Calf Production Systems Research Articles

The Technical Efficiency of Beef Calf Production Systems: Evidence from a Survey in Hebei, China

Beef calf production is a source of sustainable development for the beef cattle industry. However, no comparative studies have reported on the technical efficiency of different beef calf production systems and their influencing factors. Based on data from 218 Chinese farmers and 12 governments, in the present study, we constructed data envelopment analysis (DEA) models and conducted a comparative analysis of the technical efficiency of the main three beef calf production systems: the Simmental calf intensive production system (CIPS), Simmental calf semi-intensive production system (SCIPS) and Holstein bull calf intensive production system (BCIPS). Using Tobit models, we analyzed the effects of various factors. The results show that: (1) The technical efficiency of the production system of Simmental calf is higher than that of Holstein bull calf, and the efficiency of SCIPS is higher than that of CIPS. The technical efficiency (TE), pure technical efficiency (PTE) and scale efficiency (SE) of different systems are significantly different. (2) Policy on the environment positively affected (p < 0.01) the TE, TPE and SE of CIPS, but negatively affected the PTE of SCIPS. Therefore, appropriate environmental regulations have a positive effect on production efficiency, which means that measures should be taken according to the reality and characteristics of the production system, and policies applicable to other systems or regions may not be applicable in a given case. (3) The management level and technology training had positive effects on the TE, TPE and SE of the three systems, while the number of years of production had a negative or no significant effect. Producers are not the “perfectly rational economic man”, and the more knowledge they have, the more productive they will be. However, the “knowledge” referred to here is that which is adapted to production, not that which is traditional. The knowledge possessed by the producer should be updated continuously with the changes over time and the development of the industry, while outdated information is not considered as “knowledge” here. Therefore, to achieve sustainability, the government should fully consider the characteristics of the local breeding mode and, more importantly, the expected effects of policies to be implemented.

Antimicrobial Use and Resistance in Surplus Dairy Calf Production Systems.

Surplus calves, which consist predominately of male calves born on dairy farms, are an underrecognized source of antimicrobial-resistant (AMR) pathogens. Current production systems for surplus calves have important risk factors for the dissemination of pathogens, including the high degree of commingling during auction and transportation and sometimes inadequate care early in life. These circumstances contribute to an increased risk of respiratory and other infectious diseases, resulting in higher antimicrobial use (AMU) and the development of AMR. Several studies have shown that surplus calves harbor AMR genes and pathogens that are resistant to critically important antimicrobials. This is a potential concern as the resistant pathogens and genes can be shared between animal, human and environmental microbiomes. Although knowledge of AMU and AMR has grown substantially in dairy and beef cattle systems, comparable studies in surplus calves have been mostly neglected in North America. Therefore, the overall goal of this narrative review is to summarize the existing literature regarding AMU and AMR in surplus dairy calf production, highlight the management practices contributing to the increased AMU and the resulting AMR, and discuss potential strategies and barriers for improved antimicrobial stewardship in surplus calf production systems.

Evaluation of Strategies to Improve the Environmental and Economic Sustainability of Cow-Calf Production Systems.

Simple SummaryBeef cattle have a significant contribution to greenhouse gas emissions globally, but they have a unique ability to digest plant material that is inedible for humans, thus producing human food from grasslands and rangelands. Additionally, many people around the world depend upon cattle ranching of grasslands and rangelands for their livelihoods. Identifying the strategies likely to have the largest impact on greenhouse gas emissions while improving or maintaining economic returns is necessary to guide future research. The goal of the current study was to evaluate four potential strategies for improving the environmental and economic sustainability of cow–calf production. The four strategies included (1) decreasing the feed required for maintenance, thus increasing the feed available for growth, (2) decreasing the time for cows to rebreed after calving, (3) increasing the digestibility of pasture grass, and (4) increasing the yield of pasture grass. A computer simulation model of a cow herd in Kansas, U.S.A., was modified to create variation in the four strategies. Decreasing the feed required for maintenance improved both environmental and economic sustainability, and increasing the yield of pasture grass improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow–calf production systems.Grazing cow–calf production systems account for 60 to 70% of the greenhouse gas emissions of U.S. beef production. The objective of this analysis was to evaluate the importance of management strategies (cow maintenance energy requirements, reproductive efficiency, forage nutritive value, and forage yield) on the sustainability of cow–calf production systems using a sensitivity analysis in a production systems model. The Beef Cattle Systems Model was used to simulate a cow–calf production system in the Kansas Flint Hills using Angus genetics over a 24 year time period. The model was modified to create variation among cow herds in the base net energy for the maintenance requirement (NEm_Req), postpartum interval (PPI), grazed forage digestibility (Forage_TDN), and forage yield per hectare (Forage_Yield). The model was run for 1000 iterations/herds of a 100-cow herd. A stepwise regression analysis in conjunction with standardized regression analysis was used to identify important predictors of an indicator of greenhouse gas (GHG) emission intensity, dry matter intake per kilogram weaned, and two indicators of economic sustainability, winter feed use and returns over variable costs, using R statistical software. The most important predictor of DMI per kilogram weaned was calf weaning weight followed by NEm_Req, whereas returns over variable costs were primarily influenced by kilograms weaned per cow exposed and total purchased feed (supplement + winter feed), which were strongly influenced by NEm_Req and Forage_Yield, respectively. In conclusion, decreasing the net energy required for maintenance improved both economic and environmental sustainability, and increasing forage yield and length of the grazing season improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow–calf production systems.

