Profitable Breeding Research Articles

Comparison of two non-linear functions describing the growth of Popielno White and New Zealand White rabbits

The objective of this study was to compare growth curves of Popielno White and New Zealand White rabbits modelled by the von Bertalanffy and Gompertz functions. There were 37 Popielno White (21 males and 16 females) and 55 New Zealand White (28 males and 27 females) rabbits used. The nonlinear regression procedure (NLIN) in the SAS 9.4 software (SAS, 2014) was used for modelling rabbits growth curves from birth to 12th week of age. To see how the process of rabbit growth might run in next weeks, we extrapolated weights of rabbits up to 30th week of age. Six criteria: the mean error, mean squared error, mean absolute error, quotient between the error sum of squares and the observed sum of squares, corrected Akaike Information Criterion and Bayesian Information Criterion were used to compare models. The shape of all curves was sigmoid and both models well fitted to data from birth to 12th week of age, i.e. during interpolation process. The problem with the fit occurred later, during extrapolation process, i.e. when models were used to predict the course of the growth of animals in the next weeks of age. When body weight was extrapolated in later weeks of rabbits life, we noticed slightly worse fitting of von Bertalanffy model and overestimation of the asymptotic body weight of animals. To predict the further course of rabbit growth in practice, the Gompertz function would be a better choice. Additionally the Gompertz model could be a helpful tool for breeders to describe growth process of rabbits and to select a more economically profitable breed.

Determinação dos fatores de risco em empresas de gado e pequenos ruminantes a partir da perspectiva do seguro de vida animal: um estudo de caso na Turquia

ABSTRACT The objective of this study was to determine the risk factors in the production processes of cattle and small ruminant breeding enterprises, along with developing a scale that could be used during the insured breeding process in different regions of Turkey. In this study, we obtained information from 252 enterprises from different provinces (Afyonkarahisar, Aksaray, Ankara, Burdur, Karaman, and Konya) of Turkey. Reliability and validity analyses were conducted using the “Risk Assessment Form in Cattle and Small Ruminant Animal Production”. The Cronbach alpha (α) coefficient was used to analyze reliability, while the exploratory factor analysis was applied to analyze the validity. About 68.7% (173) of the enterprises included cattle breeding, while the remaining 31.3% (79) involved small ruminant breeding. To determine the risk factors, twenty-four questions were directed toward the livestock enterprises, and the following six factors were determined: Economic-Political Risks, Yield/Product Losses, Enterprise Technical Risks, Credit/Financing, Workforce, Enterprise Follow-up, and Registration. In the politico-economic risk scoring, the score of enterprises already having Animal life insurance (ALI) was observed to be higher than those who did not have it, with the difference being statistically significant (p<0.05). We interpreted that producers with higher politico-economic risk factor scores preferred insurance. Although the producers could determine the risk factors well, not all producers were necessarily aware of risk measures. Thus, it was necessary to improve the farmers’ perception of risks and support their efforts to manage and reduce these risks. Also, the importance of insurance practices within and out of the farm is predicted to increase gradually to develop more conscious, sustainable, and profitable breeding in agriculture and animal product markets, which are becoming more liberalized day by day.

CAUSES AND REMEDIES FOR NON-INFECTIOUS INFERTILITY IN SHEEP AND GOATS

Non-infectious infertility is particularly critical for sire rams/bucks, as seasonal breeders. This seasonal heavy use of males may lead to sexual exhaustion such that the regular semen production, libido, ejaculation, and litter yield can be seriously impaired. In severe cases, the reproductive processes may stop completely. For avoiding infertility risk, management and feeding should firstly be arranged with a flock-based approach. In reproductive management, the issues of using teaser ram/buck, male/female ratio, weekly mating number, exercise, and experience need attention. Also, inbreeding and using old breeders should be avoided. In oestrus synchronisation, necessary precautions against extremely hot/arid climatic conditions should be considered together with a sufficient number of rams/bucks used rotationally. For sustainable sheep/goat breeding, protective-preventive measures are preferred to problem-solving approaches. In enterprises where female breeder welfare is a priority, sustainable individual yield increases. Further, only the comfort level of males used heavily in season allows the expected libido and fertility to occur. In small ruminants, the necessary interest and responsibility in production provide convenience in the ideal solution with the opportunity of early interventions against undesirable fertility problems in breeders. Undoubtedly, it is vital to consider sustainable animal health and welfare for profitable breeding and husbandry in sheep/goats.

