Simulated selection for reproductive rate in beef cattle

Computer simulation was used to evaluate four selection strategies for reproductive success in beef cattle. The strategies were no culling; culling of nonpregnant heifers; culling of nonpregnant heifers and cows nonpregnant twice; culling all nonpregnant females. In addition, simulations were conducted utilizing method four for 20 yr, then changed to method three for an additional 20 yr. Cows were removed from the herd at age 10 if not previously culled. Because reproduction is a threshold character, an underlying normally distributed liability that influences whether or not a cow will produce a calf was assumed with a heritability estimate of .2, a mean of zero and a standard deviation of one. Regressions of breeding value for reproduction and calving rate on year of selection were calculated assuming initial calving rates of 80 and 90%. Linear and quadratic effects for breeding value were present for all selection methods at both initial rates. All primary breeding value regressions were different than that for no culling. At the 90% initial calving rate, methods three and four were different from method two. There were no differences among any regressions for calving rate. Progress for breeding value was more regular than for calving rate; maximum progress for breeding value in 40 yr was approximately .32 standard deviations for selection method four. Calving rate was more erratic, although calving rate increased approximately 7% as a result of 40 yr of selection using method four at the 80% initial calving rate. It appears that much of the improvement attained by any method of selection occurred in the first 20 yr.(ABSTRACT TRUNCATED AT 250 WORDS)     

Drivers,challenges and opportunities of forage technology adoption by smallholder cattle households in Cambodia

Forage technology has been successfully introduced into smallholder cattle systems in Cambodia as an alternative feed source to the traditional rice straw and native pastures, improving animal nutrition and reducing labour requirements of feeding cattle. Previous research has highlighted the positive impacts of forage technology including improved growth rates of cattle and household time savings. However, further research is required to understand the drivers, challenges and opportunities of forage technology for smallholder cattle households in Cambodia to facilitate widespread adoption and identify areas for further improvement. A survey of forage-growing households (n = 40) in July–September 2016 examined forage technology adoption experiences, including reasons for forage establishment, use of inputs and labour requirements of forage plot maintenance and use of forages (feeding, fattening, sale of grass or seedlings and silage). Time savings was reported as the main driver of forage adoption with household members spending approximately 1 h per day maintaining forages and feeding it to cattle. Water availability was reported as the main challenge to this activity. A small number of households also reported lack of labour, lack of fencing, competition from natural grasses, cost of irrigation and lack of experience as challenges to forage growing. Cattle fattening and sale of cut forage grass and seedlings was not found to be a widespread activity by interviewed households, with 25 and 10% of households reporting use of forages for these activities, respectively. Currently, opportunities exist for these households to better utilise forages through expansion of forage plots and cattle activities, although assistance is required to support these households in addressing current constraints, particularly availability of water, if the sustainability of this feed technology for smallholder cattle household is to be established in Cambodia.     

Improving reproductive efficiency in female buffaloes

Reproductive efficiency is the primary factor affecting productivity in female buffalo, but is greatly hampered by late attainment of puberty, seasonality of calving, long postpartum anoestrus and subsequent calving interval. Moreover, artificial insemination (AI) is seldom performed because of the weakness of oestrus symptoms and the variability of oestrus length, which makes oestrus detection very difficult.Researchers have tried to cope with each of the critical physiological aspects of buffalo reproductive performance mentioned above. In the present review, the main factors affecting the low reproductive efficiency in buffalo are examined and proposals made for its improvement, taking into account both our research work and literature results. Previous research on the changes in hormone profile during the oestrus cycle and in follicle development were used to develop models for improving reproductive efficiency. Hormonal treatments can be used: (1) to anticipate puberty in order to reduce the age at first calving; (2) to improve fertility in the low breeding season; and (3) to increase the effectiveness of AI programmes by overcoming the difficulty in oestrus detection.     

