Beef and dairy products suffer from a negative health image, related to the nature of their lipid fraction. Rumen lipid metabolism involves the presence of saturated lipids in ruminant tissues. Lipolysis, fatty acid biohydrogenation and formation of microbial fatty acids in the rumen and their effects on rumen outflow of fatty acids are discussed. Special emphasis is given to the formation of trans-fatty acids and the possibilities of decreasing biohydrogenation. Small differences in intestinal digestibilities of fatty acids are mentioned, followed by a discussion on transfer of absorbed fatty acids into milk and adipose tissue lipids. The preferential retention of polyunsaturated fatty acids as well as the balance between synthesis and incorporation of fatty acids in tissues is described. Dietary means for the modification of milk fat are listed, with special emphasis on the possibilities for enrichment in polyunsaturated fatty acids and the presence of conjugated linoleic acids. A description of the nature and development of fat depots in beef cattle is followed by a discussion of breed, conformation and feed effects on adipose tissue distribution and fatty acid composition. Special emphasis is given to the very lean Belgian Blue double-muscled breed. The review ends with a consideration of the limits to the modification of ruminant fats, involving considerations of consumer acceptance as well as animal welfare and environmental effects.

/pdf/targets-and-procedures-for-altering-ruminant-meat-and-milk-2pnkviyyyj.pdf

Targets and procedures for altering ruminant meat and milk lipids

Molecular biology has enabled the identification of the mechanisms whereby inactive myostatin increases skeletal muscle growth in double-muscled (DM) animals. Myostatin is a secreted growth differentiation factor belonging to the transforming growth factor-β superfamily. Mutations make the myostatin gene inactive, resulting in muscle hypertrophy. The relationship between the different characteristics of DM cattle are defined with possible consequences for livestock husbandry. The extremely high carcass yield of DM animals coincides with a reduction in the size of most vital organs. As a consequence, DM animals may be more susceptible to respiratory disease, urolithiasis, lameness, nutritional stress, heat stress and dystocia, resulting in a lower robustness. Their feed intake capacity is reduced, necessitating a diet with a greater nutrient density. The modified myofiber type is responsible for a lower capillary density, and it induces a more glycolytic metabolism. There are associated changes for the living animal and post-mortem metabolism alterations, requiring appropriate slaughter conditions to maintain a high meat quality. Intramuscular fat content is low, and it is characterized by more unsaturated fatty acids, providing healthier meat for the consumer. It may not always be easy to find a balance between the different disciplines underlying the livestock husbandry of DM animals to realize a good performance and health and meat quality.

https://www.mdpi.com/2076-2615/2/3/472/pdf

Double Muscling in Cattle: Genes, Husbandry, Carcasses and Meat.

Relationship between fat depots in carcasses of beef bulls and effect on meat colour and tenderness.

Effect of dietary energy and protein levels on fatty acid composition of intramuscular fat in double-muscled Belgian Blue bulls.

The effect of breed-production systems on the myosin heavy chain 1, the biochemical characteristics and the colour variables of Longissimus thoracis from seven Spanish beef cattle breeds

Summary

Six normal-conformation and six double-muscled Belgian White-blue bulls were involved in a 2 × 2 × 2 factorial experiment to investigate the effect of genotype (normal versus double-muscled), body weight (400 versus 600 kg) and dietary crude protein (135 versus 165 g per kg dry matter) on voluntary feed intake, digestion and its consequences on the nutritive value, metabolites in blood and urine and nitrogen retention. The diet consisted of concentrate and maize silage (50:50, dry matter basis) and was fed ad libitum. Double-muscled bulls showed a significantly lower feed consumption (67.1 g DM per kg W0.75) compared to normal bulls (81.5 g). When adjusted for dry matter intake, digestibility was not affected by beef type. Some feed components tended to be better digested when body weight (crude fibre and nitrogen-free extractives) or dietary crude protein content (dry matter, organic matter, crude protein, nitrogen-free extractives and energy) were higher. Blood urea nitrogen was not dependent on genotype, but increased with body weight and dietary protein. Creatinine concentration in the blood and daily creatinine excretion in the urine were highest in double-muscled bulls and heavier animals. Urinary 3-methylhistidine excretion was not different between double-muscled and normal bulls, but increased with body weight. This was confirmed by the fact that nitrogen retention relative to intake was similar for both beef types and decreased with a higher body weight. A negative effect of stress on feed intake, muscle protein degradation and nitrogen retention in double-muscled bulls was not excluded.



Zusammenfassung

Einflus von Genotyp, Lebendmasse und Proteingehalt der Ration auf Futteraufnahme, Verdaulichkeit, Metaboliten im Blut und Harn und Stickstoffbilanz.