Performance of Hanwoo calves fed a commercial colostrum replacer versus natural bovine colostrum.

Supplying a sufficient amount of high-quality colostrum is a prevailing challenge in Hanwoo calf production systems. This study aimed to describe the efficiency of a lacteal-derived colostrum replacer versus natural bovine colostrum (from Holstein) fed to Hanwoo calves. Forty newborn Hanwoo calves (25 males and 15 females; 30.7 ± 3.15 kg body weight [mean ± standard deviation]) were blocked by sex and birth weight and fed either natural colostrum or a commercial colostrum replacer. Calves displayed a narrow difference in the evolution of body weight and structural body dimensions when they received a commercial versus natural colostrum. Minor differences existed in the starter and total dry matter consumption between calves fed natural or commercial colostrum. Although the colostrum source had no significant effects on days to first diarrhea (average of 7.6 days; p = 0.17), the duration of diarrhea was longer in natural colostrum-fed calves (3.2 vs. 4.5 days; p = 0.04). Consumption of natural colostrum resulted in greater mean serum immunoglobulin G (IgG) on day 2 (14.7 vs. 10.8 ± 0.92 mg/mL) and day 7 (8.21 vs. 5.12 ± 0.82 mg/mL) of calf life, resulting in a greater proportion of commercial colostrum-fed calves (50% vs. 15%; day 2) to experience failure of passive transfer of immunity (serum IgG < cutoff point of 10 mg/mL). Overall, growth rate, body frame development, and incidence of diarrheal disease were not different in both groups. These results suggested that the colostrum replacer product tested in this study could be an alternative to natural colostrum derived from Holstein cow in securing calf growth and health in Hanwoo calf-rearing operations.

Assessing Extensive Semi-Arid Rangeland Beef Cow-Calf Welfare in Namibia: Part 1: Comparison Between Farm Production System's Effect on the Welfare of Beef Cows.

Simple SummaryNamibia is in the process of updating animal welfare legislation. This needs to include an assessment protocol for beef cattle production systems that is sufficiently rigorous for the country to gain and maintain access to high-value beef export markets. Beef is produced in commercial and semi-commercial systems and in communal village farms. Privately owned commercial farms allow maximum herd and rangeland management to ensure optimum productivity and profitability. Village farms (semi-commercial and communal) have limited grazing land, with consequent challenges of grazing and water management, as well as traditional customs of cattle management. A protocol was developed to assess the welfare of beef cattle in the context of these production systems. The application of the welfare assessment protocol indicated that the standards of welfare differed across production systems, with commercial farms achieving the best standard of welfare, followed by semi-commercial, then communal village farms. The greatest opportunity for change exists within the semi-commercial village farms, which need to attain to the requirements imposed by international markets to maximize their returns; hence herd management and welfare status is better than in the purely communal farms. This suggests that commercialization of communal farming may have benefits for animal welfare.A proposed animal welfare assessment protocol for semi-arid rangeland-based cow–calf systems in Namibia combined 40 measures from a protocol developed for beef cattle in New Zealand with additional Namibia-specific measures. Preliminary validation of the protocol had been undertaken with five herds in one semi-commercial village. The aim of the current study was to apply this protocol and compare animal welfare across three cow–calf production systems in Namibia. A total of 2529 beef cows were evaluated during pregnancy testing in the yards of 17 commercial, 20 semi-commercial, and 18 communal (total: 55) herds followed by an assessment of farm resources and a questionnaire-guided interview. Non-parametric tests were used to evaluate the difference in the welfare scores between the production systems. The results indicated a discrepancy of animal welfare between the three farm types, with a marked separation of commercial farms from semi-commercial, and communal village farms in the least. The differences in these production systems were mainly driven by economic gains through access to better beef export market for commercial farms and semi-commercial villages, as well as by the differences in the available grazing land, facility designs/quality, and traditional customs in the village systems. The results indicate an advantage of commercialization over communalization.

