Inclusion of Bos indicus genetics improves production traits of cattle maintained in hot climates. Limited information exists detailing pregnancy-specific events as influenced by variable amounts of Bos indicus genetics. Three experiments were completed to examine the effect of Bos taurus and Bos indicus genotypes on fetal size and plasma pregnancy-associated glycoprotein (PAG) concentrations. In all experiments, cows were bred by AI after synchronization of ovulation. Fetal measurements were completed by transrectal ultrasonography and plasma PAG concentrations were quantified from plasma harvested the day of each fetal measurement. In Exp. 1, fetal size and plasma PAG concentrations were measured at d 53 of pregnancy in cows composed of various fractions of Angus and Brahman (n = 9 to 21 cows/group). Fetus size was greater in cows containing >80% Angus genetics compared with cows containing <80% Angus influence (3.40 ± 0.28 vs. 2.86 ± 0.28 cm crown-rump length; P < 0.01). Plasma PAG concentrations were reduced (P < 0.01) in cows containing >80% Angus genetics when compared with their contemporaries (6.0 ± 1.5 ng/mL vs. 9.4 ± 1.5 ng/mL). In Exp. 2, fetal measurements and plasma PAG concentrations were determined at d 35 and 62 of pregnancy in Angus and Brangus cows. Breed did not affect fetus size at d 35, but Angus cows contained larger fetuses than Brangus cows at d 62 [3.0 ± 0.03 vs. 2.8 ± 0.03 cm crown-nose length (CNL; P > 0.01)]. Plasma PAG concentrations were not different between breed at d 35 and 62 (P > 0.1). In Exp. 3, fetal measurements and plasma samples were collected at d 33/34, 40/41, 47/48, and 54/55 post-AI in Angus and Brangus cows. Fetus size was not different (P > 0.05) between genotypes on d 33/34, 40/41, and 47/48. Angus fetuses were larger than Brangus fetuses at d 54/55 (2.1 ± 0.03 vs. 1.9 ± 0.03 cm CNL; P = 0.001). Plasma PAG concentrations were less in Angus than Brangus cows at each time point (average 4.9 ± 0.9 vs. 8.2 ± 0.9 ng/mL; P = 0.005). In conclusion, these studies determined that the Bos taurus × Bos indicus genotype impacts fetal size and rate of fetal development by 7 wk of gestation. Plasma PAG concentrations were increased in cattle with Bos indicus genetics in 2 of 3 studies, suggesting that genotype is one of several determinants of PAG production and secretion in cattle.
The objective of this study was to determine the effects of various estrous synchronization protocols utilizing the five-day controlled internal drug releasing (CIDR) In Experiment 1, overall days to estrus were greater (P ≤ 0.01) in U and P compared with C. In Experiment 2, overall days to estrus were greater (P ≤ 0.02) in U and P compared with G. In summary, the 5 d CIDR reduces the number of days required to bring ewes into estrus when compared to untreated ewes. iv ACKNOWLEDGEMENTS
Producers cannot completely control infertility in their cow herds. However, understanding and addressing the factors that affect infertility will help producers implement management practices that can improve fertility and reduce the negative impacts of infertility on the profitability of beef cow-calf operations. This 4-page fact sheet discusses reasons why beef cows fail to become pregnant or wean a calf, identification of infertile beef cows, and economic impacts of reduced fertility and infertility in beef cattle. Written by Chris Prevatt, G. Cliff Lamb, Carl Dahlen, Vitor R. G. Mercadante, and Kayln Waters, and published by the UF/IFAS Department of Animal Sciences, revised September 2018. https://edis.ifas.ufl.edu/an208
Florida has 915,000 beef cows and 125,000 replacement heifers (USDA, 2016). Developing these heifers so that they can become productive females in the cow herd is a tremendous investment in a cow/calf operation, an investment that takes several years to make a return. The good news is that there are options to develop heifers on forage-based programs with the possibility of reducing costs while simultaneously meeting performance targets required by the beef industry. Mild winters in Florida allows utilization of cool-season forages that can significantly enhance the performance of grazing heifers. During the warm-season, integration of forage legumes into grazing systems will provide additional nutrients to meet the performance required to develop a replacement heifer to become pregnant and enter the mature cow herd. In this document, we will propose a model for replacement heifer development, based on forage research performed in trials at the NFREC Marianna.
This publication aims to discuss the use of ultrasound to assist with beef cattle reproduction, which includes evaluation of the pre-service status of heifers and cows, diagnosis of pregnancy, determination of fetal age and sex, and evaluation of reproductive fitness of embryo recipients. Written by Mario Binelli, Thiago Martins, John Arthington, Kalyn Waters, Vitor Mercadante, Philipe Moriel, and Angela Gonella-Diaza, and published by the UF/IFAS Department of Animal Sciences, revised April 2023.
