Reproductive Performance Of Beef Cattle Research Articles

An investigation into the causes of low calving percentage in communally grazed cattle in Jericho, North West Province.

The communal grazing system is generally understood to have a low input, low output type of management. However, the actual inputs and outputs of the farmers are not well known and the farmers are often unaware of their problems. Although the causes of low calving percentage are well understood in commercial beef farming enterprises in South Africa, the same is not true for communal farming systems. The aim of this study was to determine the reproductive performance of beef cattle on a communal farming system in Jericho, North West Province. Ten farmers from five villages with a total of 265 cows and 13 bulls were purposively selected. The selection criteria were that each farmer had to have a minimum of 10 breeding cows and a bull and be willing to participate in the study. This was followed by a 12-month longitudinal study with monthly herd visits where cows were examined rectally and bulls (n = 13) were subjected to a single breeding soundness evaluation. The calving percentage was found to be 37.7%. This is lower than the recorded percentages for commercial beef cattle on extensive grazing. The factors playing a role in low calving percentage were ranked using field data. From this it appeared that failure of cows to become pregnant was the main cause of poor calving percentage as opposed of loss of calves through abortion or resorption. Sub-fertility of the bulls was found to be of great significance and it is proposed that this be included in extension messages and that bulls be fertility tested routinely. Poor body condition score of cows, mainly caused by poor management, was also considered to play a major role in reducing pregnancy rates. Infectious diseases like trichomonosis, campylobacteriosis and brucellosis played a much leser role than anticipated.

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.

Genetic relationships between calving date, calving interval, age at first calving and type traits in beef cattle

In this paper the genetic relationships between major reproductive traits in beef cattle (Calving Date, Calving Interval and Age at First Calving) and type traits have been estimated to evaluate the usefulness of type classification in predicting reproductive performance in beef cattle. We estimated favourable genetic correlations between Calving Interval and type traits ranging from −0.027 to −0.297. However, type traits and Calving Date appear to be genetically independent and the genetic relationships between Age at First Calving and type traits are, in general, non-favourable. Genetic correlations between type traits and Calving Date ranged from 0.0 to –0.125. Genetic correlations between Age at First Calving and Final Score, Body Depth and Tight Development were, respectively, 0.399, 0.445 and 0.447. Our results suggest that the possibility of using type classification to construct an index to improve reproductive performance is little. The more reliable possibility to build a possible selection index comprising type classification and reproductive performance would be based on Age at First Calving. Type classification at first calving could help to increase the information to select dams to stay on the farm in subsequent calvings on the basis of their expected performance.

Melengestrol acetate and estradiol-17β for synchronizing estrus and improving reproductive performance in beef cattle

Four experiments were conducted to investigate the use of melengesterol acetate (MGA) and estradiol-17β (E-17β) for synchronizing estrus and improving reproductive performance in beef cattle. Synchronized pregnancy rates were higher (P < 0.05) in heifers fed MGA after AI than controls (4 of 9 versus 0 of 7, respectively), but were not different for cows (20 of 37, 54% versus 23 of 40, 58%). Estrus rate (percentage of cows detected in estrus) was higher (P < 0.05) for cows treated with E-17β + MGA compared with those treated with cloprostenol alone (85.0 versus 65.9%). Synchronized pregnancy rates were not significantly affected by feeding MGA or grain only after detected estrus and AI (20 of 31, 64% versus 17 of 30, 57%). For 20 cows not detected in estrus and bred 100 h after cloprostenol treatment, pregnancy rate was higher (P < 0.05) for those fed MGA after AI than controls (6 of 11, 54% versus 1 of 9, 11%). Feeding MGA after breeding may help to improve pregnancy rates. Key words: Melengesterol acetate, estradiol-17β, estrus, reproductive performance, beef cattle