Activity Directions and Issues for Dissemination of the Calf Production System by the Year-round Cow-calf Grazing

Activity Directions and Issues for Dissemination of the Calf Production System by the Year-round Cow-calf Grazing

Influence of weaning date and late gestation supplementation on beef system productivity II: economic analysis1

Cow–calf production systems were analyzed using experimental data and historical economic information to model four separate production year using the 10-yr price period from 2005 to 2014. Treatments included two weaning dates, October (OCT) and December (DEC), and four winter nutritional treatments, grazing winter range with no supplement (WR0), low supplement (WR1), high supplement (WR2); or grazing corn residue with no supplement (CR) applied in a 2 × 4 factorial arrangement. Net returns at the December weaning date were greatest (P < 0.05) for DEC systems where cows were fed the WR2 level ($151.14/cow) or CR ($140.17/cow), intermediate for cows fed the WR1 ($110.44/cow), and least for cows fed WR0 ($62.23/cow). Average net returns across winter nutrition treatments at the December weaning date were greater (P < 0.01) for DEC systems ($115.99/cow) compared with OCT systems ($110.28/cow). Marketing October weaned calves in December increased net returns on average by $47.24/cow compared with October marketing. Retained and owned (RO) slaughter steer net returns sold on a hot carcass weight (HCW) basis were greatest (P < 0.05) for CR systems ($190.62/cow) or WR2 ($188.13/cow), intermediate for WR1 ($132.67/cow) and least for the WR0 ($68.08/cow) treatment. In general, purchasing weaned calves (PC) and marketing them as finished steers either on a HCW basis or on a marketing grid were not profitable. The WR2 and the CR grazing regimes were more profitable than WR0 and WR1 regardless of market end point, primarily due to reduction in replacement and production loss costs.

Benchmarking calving management practices on western Canada cow–calf operations1

: Benchmarking current calving management practices and herd demographics in the western Canadian cow–calf production system helps to fill the gap in knowledge and understanding of how this production system works. Further investigation into the relationships between management decisions and calf health may guide the development of management practices and protocols to improve calf health, especially in compromised calves after a difficult birth. Therefore, the objectives of this cross-sectional study were to describe current calving management practices on western Canadian cow–calf ranches and to investigate the association of herd demographics with herd-level incidence of calving assistance, morbidity, mortality, and use of calving and colostrum management practices. Cow–calf producers were surveyed in January 2017 regarding herd inventory and management practices during the 2016 calving season. Ninety-seven of 110 producers enrolled in the western Canadian Cow-Calf Surveillance Network responded. Average herd-level incidence of assisted calvings was 4.9% (13.5% heifers, 3.2% cows), stillbirths was 2.1% (3.3% heifers, 1.9% cows), preweaning mortality was 4.5%, and preweaning treatment for disease was 9.4% (3.0% neonatal calf diarrhea, 3.8% bovine respiratory disease, 2.6% other diseases). Greater than 90% of producers assisted calvings and would intervene with colostrum consumption if the calf did not appear to have nursed from its dam. Late calving herds (i.e., started calving in March or later) had significantly lower average herd-level incidence of assistance, treatment for disease, and mortality (P < 0.05). In earlier calving herds (i.e., started calving in January or February) producers had shorter intervals between checking on dams for signs of calving or intervening to assist with a calving (P < 0.05). In early calving herds, producers were more likely to perform hands-on colostrum management techniques such as placing the cow and calf together or feeding stored, frozen colostrum (P < 0.05). There were no associations between herd size and herd-level incidences or management techniques (P > 0.05). This study suggests that in western Canada earlier calving herds are more intensively managed, whereas later calving herds are more extensively managed. Herd demographics may be important to consider when investigating factors associated with management strategies, health, and productivity in cow–calf herds.

