TL;DR: Cattle exhibiting compensatory growth had higher redness, yellowness, cooking losses, and drip losses, but had lower Warner-Bratzler peak shear force values and the saturated fatty acid content of the fat decreased with the duration of the LGP.
Abstract: Thirty double-muscled Belgian Blue bulls were maintained at a rate of gain of .5 kg/d during four periods of time, 115 (G2), 239 (G3), or 411 (G4) d (low growth period, LGP), before fattening (rapid growth period, RGP). Ten control animals (CG) were fed a diet rich in energy and protein. The G2, G3, and G4 were fed a diet low in energy and protein and the same diet as CG during RGP. Live weight was recorded biweekly, feed intake (FI) daily, and nitrogen balance at three times for each group. At the slaughterhouse, the 7, 8, and 9th ribs were removed to determine carcass composition, meat quality, and meat and fat composition. Compensatory growth reached a maximum 2 mo after refeeding and then decreased rapidly, leading to a sharp increase in the feed conversion ratio. Nitrogen balance was higher in compensating groups ( P < .05). Compensating animals had higher carcass connective and adipose tissue contents (P < .05) but lower meat fat content (P < .05). Cattle exhibiting compensatory growth had higher redness, yellowness, cooking losses, and drip losses, but had lower Warner-Bratzler peak shear force values. The saturated fatty acid content of the fat decreased with the duration of the LGP. During the first 2 mo after refeeding, compensatory growth in double-muscled bulls was ascribed to one or more of the following mechanisms: higher FI, lower maintenance requirements, or better efficiency of lean meat production. Compensatory growth at the expense of higher FI increased peripheral fat but decreased intramuscular fat deposition.
TL;DR: The role of plasma IGF-I during compensatory growth is not clear and must be explained in connection with changes of its binding proteins, which seem to have a permissive effect on growth.
Abstract: Growth is an integrated process, resulting from the response of cells dependent on the endocrine status and nutrient availability. During feed restriction, the production and secretion of growth hormone (GH) by the pituitary gland are enhanced, but the number of GH receptors decreases. Changes of GH binding proteins induce GH resistance and are followed by reduced insulin-like growth factor-I (IGF-I) secretion. On the other hand, high circulating levels of GH enhance the mobilization of fatty acids, which are used to support energy requirements. Thus, when feed restriction in growing animals is moderate, there is mainly protein but barely fat accretion. By contrast, a severe feed restriction enhances the release of catabolic hormones and stimulates, from muscle cells, the liberation of amino acids, which are used by hepatocytes for gluconeogenesis. During refeeding and compensatory growth, the secretion of insulin is sharply enhanced and plasma GH concentrations remain high. This situation probably allows more nutrients to be used for growth processes. The role of plasma IGF-I during compensatory growth is not clear and must be explained in connection with changes of its binding proteins. Thyroxin and 3,5,3'-triiodothyronine seem to have a permissive effect on growth. The simultaneous occurrence of puberty with refeeding can exert a synergistic effect on growth. Initially, compensatory growth is characterized by the deposition of very lean tissue, similar as during feed restriction. This lasts for some weeks. Then, protein synthesis decreases and high feed intake leads to increased fat deposition.
TL;DR: It is now becoming clear that variation in other factors such as the muscle fibre type composition and the buffering capacity of the muscle together with the breed and nutritional status of the animals may also contribute to the observed variation in meat tenderness.
Abstract: Meat quality is a term used to describe a range of attributes of meat. Consumer research suggests that tenderness is a very important element of eating quality and that variations in tenderness affect the decision to repurchase. The present paper highlights recent information on the factors that affect tenderness. While the precise aetiology is not fully understood, a number of factors have been shown to affect tenderness. Of these factors, postmortem factors, particularly temperature, sarcomere length and proteolysis, which affect the conversion of muscle to meat, appear most important. However, it is now becoming clear that variation in other factors such as the muscle fibre type composition and the buffering capacity of the muscle together with the breed and nutritional status of the animals may also contribute to the observed variation in meat tenderness.
