Beef Cattle Reproduction Research Articles

Application of ultrasonic imaging technology in beef cattle breeding management

ObjectiveThe aim of this study was to explore in depth the application of ultrasonic imaging technology in beef cattle reproduction management in order to improve the efficiency and management of beef cattle reproduction. MethodsIn this study, ultrasonographic diagnostic techniques were used to follow up the follicles and corpus luteum in the uterus and ovaries of dairy cows at different stages of development as well as at different periods of gestation of dairy cows, and to detect the effects of different fattening conditions of the cows and the number of litters on the sitting rate. ResultsThe diameter of mature follicles was generally around 16 mm, and the majority of them were 11–20 mm in diameter. Ultrasonography was used to detect early pregnancy in cows at 33–55 d. Ultrasound was used to identify the sex of the foetus most easily at 70–80 d. The results of this study showed that the sex of the foetus was most easily identified in cows at 70–80 d. The fat of the cow and the number of births also had a significant impact on pregnancy rates. ConclusionUltrasound imaging technology has an important application value in the management of beef cattle reproduction, and in pregnancy detection, it can achieve early and accurate diagnosis, improve the accuracy of detection, and differentiate between heifers in estrus and pregnant heifers. In addition, it can also be used for foetal sex identification at a specific period of time, providing a basis for breeding programmes.

131 How Horn Flies Could Be Affecting Your Beef herd's Reproductive Success

Abstract Horn flies (HF) are one of the most prevalent external parasites on pastured cattle in North America, although they can be found worldwide. HF cause animals severe stress leading to increased cardiac and respiratory rates, and decreased feed efficiency, average daily gain, and milk production. All these detrimental effects caused by HF contribute to over $1 dollars in economic loss in the United States, annually. Current methods of reducing fly numbers, including manure management, feed additives, and insecticides, are being utilized with varying degrees of success. However, these methods require extensive management, are temporary, and are costly to producers. While several studies have investigated the effects of horn flies on growth and milk production traits, there have been very few studies on their potential impacts on reproduction in beef cattle. Insemination and calving data collected on cows and yearling heifers at Northwest Georgia Research and Education Center between 2015 to 2022 was used to determine the effect of HF abundance on fertility. Each animal was exposed to two insemination events. Artificial Insemination (AI) was used except for cows that did not get pregnant from the first AI which were placed on pasture with a proven bull for natural service. The outcomes (success/failure) of each insemination event and calving were recorded. Still births where the dam carried the calf to term, but the calf passed during parturition were recorded as successes. As part of a research project, no fly control methods were carried out on the farms during 2019 and 2022. During these years, images of each animal were taken twice between May and August. The best image of each animal was used to estimate HF count. Animals were placed in three abundance classes (Low: 0-150, Med: 151-400, High: 401+) to analyze the effects of fly abundance on reproduction. For the remaining years (2015-2018, 2020-2021) animals received fly control and were not assessed for fly abundance. As shown Table 1, conception rates of each breeding attempt and calving rates were lower in both years where no horn fly control was used (2019 and 2022) compared with the remaining years where fly control was utilized. The decrease in conception rates when no fly control was used suggests a detrimental effect of HF on reproductive success. Additionally, for the animals measured in 2022, the average fly count for the dams who did not calf successfully was 357 which is significantly higher than the average count for the dams who did successfully calf (290). This suggests that animals with greater fly loads are less likely to carry to term. These adverse effects on reproductive health could be mitigated by genetically selecting for animals that can tolerate a greater fly load.

Practical Uses for Ultrasound in Managing Beef Cattle Reproduction

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.

The The Effect of Age and Breed on The Quality of Bull Semen in The Regional Artificial Insemination Centre

The success of beef cattle reproduction development in Indonesia very much depends on the quality of the semen produced by the Indonesian Institute for Artificial Insemination. Good quality bull will benefit farmers, frozen semen producers, and the country in large. This study aimed to determine effect of age and breed on the libido and quality of bull semen collected in the Regional Artificial Insemination Center (RAIC). This study used PO, Simmental, and Brahman Bull in RAIC Yogyakarta, with a total amount of 15, aged 4-7 years old. Semen was collected using an artificial vagina, semen evaluation used a spectrophotometer, and eosin-nigrosin staining method used for sperm viability and abnormalities examination. The result of this study indicated that bull breed did not affect the libido value and the semen quality of bulls (P>0,05). Volume, concentration, motility, and viability in various age groups did not show significant differences (P>0,05), but age groups had a significant effect on sperm abnormalities (P<0,05). The group of bulls aged 5-6 years showed the best quality compared to other groups, with the volume 4,58 ± 1,37 ml, concentration 1,91 ± 0,36 x109/ml, motility 3,80 ± 1,30, viability 89.83 ± 10.69%, and sperm abnormalities 2.51 ± 0.81%. It can be concluded that breed did not affect the bull libido and semen quality, while age had an effect on bull sperm abnormalities.