Pet primates for sale in the United States.

Our research goal was to investigate the primate pet trade in the United States. While dogs and cats are the most common type of pet, there are an estimated 15,000 pet primates in the United States and the demand for exotic pets in general has been rising. Most research on pet primates occurs in habitat countries and little is known about these pets in the United States. We collected data from six exotic pet-trade websites twice a month for 12 months. We recorded the type of primate for sale, sex, age, location, and price. We used Chi-Square Goodness-of-Fit tests to compare whether the number of male and female pet primates for sale and the number of different age categories of pet primates for sale differed from equality and Spearman Correlation to examine associations between price and size and price and supply. We recorded 551 pet primates for sale between June 2019-June 2020, with 69.1% platyrrhines, 21.6% strepsirrhines, and 8.9% catarrhines. Marmosets were sold most often (36.7%, N = 202) followed by lemurs (21.6%, N = 119), capuchins (11.3%, N = 62), and squirrel monkeys (10.5%, N = 58). Almost two-thirds of the pet primates for sale were male (Chi-Square = 16.056, df = 1, P = 0. 00006) and 78.7% were under one year old (Chi-Square = 440.264, df = 2, P<0.00001). The median price was $3,800 though price was highly variable, even for the same taxa. There are several potential drivers for the primate pet trade, including media influence, fashion/status, and profitable breeding though these are not mutually exclusive. Primates do not make good pets and even when captive-bred, pet primates impact the conservation of their wild counterparts. Advertisement campaigns focusing on disease transmission and legal consequences and a federal ban on pet primate ownership are two avenues to pursue to end the ownership of pet primates in the United States.

Activity of Mannose-Binding Lectin on Bacterial-Infected Chickens-A Review.

Simple SummaryIn the quest to combat bacterial-related diseases in chickens, different methods, of which some are less economical and less effective on the long-term, have been adapted. However, chickens possess mannose-binding lectin (MBL) which could be vital in managing pathogenic bacteria in chickens. MBL is one of the soluble proteins secreted by the chicken’s innate immune system which can be activated when chickens are exposed to chicken-related diseases. This review explains how mannose-binding lectin activation can help in fighting bacterial pathogens in chickens. This knowledge is believed to reduce incessant use of antibiotics and to assist in developing a profitable breeding program with less or no adverse effect on the chicken, human and the environment. In recent years, diseases caused by pathogenic bacteria have profoundly impacted chicken production by causing economic loss in chicken products and by-product revenues. MBL (mannose-binding lectin) is part of the innate immune system (IIS), which is the host’s first line defense against pathogens. The IIS functions centrally by identifying pathogen-specific microorganism-associated molecular patterns (MAMPs) with the help of pattern recognition receptors (PRRs). Studies have classified mannose-binding lectin (MBL) as one of the PRR molecules which belong to the C-type lectin family. The protective role of MBL lies in its ability to activate the complement system via the lectin pathway and there seems to be a direct link between the chicken’s health status and the MBL concentration in the serum. Several methods have been used to detect the presence, the level and the structure of MBL in chickens such as Enzyme-linked immunosorbent assay (ELISA), Polymerase Chain Reaction (PCR) among others. The concentration of MBL in the chicken ranges from 0.4 to 35 µg/mL and can be at peak levels at three to nine days at entry of pathogens. The variations observed are known to depend on the bacterial strains, breed and age of the chicken and possibly the feed manipulation strategies. However, when chicken MBL (cMBL) becomes deficient, it can result in malfunctioning of the innate immune system, which can predispose chickens to diseases. This article aimed to discuss the importance and components of mannose-binding lectin (MBL) in chickens, its mode of actions, and the different methods used to detect MBL. Therefore, more studies are recommended to explore the causes for low and high cMBL production in chicken breeds and the possible effect of feed manipulation strategies in enhancing cMBL production.