TL;DR: 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.
Abstract: 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.
Cites background from "Different periods of feed restricti..."
...Feeding animals at low intake levels, followed by re-alimentation, increases the proportion of subcutaneous lipid, at the expense of intramuscular lipid (Hornick et al. 1998)....
TL;DR: During compensatory growth, protein turn-over was increased and positively related to the length of the ad libitum period as indicated by the concentration of elongation factor-2 (eEF-2) (P).
Abstract: The present experiment was designed to evaluate the effect of different time spans of ad libitum feeding of pigs prior to slaughter after a period of restricted feeding on performance and texture characteristics of the meat. Te n litters of five pigs (Duroc ✕ Landrace ✕ Large White crosses) were allocated to five feeding treatments (AA, R28A42, R43A27, R52A18 and R60A10) at the age of 70 days. AA-pigs were given ad libitum a concentrate diet from day 70 to slaughter at day 140 (approx. 100 kg live weight). R28A42, R43A27, R52A18 and R60A10 pigs were given food at a restricted level (0·6 of ad libitum) for 28, 43, 52 and 60 days, respectively, followed by ad libitum feeding for 42, 27, 18 and 10 days, respectively, until slaughter at day 140. All pigs that had been given food at a restricted level for a period (R28A42, R43A27, R52A18 and R60A10) showed a compensatory growth response in the subsequent ad libitum period. However, only pigs on ad libitum for a minimum of 27 days prior to slaughter (R28A42 and R43A27) had carcass weights and muscle mass similar to that of the control pigs (AA) at slaughter. The restricted feeding increased meat proportion, whereas the feeding strategies had no effect on technological meat quality traits (pH24, drip loss and CIE-colour traits: L*, a* and b*). During compensatory growth, protein turn-over was increased and positively related to the length of the ad libitum period as indicated by the concentration of elongation factor-2 (eEF-2) (P < 0·10), the activity of µ-calpain (P < 0·01) and the myofibrillar fragmentation index (MFI) 1 day post mortem in m. longissimus dorsi (P < 0·08) and the solubility of collagen (P < 0·01). Although not significant, the shear force at day 1 followed the same pattern of improvement as the MFI. The concentration of eEF-2 increased at a faster rate following transition to ad libitum feeding than did the activity of µ-calpain. This suggests that muscle protein synthesis increases at a faster rate after change to ad libitum feeding and reaches the same level as in the control pigs (AA) before muscle protein degradation. This time lag between the increase in protein synthesis and degradation could explain the compensatory growth response and it also suggests that in order to use the compensatory growth mechanism to improve tenderness, the optimal time of slaughter may not coincide with the period of highest growth rates, but may occur at a later stage, when muscle protein degradation is maximal. For pigs slaughtered at 100 kg live weight, we expect muscle protein degradation to be maximal some time beyond 42 days of ad libitum feeding prior to slaughter.
TL;DR: This study shows that double-muscled animals belong to a sub-population of the Belgian Blue breed rather than deviants from the non-double-Muscled animal andFat characteristics of the carcass and meat showed only limited predictive power for meat tenderness and colour.
Abstract: Four hundred and thirty-three double-muscled and two hundred and two non-double-muscled Belgian Blue bulls, with mean cold carcass weights of 470±27 and 414±33 kg, respectively, were studied to investigate the relationships between the SEUROP fat grade, the anatomical fat content in the carcass (adipose tissue) and the chemical fat content in the Longissimus thoracis The relationships between the shear force value and the lightness of the meat and fat characteristics were also studied A moderate correlation was found between the fat characteristics within each data set with correlation coefficients, ranging from 04 to 06 The correlation coefficients increased to 070–085 when the data sets were pooled Fat characteristics of the carcass and meat showed only limited predictive power (R2<015) for meat tenderness and colour This study also shows that double-muscled animals belong to a sub-population of the Belgian Blue breed rather than deviants from the non-double-muscled animal