To determine whether supplementation of anti-phospholipase A antibody (aPLA) would alter voluntary DMI, feed efficiency (FE), acute-phase protein concentration, and blood differentials (BD) due to a change in diet from a forage-based to a grain-based diet, individual daily DMI was measured on 80 cross-bred steers during a 141-d period. On d 0, steers were blocked by BW and randomly assigned to receive a growing forage diet containing 1) no additive (CON; = 20), 2) inclusion of 30 mg of monensin and 8.8 mg of tylosin per kg of diet DM (MT; = 20), 3) inclusion of an aPLA supplement at 0.4% of the diet DM (0.4% aPLA; = 20), and 4) inclusion of an aPLA supplement at 0.2% of the diet DM (0.2% aPLA; = 20). On d 60, steers were transitioned into a grain-based diet (90% concentrate) over a 21-d "step-up" period while continuing to receive their supplement treatments and were maintained on the high-grain diet until the end of the trial on d 141. On d 0, 60, 81, and 141, individual shrunk BW was recorded. Blood samples were collected on d 60, 63, 65, 67, 70, 72, 74, 77, 79, 81, and 84 for determination of concentration of plasma ceruloplasmin, haptoglobin, and BD. During the growing forage-diet period, steers from the 0.2% aPLA and 0.4% aPLA treatments had lower ( < 0.05) residual feed intake (RFI; -0.12 ± 0.13 and -0.22 ± 0.13 kg/d, respectively) than steers from the CON treatment (0.31 ± 0.13 kg/d). During the grain-based diet period, the 0.2% aPLA (-0.12 ± 0.10 kg/d), 0.4% aPLA (0.36 ± 0.10 kg/d), and MT (0.10 ± 0.10 kg/d) steers had greater ( = 0.04) RFI than CON steers (-0.37 ± 0.10 kg/d). During the transition phase, white blood cell counts were greater ( = 0.04) for the 0.2% aPLA treatment (13.61 × 10 ± 0.42 × 10 cells/μL) than the 0.4% aPLA and MT treatments (12.16 × 10 ± 0.42 × 10 and 12.37 × 10 ± 0.42 × 10 cells/μL, respectively) and concentrations of lymphocytes also were greater ( = 0.01) for the 0.2% aPLA treatment (7.66 × 10 ± 0.28 × 10 cells/μL) than the 0.4% aPLA and MT treatments (6.71 × 10 ± 0.28 × 10 and 6.70 × 10 ± 0.28 × 10 cells/μL, respectively). Concentrations of plasma ceruloplasmin and haptoglobin were reduced ( < 0.05) for CON compared to aPLA steers (22.2 ± 0.83 vs. 24.4 ± 0.83 mg/dL and 0.18 ± 0.05 vs. 0.26 ± 0.05 mg/mL, respectively). Supplementation of aPLA improved FE of steers fed a forage-based growing diet but not when feeding grain-based diets. The 0.4% aPLA and MT treatments had decreased white blood cell counts and concentration of lymphocytes during the transition period compared to the 0.2% aPLA treatment, and CON steers had reduced concentrations of plasma ceruloplasmin and haptoglobin during the diet transition phase.
In Exp. 1, individual performance and daily DMI was measured on 70 crossbred weaned calves during a 70-d period using a GrowSafe system (GrowSafe Systems Ltd., Airdrie, AB, Canada) at the University of Florida North Florida Research and Education Center Feed Efficiency Facility (FEF). Calves were fed a low-concentrate (LC) growing diet, blocked by weight and sex, and then randomly assigned to pens to receive either no additional supplement (CON; n = 35) or receive a supplement of anti-phospholipase A2 antibody (aPLA2) at an inclusion rate of 0.6% of the diet DM (n = 35). After the 70-d feed efficiency (FE) trial (Phase 1), calves were loaded into a commercial livestock trailer and were driven for approximately 1,600 km during 24 h. Upon return to the FEF (Phase 2), calves were relocated to the same pens and groups and received the same diets and treatments for 28 d. Blood samples from each calf were collected on d 0, 1, 3, 5, 7, 14, 21, and 28 relative to initiation of transportation and were analyzed for determination of concentrations of plasma ceruloplasmin and haptoglobin. In Phase 1, initial BW (242.0 ± 3.7 kg; P = 0.92), BW at d 70 (313.0 ± 4.1 kg; P = 0.79), and ADG (1.01 ± 0.02 kg; P = 0.95) were similar between treatments. However, daily DMI was greater (P = 0.01) for CON (9.18 ± 0.15 kg) than aPLA2 (8.53 ± 0.15 kg). In addition, residual feed intake was greater (P = 0.002) for CON (0.389 ± 0.110 kg/d) than aPLA2 calves (-0.272 ± 0.110 kg/d). In Phase 2, after transportation, there were no differences between treatments on BW loss due to transportation shrink (26.0 ± 0.6 kg; P = 0.86), BW at d 28 (339.0 ± 4.1 kg; P = 0.72), ADG (1.28 ± 0.03 kg/d; P = 0.72), G:F (0.164 ± 0.004; P = 0.83), and concentrations of plasma haptoglobin (0.08 ± 0.02 mg/mL; P = 0.41). However, concentrations of plasma ceruloplasmin were greater (P < 0.001) for CON calves (14.3 ± 0.3 mg/dL) compared to aPLA2 calves (13.0 ± 0.3 mg/dL). In Exp. 2, the effects of aPLA2 inclusion on LC and high-concentrate (HC) substrates on in vitro fermentation parameters were assessed. Addition of aPLA2 had no effects on in vitro fermentation parameters of LC and HC substrates. In conclusion, supplementation of aPLA2 improved FE of growing beef calves when fed LC diets in Phase 1 and addition of aPLA2 had no effect on fermentation parameters of LC and HC substrates. In addition, calves supplemented with aPLA2 had reduced concentrations of plasma ceruloplasmin after 24 h of transportation.
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