Prevalence and Transmission of Antimicrobial Resistance in a Vertically Integrated Veal Calf Production System.

Transmission of antimicrobial resistance (AMR) from animal production systems to humans through the food supply is a public health concern. Currently, little is known about the prevalence of AMR among veal calves in the United States. Therefore, the objective of this prospective cohort study was to estimate the prevalence of AMR and multidrug resistance (MDR) among Escherichia coli within a vertically integrated production system. In addition, this study aimed to identify genes associated with phenotypic resistance to third- and fourth-generation cephalosporins (3GC and 4GC). Calves from four veal cohorts were randomly sampled resulting in a total of 166 farm fecal samples, 159 harvest fecal swabs, 164 preevisceration swabs, and 122 final carcass swabs. The prevalence of MDR among random-pick E. coli isolates recovered from the respective samples was 97% (161/166), 35% (55/159), 61% (51/84), and 24% (5/21). A selective isolation protocol found cefotaxime (a 3GC)-resistant isolates in 91% (127/140) of farm fecal samples, 34% (55/164) of preevisceration swabs, and 19% (23/122) of final carcass swabs tested. Isolates resistant to cefepime, a 4GC, were found among 24% (33/140), 6.7% (11/164), and 0.8% (1/122) of the same, respective samples. Isolates resistant to ciprofloxacin, a fluoroquinolone, were recovered from 75% (73/98) of farm fecal samples, 23% (38/164) of preevisceration swabs, and 6.6% (8/122) of final carcass swabs. The blaCMY-2 and blaCTX-M resistance genes were found in 89% (93/105) and 100% (42/42) of tested subsets of 3GC- and 4GC-resistant isolates, respectively. Pulsed-field gel electrophoresis (PFGE) analysis conducted on 3GC- and fluoroquinolone-resistant isolates showed three indistinguishable PFGE patterns from cefotaxime-resistant isolates recovered at farm and from two preevisceration carcass swabs. Although the prevalence of resistance declined between initial farm fecal samples and final carcass swabs, resistant bacteria recovered from carcasses illustrate the potential transmission of AMR to the human food supply.

SORO DO LEITE EM SUBSTITUIÇÃO AO LEITE NA CRIA DE BEZERROS

O uso de leite na alimentação de bezerras representa o maior custo na fase de cria. Com o objetivo de avaliar a viabilidade técnica da utilização de diferentes quantidades de dieta líquida na alimentação de bezerros da Raça Holandês, utilizou-se 160 ou 240 litros de dieta líquida, durante um período de 53 dias (do quarto ao 56o dia de vida) de aleitamento com diferentes níveis de inclusão de soro de leite em substituição ao leite integral (0, 10 e 20%), em esquema fatorial 2x3 (160 ou 240 litros de dieta líquida e 0, 10 ou 20% de inclusão de soro do leite), conduzido no Laboratório de Bovinocultura Leiteira da Universidade Federal de Santa Maria. Os animais foram distribuídos inteiramente ao acaso em seis tratamentos, com quatro repetições por tratamento. Foram avaliados o consumo de matéria seca do concentrado (CMSC), da matéria seca total (CMST), ganho médio diário (GMD), conversão alimentar (CA), peso vivo final (PVF) e o comportamento dos animais. Para os níveis de soro do leite, ocorreu uma resposta quadrática (p&lt;0,05) para o CMSC, CMST, GMD e CA. Os bezerros que receberam 160 litros de leite apresentaram maior (p&lt;0,05) CMSC, porém pior CA. O CMST, o GMD e o PVF foram superiores (p&lt;0,05) para os bezerros que consumiram 240 litros de leite durante o período experimental, com melhor CA para esse grupo de animais. Na análise do comportamento não foi determinada diferença significativa para os parâmetros avaliados (p&gt;0,05).