REPRODUCTION PERFORMANCE OF CATTLE LIVESTOCK IN THE NATIONAL MEAT PRIVATE FRAME IN MUNA DISTRICT

Muna Regency is an area that has the largest beef cattle population in Southeast Sulawesi Province. The purpose of this study was to determine the performance of beef cattle reproduction carried out for 5 months in the Muna Regency. The method used in this research is purposive sampling method, while the data used are primary and secondary data. Primary data were obtained through interviews of 250 respondents while secondary data were obtained from the District, village and related government offices. The results showed that the reproductive performance of beef cattle in the Muna District showed a positive trend because it was supported by the population of beef cattle, ownership scale, availability of breeds, system and maintenance patterns, reproductive performance, lust cycle, and mating system.

140 Virginia Tech Graduate Extension Scholars program: Report of a scholar

Abstract The Graduate Extension Scholar program has the purpose of providing graduate students a unique professional development opportunity to develop high quality outreach programs, where the students actively participate in youth and adult education. The graduate scholar is assigned to an extension agent and a high school teacher. The program director and the graduate assistants hold weekly seminars, where program development and engagement strategies are presented to prepare the scholar for the task. The program has existed since 2014, with 14 scholars participating. The present report is related to a single program during the fall of 2017. A beef cattle reproduction symposium of a total of 5 lectures were taught for juniors and seniors in the Holston High School’s (Damascus, VA) agricultural class. The lectures were planned to provide the students both theoretical and hands-on activities on the topic of beef cattle reproduction. The theoretical portion of the class consisted of PowerPoint presentations on anatomy and physiology, as well as applied topics, such as factors influencing fertility and discussion case studies. The hands-on portion of the class consisted of activities related to reproduction, such as bovine female reproductive tracts anatomy and artificial insemination, simulation of rectal palpation with a mannequin (Breed’n Betsy) and demonstration of materials and technologies used in the field (nitrogen tank for semen storing and ultrasound). In addition, student assessment of knowledge was conducted and scores were used for the agricultural class final grade. Final grade mean for the class was 95. Finally, a field trip was organized to a local farm where students were able to perform rectal palpation and ultrasound in cattle. At the completion of the program, a survey was performed and all students considered the program positive and claimed to have gained knowledge of the subject.

Animal Welfare As Stress Management to Improve Beef Cattle Reproduction

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Pemanfaatan Jerami Kedelai pada Pakan Induk Sapi Silangan Simmental-Peranakan Ongole

The onset of first postpartum estrous is an indicator in the beef cattle reproduction efficiency. Soybean straw is a local feed ingredients that contain phytoestrogen compounds. The present experiment was conducted to determine the effect of the use of soybean straw as a source of phytoestrogen to accelerate the onset of the first postpartum estrous of Simmental – Ongole crossbred cows. This research applies by completely randomized design (CRD) consisted three treatments and each treatment is repeated five times. Treatment consist of : P0: control (standar feed), P1: control + 5 g of phytoestrogen (1.8 kg of soybean straw), and P2: control + 10 of g phytoestrogen (3.6 kg of soybean straw). The result showed that the use of soybean straw as a source of phytoestrogen increase consumption CP (P<0,05), whereas DM and TDN comsumption increased only slighthy (P>0,05). Supplementation of soybean straw as a source phytoestrogen are also likely to accelerate the first postpartum estrous. Â

A Multi-Trait, Meta-analysis for Detecting Pleiotropic Polymorphisms for Stature, Fatness and Reproduction in Beef Cattle

