Intramuscular fat (IMF) content plays a key role in various quality traits of meat. IMF content varies between species, between breeds and between muscle types in the same breed. Other factors are involved in the variation of IMF content in animals, including gender, age and feeding. Variability in IMF content is mainly linked to the number and size of intramuscular adipocytes. The accretion rate of IMF depends on the muscle growth rate. For instance, animals having a high muscularity with a high glycolytic activity display a reduced development of IMF. This suggests that muscle cells and adipocytes interplay during growth. In addition, early events that influence adipogenesis inside the muscle (i.e proliferation and differentiation of adipose cells, the connective structure embedding adipocytes) might be involved in interindividual differences in IMF content. Increasing muscularity will also dilute the final fat content of muscle. At the metabolic level, IMF content results from the balance between uptake, synthesis and degradation of triacylglycerols, which involve many metabolic pathways in both adipocytes and myofibres. Various experiments revealed an association between IMF level and the muscle content in adipocyte-type fatty acid-binding protein, the activities of oxidative enzymes, or the delta-6-desaturase level; however, other studies failed to confirm such relationships. This might be due to the importance of fatty acid fluxes that is likely to be responsible for variability in IMF content during the postnatal period rather than the control of one single pathway. This is evident in the muscle of most fish species in which triacylglycerol synthesis is almost zero. Genetic approaches for increasing IMF have been focused on live animal ultrasound to derive estimated breeding values. More recently, efforts have concentrated on discovering DNA markers that change the distribution of fat in the body (i.e. towards IMF at the expense of the carcass fatness). Thanks to the exhaustive nature of genomics (transcriptomics and proteomics), our knowledge on fat accumulation in muscles is now being underpinned. Metabolic specificities of intramuscular adipocytes have also been demonstrated, as compared to other depots. Nutritional manipulation of IMF independently from body fat depots has proved to be more difficult to achieve than genetic strategies to have lipid deposition dependent of adipose tissue location. In addition, the biological mechanisms that explain the variability of IMF content differ between genetic and nutritional factors. The nutritional regulation of IMF also differs between ruminants, monogastrics and fish due to their digestive and nutritional particularities.

https://researchrepository.murdoch.edu.au/6455/1/fat_content_in_meat%2Dproducing_animals.pdf

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers.

Background Dietary protein , particularly essential amino acids, is important in the adult diet to help the body repair and regenerate cells and is important in the diet of children and adolescents for growth and development. In recent years, consumers are becoming more diverse when choosing foods to consume. Specifically, there is an increase around the world in the population of people who choose to consume a non-meat diet, and eat non-meat foods as their source of protein. Scope and Approach This review focused on comparing nutrient density and nutritional value (based on US dollars) of meat products and non-meat foods high in protein. Twenty-five meat products (beef, pork, lamb, and poultry), six fish products, and eighteen non-meat foods were compared for nutrient composition. Nutrient composition information was used to assign value based on nutrient density. Nutrient cost was expressed in nutrients available per US dollar and prices were assessed from the USDA economic research service and the USDA agricultural marketing service when available, and with a marketplace assessment when information was unavailable otherwise. Key Findings and Conclusions Consideration needs to be made when replacing meat in the diet with non-meat foods, because most non-meat foods contain only 20–60% protein density of meat. Additionally, when protein cost was evaluated, meat and non-meat foods had a similar cost when expressed as grams of protein/US dollar. While the total amount of zinc and iron was similar in meat and some non-meat foods, more investigation of digestibility and availability of nutrients is warranted.

Review: Nutrient density and nutritional value of meat products and non-meat foods high in protein

Halal and kosher slaughter methods and meat quality: a review.

http://a.uan.mx/a/sip/revistas_indexadas/pdf_2012/01_avocado_german.pdf

Avocado, sunflower and olive oils as replacers of pork back-fat in burger patties: Effect on lipid composition, oxidative stability and quality traits

Goat meat production, composition, and quality

The animal fat paradox and meat quality.

The objective of this study was to evaluate the effects of Kosher (Shechita) and conventional slaughter methods on shear force, drip and cooking losses of beef (m. longissimus dorsi samples) from South African feedlot cattle. Results revealed significantly lower shear force values for meat samples from cattle slaughtered by the Kosher method compared to those from cattle slaughtered by the conventional slaughter method. Cooking loss was significantly higher for meat samples from cattle slaughtered in the conventional way compared to those from cattle slaughtered by Kosher method. However, no significant difference was observed for drip loss between slaughter methods. These findings suggest that captive bolt stunning before sticking resulted in higher cooking losses and yielded less tender meat compared to the Kosher slaughter method.