Producing higher value wool through a transition from Romney to Merino crossbred ii: Cashflow and profit

• Bio-economic system-dynamics modelling of a Romney flock bred with Merino sires for whole flock breed transition. • Profit decreased during transition, but was greater post-transition than for Romney flock. • Economic benefit of transition ranged from zero to an increase of up to 26 %. • Greatest economic benefit with higher lamb selection intensity and longer transition. • With higher selection intensity, post-transition wool had lower fibre diameter and higher value. Data suggests crossbreeding a Romney ewe flock with Merino sires to achieve a second cross ¾ Merino ¼ Romney (¾M¼R) flock would reduce wool fibre diameter and increase income from wool sales. It is not known how cashflow would vary during such a breed transition and which factors would affect the profitability of such a strategy. A bio-economic system-dynamics modelling study was conducted to simulate the breed transition with low or high selection intensity (24 % vs. 35 % of crossbred ewe lambs not retained at each of two selection events) and either consistent lambing rate (132 % for all flocks) or breed specific lambing rate (lower for Merino-Romney crossbred flocks). Although sheep enterprise profit was always greater post-transition compared with the base Romney flock, during transition annual profit was reduced below that of the base Romney flock. The total cashflow of the breed transition (i.e. twelve years) ranged from relatively small or no economic benefit, to up to 26 % greater than maintenance of the base Romney flock. The most profitable breed transition strategies modelled had higher Merino-Romney ewe lamb selection intensity, achieved greater wool fibre diameter reductions, and occurred over a longer breed transition period.

Management of lethal recessive alleles in beef cattle through the use of mate selection software

BackgroundRecessive loss-of-function (LOF) alleles at genes which are essential for life, can result in early embryonic mortality. Cattle producers can use the LOF carrier status of individual animals to make selection and mate allocation decisions.MethodsTwo beef cattle breeding strategies i.e. (1) selection against LOF carriers as parents and (2) simultaneous selection and mate allocation to avoid the occurrence of homozygous offspring in three scenarios, which differed in number and frequency of LOF alleles were evaluated using the mate selection program, MateSel. Scenarios included (a) seven loci with high-frequency LOF alleles, (b) 76 loci with low-frequency LOF alleles, and (c) 50 loci with random high- and low-frequency LOF alleles. In addition, any savings resulting from the information obtained by varying the percentage (0–100%) of the herd genotyped, together with segregation analysis to cover ungenotyped animals, were calculated to determine (1) which percentage optimized net profit for a fixed cost of genotyping ($30/test), and (2) the breakeven cost for genotyping.ResultsWith full knowledge of the LOF alleles carried by selection candidates, the most profitable breeding strategy was always simultaneous selection and mate allocation to avoid homozygous affected offspring (aa) as compared to indiscriminate selection against carrier parents (Aa). The breakeven value of genotyping depended on the number of loci modeled, the LOF allele frequencies, and the mating/selection strategies used. Genotyping was most valuable when it was used to avoid otherwise high levels of embryonic mortalities. As the number of essential loci with LOF alleles increased, especially when some were present at relatively high minor allele frequencies, embryonic losses increased, and profit was maximized by genotyping 10 to 20% of a herd and using that information to reduce these losses.ConclusionsGenotyping 100% of the herd was never the most profitable outcome in any scenario; however, genotyping some proportion of the herd, together with segregation analysis to cover ungenotyped animals, maximized overall profit in scenarios with large numbers of loci with LOF alleles. As more LOF alleles are identified, such a mate selection software will likely be required to optimally select and allocate matings to balance the rate of genetic gain, embryonic losses, and inbreeding.