Investigating the financial impact of porcine reproductive and respiratory syndrome on smallholder pig farmers in Cambodia

Porcine reproductive and respiratory syndrome (PRRS) was first identified in Cambodia in 2010, causing serious problems on affected farms, although the costs of the disease have not been well defined. The household financial impact of a PRRS outbreak in Cambodia was investigated using partial budget analysis, examining the economic benefit of three proposed interventions: (i) quarterly PRRS vaccine use, (ii) biosecurity implementation, and (iii) implementation of vaccination and biosecurity. The analyses were applied to three farm models: (i) a two-sow breeder; (ii) a five-pig fattener; and (iii) a single-sow, three-pig farrow-to-finish/breeder. Data was derived from a knowledge, attitude, and practice survey of 240 smallholder farmers (61 with pigs) from 16 villages across 5 provinces, plus case studies of 12 farmers selected for more detailed financial analysis. The study indicated that financial losses associated with PRRS were severe, with a 25% mean loss to the annual household income of 61 interviewed farmers. Partial budget analysis identified a strongly positive incentive for vaccination and biosecurity to be implemented in combination, with the highest annual net benefit of USD 357.10 realised by the breeder system. However, due to current scarcity of the PRRS vaccine and its high cost to smallholders, biosecurity interventions may be more cost-effective, especially for low PRRS incidence regions. It was concluded that PRRS critically constrains the profitability of smallholder pig farms and that these findings will assist development of village-level livestock disease risk management programmes that encourage adoption of vaccination and biosecurity practices to enhance farmer livelihoods in Cambodia.     

Improving calving management to further enhance reproductive performance in dairy cattle

The aim of this study was to develop a system for the monitoring of calving to both reduce perinatal morta1ity and improve dairy cow fertility by preventing the majority of post-partum reproductive pathologies. Eighty dairy cows were assigned to the protocol of calving monitoring using GSM (Global System for Mobile Communications) technology. The application of GSM technology and the proper management of calving facilities comprise reliable approaches for calving assistance and improvements in reproductive efficiency and neonata1 viability. Based on the results of this study, we advocate the use of GSM technology on large farms for intensive mi1k production.     

Genetic effects for reproductive traits in beef cattle and predicted performance

Reproductive data were collected on 4,595 cow exposures and subsequent calvings over four generations in a rotational crossbreeding study involving Angus, Brahman, Charolais and Hereford breeds. Direct and maternal additive (Ig and Mg) and nonadditive (Ih and Mh) genetic effects were estimated for calving rate, calf survival, weaning rate, calving assistance and calf birth date. Genetic effects were estimated by regressing individual animal response on the proportion of genes from breed of origin and gene combinations expected for the four breeds in offspring and in dams. Breed direct and maternal additive and nonadditive genetic effects were expressed as a deviation from the least squares mean. Brahman Ig effects decreased calving and weaning rate (-9.5 +/- 4.0 and -11.8 +/- 4.4%) but Mh effects for weaning rate that included Brahman were positive, ranging from 16.5 +/- 6.7% for Angus-Brahman to 27.8 +/- 6.9% for Brahman-Hereford. The Brahman Ig effect delayed calf birth date (9.8 +/- 2.1 d; P less than .01), whereas Angus and Hereford Ig effects influenced earlier calf birth dates (-4.3 +/- 1.9 and -4.1 +/- 1.9 d; P less than .05). Brahman combination Mh effects also influenced earlier calf birth dates (P less than .01). The Charolais Ig effect for calving assistance was positive (4.3 +/- 1.9%; P less than .05), whereas Angus-Brahman and Brahman-Charolais Mh effects for calving assistance were negative (-6.5 +/- 3.2 and -7.0 +/- 3.2%; P less than .05) and more desirable. Predicted reproductive traits for rotational mating systems were intermediate between predicted reproductive traits for two- and three-breed terminal crosses. Predicted calving and weaning rates were maximized when Brahaman first-cross and Charolais-Hereford cows were used in three-breed cross mating systems.     

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).     

Pilocarpine and digestive efficiency in beef cattle fed a high-concentrate diet

The effect of pilocarpine HCl, a parasympathetic muscarinic agonist, on digestive characteristics was evaluated in growing beef steers fed a high-grain diet. Oral doses of 0, 2 or 4 mg/kg BW were administered daily to each of eight steers immediately prior to offering an 88% concentrate: 12% hay diet in this three-period crossover design (19 d/period). Treatments did not improve digestibilities of dry matter, organic matter and nitrogen, ruminal liquid volume and fractional dilution rate, body weight gain or feed efficiency. Although daily voluntary feed intake was not altered by treatment (P = .25), there was a dose-dependent slowing of the rate at which feed was consumed (P less than .01). Also, ruminal fluid pH was increased with increasing dose (5.36, 5.55 and 6.11 respectively; P = .10). These observations indicate that the digestive improvements due to pilocarpine reported to occur in mature, nongrowing cattle consuming a high-forage diet are not observed in growing steers fed a production-type diet.     