/pdf/influence-of-kosher-shechita-and-conventional-slaughter-2dzmumktt9.pdf

Influence of Kosher (Shechita) and conventional slaughter techniques on shear force, drip and cooking loss of beef

Animal welfare has become an important determinant of meat quality with poor animal temperament leading to huge economic losses to the meat industry due to carcass bruising and condemnation. Handling and transport of live animals is a stressful experience for animals. The temperaments of cattle affect their behaviour and differ between breeds, i.e. studies have shown that Bos indicus types are more temperamental than Sanga and Bos taurus types. Catecholamines (CAT’s) are considered as indicators of stress, because higher concentrations of CAT’s in brain tissue were noted in animals that are better adapted to stressful situations. In the present study, urinary CAT’s of three beef breeds were determined immediately post mortem. Brahman cattle represented Bos indicus types, Simmentaler cattle represented Bos taurus types and Nguni cattle represented the Sanga type. Nguni steers showed higher urinary norepinephrine (NE) and epinephrine (E) concentrations than Brahman and Simmentaler steers. Simmentaler steers showed a higher concentration of urinary dopamine (DA) than Br and Ng. The results suggest that Nguni cattle are less stress sensitive compared to the other beef breeds studied. These observations may be due to the process of domestication and selection for specific genes that influence tameability and consequently resulting in a shift in circulating concentrations of urinary CAT’s. Keywords : Animal welfare, breed divergence, animal temperament, stress

/pdf/urinary-catecholamine-concentrations-in-three-beef-breeds-at-24j7dgf279.pdf

Urinary catecholamine concentrations in three beef breeds at slaughter

In previous reports, Nguni type cattle have shown to have a lower glycolytic potential with less glycogen measured in muscles 1 h post-mortem. With the release of catecholamines in the immediate preslaughter period, there is potential for depletion of muscle glycogen, because of the fact that epinephrine activates muscle adenylate cyclase and thereby stimulates glycogen breakdown. Epinephrine and norepinephrine are secreted as a result of any “fight or flight” situation. Tyrosine is a conditionally non-essential large neutral amino acid and the precursor of the neurotransmitters dopamine, nor-epinephrine and epinephrine. Ante-mortem stress experienced by an animal may be influenced by amino acids that provide substrates for neurotransmitter synthesis. The Nguni type cattle showed 55.8% and 55.1% greater urinary nor-epinephrine values than for the Brahman- and Simmental type cattle respectively. The Nguni type cattle showed 35.6% and 43.8% greater urinary epinephrine values than the Brahman- and Simmental type cattle respectively. The higher urinary nor-epinephrine and epinephrine levels measured in Nguni type cattle could either be explained by a greater neuronal out flux immediately prior to slaughter or a slower re-uptake.

/pdf/the-conversion-of-dopamine-to-epinephrine-and-nor-40zptws5kz.pdf

The conversion of dopamine to epinephrine and nor-epinephrine is breed dependent

Bonsmara type steers were used to determine the effect of dietary zilpaterol hydrochloride (ZH) in combination with different dietary crude protein (CP) levels (100, 120 and 140 g CP/kg) on growth performance and meat quality. Treatment groups (T) consisted of 12 steers each. T1 ‐ 100 g CP/kg + 0.15 mg ZH/kg live weight (LW); T2 ‐ 120 g CP/kg + 0.15 mg ZH/kg LW; T3 ‐ 140 g CP/kg + 0.15 mg ZH/kg LW and T4 ‐ 120 g CP/kg + 0 mg/kg LW. Steers received the diets from an initial LW of 278 kg and fed to a target mass of 390 kg. After a seven day ZH withdrawal period the steers were slaughtered and carcasses electrically stimulated. Samples from m. longissimus thoracis, m. semitendinosus and m. triceps brachii were kept in airtight polyethylene bags and matured for ten days at 4 °C. Zilpaterol treatment increased the average daily gain (ADG) non-significantly (NS) by 9.6%. Zilpaterol treatment improved feed conversion ratio (FCR) by 20% (NS). T2 showed a significant 39.4% improvement in FCR in comparison with T4. Warner-Bratzler shear force (WBSF) of m. semitendinosus and m. biceps brachii samples differed between ZH treated groups. Cooking loss (CL) for m. longissimus thoracis was lower for T2 in comparison with T1, T3 and T4. ZH treatment for 35 days, electrical stimulation and a maturation period of 10 days generally left the WBSF and CL unaffected while the FCR in combination with 120 g CP/kg improved significantly.

/pdf/interactive-effect-of-dietary-protein-level-and-zilpaterol-3pxhz1e8n4.pdf

Interactive effect of dietary protein level and zilpaterol hydrochloride on feedlot performance and meat quality of steers

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