Polymorphisms that affect complex traits or quantitative trait loci (QTL) often affect multiple traits. We describe two novel methods (1) for finding single nucleotide polymorphisms (SNPs) significantly associated with one or more traits using a multi-trait, meta-analysis, and (2) for distinguishing between a single pleiotropic QTL and multiple linked QTL. The meta-analysis uses the effect of each SNP on each of n traits, estimated in single trait genome wide association studies (GWAS). These effects are expressed as a vector of signed t-values (t) and the error covariance matrix of these t values is approximated by the correlation matrix of t-values among the traits calculated across the SNP (V). Consequently, t'V−1t is approximately distributed as a chi-squared with n degrees of freedom. An attractive feature of the meta-analysis is that it uses estimated effects of SNPs from single trait GWAS, so it can be applied to published data where individual records are not available. We demonstrate that the multi-trait method can be used to increase the power (numbers of SNPs validated in an independent population) of GWAS in a beef cattle data set including 10,191 animals genotyped for 729,068 SNPs with 32 traits recorded, including growth and reproduction traits. We can distinguish between a single pleiotropic QTL and multiple linked QTL because multiple SNPs tagging the same QTL show the same pattern of effects across traits. We confirm this finding by demonstrating that when one SNP is included in the statistical model the other SNPs have a non-significant effect. In the beef cattle data set, cluster analysis yielded four groups of QTL with similar patterns of effects across traits within a group. A linear index was used to validate SNPs having effects on multiple traits and to identify additional SNPs belonging to these four groups.

Neospora caninumand reproductive wastage in extensively managed Queensland beef herds

To compare reproduction in extensively managed, tropically adapted beef cows that were either seropositive or seronegative to Neospora caninum. Longitudinal study of cows within management groups. Compare pregnancy with weaning outcomes for 502 seropositive and 3255 seronegative cows in 25 management groups. We found N. caninum in all herds, with an average of 20% of 2640 tested animals seropositive within management group; prevalence varied between 0% and 94%. At 7 of 10 sites assessed, there was evidence of horizontal transmission of N. caninum. There was no overall difference in pregnancy rate (79% vs 75%; P > 0.05), reproductive wastage after confirmed pregnancy diagnosis (11% vs 10%; P > 0.05) or weaning rate (67% vs 68%; P > 0.05) between seronegative and seropositive cows, respectively. In one herd where a combination of risk factors for N. caninum was present, a significant reduction in pregnancy rate occurred after the 6 months mating (85% vs 69%; P < 0.05). The fetal and calf losses observed were lowest in south-east Queensland (4.3% of 117 pregnancies), highest in north-west Queensland (15.5% of 413 pregnancies) and intermediate in north-east Queensland (10.2% of 1625 pregnancies). Other infectious agents that are known to cause reproductive wastage were endemic in many herds, though none appeared to cause significant fetal or calf loss in this study. Despite a high prevalence of N. caninum, there was no apparent effect on beef cattle reproduction, but there is potential to cause reproductive wastage if known risk factors to neosporosis are in effect.

Genome-wide association studies of female reproduction in tropically adapted beef cattle1

The genetics of reproduction is poorly understood because the heritabilities of traits currently recorded are low. To elucidate the genetics underlying reproduction in beef cattle, we performed a genome-wide association study using the bovine SNP50 chip in 2 tropically adapted beef cattle breeds, Brahman and Tropical Composite. Here we present the results for 3 female reproduction traits: 1) age at puberty, defined as age in days at first observed corpus luteum (CL) after frequent ovarian ultrasound scans (AGECL); 2) the postpartum anestrous interval, measured as the number of days from calving to first ovulation postpartum (first rebreeding interval, PPAI); and 3) the occurrence of the first postpartum ovulation before weaning in the first rebreeding period (PW), defined from PPAI. In addition, correlated traits such as BW, height, serum IGF1 concentration, condition score, and fatness were also examined. In the Brahman and Tropical Composite cattle, 169 [false positive rate (FPR) = 0.262] and 84 (FPR = 0.581) SNP, respectively, were significant (P < 0.001) for AGECL. In Brahman, 41% of these significant markers mapped to a single chromosomal region on BTA14. In Tropical Composites, 16% of these significant markers were located on BTA5. For PPAI, 66 (FPR = 0.67) and 113 (FPR = 0.432) SNP were significant (P < 0.001) in Brahman and Tropical Composite, respectively, whereas for PW, 68 (FPR = 0.64) and 113 (FPR = 0.432) SNP were significant (P < 0.01). In Tropical Composites, the largest concentration of PPAI markers were located on BTA5 [19% (PPAI) and 23% (PW)], and BTA16 [17% (PPAI) and 18% (PW)]. In Brahman cattle, the largest concentration of markers for postpartum anestrus was located on BTA3 (14% for PPAI and PW) and BTA14 (17% PPAI). Very few of the significant markers for female reproduction traits for the Brahman and Tropical Composite breeds were located in the same chromosomal regions. However, fatness and BW traits as well as serum IGF1 concentration were found to be associated with similar genome regions within and between breeds. Clusters of SNP associated with multiple traits were located on BTA14 in Brahman and BTA5 in Tropical Composites.

