The energetic efficiency of growthRendement d'utilisation de l'énergie pour la croissanceDer energetische wirkungsgrad beim wachstum

Metabolizable energy consumed by a growing animal is partitioned between heat production and gains in body tissues, principally protein and fat. The laws of growth that govern this partition are discussed. The apparent energy costs of protein and fat deposition in rats and pigs are about 53 kJ/g. Heat production is, however, related much more closely to total protein synthesis, most of which takes place in tissues other than ‘meat’. Ways and means of manipulating protein synthesis and the energy cost of growth by nutrition, anabolic agents and anti-microbial growth promoters are considered.     

Commercial moose meat production in SwedenLa production commerciale de viande d'élan en SuèdeGewerbliche produktion von elchfleisch in Sweden

Moose meat is produced commercially in Sweden by the hunting of wild, free-range animals. Extensive forests, continual rejuvenation of the browse resource, a moderate climate, and the relative absence of natural causes of mortality contribute to the maintenance of a large and productive moose population. Hunting rights are owned by the landowner and both hunting rights and harvested animals are marketed. Exported moose meat is federally inspected and carcasses are processed in federally approved abattoirs. One commercial operation studied in detail in 1979 had fewer than 1% of its processed carcasses condemned. All traumatized tissue was removed from carcasses during processing. Weight loss associated with carcass cooling plus removal of traumatized tissue averaged 10% of fresh carcass weight. The average retail value of boneless moose meat sold on the Swedish market in 1979 was approximately U.S. $10.00 per kg. The annual moose harvest in 1981 totalled 152 000 animals with an estimated total carcass yield of 19.7 million kg. The present level of commercial production is insufficient to meet the demands of foreign or domestic markets. Not all harvested moose are marketed, however, and the commercial sale of moose meat is increasing, a trend that will probably continue if the recent levels of moose harvest are maintained.     

New perspectives in animal breeding by embryo manipulationNouvelles perspectiveas de l'amélioration génétique des animaux par la manipulation d'embryonsNeue perspektive in der tierzucht mittels embryomanipulation

Micromanipulation of embryos may provide a new and valuable biological tool for animal breeders, but its routine application is still some way off. However, once practicable, the economic and scientific value should be considerable. Various possibilities, their chances of realization and the low success rate are discussed, along with their uses in animal breeding: complete homozygosity, multiplication of the same genotype, effect of extraneous genes or cells in one organism, preservation of genotypes and sex diagnosis.     

Genetic aspects of female fertility in dairy cattleAspects genétiques de la fertilité des femelles chez bovins laitiersGenetische aspekte der weiblichen fruchtbarkeit von milchrindern

The problem area of female fertility in dairy cattle has been discussed, especially as regards its genetic variation and correlation with production, in the light of recently published results. Furthermore, the implications for selection of the parameters found have been illuminated.It is concluded that the magnitude of the additive genetic variance in several fertility traits is considerable, despite the generally low heritability values of individual insemination results. The genetic effect of cow culling within herds for poor fertility is almost negligible, while progeny testing of bulls for daughter fertility offers valuable information for selection purposes.Several recent investigations appear to indicate antagonistic relationships between production and fertility. However, the findings are somewhat ambiguous. When unfavourable, even though not very strong, correlations do exist, detrimental effects on fertility will occur as a consequence of intense long-term selection for yield if the fertility of daughters is not considered simultaneously with production in selection programmes.     

Energetic aspects of feed conversion in growing pigsL'indice de consommation chez le pore en croissanceEnergetische aspekte der futterverwertung beim wachsenden schwein

Feed conversion ratio (FCR), which defines the feed requirement in kg per kg body weight gain, is an important measure for judging the economic and breeding performance of a fattening pig. It is dependent on many different factors which include (1) the level of feeding, which affects the maintenance requirements, (2) the energy value of the ration and (3) the energy concentration of the body weight gains (c_g). The influence of these factors on FCR and, in general, on growth performance, is discussed using results from growth and balance experiments. Some inter-relationships between the factors are described and integrated into a model which predicts FCR.An increase in the level of feeding can reduce FCR. Experimental results indicate that the ad libitum fed pig has a lower maintenance requirement than the restrictively fed animal due to a reduction in its physical activity. As the level of feeding increases, there is usually a rise in c_g and an accompanying decline in FCR. However, FCR is only a useful indicator for judging the energetic efficiency of growth when c_g is known. A small FCR is only found when body weight gains are high and c_g low.     