Evaluation of greenhouse gas emissions from hog manure application in a Canadian cow–calf production system using whole-farm models

The development of beneficial management practices is a key strategy to reduce greenhouse gas (GHG) emissions from animal agriculture. The objective of the present study was to evaluate the impact of time and amount of hog manure application on farm productivity and GHG emissions from a cow–calf production system using two whole-farm models. Detailed model inputs (climate, soil and manure properties, farm operation data) were collected from a 3-year field study that evaluated the following three treatments: no application of hog manure on grassland (baseline); a single application of hog manure on grassland in spring (single); and two applications of hog manure as fall and spring (split). All three treatments were simulated in a representative cow–calf production system at the farm-gate using the following whole-farm models: a Coupled Components Model (CCM) that used existing farm component models and the Integrated Farm System Model (IFSM). Annual GHG intensities for the baseline scenario were 17.7 kg CO2-eq/kg liveweight for CCM and 18.1 kg CO2-eq/kg liveweight for IFSM. Of the total farm GHG emissions, 73–77% were from enteric methane production. The application of hog manure on grassland showed a mean emission increase of 7.8 and 8.4 kg CO2-eq/kg liveweight above the baseline for the single and split scenarios, respectively. For the manured scenarios, farm GHG emissions were mainly from enteric methane (47–54%) and soil nitrous oxide (33–41%). Emission estimates from the different GHG sources in the farm varied between models for the single and split application scenarios. Although farm productivity was 3–4% higher in the split than in single application (0.14 t liveweight/ha), the environmental advantage of applying manure in a single or split application was not consistent between models for farm emission intensity. Further component and whole-farm assessments are required to fully understand the impact of timing and the amount of livestock manure application on GHG emissions from beef production systems.

Economic and environmental impacts of changes in culling parity of cows and diet composition in Japanese beef cow–calf production systems

The effects of changes in culling parity of cows and diet composition on economic and environmental outputs in Japanese beef cow–calf production systems were deterministically analyzed using a herd model simulation. The model simulated the annualized net revenue as an economic indicator and the overall environmental index derived from a life cycle assessment (LCA) as an environmental indicator. Biological factors (survivability, growth, reproduction, and feed requirements) and economic factors (returns from sales of live calves and cows’ carcasses and production costs) were included in the model. The model also included modified feed formulation methods, allowing us to analyze the effect of reductions in environmental loads caused by the change in diet compositions. The results of the present study indicated that later culling was economically and environmentally optimal under the current production system, which suggested that the selection of economically optimal culling parity of cows could result in environmentally optimization of the beef cow–calf production system. The difference in feed composition derived from the difference in feed formulation methods did not affect the determination of optimal culling parity, whereas the use of modified feed formulation methods could reduce environmental loads at a higher rate than that of economic benefits. However, the reduction rate of the environmental impact was much higher in the case of selection of the optimal culling parity than in the case of use of modified feed formulation methods, which stressed the importance of choosing the optimal culling parity of cows both from the economic and environmental points of view.

Optimal culling strategy in relation to biological and economic efficiency and annualized net revenue in the Japanese Black cow–calf production system

SUMMARYThe objective of the present study was to determine the optimal culling strategy in relation to biological and economic efficiency (BE and EE, respectively) and annualized net revenue (AN) in the Japanese Black cow–calf production system with special reference to the beef quality of culled cows. The herd model focused on two ways of mating: one-mating trial system (ONE) and continuous-mating trial system (CON). ONE assumed that heifers that fail to conceive are culled and cows that fail to conceive are culled at weaning of their calves, while CON assumed that mating continues until all females theoretically conceive. Least square means of carcass data of Japanese Black cows collected from a cooperative farm in Japan were used to estimate the carcass price of a cow by parity and Beef Marbling Standard (BMS) number. The simulation, assuming the current production situation in Japan, indicated that sales of culled cows accounted for 0·10–0·20 of total sales and was an important element in total production. Comparisons between ONE and CON showed that production efficiency in the current situation is higher in CON. The BE, EE and AN were higher in CON than in ONE. The two economic indicators were less sensitive to changes in annual discount rate but highly sensitive to changes in female calf price and BMS number of cows, indicating the importance of considering fluctuations in calf price and potential quality of culled cows’ carcasses when estimating the economically optimal parity of culling. The three indicators derived different optimal solutions even in the same mating trial systems, stressing the importance of choice of production indicators when determining the culling strategy and evaluating animal production.

