scholarly journals Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

2020 ◽  
Vol 98 (2) ◽  
Author(s):  
Reinaldo F Cooke ◽  
Rodolfo C Cardoso ◽  
Ronaldo L A Cerri ◽  
G Cliff Lamb ◽  
Ky G Pohler ◽  
...  
Keyword(s):  
United States ◽  
Bos Indicus ◽  
Reproductive Function ◽  
Fixed Time ◽  
The United States ◽  
Beef Industry ◽  
Tropical Regions ◽  
Reproductive Management ◽  
Adaptation Response ◽  
Equine Chorionic Gonadotropin

Abstract Efforts to understand biological functions and develop management schemes specific to Bos indicus-influenced cattle raised in tropical and subtropical environments are critical to meet the increasing global demand for protein. In the United States, B. indicus breeds are mostly used to generate B. indicus × B. taurus crosses with increased thermal and parasite tolerance, while retaining some productive characteristics of B. taurus cattle. Although crossbreeding represents a proven strategy to improve cattle adaptation almost immediately, research has also attempted to identify B. taurus genetics that can withstand subtropical and tropical climates. Reduced milk production and delayed reproductive maturation appear to be related with tropical adaptation of B. taurus breeds, as a means to conserve energy under stressful conditions and limited nutrition. Moreover, longevity may be the ultimate adaptation response to unfavorable environments, and retention of bulls and heifers from proven cows is the recommended strategy to improve longevity in B. indicus-influenced herds. Besides selection for longevity, other aspects should be considered when planning reproductive management in tropical and subtropical regions. Bos indicus and B. taurus breeds have multiple differences pertaining to reproductive function, including age at puberty, ovarian dynamics, and pregnancy development. Nutritional strategies such as the stair-step regimen, and use of exogenous progesterone (P4) inserts are options to hasten puberty attainment of late-maturing B. indicus-influenced heifers. Yet, limited pharmacological alternatives are available for reproductive management of B. indicus-influenced females in the United States, which rely on GnRH-based protocols not specifically designed to the reproductive function of B. indicus breeds. In contrast, hormonal protocols based on exogenous P4, estradiol esters, and equine chorionic gonadotropin are available for use in B. indicus females in South America. These include protocols tailored to prepubertal heifers, anestrous cows, and cycling nulliparous or parous females, which often yield pregnancy rates of 50% to fixed-time artificial insemination. The global dairy industry also faces similar challenges in increasing demand and production as the beef industry. Selection of cows capable of sustaining optimal milk yield, reproductive success, and health status in hot and humid conditions is essential for optimal dairy production in subtropical and tropical regions.

scholarly journals Considerations for reproductive management of bos indicus-influenced beef heifers

2017 ◽  
Author(s):  
◽  
James William Cameron Locke
Keyword(s):  
United States ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Fixed Time ◽  
The United States ◽  
Pregnancy Rates ◽  
Breeding Period ◽  
Beef Heifers ◽  
Reproductive Management ◽  
Natural Service

The Bos indicus species of beef cattle presents a number of unique reproductive challenges, especially with regard to those that influence reproductive efficiency including timely attainment of puberty, response to certain pharmaceutical drugs used to control estrus and ovulation, and response to physiological stressors. Cattle of this biological type comprise a substantial percentage of the beef cattle population in southern regions of the United States because of their ability to withstand high ambient temperatures and relative humidity. Additionally, Bos indicus cattle are regarded to exhibit increased parasite and disease resistance, resulting in improved production in subtropical climates as compared to Bos taurus cattle in those same regions. Research utilizing composite breeds of Bos taurus and Bos indicus beef heifers has been limited in the United States, and adoption of reproductive technologies such as artificial insemination and estrus synchronization has been sluggish compared to Bos taurus cattle in other regions of the country. To help answer a number of questions about this biological type, an experiment was designed to evaluate reproductive performance of Bos indicus-influenced heifers (n = 1,456). Weights and reproductive tract scores (RTS; Scale 1-5) were obtained for heifers prior to assignment of one of five treatments: Non-synchronized + natural service (NS); melengestrol acetate + natural service (MGA + NS; 0.5 mg x animal-1 x d-1); 14-d controlled internal drug release + natural service (CIDR + NS; 1.38g progesterone); 14-d MGA-PG + fixed-time AI (FTAI); and 14-d CIDR-PG + FTAI. Heifers in the three NS treatments were exposed to fertile bulls for 65 d, beginning 10 d after progestin removal for CIDR + NS and MGA + NS groups. Heifers in FTAI treatments were administered PGF2[alpha] (PG; 25 mg, IM) 16 or 19 d following CIDR or MGA removal. Fixed-time AI was performed 66 and 72h after PG for CIDR-PG and MGA-PG treatments, respectively. Gonadotropin-releasing hormone (GnRH; 100[mu]g, i.m.) was administered at FTAI. Estrus detection aids were applied at PG for heifers in FTAI treatments and evaluated at AI. Heifers in FTAI treatments were exposed to fertile bulls 12 d following FTAI. Blood samples were collected and ovarian ultrasounds performed at PG administration and FTAI to compare serum concentrations of estradiol and progesterone and to evaluate follicular dynamics among a subset of heifers assigned to FTAI treatments. Pregnancy status was determined at the end of a 65-d breeding period. Data were analyzed using PROC FREQ and GLIMMIX procedures of SAS. Mean concentrations of estradiol at AI differed between MGA- versus CIDR-treated heifers (P = 0.04; 8.2 versus 6.6 pg/ml), however estrous response after PG (52% versus 53%) and pregnancy rates after FTAI (40%) did not differ between MGA- and CIDR-PG treatments, respectively. Across all treatments, pregnancy rates were compared on 21, 30 and 60 d of the breeding period based on pubertal status (prepubertal RTS = 1 and 2; peripubertal RTS = 3; pubertal RTS = 4 and 5). Pregnancy rates differed at each time point based on pretreatment pubertal status (P [less than or equal to] 0.02) and weight (P [less than or equal to] 0.05). No differences were apparent with regard to progestin type at any time point, although higher pregnancy rates (P [less than or equal to] 0.004) were observed among NS treatments than FTAI followed by NS exposure at Days 30 and 60. This experiment is the largest comprehensive field trial conducted in the United States and reported in the literature involving Bos indicus-influenced beef heifers utilizing estrus synchronization prior to natural service or FTAI. This study reinforced results from previous studies, however raises a number of questions yet to be answered for heifers of this biological type. These data should be used as a basis for improvements in reproductive management of Bos indicus-influenced beef heifers prior to their first breeding season, and creates a number of possibilities for future research trials that build upon results reported in this thesis. Selection, management, and post-weaning to pre-breeding development of Bos indicus-influenced replacement beef heifers should involve the cooperative efforts of beef producers, veterinarians, and research scientists to further investigate methods to improve reproductive efficiency and genetic merit of these herds.