A dual colour FISH method for routine validation of sexed Bos taurus semen

BackgroundUsage of sexed semen that allows to choose the gender of the calves, is commonly practiced in livestock industry as a profitable breeding alternative, especially in dairy farming. The flow cytometric cell sorting is the only commercially available method for bovine sperm sexing. For validation of the sexing procedure several methods have been developed including sperm fluorescence in situ hybridisation techniques. Latter usually include the use of pre-labelled nucleotides for probe synthesis which is relatively expensive approach compared to combined application of aminoallyl-dUTP and chemical binding of fluorescent dyes. Here a sex determining dual colour bovine sperm fluorescence in situ hybridisation method is presented which is considered more cost-effective technique than the previously reported approaches.ResultsThe reliability of sex chromosome identifying probes, designed in silico, was proven on bovine metaphase plate chromosomes and through comparison with a commercially available standard method. In the dual colour FISH experiments of unsexed and sexed bovine sperm samples the hybridisation efficiency was at least 98%, whereas the determined sex ratios were not statistically different from the expected. Very few cells carried both of the sex chromosome-specific signals (less than 0.2%).ConclusionsA protocol for a dual colour bovine sperm FISH method is provided which is cost-effective, simple and fast for sex determination of spermatozoa in bull semen samples.

A deterministic evaluation of heat stress mitigation and feed cost under climate change within the smallholder dairy sector

In the global South, dairying is often promoted as a means of poverty alleviation. Yet, under conditions of climate warming, little is known regarding the ability of small-scale dairy producers to maintain production and/or the robustness of possible adaptation options in meeting the challenges presented, particularly heat stress. The authors created a simple, deterministic model to explore the influence of breed and heat stress relief options on smallholder dairy farmers in Odisha, India. Breeds included indigenous Indian (non-descript), low-grade Jersey crossbreed and high-grade Jersey crossbreed. Relief strategies included providing shade, fanning and bathing. The impact of predicted critical global climate parameters, a 2°C and 4°C temperature rise were explored. A feed price scenario was modelled to illustrate the importance of feed in impact estimation. Feed costs were increased by 10% to 30%. Across the simulations, high-grade Jersey crossbreeds maintained higher milk yields, despite being the most sensitive to the negative effects of temperature. Low-capital relief strategies were the most effective at reducing heat stress impacts on household income. However, as feed costs increased the lower-grade Jersey crossbreed became the most profitable breed. The high-grade Jersey crossbreed was only marginally (4.64%) more profitable than the indigenous breed. The results demonstrate the importance of understanding the factors and practical trade-offs that underpin adaptation. The model also highlights the need for hot-climate dairying projects and programmes to consider animal genetic resources alongside environmentally sustainable adaptation measures for greatest poverty impact.

Productivity, Cost-Benefit Analyses, Market Prices and Constraints to Poultry Farming in the Northern Districts of Bangladesh

A total of 6,41,004 chickens were produced by 10 farms, of which Cobb 500 (broilers) in P1 were the highest in number (2,43,000) and G1 yielded the lowest (10,117 Fayoumi, RIR and Sonali breeds). The most common chicken breed reared in the area was Cobb 500 (2,76,350) and the least common was ISA Brown (43,163). With regard to productivity, significant differences existed among the farms (F9, 103= 29.32; P&lt;0.001), among the chicken breeds (F4, 108= 3.03; P&lt;0.05), as well as between the government and private farms (F1, 111= 6.17; P&lt;0.05). It was interesting to note that all the government farms were losing concerns (G2 &gt; G3 = G4 &gt; G1), while all the private farms were making profits (P1 &gt; P3 &gt; P2 &gt; P6 &gt; P4 = P5). The overall profitability index (PI) values of government farms ranged between -0.09 and -0.13, whereas those of private farms between 0.18 and 0.52. Cobb 500 was the commonest but the least profitable breed, and Sonali was the most popular and cheapest one; and the growers achieved the maximum profit from Fayoumi. High feed cost, outbreak of diseases, inadequate supply of vaccines/medicines, lack of credit facilities and capital funding were recognized to be the major constraints to the poultry farming in the study area. DOI: http://dx.doi.org/10.3329/jles.v7i0.20117 J. Life Earth Sci., Vol. 7: 21-27, 2012