Der Einflus von Genotyp (konventionell oder Doppellender), Lebendmasse (400 und 600 kg) und Proteingehalt der Ration (135 oder 165 g Rohprotein pro kg Trockensubstanz) auf Verdaulichkeit, Metaboliten im Blut und Harn und Stickstoffbilanz wurde mit 6 konventionellen Bullen und 6 Doppellendern der Belgischen weisblauen Rasse untersucht. Die Ration bestand aus Kraftfutter und Maissilage (50:50 auf Basis von Trockensubstanz) und wurde ad libitum gefuttert. Die Trockensubstanzaufnahme der Doppellender lag niedriger im Vergleich mit den konventionellen Bullen (67, 1 bzw. 81, 5 g pro kg LM0.75). Nach mathematischer Anpassung an die verschiedene Trockensubstanzaufnahme war die Verdaulichkeit nicht durch den Genotyp beeinflust. Die Verdaulichkeit einiger Futterkomponenten lag hoher, wenn die Lebendmasse (Rohfaser, N-freie Extraktstoffe) und der Proteingehalt (Trockensubstanz; Organische Substanz, Protein, N-freie Extraktstoffe und Energie) hoher waren. Die Blutharnstoffkonzentration war nicht abhangig vom Genotyp, aber sie erhohte sich mit der Lebendmasse und dem Proteingehalt. Die Blutkreatininkonzentration und die tagliche Exkretion im Harn lagen hoher bei den Doppellendern und den schweren Tieren. Die 3-Methylhistidinexkretion im Harn war nicht verschieden zwischen Doppellendern und konventionellen Bullen, erhohte sich aber mit der Lebendmasse. Die prozentuale Stickstoffretention war ahnlich zwischen beiden Genotypen nahm aber mit hoherer Lebendmasse ab. Ein negativer Einflus von Stres auf Futteraufnahme, Muskelproteindegradation und Stickstoffretention bei den Doppellendern kann nicht ausgeschlossen werden.

Effect of beef type, body weight and dietary protein content on voluntary feed intake, digestibility, blood and urine metabolites and nitrogen retention

The effect of three protein (77, 97 and 117 g DVE (true protein digested in the small intestine) per kg dry matter (DM)) and two energy levels (7·38 and 8·03 MJ NEF (net energy for fattening) per kg DM) on the performance of Belgian White-blue double-muscled finishing bulls and on the quality of their carcasses and meat was investigated. The diet, offered ad libitum, consisted of 650 g/kg concentrates and 350 g/kg maize silage on DM basis.No significant influence was found of the energy level on the growth rate. The low protein level reduced live-weight gain, from 370 to 501 kg (1·43 kg on average v. 2·60 and 1·66 kg daily; P < 0·02). The growth rate during the entire period (370 to 692 kg) and the live weight at slaughter were significantly influenced by the protein content.The bulls given the high energy level lost less weight during the 20-h fasting period before slaughter. Their carcasses were classified with a higher fatness score and a better conformation. These carcasses had a higher fat content, while the proportion of bone in the carcass was lower than in the low energy groups. The cold carcass weight of the low protein groups (456 kg on average) was significantly smaller than that of the four other groups (470 kg on average). Although no differences between the six groups were found concerning the dressing proportion, this measurement was significantly influenced by the protein level (685 g/kg for low protein v. 692 for high protein). The SEUROP conformation was positively influenced by the protein and the energy level, while the fatness score was influenced only by the energy level (5·5 v. 6·0 for the low and the high energy level, respectively). Although the differences in conformation, fatness score and dressing proportion are significant, because of the small variation, the practical meaning is less important.

The influence of dietary energy and protein levels on performance, carcass and meat quality of Belgian White-blue double-muscled finishing bulls.

Zusammenfassung

Zum Einflus des Proteingehaltes auf Gewichtsentwicklung, Schlachtkorper- und Fleischqualitat, Hormongehalt im Blut und Stickstoffbilanz bei Belgischen weisblauen Doppellenderbullen.



Der Einflus von drei Proteingehalten auf Gewichtsentwicklung, Schlachtkorper- und Fleischqualitat wurde mit 24bzw. 51 Belgischen weisblauen Doppellenderbullen zwischen 375 und 720 kg in zwei aufeinanderfolgenden Jahren untersucht. Der Proteingehalt der Rationen betrug 77 (L), 85 (M) und 97 (H) g darmverdauliches Protein (DVP), oder 137, 146 und 166 g Rohprotein pro kg Trockensubstanz. Zu Beginn lag die tagliche Lebendmassezunahme der Gruppe L mit 1,41 kg niedriger als die der Gruppen M und H mit 1,48 kg. Danach kompensierten die Tiere von Gruppe L teilweise die Minderzunahmen, so das die tagliche Zunahme fur die ganze Versuchsdauer nicht unterschiedlich war (L: 1,30 kg; M und H: 1,34 kg). Die tagliche Aufnahme an Trockensubstanz und Energie pro kg LM0,75wurden nicht durch einen erhohten Proteingehalt beeinflust, dagegen war der Futteraufwand pro kg Zuwachs leicht reduziert. Die Schlachtkorperqualitat zeigte keine wesentlichen Unterschiede. Ein Proteingehalt uber 77 g DVP oder 137 g Rohprotein in der Ration verbesserte die Produktionsmerkmale nicht. Hohere Proteingehalte reduzierten die Konzentration von Thyroxin und Trijodthyronin im Blutserum. Stickstoffbilanzen mit 6 zusatzlichen Bullen bei 400 und 600 kg Lebendmasse zeigten eine 32% hohere Stickstoffretention fur den hochsten Proteingehalt (54.3 g/Tag) im Vergleich mit dem niedrigsten Proteingehalt (41 g/Tag). Dieser Effekt konnte nicht gesichert werden wegen der grosen Variation. Die Stickstoffausscheidungen waren erhoht.

Effect of protein level on performance, carcass and meat quality, hormone levels and nitrogen balance of finishing Belgian white‐blue double‐muscled bulls

D. F. Bogaerts

Papers

Effect of beef type, body weight and dietary protein content on voluntary feed intake, digestibility, blood and urine metabolites and nitrogen retention

The influence of dietary energy and protein levels on performance, carcass and meat quality of Belgian White-blue double-muscled finishing bulls.

Effect of protein level on performance, carcass and meat quality, hormone levels and nitrogen balance of finishing Belgian white‐blue double‐muscled bulls

O125 Use of alternative protein sources to replace soybean meal and its impact on broiler performance