Fat supplementation and reproduction in beef females.

Inadequate dietary energy intake and poor body condition can negatively affect reproductive function. Supplemental lipids have been used to increase energy density of the diet and may also have direct positive effects on reproduction in beef cattle. Several fatty acid sources have been studied as they relate to reproductive function. Common sources include sunflower, safflower, cottonseed, rice bran, soybeans, fishmeal, animal tallow, and calcium salts of fatty acids. Fats have been fed before and after calving, during the breeding season, and during heifer development. Response to fat has been investigated through measuring body weight and body condition score, age at puberty, postpartum interval, first-service conception rates, pregnancy rates, calving interval, calving difficulty, and calf birth and weaning weight. Animal response seems to depend on body condition score, age (parity), nutrients available in the diet, and type of fat supplemented. To elucidate potential mechanisms of action, scientists have investigated changes in follicular and uterine development, hormonal profiles, brain function, and embryonic development. Feeding supplemental fat has resulted in varied and inconsistent effects on reproductive function. Elucidating how supplemental fat can influence reproductive function has been a difficult process. The complexity of the reproductive system and makeup of fat supplements are often confounded by management conditions and forage quality both in research and commercial feeding situations.

A missense mutation in the bovine leptin gene in Iranian Taleshi cattle

Candidate gene approaches facilitate discovering and localizing causative genes for quantitative traits and polymorphisms within selected candidate genes can be tested for association with variationin the quantitative trait (Campbell et al., 2003). Leptin is a 16-kDa protein that is synthesized and secreted predominantly by white adipocytes tissue and its expression is regulated by body fatness and energy balance. Leptin gene expressed in a variety of tissues including adipose tissue, placenta, mammary glands, skeletal muscles, gastric mucosa, brain and pituitary glands. In cattle, the leptin gene is located on chromosome 4 and consists of three exons. Several studies shown the association between polymorphism at the leptin gene and feed intake, energy balance, fertility and immune functions. It has been shown that leptin gene influences milk performance in cattle and reproduction in beef cattle(Liefers et al., 2002). Buchanan et al. (2002) described a cytosine (C) to thymine (T) substitution in exon 2 of the leptin gene of the B. taurus breeds, suggesting the existence CC, TT and CT genotypes. The aim of this study was to identify the single nucleotide polymorphism of exon 2 in Iranian Taleshi cattle.

Molecular markers in the LEP gene and reproductive performance of beef cattle

SummaryThe present study investigated four restriction fragment length polymorphisms (RFLPs) in the leptin gene and five short tandem repeats (STRs) in its vicinity in 160 females from a synthetic beef cattle breed (5/8 Aberdeen Angus and 3/8 Nelore), and evaluated possible associations between these markers and reproductive performance. A high level of genetic diversity was observed, STRs being more variable than RFLPs. Heterozygosities ranged from 0.67 to 0.87 in STRs and from 0.12 to 0.49 in RFLPs, suggesting that the selective process applied to the Brangus‐Ibage cattle had not affected the total genetic diversity expected for crossbreeds. Two alleles (IDVGA51*181 and LEPSau3A1*+) seem to increase calving interval (CI) by about 79 and 81 days, respectively. Therefore, selection against carriers of these mutations could improve CI by at least 2 months, despite the seasonality of the mating period employed here. LEPSau3AI system seems to influence weight at first calving (WFC). Heterozygotes (LEPSau3AI*+/LEPSau3AI*−) had higher WFC than LEPSau3AI*−/LEPSau3AI*− homozygote. Selection for animals with this genotype could result in some advantages for post‐calving recovery. CI and WFC are indirect measurements of reproduction reflecting also animal body conditions, and therefore it is difficult to determine whether or not IDVGA51*181 and LEPSau3A1*+ alleles directly affect the reproductive system. Although further analysis of other herds should be performed to confirm these data, the association of genetic markers with better reproductive performance is a very interesting finding and could be used in marker‐assisted selection to improve reproduction in beef cattle.