Problems in estimating maternal effectsProblèmes posés par l'estimation des effets maternelsProbleme der schätzung maternaler effekte

The basic problems inherent in the estimation of maternal effects are considered. A maternal effect is defined as an effect contributed to the phenotypic value of an offspring by his dam. The two most important problems are the confounding of the maternal effect of the dam and her genetic contribution to the genotypic value of her offspring and the possibility of a negative genetic correlation between the direct and maternal effect. The literature on maternal effect theory is reviewed. A general genetic model for the study of maternal effects is developed. Then problems arising in the estimation of genetic variance and covariance using covariances between relatives are studied and the examination of problems arising in the estimation of maternal effects for genetic groups and their cross combinations are considered.     

Immunization against 5α-androstenone in boarsL'immunisation contre la 5-androsténone chez le verratImmunisierung gegen 5α-Androstenon in Ebern

The effects of specific immunization against 5α-androstenone have been examined in large, genetically homologous groups of boars reared either to bacon weight (90–95 kg live weight) or to heavy manufacturing weight (115–120 kg live weight). At the lighter weight, immunization significantly (P < 0.05) reduced the concentration of androstenone in the adipose tissue from a mean value of 1.77 (S.E. 0.2) μg g^?1 fat in untreated boars (n=39) to 1.10 (S.E. 0.18) μg g^?1 for animals (n=19) treated with 5α-androstene-3-BSA. In contrast, boars (n=20) treated with 5α-androstenone-11-BSA as immunogen accumulated androstenone to a level of 1.99 μg g^?1 fat (S.E. 0.38). At the heavier weight, immunization reduced the accumulation of androstenone in adipose tissue from a mean value of 1.81 μg g^?1 fat (S.E. 0.22) in untreated boars (n=76) to 1.17 μg g^?1 (S.E. 0.19) for animals (n=22) treated with androstene-3-BSA as immunogen. In contrast, boars (n=21) treated with androstenone-11-BSA as immunogen accumulated androstenone to a mean level of 1.74 μg g^?1 fat (S.E. 0.46). No detrimental side-effects were observed in the immunized animals and the advantages of male-type performance and carcass composition were fully preserved.     

Halothane-induced malignant hyperthermia in Irish pig breedsHyperthermie maligne induite par l'halothane dans les races porcines irlandaisesHalothan induzierte maligne hyperthermie bei Irischen schweinerassen

A total of 567 young pigs entering one of the national testing stations were tested for sensitivity to halothane between October 1976 and May 1978. They included 443 Landrace, 76 Large White and 48 Irish Welsh. The average weight at testing was 25.6 kg. A total of 24 pigs reacted positively to the test, 21 (4.6%) of the Landrace and 3 (6.3%) of the Irish Welsh. No reactors were found in the Large White breed.Meat quality estimates in the form of the pH in the longissimus dorsi muscle 45 min post-mortem (pH₁) were recorded on the 324 slaughtered pigs. Reactor pigs (ten) had significantly lower values than non-reactors, indicating a greater tendency to develop quality problems such as pale, soft, exudative (PSE) meat. There was an indication that reactor pigs might have slightly reduced daily gains and lower backfat thickness.     

Means of assessing the adequacy of nutrition of pregnant ewesMéthodes d'appréciation de l'état nutritionnel des brebis gestantesMöglichkeiten der Einschätzung einer nicht angemessenen ernährung bei tragenden mutterschafen

The adequacy of nutrition of pregnant ewes can be assessed by means of changes in body condition and live weight, particularly during early (0–30 days) and mid- (30–90 days) pregnancy. In late pregnancy (90–147 days), however, the rapid growth of the foetus makes changes in live weight difficult to interpret, while the time taken to detect meaningful changes in body condition may well be too great to allow any necessary increases in nutrition to be made at the proper time. A means of regulating food inputs according to levels of blood metabolites, such as plasma 3-hydroxybutyrate concentrations, to maintain within prescribed limits the degree of undernutrition known to be consistent with satisfactory lambing results, has been shown to be practicable in both individual feeding and flock situations (1.1 and 0.8 mmol 3-hydroxybutyrate per litre, respectively).     