Comparison of reproductive performance in Belgian dairy and beef cattle

A computerized program was written to collect, evaluate and compare reproductive performance data of 2004 beef (Belgian Blue breed) and 1649 dairy (Friesian Holstein and German Red) cattle in 35 Belgian herds (6 suckler beef herds, 9 milked beef herds and 20 dairy herds). Reproduction data were collected at monthly herd health visits. No difference in age at first calving was observed. Significant differences were observed among the 3 kinds of herds, and the best results were obtained in dairy herds for the calving interval, interval from calving to the first estrus, interval from calving to the first service and average number of days open. Concerning these parameters, first calvers had lower results than multiparous cows, mainly in suckler and milked beef herds. Significant differences were noted in the number of services per pregnancy. Heifers that had never calved presented the highest fertility. Primiparous beef cows had higher fertility than pluriparous cows. In dairy herds, pluriparous cows had higher fertility than primiparous cows. Estrus detection was better in milked beef herds than in suckled beef and dairy herds. Suckled beef herds had the lowest incidence of metritis and ovarian cysts of the three types of herds. Rates of abortion, overall culling and retained fetal membranes were similar in all the herds. The percentage of animals removed for infertility was highest in milked beef herds and lowest in dairy herds. Because 90% of the 1159 calvings recorded in the beef herds required a caesarean section, the reproductive performance of beef cattle represent results after caesarean section.

The Effects of Nutrition on Reproductive Performance of Beef Cattle

The concept of feeding for optimal reproductive performance is not new. The effects of prepartum and postpartum nutritional levels on return to postpartum estrus and conception rates was reported in 1962. The effect of body condition regardless of nutrition regimen was first reported in 1975. Body condition scoring has become a popular topic for Extension and practitioner sponsored producer meetings. To effectively promote a management change that requires increased cash flow and does not have an immediate return requires demonstration of cost-effectiveness. This requires knowledge of the biologic information and transformation of that knowledge (through partial budget analysis) into additional profit for the producer. Controlling reproduction through proper nutrition at critical times of the reproductive cycle requires: 1. Calving and breeding seasons of 60 days. 2. Cows to be in moderate to good body condition at calving (BCS 5-7). 3. Cows to be slightly gaining at the beginning of the breeding season. 4. Cows to be bred to fertile bulls. 5. Evaluation and correction of body condition well in advance of the actual impact of BCS on reproductive function. 6. Producer to be prepared to initiate "alternate" plans (i.e., early weaning or 48 hour calf removal).

Structure and behavior of a deterministic model of reproductive performance in beef cattle

The structure and behavior of a deterministic model of reproductive performance in beef cattle is presented. The model is written in PASCAL and runs rapidly on a microcomputer using a one day timestep and producing yearly output. Annual calving percentage is calculated based on three biological variables (gestation length, length of postpartum anestrus and conception rate) and one managerial variable (breeding season length). Convergence to a steady state calving percentage was observed for a wide variety of initial parameter values, indicating a convergence of distribution from an initial uniform distribution. Steady state values display nonlinear responses to changes in the driving variables, typical of beef production operations in North America. The model was challenged by testing predicted values of annual calving percent against values observed in 136 single-sire herds over eight years as breeding season length changed. Results of the challenge indicate that the model adequately predicts reproductive performance, but changing only breeding season length resulted in consistent overprediction of annual calving percent. Accurate prediction requires accurate measurement of all four driving variables.

Effects of Breeding System, Cow Weight and Milk Yield on Reproductive Performance in Beef Cattle

Effects of Breeding System, Cow Weight and Milk Yield on Reproductive Performance in Beef Cattle

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.

Reproductive and leptospiral studies on beef cattle in central Queensland.

The effect of rainfall on reproductive performance in beef cattle and the effects of rainfall and soil type on the prevalence of leptospirosis in beef cattle in inland central Queensland are described. Low annual rainfall produced a significant (P less than 0.05) decrease in calf branding rates. Leptospirosis (due to serovar hardjo) was serologically more prevalent after rain and on farms with high water holding capacity soils but there was no significant difference in branding rates between cattle on high or low water holding capacity soils. As a secondary mid-year rainfall peak is a feature of the area, leptospirosis due to serovar hardjo will tend to spread when most of the breeding herd is in the last trimester of pregnancy. The prevalence of leptospirosis due to serovar pomona is significantly lower in the region.

Postpartum ovarian function and fertility in beef cattle that produce twins.