Associations between oil- and gas-well sites, processing facilities, flaring, and beef cattle reproduction and calf mortality in western Canada

From the fall of 1992 through calving 1996, detailed cow breeding outcome records were maintained actively for seven large cow–calf herds in western Canada. The numbers of mature females in the study for the breeding seasons beginning in 1992, 1993, 1994, and 1995 were 1122, 1177, 1251, and 1236, respectively. Outcomes included pregnancy status, calving interval, and the occurrence of twins, abortions, stillbirths, and neonatal mortality. Information also was collected on other risk factors known to influence beef-herd health and productivity. Detailed maps of active and inactive oil and natural-gas sites, batteries, compressor stations and processing plants were verified. Records of flaring activity at each facility were obtained from the government regulatory agency. Each flaring site then was classified as sour or sweet based on the presence or absence of hydrogen sulfide in the flared gas. A detailed inventory was prepared itemizing the type and number of facilities within 1.6 km (1 mile) of the center of each quarter section used for pasture. The total volume of gas flared within 1.6 km of the center of each pasture was determined for each month of the study. Appropriate risk periods where specified for each outcome and a cumulative exposure calculated for each breeding female (using detailed individual-animal records of cow movements between pastures and herd-management groups). Generalized estimating equations were used to evaluate the association between exposure and outcome and to adjust for potential confounders and clustering of binomial outcomes within herd. Increased risk of non-pregnancy was sometimes associated with exposure to one or more of the following facility types: sour-gas flaring battery facilities, all battery-flaring sites, active gas wells, and larger field facilities. The associations were not, however, consistent among years or even among risk periods for the same year. Facility proximity and flaring were not associated with increased abortion risk. Volume of flared sour gas from battery sites was associated with increased risk of stillbirth. Finally, sour-gas flaring was associated with increased calf-mortality risk for the 1992–1993 calf crop. Several examples of associations between exposure and increased productivity also were found (most of which involved either oil wells or all well sites).

Which trait for genetic improvement of beef cattle reproduction: calving rate or calving day?

SummaryThe relative merits of calving rate (CR) and calving day (CD) as reproduction traits were examined in the context of a comprehensive breeding objective for beef cattle. It is shown that some criticsms made of CD are not justified. Reproductive rate made the greatest contribution to genetic gain in economic units, no matter which one (CR or CD) of the reproduction traits was in the breeding objective. Genetic gain in reproductive rate and total gain in economic units were greater when CR (instead of CD) was included in the breeding objective, even if it was assumed to have a slightly lower heritability than CD (0.05 vs 0.08). The results were attributed to the greater phenotypic variance of CR under the circumstances assumed in the present study. It is concluded that either CR or CD should be included in performance recording schemes servicing beef cattle breeds used in a multiple purpose or in a maternal role. However, more work is required before the relative advantages of CR and CD can be clearly established.ResumenCuál rasgo para mejora genética de la reproducción en ganado vacuno de carne: tasa de parición o día de parición?Se examino el merito relativo de la tasa de paricion (CR) y del dia de paricion (CD) como rasgos de reproduccion en el contexto de un objetivo global de seleccion para ganado vauno de carne. Se muestra que algunas de las criticas acerca de CD no se justifican. La tasa reproductiva hizo la major contribucion a la ganancia genetica en unidades economicas, independientemente de cual (CR o CD) de los rasgos de reproduccion se incluyese en el objectivo. La ganancia genetica en tasa reproductiva y la ganancia total en unidades economicas fueron mayores cuando se incluyo CR (en lugar de CD) en el objectivo de seleccion, aun suponiendo que esta tuviese una heredabilidad algo menor que CD (0.05 vs 0.08). Los resultados fueron atribuidos a la mayor variancia fenotipica de CR bajo las circunstancias supuestas en el presente estudio. Se concluye que una da las dos, CR o CD, deberia incluirse en los servicios de registros de produccion para razas vacunas de carne utilizadas en un papel multiple proposito o maternal. Sin embargo, se requiere efectuar mas trabajo antes de poder establecer clararamente las ventajas relativas de CR y CD.ZusammenfassungZuchtziele bei Mutterkühen: Abkalberate oder Abkalbetag?Die relativen Vorteile der Abkalberate (CR) und Abkalbetag (CD) als Reproduktionsmerkmale wurden im Rahmen eines umfassenden Zuchtzieles für Fleischrinder geprüft. Es wird gezeigt, daß Kritik an CD nicht gerechtfertigt ist. Reproduktionsrate bringt den größten Beitrag zum genetischen Fortschritt in wirtschaftlicher Hinsicht, gleichgültig welches Merkmal der beiden (CR oder CD) im Zuchtziel berücksichtigt wurde. Genetischer Fortschritt in Reproduktionsrate und Gesamtfortschritt in wirtschaftlichen Einheiten waren bei CR größer als bei CD, auch wenn angenommen wird, daß erstere eine etwas geringere Heritabilität als CD hatte (0.05 gegenüber 0.08). Die Resultate wurden der größeren phänotypischen Varianz von CR unter den in dieser Untersuchung angenommenen Verhältnissen zugeschrieben. Es wird empfohlen, sowohl CR wie auch CD im Rahmen der Leistungserhebungen zu berücksichtigen, gleichgültig ob die Herde in Mehrzweck oder einer maternalen Rolle Verwendung findet. Allerdings sind mehr Untersuchungen notwendig, bevor die relativen Vorteile von CR oder CD deutlich gemacht werden können.