Life cycle assessment of greenhouse gas emissions from beef production in western Canada: A case study

A life cycle assessment (LCA) was conducted to estimate whole-farm greenhouse gas (GHG) emissions from beef production in western Canada. The aim was to determine the relative contributions of the cow–calf and feedlot components to these emissions, and to examine the proportion of whole-farm emissions attributable to enteric methane (CH 4). The simulated farm consisted of a beef production operation comprised of 120 cows, four bulls, and their progeny, with the progeny fattened in a feedlot. The farm also included cropland and native prairie pasture for grazing to supply the feed for the animals. The LCA was conducted over 8 years to fully account for the lifetime GHG emissions from the cows, bulls and progeny, as well as the beef marketed from cull cows, cull bulls, and progeny raised for market. The emissions were estimated using Holos, a whole-farm model developed by Agriculture and Agri-Food Canada. Holos is an empirical model, with a yearly time-step, based on the Intergovernmental Panel on Climate Change methodology, modified for Canadian conditions and farm scale. The model considers all significant CH 4, N 2O, and CO 2 emissions and removals on the farm, as well as emissions from manufacture of inputs (fertilizer, herbicides) and off-farm emissions of N 2O derived from nitrogen applied on the farm. The LCA estimated the GHG intensity of beef production in this system at 22 kg CO 2 equivalent (kg carcass) −1. Enteric CH 4 was the largest contributing source of GHG accounting for 63% of total emissions. Nitrous oxide from soil and manure accounted for a further 27% of the total emissions, while CH 4 emissions from manure and CO 2 energy emissions were minor contributors. Within the beef production cycle, the cow–calf system accounted for about 80% of total GHG emissions and the feedlot system for only 20%. About 84% of enteric CH 4 was from the cow–calf herd, mostly from mature cows. It follows that mitigation practices to reduce GHG emissions from beef production should focus on reducing enteric CH 4 production from mature beef cows. However, mitigation approaches must also recognize that the cow–calf production system also has many ancillary environmental benefits, allowing use of grazing and forage lands that can preserve soil carbon reserves and provide other ecosystems services.

Growth, feed intake and maternal performance of Angus heifers selected for high or low growth and milk production

Weight of calf weaned per cow that incorporates both growth and maternal component traits is an important determinant of profitability for cow–calf production systems. In New Zealand, there is little objective information available on the performance of progeny from bulls selected for either growth or maternal ability when compared under similar pastoral farming conditions. The present experiment produced 84 Angus heifers sired by Angus bulls divergently selected for high (Hi-Gr) or low (Lo-Gr) estimated breeding value (EBV) 600-day weight or high (Hi-Milk) or low (Lo-Milk) 200-day maternal EBV. Each heifer had their liveweight gain from weaning to just before first calving, herbage intake from pasture using the n-alkane method, and maternal performance (calf production after first and second parity) assessed. Liveweights of heifers born to Hi-Gr bulls were generally greater than for all other lines, while there was no difference between Lo-Gr and either of the maternal lines. There was no difference (P &gt; 0.05) in herbage intake between the different genetic lines when measured at Days 310 (days of age from birth) and 880. At Day 400, the Lo-Milk selection line had higher (P &lt; 0.05) intakes than the Hi-Milk, Hi-Gr and Lo-Gr lines. Calves born to the Lo-Gr heifers at the first parity were lighter while the birth weights of calves born at the second parity calving were similar for all the selection lines. Calf weaning weight was lowest (P &lt; 0.05) after both the first and second parity weaning for the Lo-Milk sired heifers. The Lo-Milk heifers produced the least milk at Day 50 during their first lactation while the Hi-Milk heifers produced the most. This experiment confirms that for beef cattle, producers who wish to select bulls to use in their herds based on either high growth rate or high milk EBV, the resultant progeny will outperform those that are average or below average for those particular traits.

