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Global warming is a major challenge to the sustainable and humane production of food because of the increased risk of livestock to heat stress. Here, the example of the prolactin receptor (PRLR) gene is used to demonstrate how gene editing can increase the resistance of cattle to heat stress by the introduction of mutations conferring thermotolerance. Several cattle populations in South and Central America possess natural mutations in PRLR that result in affected animals having short hair and being thermotolerant. CRISPR/Cas9 technology was used to introduce variants of PRLR in two thermosensitive breeds of cattle – Angus and Jersey. Gene‐edited animals exhibited superior ability to regulate vaginal temperature (heifers) and rectal temperature (bulls) compared to animals that were not gene‐edited. Moreover, gene‐edited animals exhibited superior growth characteristics and had larger scrotal circumference. There was no evidence for deleterious effects of the mutation on carcass characteristics or male reproductive function. These results indicate the potential for reducing heat stress in relevant environments to enhance cattle productivity. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the impact of factors associated with the management of the mother and the quality of colostrum on the calf rearing during lactation, in the small-scale milk production system. In 13 dairy farms, information was obtained on body growth, colostrum feeding and information associated with the mother of 220 Holstein calves. The variables of interest were: morbidity, concentration of immunoglobulins in colostrum (CIC; <110 mg/ml), serum protein concentration (SPC; <6.6 g/dL), daily weight gain (DWG; <0.650 kg/d) and daily height gain (DHG; <0.222 cm/d). The study factors were: body weight at birth (BWB; <42 kg), height at birth (HB; <82 cm), colostrum consumed on the first day (CCFD; <4 l), colostrum consumed on the first day/kg of LW (CFDLW), body condition at calving (BCC; <3), length of the dry period (LDP; >68 d), primiparous cows (PC) and cows without a challenge diet (CWCD). To determine the impact of the study factors on the events of interest, the odds ratio was obtained from multiple logistic regression analyses. The factors identified for morbidity were CCFD and PC (P<0.1). The factors for CIC were LDP and CWCD (P<0.1), while for DWG, it was CWCD (P<0.1). Finally, the factors for DHG were CWCD, BWB, HB and CFDLW (P<0.1). These results suggest that the mother’s nutrition during late gestation has an important impact on the health and body development of calves during lactation. Further studies should determine long-term effects. [ABSTRACT FROM AUTHOR]

The profitability of dairy farms is closely linked to reproductive performance. Identifying risk factors that compromise this performance is vital to implementing strategies to improve productivity. An analysis was done of the effects on reproductive performance of artificial insemination (AI) use, herd size and high seroprevalence of reproductive infectious diseases. Data on reproductive events were collected from 52 farms (10-100 cows; 959 lactations) over 18 mo (births 2011-2012). Neosporosis, bovine infectious rhinotracheitis (IBR) and bovine viral diarrhea (BVD) seroprevalences were documented at each farm. Multiple logistic regression analyses were applied to determine the degree of association (odds ratio, OR) between potential risk factors and reproductive variables. Herds of 33 or more cows (OR= 1.5) and high neosporosis seroprevalence (OR= 2.3) were risk factors for assisted calving. High IBR and BVD seroprevalences (OR= 1.3 and 1.9, respectively) were risk factors for days to first service over 70 d in milk (DFS>70). Artificial insemination was a common risk factor for DFS>70 (OR= 2.4) and days open over 110 days in milk (OR= 1.3). Herds of 33 or more cows was a risk factor for nonpregnant cows at first service (OR= 1.7). Artificial insemination, herds of 33 or more cows and high neosporosis, IBR and BVD seroprevalences are factors associated with reproductive performance in small-scale dairy farms in various geographical regions in Mexico. [ABSTRACT FROM AUTHOR]