A comparison of the mitogenic effects of a phorbol ester on lymphocytes from bovine spleen,lymph node and peripheral bloodComparaison des effets mitogenes d'un ester de phorbol sur des lymphocytes bovins de rate,de ganglions lymphatiques et de sang peripherique

A comparison of the mitogenic effects of a phorbol ester on lymphocytes from bovine spleen, lymph node and peripheral blood.Bovine lymphocytes from three tissues, lymph node, spleen and peripheral blood were compared for their mitogenic responses to 12-O-tetraecanoylphorbol-13-acetate (TPA), a phorbol ester tumor promoter. TPA alone was found to be either not mitogenic or caused only a weak response when compared with the mitogenic lectin phytohemagglutinin (PHA). Of the three lymphocyte preparations, blood cells showed the greatest proliferative response to TPA. However, all three, lymph node, blood and spleen cells, showed a co-mitogenic response to TPA. That is, TPA synergistically enhanced DNA synthesis in cells stimulated with a suboptimal concentration of PHA.     

Hormonal control of oestrous cycle in the ewe (a review)Contrôle hormonal de l'oestrus chez la brebis: revueHormonelle Kontrolle des Brunstzyklus beim Mutterschaf

During the cycle, the secretion of progesterone by the corpus luteum inhibits the positive feedback of oestrogens and thus prevents the LH discharge, and also primes the central nervous system for oestrous behaviour. Prostaglandin F_2α has been identified as the hormone produced by the uterus which causes luteal regression. The LH discharge leading to ovulation follows the demise of the CL. None of the characteristics of the LH surge (duration, maximum level, total release) can be related to ovulation rate. However, the interval from onset of oestrus to the beginning of the LH discharge is greater in highly prolific breeds than in less prolific ones.The knowledge of these physiological processes leading to oestrus and ovulation makes possible the control of ovarian activity in the ewe. In cyclic females, the control of the timing of the LH discharge and ovulation can be obtained either by inducing luteolysis with PGF_2α or its synthetic analogues after day 4–5 of the cycle, or by artificially lengthening the luteal phase with exogenous progesterone or progestagens.During the seasonal and post-partum anoestrus, PGF_2α is ineffective and progesterone or progestagens alone are generally unable to induce oestrus and ovulation. Addition at the end of progestagen treatment of inducers of follicular growth and LH release is necessary. Both PMSG and synthetic GnRH are used for this purpose.     

Immunizing efficacy of Toxoplasma gondii strains isolated from different hostsEfficacite d'immunisation par differentes souches de Toxoplasma gondii isolees de differents hotes

Studies were carried out to determine the fate of virulent Toxoplasma gondii challenge in immune animals. Toxoplasma strains isolated from human, swine, rabbit and cat hosts were used for the primary immunization of mice. Brains were removed at various intervals after the challenge and subinoculated into normal mice. Prior immunization with one of the nine toxoplasma strains enabled the mice either to eliminate or harbour the challenge organisms without loss of virulence. The outcome of challenge infection was dependent on the parasite strain used for the immunization and the time interval between challenge and subinoculation. Mice immunized with strain KSU isolated from a cat eliminated repeatedly administered challenge from 80% of animals. Strain S 162 isolated from a swine eliminated similar challenge from only 20% of animals. The results indicate that the extent of protection against virulent T. gondii can vary widely and is related to the immunogenicity of the original immunizing strain.     

Genetic and environmental aspects of the immune responseAspects de la résponse immunitaire liés à la génétique l'environmentGenetische und umweltbedingte aspekte der immunreaktion

The main characteristic of the immune system is the potency to detect and resist invasions of foreign substances such as viruses, bacteria, parasites and transformed malignant cells. This ability is characterized and determined mostly by macrophage activity and T and B lymphocytes.These three major components of the immune response are independently genetically regulated. This makes selection on the basis of the immune response difficult.Environmental factors can induce stress situations which result in high blood corticosteroid levels. Corticosteroids can be immunosuppressive. In modern animal husbandry practice such factors exist and can influence disease resistance resulting in multifactorial diseases.     