Beef cow–calf production system integrated with sugarcane production: Simulation model development and application in Japan

The objective of this study was to develop a simulation model for the integration of a beef cow–calf production system and sugarcane production system on Tanegashima Island. A survey was carried out to characterize and identify the role of sugarcane as an alternative feed resource and determine the different interactions within the system. The model was divided into two sub-systems; beef cow–calf and sugarcane and manure production sub-systems. The model is able to simulate the total requirement for energy and protein, and subsequent losses of nitrogen via faeces and urine, throughout the reproductive cycle of a mature cow and the growing stages of her calf. It also estimates the area under sugarcane cultivation for feed and the area on which manure can be applied to complement inorganic fertilizer. A linear programming (LP) approach was used to formulate the least-cost diet and a system simulation method was used to calculate the nitrogen (N) excretion for a cow and her post-weaning calf in the different physiological stages. The model was used to evaluate two scenarios (integrated and specialized scenarios) using production conditions on Tanegashima Island. In the integrated scenario, sugarcane tops were the principal roughage source and organic (manure) was used to complement inorganic fertilizer. In the specialized scenario, Italian ryegrass was the principal feed source and manure was not used. These two scenarios were compared based on the respective feed and fertilizer costs, and the difference between the two scenarios was evaluated as the merit of integration. Sensitivity analyses were also performed to determine the effects of changes in nutritional and management conditions, animal genotype parameters and manure variables on economic variables. The results showed that feed and fertilizer costs were lower in the integrated than in the specialized scenario. Economic variables were sensitive to changes in feeding strategies, especially the metabolizability of feed, days of availability of sugarcane tops, mature liveweight, and manure variables. Utilization of sugarcane tops and manure is economically feasible under the conditions on Tanegashima Island. It is proposed that the developed model is capable of evaluating the biological and economic interaction of beef cow–calf production and sugarcane production systems.

Simulação dos efeitos dos preços de produtos e insumos na avaliação econômica de três sistemas alternativos de bovinocultura de cria

Avaliou-se a sensibilidade de indicadores econômicos de três sistemas alternativos de produção de bovinos à variação de preços de insumos e produtos. Observou-se que o sistema de produção de bezerros F1 Holandês × Gir apresentou maior eficiência econômica que os sistemas de produção de bezerros Nelore e de produção de bezerros F1 Angus × Nelore, principalmente devido ao maior valor agregado de seu principal produto (novilha F1). O preço do sêmen não teve importância econômica significativa para o sistema de produção de bezerros F1 Holandês × Gir. Os preços da terra e da matriz Gir só tiveram importância para a avaliação econômica quando se utilizaram indicadores que levaram em conta o capital investido na atividade.

Comparative economics of Holstein/Gir F 1 dairy female production and conventional beef cattle suckler herds – A simulation study

Three cow–calf production systems were compared using simulation: N (straightbred Nelore), AN (Nelore cows producing Angus by Nelore calves) and HG (Gir cows producing Holstein by Gir calves). All three systems produced their own straightbred replacement females. Male calves were sold at weaning and female calves in excess of those required to keep the herd size constant were sold at one year of age. In the base situation, F 1 HG females were priced at twice as much as the price per kg of the beef male calves, according to present market values. Typical 1000 ha beef cattle farms were simulated for each system, based on Brachiaria brizantha pastures managed according to recommended practices. Herd dynamics were controlled by reproduction and survival. Literature figures on monthly pasture nutrient production, live weights and milk yield were used to estimate nutrient requirements to match stocking rate to nutrient availability in each system. For calving rate set to 0.8 in all three systems, the total numbers of cows for the N, AN and HG systems were, respectively, 803, 795 and 885 and the total live weight sold annually was 129,070, 133,120 and 127,680 kg. The annual economic return on investment was 5.21%, 5.81% and 10.84%, respectively, for the N, AN and HG systems. Reducing the relative price of the HG heifers diminished the economic superiority of this system over N and AN. The difference was zero when the price of HG heifers was reduced to approximately 1.2 times the beef calf price. This also happened when the calving rate of the Gir cows was set to 0.6 keeping N cows at 0.8 or higher.

A model for simulating rule-based management of cow–calf systems

Pastoral livestock farms are complex and dynamic systems, and are subject to many forms of external disturbance. Management strategies can be aimed to minimize system variations in order to control the system and to achieve specific goals. A research simulation model was developed to study the long term dynamics of complete cow–calf production systems for the Salado Region of Argentina. In the model, the operation of the farm is simulated by decision rules entered by the user. The purpose of the model is to assist in the design and evaluation of pastoral beef breeding systems. This paper discusses the model design in detail and an example is then given in which different strategies of hay use during the winter are compared. The results of the simulations were reasonable, indicating the advantages of using hay in reducing the variability of system productivity, but the different patterns of hay use did not show any impact on the long run performance. The design principles used give considerable flexibility, so the model can be used to simulate and study management combinations available to the farmers.