOFLPT compared with SOFLP and SOFT (interaction, P = 0.002); superior embryo grades were also associated with increased numbers of placentomes (P = 0.024). In conclusion, the interactive effects of lipoprotein and Trolox inclusion on in vitro embryo development were also evident in fetal development at Day 70.