On the relationships between glucocorticoids and feed efficiency in beef cattle

Improvement in the utilization of feed in livestock is an important target of breeding and nutritional programs. Recent evidence indicates a potential association between feed efficiency and fecal cortisol metabolites, which could eventually be used as an indirect assessment of this trait. This evidence is more comprehensively evaluated in here with samples for plasma cortisol (PC; ng/ml) and fecal cortisol metabolites (FCM; ng/ml) collected more often during the entire finishing phase in beef steers. Individual daily feed intake of 112 steers fed a high-moisture corn-based and haylage diet was measured over 168 d. Body weight, blood and fecal samples were collected every 14 d and ultrasound measures of backfat thickness and longissimus muscle area were taken every 28 d. Four productive performance traits were calculated: daily dry matter intake (DMI), average daily gain (ADG), feed to gain ratio (F:G) and residual feed intake (RFI). At the end of the feedlot phase, steers were ranked according to RFI and samples were analyzed for PC and FCM from the 32 steers with greatest and 32 steers with lowest feed efficiency. In addition, a sub-group of 12 steers from each of these two groups with divergent feed efficiency were subjected to hourly blood sampling for 24 h. Less efficient steers had greater DMI, F:G and consumed 1.5 kg/d more DMI (P<0.05) than steers with improved feed efficiency. No differences (P>0.10) in PC over the 12 biweekly sampling periods between steers with divergent feed efficiency were observed. However, a trend toward significance between 19:00 and 02:00 h over the hourly sampling evaluation was noticed, with the sub-group of more feed efficient steers presenting higher levels of PC in this period of the day (P=0.08). On the other hand, FCM levels displayed a distinct pattern between RFI groups over the biweekly sampling period, with more efficient cattle presenting greater levels of these metabolites (P<0.05). This study reinforces the positive association between improved feed efficiency and FCM levels over the finishing phase; and the lack of association between feed efficiency and PC when single samples are collected every two weeks through a single jugular venipuncture performed after handling the cattle for sampling. Further studies to develop sampling protocols for assessing FCM as an indicator trait for feed efficiency are warranted, as well as, studies to understand the role of endogenous glucocorticoids in the performance of the bovine.     

Candidate genes for male and female reproductive traits in Canchim beef cattle

Background: Beef cattle breeding programs in Brazil have placed greater emphasis on the genomic study of reproductive traits of males and females due to their economic importance. In this study, genome-wide associations were assessed for scrotal circumference at 210 d of age, scrotal circumference at 420 d of age, age at first calving, and age at second calving, in Canchim beef cattle. Data quality control was conducted resulting in 672,778 SNPs and 392 animals.Results: Associated SNPs were observed for scrotal circumference at 420 d of age(435 SNPs), followed by scrotal circumference at 210 d of age(12 SNPs), age at first calving(six SNPs), and age at second calving(four SNPs). We investigated whether significant SNPs were within genic or surrounding regions. Biological processes of genes were associated with immune system, multicellular organismal process, response to stimulus, apoptotic process, cellular component organization or biogenesis, biological adhesion, and reproduction.Conclusions: Few associations were observed for scrotal circumference at 210 d of age, age at first calving, and age at second calving, reinforcing their polygenic inheritance and the complexity of understanding the genetic architecture of reproductive traits. Finding many associations for scrotal circumference at 420 d of age in various regions of the Canchim genome also reveals the difficulty of targeting specific candidate genes that could act on fertility; nonetheless,the high linkage disequilibrium between loci herein estimated could aid to overcome this issue. Therefore, al relevant information about genomic regions influencing reproductive traits may contribute to target candidate genes for further investigation of causal mutations and aid in future genomic studies in Canchim cattle to improve the breeding program.     