The Effects of Essential Trace Minerals on Reproduction in Beef Cattle

A discussion of the interaction of arsenic, chromium, fluorine, nickel, silicon, tin, and vanadium in the reproductive function of grazing beef cattle.

Size and management effects on reproduction in first-, second- and third-parity beef cows.

The effects of size, management and size x management interactions on reproduction in beef cattle were determined by using 3,126 breeding and calving records from 1980 to 1985. Cows were from three synthetic lines that differed in mature size (small, medium and large). The lines differed also in the percentages of Jersey, Angus and Simmental. Each line was replicated in two herds. One herd (Rhodes) followed a spring calving schedule and weaned calves at about 180 d of age. The other herd (McNay) calved cows in the fall and weaned calves early at about 45 d of age. Cycling rate, conception rate, abortion rate and calving rate were each evaluated for first-, second- and third-parity dams. An important interaction (P less than .05) was found between lines and management in heifers. Cycling rate and calving percentage were almost identical for all three lines in the Rhodes herd, but small heifers in the McNay herd had about 20% higher cycling (83.8 vs 63.1%) and calving rates (73.8 vs 53.0%) than large heifers. Line x management interactions were not significant in second- and third-parity dams, but line did remain a significant source of variation in calving rate. Calving rates in second-parity dams were 85.0, 78.1 and 70.7% for small, medium and large cows, respectively. In third-parity dams, small cows had a higher calving rate (P less than .05) than either medium or large cows (80.9 vs 66.1 or 68.7%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship Between Nutrition and Reproduction in Beef Cattle

The primary nutrient consideration for optimum reproductive performance in beef cattle is energy. Low energy intake delays the onset of puberty in heifers and bulls. Heifers should reach approximately 66 per cent of mature body weight by 14 to 15 months of age and be bred 30 days prior to breeding the main cow herd. Body conditioning scores (BCS) (1 = emaciated, 9 = obese) should be used to evaluate pregnant cows entering their third trimester. Cows should calve with body conditioning score 5 to 7. Forage quality and environmental factors influence maximum dry matter intake and nutrient requirements and must be considered in the clinical setting. Crude protein dietary content should be 11 to 12 per cent for lactating beef cattle. Mineral (calcium, phosphorus, magnesium, potassium, sulfur, sodium, chloride) nutrition is not a major cause of decreased reproductive performance in beef cattle. Trace mineral deficiencies (particularly selenium, copper, and zinc) can cause decreased reproductive performance. Diagnosis of these trace mineral deficiencies can be confirmed by elemental analysis of blood or tissues.

The effects of temporal variation in the water climate on beef cattle reproduction in the seasonally dry tropics of Australia

The effects of temporal variation in the water climate on beef cattle reproduction in the seasonally dry tropics of Australia