A study was conducted to determine the effect of suckling on ovarian function and postpartum reproductive performance in beef cattle induced to produce twins by embryo transfer. This study involved 31 pluriparous Hereford, Angus and Hereford X Angus crossbred cows and 24 Hereford, Angus and Hereford X Angus crossbred heifers. Seventeen of the cows and 16 of the heifers calved twins, and the remainder produced single calves. From 45 d postpartum, the dams were exposed to three Hereford bulls until pregnancy was confirmed. The first postpartum ovulation was estimated from an increase in serum progesterone level. The interval to first postpartum ovulation was slightly, but not significantly longer for dams that calved and suckled twins than for dams that calved and suckled singles or calved twins and suckled singles (50.7 +/- 3.1, 43,5 +/- 3.4, and 37.7 +/- 5.6 d, respectively). This delay, however, did not significantly affect the number of days to conception for dams that suckled or calved twin or single calves. Once estrous cycles were initiated, the interval to conception for dams with twins was similar to that for dams with single calves. Under the management scheme used, postpartum ovulation and conception in beef heifers and cows were not significantly reduced by the production of twins.

Role of Liver Fluke in Infertility of Beef Cattle

This study was initiated to determine the effect of liver flukes on the reproductive performance of beef cattle. Results are based on field studies with naturally infected cattle in Texas and Idaho and a study with experimentally infected cattle. Attention was called to the problem because poor reproduction was a consistent finding in selected herds with liver fluke infections.

REPRODUCTIVE PERFORMANCE OF BEEF CATTLE IN NORTHWESTERN QUEENSLAND

The reproductive performance of beef cattle in 5 herds mated all year round in north-west Queensland was examined from 1970 to 1973. Conception rates, conception patterns and branding rates were used to assess annual reproductive performance. The level of loss between the times of confirmed pregnancy and branding was defined. The mean annual conception rate was 83.1% with individual property means ranging from 75.4 to 90.9%. Conception rates for heifers, first calf cows and mature cows were 83.9%, 80.6% and 84.7% respectively. Conception patterns were influenced by seasonal conditions, 68.1% of conceptions occurring in the wet season, between December and May. In this region, conception patterns were highly correlated with rainfall during the previous month. Losses between the times of confirmed pregnancy and branding ranged from 5.9 to 27.7%. Body condition of animals varied and was dependent upon lactation, seasonal and parity effects.

REPRODUCTIVE PERFORMANCE OF BEEF CATTLE IN NORTHWESTERN QUEENSLAND.

The reproductive performance of beef cattle in 5 herds mated all year round in north-west Queensland was examined from 1970 to 1973. Conception rates, conception patterns and branding rates were used to assess annual reproductive performance. The level of loss between the times of confirmed pregnancy and branding was defined. The mean annual conception rate was 83.1% with individual property means ranging from 75.4 to 90.9%. Conception rates for heifers, first calf cows and mature cows were 83.9%, 80.6% and 84.7% respectively. Conception patterns were influenced by seasonal conditions, 68.1% of conceptions occurring in the wet season, between December and May. In this region, conception patterns were highly correlated with rainfall during the previous month. Losses between the times of confirmed pregnancy and branding ranged from 5.9 to 27.7%. Body condition of animals varied and was dependent upon lactation, seasonal and parity effects.

Reproductive performance of beef cattle in the Northern Territory.

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Effects of supplemental energy and season of breeding on the reproductive performance of beef cattle.

Data were collected on 324 winter bred and 168 spring bred Hereford cows to examine the effects of flushing and season of breeding on their productivity. Winter bred control cows received 23 lb. (10.4 kg) of hay and 2 lb. (.9 kg) of cottonseed meal (CSM) during the 75-day winter test period. Grain flushed cows received the control ration and also were fed 11 lb. (4.9 kg) of ground corn per day the first 30 days of the test period. Cows flushed with supplemental winter pasture were maintained on wheat and ryegrass during the test period. Spring bred control cows were grazed on bermudagrass pasture during the 75-day spring test period. Grain flushed cows received 6 lb. (2.7 kg) of ground corn per day in addition to bermudagrass for the first 30 days of the test period. Winter and spring test periods began on December 1 and April 1, respectively. Sixty day breeding seasons began on December 15 and April 15, respectively. Grain flushing had no significant (P> .05) effect on calving percent in either season of breeding. Grain flushing had no significant effect on calf weights at the end of the test period or at weaning. Winter pasture calves were significantly heavier (P< .01) than other winter calves at the end of the test period and at weaning. Winter bred cows lost significantly (P < .01) more weight on test than spring bred cows, but had significantly higher (P< .01) calving percents. Spring calves were significantly (P < .01) heavier at the end of the test period, but there were no significant (P> .05) differences in adjusted weaning weights.