Evaluation of breeding objectives for purebred and crossbred selection schemes for adoption in indigenous chicken breeding programmes

1. The aim of the study was to evaluate the genetic and economic breeding objectives for an indigenous chicken (IC) breeding programme in Kenya. 2. A closed three-tier nucleus breeding programme with three breeding objectives and two selection schemes was simulated. The breeding objectives included IC dual-purpose (ICD) for both eggs and meat, IC layer (ICL) for eggs and IC broiler (ICB) for meat production. 3. Pure line selection scheme (PLS) for development of IC pure breeds and crossbreeding scheme (CBS) for the production of hybrids were considered. Two-and three-way crossbreeding strategies were evaluated under CBS and the impact of nucleus size on genetic gains and profitability of the breeding programme were investigated. 4. Males were the main contributors to genetic gains. The highest genetic gains for egg number (2·71 eggs) and growth traits (1·74 g average daily gain and 57·96 g live weight at 16 weeks) were realised under PLS in ICL and ICB, respectively. 5. The genetic response for age at first egg was desirable in all the breeding objectives, while that for fertility and hatchability were only favourable under ICL and PLS in ICD. Faecal egg count and immune antibody response had low, but positive gains except under PLS where the later was unfavourable. ICB was the most profitable breeding objective, followed by ICD and ICL under all the selection schemes. 6. Although PLS was superior in genetic gains and profitability and recommended in breeding programmes targeting ICL and ICB, a three line CBS should be considered in development of a dual-purpose breed. 7. Increasing the nucleus size beyond 5% of the IC population was not attractive as it resulted in declining profitability of the breeding programme.

Reproductive Performance and Milk Production of Assaf Sheep in an Intensive Management System

The Assaf breed of dairy sheep, a stabilized cross of the Awassi and East Friesian breeds, has replaced the Awassi as the breed of choice in its country of origin, Israel, and has spread to other Mediterranean countries. In Israel the Assaf breed is managed under an intensive production system involving weaning lambs at birth, rearing them artificially, and milking ewes after parturition. There are several breeding periods in the year when ewes are mated following hormonally synchronized estrus. Records of 18,976 lactations from 5 farms were analyzed to investigate factors that influenced Assaf milk and reproductive performance. Lactation curves were fitted to each lactation, and a range of parameters and calculated values were analyzed. Daily milk yield records also were analyzed to describe a typical Assaf lactation and compared with those of the Awassi breed. Factors affecting age at first lambing also were studied. An average Assaf ewe kept under this intensive management regimen was found to produce 334L of milk during a 173-d lactation. Mean litter size was 1.57 lambs/ewe lambing, and lambing interval was 272 d. Milk production was affected by litter size, with twin- and triplet-bearing ewes producing approximately 20L more milk per lactation than single-bearing ewes. Day length was the major environmental variable influencing milk yield. The difference between midsummer and midwinter day lengths accounted for a difference in daily milk yield of 0.44L in favor of summer. Ewe lambs that were mated for the first time at later ages produced more lambs and more milk due to greater early lactation characteristics. Milk production was found to be negatively associated with subsequent reproductive performance. Comparing these results with those from an earlier study in the Awassi breed, the Assaf was found to produce less milk during a shorter lactation than the Awassi, but its greater litter size made it a more profitable breed.

Positive interactions between migrant and resident birds: testing the heterospecific attraction hypothesis.

