The objective of this study was to investigate the growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality. Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus as a beef type, Galloway as a hardy type, Holstein Friesian as a dairy type, and double-muscled Belgian Blue as an extreme type for muscle growth were used. Between 5 and 17 bulls of each breed were slaughtered at 0, 2, 4, 6, 12, 18, and 24 mo of age. Muscle fiber traits were determined and classified by computerized image analysis, and several measures of meat quality were also determined, including shear force value, meat color, and i.m. fat content. The postnatal growth of semitendinosus muscle in cattle was characterized by a nearly 10-fold increase of muscle fiber area from birth to 24 mo of age. In the first few months after birth, a transformation of type IIA fibers into IIB fibers was found, whereas type I fibers were nearly unaffected by age. The apparent total muscle fiber number of semitendinosus muscle did not increase during postnatal life. These results confirm that the fiber number is determined in embryonic development. Throughout the study, the double-muscled Belgian Blue (BBDM) bulls had almost twice the fiber number of the other breeds, emphasizing a more extensive hyperplasia of muscle fibers during embryonic development in BBDM compared with the other three breeds. The apparent number of type I fibers was, however, not affected by breed, which suggests that the additional fibers found in BBDM postnatally were type IIB and IIA fibers. We did not find significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM. Having pooled the four breeds, paler meat was related to a higher frequency of type IIB fibers, a lower area of type IIA and type I fiber, and a higher total muscle fiber number. These findings based on data of double muscling give us some hints for biological causes for the variation of meat quality. Further investigation, in particular within each breed, is necessary to identify the superior fiber traits for bovine meat production.

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Abstract. The objective of this study was to investigate the phenotypical differences in feed conversion, carcass composition, and meat quality of two cattle breeds representing either the accretion type (Charolais) or the secretion type (Holstein). Eighteen Charolais bulls and 18 German Holstein bulls were raised and fattened under identical conditions on a high energy level with concentrates and hay. The animals were slaughtered at the age of 18 months. Charolais bulls had a body weight (BW) of 750.6 kg and an average daily gain (ADG) of 1377 g. German Holstein bulls were 84.7 kg lighter with an ADG of 1197 g. The energy expense per kg BW gain was 14% lower in the Charolais bulls compared with German Holstein. Charolais bulls gained more energy in protein than the Holstein bulls and needed less energy per kg protein gain in the hot carcass weight (HCW). The Charolais bulls showed a greater carcass weight and a higher yield grade as well as a greater cross sectional area of the M. longissimus dorsi (LD). Holstein bulls showed a greater marbling score, darker color, and more water binding capacity of the LD. The Holstein bulls gained more subcutaneous, intramuscular, and visceral fat during growth, which reflects the ability of the Holstein as a dairy breed to deposit fat as an energy source for milk production and points out the capability of Charolais for extended protein accretion. The genetic background of the recorded different nutrient utilization and turnover will be investigated in further experiments.

Livestock populations are usually kept in groups. As a consequence, social interactions among individuals affect productivity, health, and welfare. Current selection methods (individual selection), however, ignore those interactions and yield suboptimal or in some cases even negative responses. In principle, selection between groups instead of individuals offers a solution, but has rarely been adopted in practice for two reasons. First, the relationship between group selection theory and common animal breeding concepts, such as the accuracy of selection, is unclear. Second, application of group selection requires keeping selection candidates in groups, which is often undesirable in practice. This work has two objectives. First, we derive expressions for the accuracy of individual and group selection, which provides a measurement of quality for those methods. Second, we investigate the opportunity to improve traits affected by interactions by using information on relatives kept in family groups, while keeping selection candidates individually. The accuracy of selection based on relatives is shown to be an analogy of the classical expression for traits not affected by interactions. Our results show that selection based on relatives offers good opportunities for effective genetic improvement of traits affected by interactions.

BackgroundMeasures of the expected genetic variability among full-sibs are of practical relevance, such as in the context of mating decisions. An important application field in animal and plant breeding is the selection and allocation of mates when large or small amounts of genetic variability among offspring are desired, depending on user-specific goals. Estimates of the Mendelian sampling variance can be obtained by simulating gametes from parents with known diplotypes. Knowledge of recombination rates and additive marker effects is also required. In this study, we aimed at developing an exact method that can account for both additive and dominance effects.ResultsWe derived parent-specific covariance matrices that exactly quantify the within-family (co-)variability of additive and dominance marker effects. These matrices incorporate prior knowledge of the parental diplotypes and recombination rates. When combined with additive marker effects, they allow the exact derivation of the Mendelian sampling (co-)variances of (estimated) breeding values for several traits, as well for the aggregate genotype. A comparative analysis demonstrated good average agreement between the exact values and the simulation results for a practical dataset (74,353 German Holstein cattle).ConclusionsThe newly derived method is suitable for calculating the exact amount of intra-family variation of the estimated breeding values and genetic values (comprising additive and dominance effects).

The objective of this study was to investigate the growth- and breed-related changes of marbling characteristics in cattle. Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus, as a typical beef cattle; Galloway, as a smaller, environmentally resistant beef cattle; Holstein-Friesian, as a dairy-type cattle; and double-muscled Belgian Blue, as an extreme type for muscle growth, were used. These 4 breeds were expected to have differences in muscle development and i.m. fat deposition. Between 5 and 15 bulls of each breed were slaughtered at 2, 4, 6, 12, or 24 mo of age. Marbling characteristics were determined and classified in LM and semitendinosus muscle by computerized image analysis. Among breeds, differences appeared in the quantity, structure, and distribution of the marbling flecks in both muscles. The deposition of fat in the double-muscled Belgian Blue bulls remained substantially inferior to that of the other breeds, up to the age of 24 mo. Marbling in German Angus bulls particularly showed larger (P < 0.05) marbling fleck areas. Galloway cattle had the greatest (P < 0.05) number and the most regular (P < 0.05) distribution of the marbling flecks in young animals. Furthermore, for marbling characteristics in Holstein-Friesian animals, a great number and slightly finer structure were observed compared with the other breeds investigated. Postnatal growth-related changes of marbling in LM were characterized by as much as a 40-fold increase in the number of marbling flecks from 2 to 24 mo of age but also by up to a 4-fold enlargement in the area of the marbling flecks. The structure of marbling flecks was determined by 2 development trends. On the one hand, the marbling flecks became larger (P < 0.05), and the structure became coarser, which was reflected by an increasing (P < 0.01) proportion of long marbling flecks as well as an increasing (P < 0.01) maximum skeleton line length. On the other hand, continually new small, round marbling flecks appeared. This caused a decrease (P < 0.01) in the proportion of the 3 largest marbling fleck areas. The distribution of the marbling flecks became more regular (P < 0.05) with increasing proportion and number of marbling flecks. The results suggest that hyperplasia of adipocytes plays an important role in marbling during growth of muscle in cattle.

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