Complete diallel cross between five strains of Atlantic salmonCroisement diallèle complet entre cinq souches de saumon de l'AtlantiqueVollständige diallele paarung zwischen fünf herkünften des Atlantik- lachses

The effect of cross-breeding on survival, growth and maturity when crossing five Norwegian strains of Atlantic salmon has been investigated. A diallel cross including purebred strains and their reciprocal crosses was used. Additive, maternal and heterosis effects were studied. Total heterosis was partitioned into average, general and specific heterosis. Growth of maturing and immature males and females was also considered.Significant total heterosis was found for survival of fry, survival of fish after marking (marked at one year of age), body weight of fingerlings and body weight of adults. However, average heterosis was low for all traits. For survival of eyed-eggs, alevins and fingerlings, dressing percentage and maturity, total heterosis was not significantly different from zero.It is concluded that cross-breeding Norwegian strains of Atlantic salmon seems to have little practical significance in a future breeding program.     

Inbreeding and the inheritance of fertility in the thoroughbred mareLa consanguinité et l'hérédite de la fertilité chez la jument de pur sangInzucht und vererblichkeit der fruchtbarkeit bei voliblutstuten

The reproductive efficiency of the thoroughbred mare in Britain and Ireland is low Weatherby's General Stud Book shows an average annual foaling rate of 67%. The primary aim of this study was to measure the extent to which the poor foaling rate was attributable to inbreeding. Coefficients of inbreeding were calculated and lifetime reproductive histories were assembled for 6550 mares at stud in Britain and Ireland in the early 1960s. The average degree of inbreeding for the five most recent generations was found to be only 0.01, there was little variation among animals in amount of inbreeding, and the mating of sibs or parents and offspring was rare. Coefficients of total inbreeding were calculated for a group of 60 mares. For the 21.5 recorded generations from the foundation of the breed in the seventeenth century to 1964 the average degree of inbreeding was 0.125. There was considerable variation among estimates for different animals, but this was mainly attributable to sampling within pedigrees.Each mare's lifetime reproductive performance was summarised as the proportion of her successful years at stud, adjusted for the decline in fertility with age, scaled to have an average of 1.0, and transformed to stabilise variance. An analysis of variance of the resulting fertility measures was carried out. Recent inbreeding was not an important source of variation in fertility since the mating of close relatives was rare.Although lower fertility was associated with inbreeding, the effect was not statistically significant. The largest source of variation in fertility was the number of years at stud and there were significant differences among year of birth groups. In addition, there were significant differences among groups of paternal half sibs, and the heritability of fertility was estimated as 0.077 ± 0.030. Over the recorded history of the breed it is probable that selection, both natural and artificial, has counteracted any effect of inbreeding on fertility.     

Changes in the phenotype for halothane sensitivity in pigsChangement du phénotype de sensibilité, à l'halothane chez le porcPhänotypische veränderungen in der empfindlichkeit auf halothan bei schweinen

One hundred-and-one hybrids of the Canadian Landrace, Large White, Belgian Landrace and Duroc breeds were repeatedly tested for sensitivity to halothane at the age of 8–15 weeks. Changes in the number of reactors were recorded in the experiment. The number of reactors was 40 in the first test, 33 in the second and 30 in the third. Two individuals changed from non-reactors to reactors; 12 reactors assessed by the standard halothane test ceased to differ during repeated tests from non-reactors. However, these individuals with secondary non-reactivity transmitted halothane-sensitivity to the progeny.     

Comparison of several sire evaluation methods in dairy cattle breedingComparison de différentes méthodes d'évaluation des tauraux en élevage laitierVergleich verschiedener Methoden für die Zuchtwertschätzung von Bullen in der Milchviehzucht

The objectives are discussed of sire evaluation where AI is used but herd sizes are small. In every evaluation scheme, the question arises as to what kind of information should be used, apart from daughter records. Further, we have to consider whether it is worthwhile to wait for the second lactation of the daughters. In sire evaluation, we are nearly always concerned with several traits, and the usual way of getting the aggregate genetic-economic value of an animal is by the application of an index ignoring any correlations between traits. Though that is not optimal, the loss in efficiency is unlikely to be large. Another important point is the determination of the appropriate classification within which the comparison should be made, e.g. should we use herd-year-seasons or herd-years or even group the herds by mean yields. The herd mate method, the contemporary comparison method, the modified cumulative difference method, least squares, regressed least squares and BLUP are discussed, and their relationships to each other are pointed out.     