We experimentally tested the conditions where heterospecific attraction is more likely to occur. The heterospecific attraction hypothesis predicts that colonizing or migrant individuals use the presence of resident species as a cue for profitable breeding sites. In other words, increasing resident densities will result in increased migrant densities until the costs of interspecific competition override the benefits of heterospecific attraction. The experiment consisted of a reference and a manipulation year. In the reference year, resident titmice were permitted to breed at intermediate densities whilst in the manipulation year, resident densities were manipulated in nine study plots. Three treatments were performed as low, intermediate and high resident densities and migrant density responses were measured in both years. Relative between-year migrant and resident densities were analyzed by regression analysis. Migrant foliage gleaning guild densities responded linearly and positively, as did densities of habitat generalists, in particular Chaffinch ( Fringilla coelebs),. The ground-foraging guild did not show a response. This study provides support for predictions of the heterospecific attraction hypothesis and suggests that information on habitat quality with reference to both food availability and safe breeding sites are important in using heterospecifics as cues. Based on Chaffinch response data, artificially increased resident densities were not high enough for competitive effects between residents and migrants to decrease heterospecific attraction. It seems unlikely that in northern environments natural resident densities will reach high levels where competitive effects would occur, therefore heterospecific attraction will always be beneficial. This study again shows the importance of heterospecific attraction in migrant habitat selection and as a process promoting species diversity in northern breeding bird assemblages.

Heterospecific attraction among forest birds: a review

In this paper we review the evidence for a habitat selection process where colonizing individuals use other species presence as cues to profitable breeding sites. Our experimental studies in Fennoscandia and North America have shown that den- sity and species richness of migrant birds breeding in the forests respond positively to experimentally augmented titmice densities. We used analytical modeling to analyze ecological conditions, which may favor a habitat selection process where later arriv- ing individuals (colonists) use the presence of earlier established species (residents) as a cue to profitable breeding sites. We compared the fitness of two colonist strate- gies: colonists could either directly sample the relative quality of the patches (termed samplers) or, alternatively, they could also use residents as a cue of patch quality (cue-users). Model results suggested that cue-using strategy is more beneficial in most ecological conditions and that this may result in heterospecific attraction. Fur- ther field experiments showed that migrant individuals selected nest sites at close vicinity of nesting titmice, and bred earlier and reproduced better. We conclude that heterospecific attraction may be a common and widespread process among forest birds particularly in seasonal environments.

Epidemiology of reproductive performance in dairy cows

The objectives of this presentation are to review results of our previous and on-going research with respect to the risk factors and consequences of poor reproductive performance in dairy cows, and to develop an economic framework to optimize decisions related to dairy cow reproductive performance. To make profitable breeding and replacement decisions, the farmer must account for factors including age, production level, lactation stage, pregnancy status, and disease history of the cows in the herd. Establishing the interrelationships among disease, milk yield, reproduction, and herd management is necessary for developing a decision model for disease treatment, insemination, and replacement. The data for the studies reviewed in this presentation incorporate health, production, and management components from Holsteins in the Northeast USA and Ayrshires from Finland. Data were analyzed using the Cornell Theory Center Supercomputer. The effect of risk factors on reproductive disorders was modeled with logistic regression, and on conception, insemination, and culling with survival analysis. The effect of reproductive disorders on milk yield was analyzed with mixed models. Economic optimization of reproductive performance was done with dynamic programming (DP). High milk yield, high parity, and calving in winter were risk factors for several reproductive disorders. These disorders, in turn, delayed insemination and conception in dairy cows, and some of them increased the risk of culling. Dystocia, retained placenta, and early metritis led to a short-term drop in milk production. High milk yield was not a major factor in delaying conception, except in first parity cows. However, higher yielders were more likely to be inseminated, and less likely to be culled. Non-pregnant cows had a higher risk of being culled. Reproductive performance of dairy cows influenced a herd's profitability, and good heat detection and conception rates provided opportunities for management control. It was not always economically advantageous to get cows pregnant as soon as possible, and there was no one optimal value for the calving interval length for all cows in a herd.

Evolution of heterospecific attraction: using other species as cues in habitat selection

We analyzed the ecological conditions that may favor a habitat selection process in which later arriving individuals (colonists) use the presence of earlier established species (residents) as a cue to profitable breeding sites (heterospecific attraction). In our model, colonists assessing potential breeding patches could select between high-quality source and low-quality sink patches. A proportion of the source patches were occupied by residents. Colonists could either directly sample the relative quality of the patches (termed samplers) or, alternatively, they could also use residents as a cue of patch quality (cue-users). Cue-users gained benefit from lowered costs when assessing occupied source patches. The cue-using strategy is an efficient way to choose the best possible patch not only when interspecific competition is intense, but also when benefits from social aggregation exceed the effects of competition. High relative cost of sampling empty patches increases the fitness of the cue-using strategy relative to samplers. The strongest attraction to heterospecifics was predicted when the benefit from aggregating with residents exceeded the effects of competition, and approximately half of the landscape consisted of occupied, high-quality source patches.