Calving date versus calving interval as a reproductive measure in beef cattle

Calving date and calving interval records obtained from the Beef Cattle Division of Pioneer Hi-Bred International, Des Moines, Iowa, were studied to determine the reproductive measure of choice when a fixed breeding season is employed. Fixed model, least-squares procedures were used to analyze 2,411 records collected on purebred Red Angus, Angus and Hereford cows during the years 1969 through 1976. Calving interval decreased .86 d and calving date was delayed .11 d for each 1-d delay in previous calving date. A 1-d increase in gestation length was associated with a 1.17-d delay in calving date and 1.17-d increase in calving interval. The bias caused by the use of a fixed breeding season was determined to be much greater for calving interval than for calving date, as evidenced by the strong dependence of calving interval on previous calving date. Because calving date is likely to be more heritable and has clear economic significance, and because selection for earlier calving date should not lead to adverse response in other reproductive traits, calving date was preferred over calving interval as a reproductive measure.     

The use of ultrasound in monitoring reproductive physiology of beef cattle.

Real-time, B-mode ultrasonography provides the opportunity to improve the methods of evaluation of ovarian function and diagnoses of pregnancy in beef cattle. Determination of the sex of a fetus early in pregnancy (d 55 to 85) and verification of embryo viability by monitoring fetal heartbeat are unique methods involving ultrasound scanning. These techniques and a method for evaluating the technique of artificial insemination can be used to improve reproductive management of cattle. The way in which ultrasound technology may have its greatest impact is as a tool for improving on the method of palpation per rectum for monitoring ovarian function and pregnancy in beef cows and heifers. Determination of fetal sex and monitoring embryo mortality are less likely to be applied regularly in herd management, but these procedures will be valuable in conducting research in reproductive physiology of beef cattle.     

Small intestine histomorphometry of beef cattle with divergent feed efficiency

Background

The provision of feed is a major cost in beef production. Therefore, the improvement of feed efficiency is warranted. The direct assessment of feed efficiency has limitations and alternatives are needed. Small intestine micro-architecture is associated with function and may be related to feed efficiency. The objective was to verify the potential histomorphological differences in the small intestine of animals with divergent feed efficiency.

Methods

From a population of 45 feedlot steers, 12 were selected with low-RFI (superior feed efficiency) and 12 with high-RFI (inferior feed efficiency) at the end of the finishing period. The animals were processed at 13.79 ± 1.21 months of age. Within 1.5 h of slaughter the gastrointestinal tract was collected and segments from duodenum and ileum were harvested. Tissue fragments were processed, sectioned and stained with hematoxylin and eosin. Photomicroscopy images were taken under 1000x magnification. For each animal 100 intestinal crypts were imaged, in a cross section view, from each of the two intestinal segments. Images were analyzed using the software ImageJ®. The measurements taken were: crypt area, crypt perimeter, crypt lumen area, nuclei number and the cell size was indirectly calculated. Data were analyzed using general linear model and correlation procedures of SAS®.

Results

Efficient beef steers (low-RFI) have a greater cellularity (indicated by nuclei number) in the small intestinal crypts, both in duodenum and ileum, than less efficient beef steers (high-RFI) (P < 0.05). The mean values for the nuclei number of the low-RFI and high-RFI groups were 33.16 and 30.30 in the duodenum and 37.21 and 33.65 in the ileum, respectively. The average size of the cells did not differ between feed efficiency groups in both segments (P ≥ 0.10). A trend was observed (P ≤ 0.10) for greater crypt area and crypt perimeter in the ileum for cattle with improved feed efficiency.

Conclusion

Improved feed efficiency is associated with greater cellularity and no differences on average cell size in the crypts of the small intestine in the bovine. These observations are likely to lead to an increase in the energy demand by the small intestine regardless of the more desirable feed efficiency.     