scholarly journals Lack of Selection and Limits to Delegation: Firm Dynamics in Developing Countries

2021 ◽  
Vol 111 (1) ◽  
pp. 231-275
Author(s):  
Ufuk Akcigit ◽  
Harun Alp ◽  
Michael Peters
Keyword(s):  
United States ◽  
Developing Countries ◽  
Firm Growth ◽  
Firm Dynamics ◽  
Fixed Time ◽  
The United States ◽  
Factors Affecting ◽  
Poor Countries ◽  
Managerial Practices ◽  
Managerial Delegation

Delegating managerial tasks is essential for firm growth. Most firms in developing countries, however, do not hire outside managers but instead rely on family members. In this paper, we ask if this lack of managerial delegation can explain why firms in poor countries are small and whether it has important aggregate consequences. We construct a model of firm growth where entrepreneurs have a fixed time endowment to run their daily operations. As firms grow large, the need to hire outside managers increases. Firms’ willingness to expand therefore depends on the ease with which delegation can take place. We calibrate the model to plant-level data from the United States and India. We identify the key parameters of our theory by targeting the experimental evidence on the effect of managerial practices on firm performance from Bloom et al. (2013). We find that inefficiencies in the delegation environment account for 11 percent of the income per capita difference between the United States and India. They also contribute to the small size of Indian producers, but would cause substantially more harm for US firms. The reason is that US firms are larger on average and managerial delegation is especially valuable for large firms, thus making delegation efficiency and other factors affecting firm growth complements. (JEL D22, G32, L25, L26, O14)

scholarly journals Ground Beef: Implications for the Southeastern U.S. Beef Industry

1979 ◽  
Vol 11 (2) ◽  
pp. 21-26
Author(s):  
J. Richard Conner ◽  
Robert W. Rogers
Keyword(s):  
United States ◽  
Fast Food ◽  
Ground Beef ◽  
The United States ◽  
Beef Industry ◽  
Increasing Trend ◽  
Fast Food Restaurants ◽  
Eating Out ◽  
At Home

Currently the United States consumes an estimated 39 to 45 percent of its beef in the “ground” form [3, 7, 8]. As recently as 1972 the estimated percentage of beef consumed as ground was only 33 [3] and some industry leaders have estimated the proportion by 1985 to be from 50 to 65 percent [5, 8, 11, 12]. This increasing trend in the percentage of beef consumed in the ground form is often attributed to several factors including (1) an increase in the percentage of wives working away from home which results in more “eating out” and less home preparation of “traditional” meat dishes for those meals consumed at home, and (2) the continuing growth of the fast-food restaurants and their popular “hamburger” meals [5, 8, 11, 12].

scholarly journals A UT/LS ozone climatology of the nineteen seventies deduced from the GASP aircraft measurement program

2007 ◽  
Vol 7 (2) ◽  
pp. 3451-3517 ◽  
Author(s):  
C. Schnadt Poberaj ◽  
J. Staehelin ◽  
D. Brunner ◽  
V. Thouret ◽  
V. Mohnen
Keyword(s):  
United States ◽  
Large Scale ◽  
The United States ◽  
Eastern United States ◽  
Nineteen Seventies ◽  
Large Variability ◽  
Tropical Regions ◽  
Mixing Ratios ◽  
Research Aircraft ◽  
Atmospheric Sampling