Heterospecific attraction and food resources in migrants' breeding patch selection in northern boreal forest.

We studied experimentally how heterospecific attraction may affect habitat selection of migrant passerine birds in Finnish Lapland. We manipulated the densities of resident tit species (Parus spp.). In four study plots residents were removed before the arrival of the migrants in the first study year, and in four other plots their densities were increased by releasing caught individuals. In the second year the treatments of the areas were reversed, allowing paired comparisons within each plot. We also investigated the relative abundance of arthropods in the study plots by the sweep-net method. This allowed us to estimate the effect of food resources on the abundance of birds. The heterospecific attraction hypothesis predicts that densities of migrant species (especially habitat generalists) would be higher during increased resident density. Results supported this prediction. Densities and number of the most abundant migrant species were significantly higher when resident density was increased than when they were removed. On the species level the redwing (Turdus iliacus) showed the strongest positive response to the increased abundance of tits. Migrant bird abundances seemed not to vary in parallel with relative arthropod abundance, with the exception of the pied flycatcher (Ficedula hypoleuca) which showed a strongly positive correlation with many arthropod groups. The results of the experiment indicate that migrants can use resident tit species as a cue to a profitable breeding patch. The relationship between the abundance of the birds and arthropods suggests that annual changes in food resources during the breeding season probably do not have a very important effect on bird populations in these areas. The results stress the importance of positive interspecific interactions in structuring northern breeding bird communities.

Economic analysis of crossbreeding dairy cattle

The economics of first generation two-breed crosses between Holstein and Ayrshire lines over three lactations were compared with those of the two purebreds. Results of the analysis of variance for breed performance traits indicated no significant difference between breeds for age at first calving. Holstein had the lowest milk fat percentage, and the purebred Ayrshire exceeded the two crossbreeds for milk fat percentage. The 4% fat corrected milk was the most important variable in explaining the variation in net present value in the profit function model. It was found that purebred Holstein was the most profitable breed, and purebred Ayrshire the least; the two crossbreeds were intermediate.

ECONOMICS OF CALF PRODUCTION WITH FOREIGN CATTLE BREED CROSSES IN THE SHORT-GRASS PRAIRIES

The net farm income per Hereford-Angus unit dam (NFIPD) from calf production in the short-grass prairies was evaluated for calves of 31 three-breed crosses of foreign and British breeding. The data were from progeny produced near Manyberries, Alberta by utilizing Beefmaster and Red Angus sires for the first mating and Charolais (C), Simmental (S), Limousin (L) and Chianina (Chi) terminal sires for subsequent matings. There were 10 first-cross dam crosses consisting of Hereford (H) × Angus (A) as the control (HA), and nine dam cross combinations produced by mating C, S and L sires with H, A and Shorthorn (N) dams. There were 578 F1 females that entered the project, giving birth to 2079 calves and weaning 1866 calves during six consecutive years of the program. Rankings of the three-breed cross calves by NFIPD indicated that the L sire bred to a SA dam (LSA) and the C sire bred to a SA dam (CSA) returned the highest NFIPD. The next most profitable breed crosses were the LCN, LCH and CSH with NFIPD all within $15 of the LSA. The LH F1 dams were the least profitable with NFIPD up to $146 less than the LSA. The LH were followed by the LN and SN F1 female crosses for being unprofitable. The terminal sires ranked L = C &gt; S = Chi, the breed of sire of dam ranked C = S &gt; L, and the breed of dam ranked A &gt; H = N. The primary determinants of NFIPD differences among the breed crosses were birth weight, preweaning average daily gain, conception rates, calf deaths, calving rate, difficult calvings, and daily digestible energy requirements for the dam. Key words: Economics, cow-calf, foreign breeds, prairies