Choline is a nutrient that plays a role as a precursor for the neurotransmitter acetylcholine, the membrane phospholipid phosphatidylcholine, and the methyl donor betaine. Embryos produced in vitro are usually cultured without an exogenous choline source. We hypothesized that exposure to 1.8 mM choline chloride would increase percent of embryos becoming blastocysts in culture and pregnancy rate after transfer of embryos into recipients. A total of 39 Brahman and Senepol donors were used to produce embryos for transfer into recipient crossbred females. Donors were assigned to have their embryos cultured in either 1.8 mM choline chloride or, as a control, 1.8 mM extra NaCl. The percent of oocytes cleaved were measured 3 days after insemination and percent blastocyst at day 7.5. Embryos were transferred into recipient cows and pregnancy was diagnosed at 28-31 days of gestation and then confirmed at 50-56 days. Data were analyzed using PROC GLIMMIX in SAS. Treatment did not affect cleavage rate (67.3 + 1.6 vs 68.6 + 1.6% for choline vs control; P = .0.5632) or percent of cleaved embryos becoming blastocysts (17.6 + 1.3 vs 18.1 + 1.3%; P = 0.5355). Similarly, there was no effect of treatment on pregnancy days 28-31 [42.5% (48/113 cows) vs 47.3% (54/114 cows) for choline vs control; P = 0.4339] or at days 50-56 [39.1% (36/92) vs 38.5% (32/83); P = 0.5348]. In summary, 1.8 mM choline chloride does not impact embryo development to the blastocyst stage or pregnancy establishment. Further investigation is needed to evaluate the phenotype of the subsequent calves to determine whether early exposure to choline has consequences for postnatal function. Support: USDA-NIFA 2020-67015-30821. [ABSTRACT FROM AUTHOR]

Choline is a known developmental programming agent of the bovine preimplantation embryo. Culture of the embryo with 1.8 mmol/L choline, a concentration much higher than in blood, alters development to cause increased weaning weight and other changes during the postnatal period. It was hypothesized here that choline exerts similar effects on the developmental program of the embryo when added at concentrations similar to those in peripheral blood (i.e., 4 mol/L). Oocytes were collected via ovum pick up and embryos were produced in vitro. Embryos were cultured until day 7 after fertilization in medium with 4 mol/L choline chloride, or, as a vehicle control, with an additional 4 mol/L sodium chloride. Blastocysts were transferred into recipients and pregnancy was diagnosed at approximately 28 d of gestation. Subsequent calves (n=37 for vehicle and n=35 for choline) were weighed at birth and at weaning. Addition of choline to culture medium did not affect the proportion of embryos that became blastocysts or the proportion of transferred blastocysts that produced a pregnancy. Birth weight was unaffected by treatment but calves derived from choline-treated embryos were heavier at time of weaning and gained more per day from birth until weaning than calves derived from embryos treated with vehicle. Results demonstrate that choline can act on the preimplantation embryo at a physiologically-relevant concentration to alter postnatal phenotype. Observations are further evidence for the importance of the first days of embryonic development for the phenotype of the resulting calf.

Choline is a vital micronutrient. In this study, we aimed to confirm, and expand on previous findings, how choline impacts embryos from the first 7 days of development to affect postnatal phenotype. Bos indicus embryos were cultured in a choline-free medium (termed vehicle) or medium supplemented with 1.8 mM choline. Blastocyst-stage embryos were transferred into crossbred recipients. Once born, calves were evaluated at birth, 94 days, 178 days, and at weaning (average age = 239 days). Following weaning, all calves were enrolled into a feed efficiency trial before being separated by sex, with males being slaughtered at ~580 days of age. Results confirm that exposure of 1.8 mM choline chloride during the first 7 days of development alters postnatal characteristics of the resultant calves. Calves of both sexes from choline-treated embryos were consistently heavier through weaning and males had heavier testes at 3 months of age. There were sex-dependent alterations in DNA methylation in whole blood caused by choline treatment. After weaning, feed efficiency was affected by an interaction with sex, with choline calves being more efficient for females and less efficient for males. Calves from choline-treated embryos were heavier, or tended to be heavier, than calves from vehicle embryos at all observations after weaning. Carcass weight was heavier for choline calves and the cross-sectional area of the longissimus thoracis muscle was increased by choline., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)