Abstract. The knowledge of historical ozone in the upper troposphere/lower stratosphere (UT/LS) region is mostly confined to regular measurements from a number of ozonesonde stations. We present ozone measurements of the Global Atmospheric Sampling Program (GASP) performed from four commercial and one research aircraft during 1975 to 1979. Using GASP data, a UT/LS ozone climatology of 1975–1979 was built. Seasonality and concentrations of GASP UT ozone in the middle, subtropical and tropical regions of the northern hemisphere (NH) are generally in agreement with other published observations, derived from ozonesondes or aircraft campaigns. In regions where both GASP (1970s) and MOZAIC (1990s) data are available, similar ozone concentrations are found and seasonal cycles agree well confirming the reliability of GASP ozone. GASP provides unique large-scale climatological information on UT/LS ozone above the NH Pacific region. Agreement is found with observations from individual ozonesonde sites and aircraft campaigns carried out over this region. Tropical UT ozone is seen to be lower near the dateline than further east, presumably related to uplift of ozone poor air within convection. Over the west coast of the United States, summer UT ozone is higher than over the adjacent Pacific, probably caused by air pollution over southern California in the 1970s. GASP offers an unprecedented opportunity to link to European, Canadian and U.S. American ozonesonde observations of the 1970s. For the quantitative comparison, an altitude offset was applied to the sonde data to account for the slow response time of the sensors. In the LS, the European and Canadian Brewer-Mast (BM) sensors then agree to ±10% with the GASP instruments in all seasons. In the UT, the European BM sondes record similar to slightly less average ozone than GASP, however, with large variability overlaid. Over the eastern United States, systematic positive deviations of the Wallops Island ECC sondes from GASP of +20% are found. The comparisons over Europe and the eastern United States corroborate earlier findings that the early ECC sensors may have measured 10 to 25% more ozone than the BM sensors. Our results further indicate that applying the correction factor to the 1970s BM ozonesondes is necessary to yield reliable ozone mixing ratios in the UT/LS.

scholarly journals Genomics in the United States beef industry

2014 ◽  
Vol 166 ◽  
pp. 84-93 ◽  
Author(s):  
Megan M. Rolf ◽  
Jared E. Decker ◽  
Stephanie D. McKay ◽  
Polyana C. Tizioto ◽  
Kimberly A. Branham ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Beef Industry

scholarly journals 34 Reproductive management of beef females in tropical and sub-tropical environments

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 37-37
Author(s):  
Nicola Oosthuizen ◽  
Pedro Levy Piza Fontes ◽  
G Cliff Lamb
Keyword(s):  
Assisted Reproductive Technologies ◽  
Bos Taurus ◽  
Management Strategies ◽  
Bos Indicus ◽  
The United States ◽  
Reproductive Technologies ◽  
Pregnancy Rates ◽  
Embryo Production ◽  
Reproductive Management

Abstract Bos indicus and Bos taurus cattle diverged from an evolutionary standpoint more than 110,000 years ago. Since then, Bos indicus cattle have undergone genetic adaptations beyond the commonly discussed increased thermo-tolerance and parasite resistance. Several physiological differences exist between Bos indicus and Bos taurus cattle, and it is important to consider these differences when establishing reproductive management strategies. It has been well described that Bos indicus cattle have a delayed onset of puberty and longer periods of postpartum anestrus, yet through the utilization of estrus synchronization protocols these challenges can be attenuated. However, when Bos indicus females are exposed to these protocols, they are known to have smaller dominant follicles, lower expression of estrus, and decreased pregnancy rates to artificial insemination (AI) when compared to Bos taurus females. These factors can be overcome through the utilization of estradiol and progesterone based synchronization protocols, which improve follicular dynamics and yield acceptable pregnancy rates to assisted reproductive technologies in cattle adapted to tropical or subtropical conditions. However, the use of estrogens for synchronization purposes is not permitted in the United States, and cattle producers need to rely on GnRH-based protocols. Another key difference between subspecies, is that Bos indicus females have greater antral follicle counts than Bos taurus females, which proves beneficial for in vitro embryo production. Therefore, an opportunity exists to explore the greater productivity of donors in embryo production in order to improve genetics in herds that utilize these breeds.

Equine chorionic gonadotropin improves the efficacy of a progestin-based fixed-time artificial insemination protocol in Nelore (Bos indicus) heifers

2010 ◽  
Vol 118 (2-4) ◽  
pp. 182-187 ◽  
Author(s):  
M.F. Sá Filho ◽  
J.R.S. Torres-Júnior ◽  
L. Penteado ◽  
L.U. Gimenes ◽  
R.M. Ferreira ◽  
...  
Keyword(s):  
Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Bos Indicus ◽  
Fixed Time ◽  
Equine Chorionic Gonadotropin
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