A review of requirements of dairy and beef cattle for major elementsLes besoins en éléments majeurs des bovins de production laitière et de viande: une revue bibliographiqueDer bedarf von milch- und fleischrindern an mengenelementen

The estimates of the needs of cattle for macro-elements vary widely between the different committees, most variation being seen in the values for calcium and phosphorus and between those of United Kingdom Agricultural Research Council and other published systems. The main factors responsible are the values adopted for the absorbability of calcium in the diet and for the maintenance requirements of phosphorus.Agricultural Research Council have adopted a value of 0.68 to convert net into dietary calcium requirements. This value represents the maximum efficiency of absorption of dietary calcium and was derived from balance trials. Other systems have derived a figure based on values from radioactive studies which rarely exceed 0.45. Agricultural Research Council used a figure of 12 mg kg^?1 liveweight day^?1 for the minimum maintenance value of phosphorus. This value has subsequently been shown to apply only to situations where dietary P is absorbed with high efficiency (0.70–0.80). For other situations maintenance requirements increase as the absorbability of dietary P decreases. For instance, the maintenance requirements of adult cattle increases to 20 mg kg^?1 liveweight day^?1, a value close to those used by other systems.At present there is insufficient information on which to arrive at a scientifically based margin of safety to cover variation in the availability of macro-elements between diets and in the efficiency of absorption amongst animals.     

Heritability of racing ability in thoroughbreds — A reviewHéritabilité de l'aptitude à la course chez le Pur Sang — une revueDie Heritabilität der Renneigenschaften beim Vollblutpferd — eine Übersicht

A survey is made of heritability estimates of timing (h² < 0.20), weight handicaps, performance rates and earnings (0.30 < h² < 0.40). The problem of genetic progress is then examined because, the progression of record times being slow or inexistent, it has been recognised for many years that the population has reached its selection plateau. Several hypotheses for explaining this phenomenon are reviewed. They can be ranked into two groups: the first includes those hypotheses which assume that the heritability values found correspond to a true genetic variability; and the second includes those hypotheses enumerating the causes of overestimations.In the first analysis, the theory of a reduction of the variance parallel to an increase of the mean, according to which high heritabilities might be explained without any observation of progress during important races, is not confirmed. In addition, it also does not seem to be justifiable to assume that the breed fights against fitness. However, it is to be noticed that there is no contradiction between the slow progress of record times and low heritability values of timings, especially as selection is not made directly on timing measures, but on race performance criteria with which they are not necessarily strongly correlated (a correlation of about ?0.50 only).In the second analysis, many sources of heritability overestimation can be pointed out: assortative mating, high homogeneity of the harems and distribution of environmental effects according to the quality of the parents.These considerations lead to the question of the genotype-environment correlation, which should not deliberately be discarded in the case of thoroughbreds.     

Levels of investment in testing the genetic improvement of livestockNiveau des investissements dans le testage pour l'amélioration génétique du bétailUmfang des prüfungsaufwandes bei der genetischen verbesserung landwirtschaftlicher nutztiere

The general form of the response curve for benefits (discounted returns—costs) expected from different levels of investment in testing and selection has been studied. While costs tend to increase linearly with the level of testing, returns increase log-linearly. Thus there is an optimum level of testing to obtain maximum benefits. However, the response curve has a broad flat top, so a wide range of testing levels are only marginally sub-optimal. At low levels of testing the benefit/cost ratios are high, so the level can be chosen to make livestock improvement competitive with other investment opportunities.In practice, reproductive rate sets upper limits on the rate of genetic change possible. This, and an acceptance of a higher rate of inbreeding, may allow small breeding enterprises to make almost as much genetic improvement as large breeding programmes. Excessive testing, and duplication of selection effort, may be wasteful, while diversification to alternatives as an insurance may be worthwhile.