从肉牛到牛肉的经济指标分析

【目的】为了解现阶段肉牛到牛肉之间的联系现状和产出能力,掌握主要经济指标,确定计算肉牛产值的依据。 【方法】以张掖市肉牛与牛肉之间的联系现状为例,从中选取１个能够代表现阶段生产水平的随机样本（n=11777）,利用统计分析方法进行分类和分组,列出次数分布表与分布图,研究宰前重、胴体重、净肉重、屠宰率和净肉率5个变量的频率分布,并根据平均数() 和标准差（S）及其分布规律推算出总体平均数u的概率置信区间代表群体生产水平,作为计算肉牛产值的依据。【结果】现阶段进行肉牛生产的主要品种为西门塔尔、安格斯和荷斯坦,公牛育肥产肉占84.54%。其中西门塔尔占74.61%居主导地位,安格斯占16.08%,荷斯坦占9.31%。西门塔尔牛以宰前重在500~700kg的小架子牛育肥产肉占56.12%居主导地位,依次为大架子育肥占39.28%、小牛肉占2.57%和成年牛占2.03%。肉牛宰前重、胴体重、净肉重和屠宰率、净肉率5个指标样本分组频率与正态分布理论概率相关度高、绝对差值小,概率相近。 【结论】现阶段生产牛肉的主要品种有西门塔尔、安格斯和荷斯坦,以公牛育肥为主。主导品种西门塔尔牛生产周期有缩短趋势,小牛肉生产起步。 西门塔尔牛群的宰前重、胴体重、净肉重和屠宰率、净肉率均值为：684.94kg、385.16kg、316.85kg和56.47%、45.71%时,区间为：581.33≦x≦788.55、321.9≦x≦448.40、266.09≦x≦367.61、53.85≦x≦59.09、42.57≦x≦48.85。 大群体宰前重、胴体重和屠宰率的均值为：678.13kg、379.54kg和55.81%%,区间为572.63≦x≦783.63 、311.42≦x≦447.66、52.34≦x≦59.28 。 反映肉牛生产水平的5个经济指标的概率分布为正态分布,平均值（）一倍标准差左右取值概率为0.6827,可用概率密度函数公式进行相应的计算。根据正态分布特点,平均值左右一倍标准差范围内取值的概率最大为,平均值即为群体盈亏平衡点,且主导品种的宰前重、胴体重和屠宰率较大群体分别高6.81kg、5.62kg和0.66%。 祁连牧歌实业有限公司为张掖市规模最大肉牛屠宰加工企业,屠宰牛源为周边规模养殖场育肥牛,该结果能够代表张掖市域内肉牛大群体生产水平,指标平均值（）可以作为计算肉牛产值的统计依据。 生产中可以此为标准对经营情况进行分析,当个体牛只或经营单位的宰前重、胴体重、净肉重和屠宰率、净肉率高于平均值时说明该牛只育肥状况较好或该经营单位经营状态良好,大概率保持盈利。     

Brucellosis among smallholder cattle farmers in Zambia

A cross-sectional study was performed in Southern and Lusaka provinces of Zambia between March and September 2008 to estimate Brucella seroprevalence in cattle kept by smallholder dairy farmers (n = 185). Rose Bengal test (RBT) was used as a screening test followed by confirmation with competitive ELISA (c-ELISA). We investigated 1,323 cattle, of which 383 had a history of receiving vaccination against brucellosis and 36 had a history of abortion. Overall seroprevalence was 6.0% with areas where vaccination was practiced having low seroprevalence. Age was associated with Brucella seropositivity (P = 0.03) unlike cattle breed (P = 0.21) and sex (P = 0.32). At area level, there was a negative correlation (Corr. coeff = −0.74) between percentage of animals with brucellosis vaccination history (vaccination coverage) and level of brucellosis; percentage of animals with history of abortion (Corr. coeff. = −0.82) and brucellosis vaccination coverage. However, a positive correlation existed between brucellosis infection levels with percentage of animals having a history of abortion (Corr. coeff. = 0.72). History of vaccination against brucellosis was positively associated with a positive Brucella result on RBT (P = 0.004) whereby animals with history of vaccination against brucellosis were more likely to give a positive RBT test results (OR = 1.52). However, the results of c-ELISA were independent of history of Brucella vaccination (P = 0.149) but was positively associated with history of abortion (OR = 4.12). Our results indicate a relatively low Brucella seroprevalence in cattle from smallholder dairy farmers and that vaccination was effective in reducing cases of Brucella infections and Brucella-related abortions. Human exposure to Brucella through milk from smallholder farmers could result through milk traded on the informal market since that milk is not processed and there no quality and safety controls.