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

Crossbred young bulls and heifers sired by double-muscled Piemontese or Belgian Blue bulls exhibit different effects of sexual dimorphism on fattening performance and muscularity but not on meat quality traits

As double-muscled Belgian Blue (BB) and Piemontese (PIEM) breeds are heavily selected for different objectives (the former mainly for muscularity, the latter for ease of calving), the aim of this study was to compare sexual dimorphism in 56 crossbred young bulls and heifers obtained from dairy cows mated to bulls of the two beef breeds. Young PIEM- and BB-sired bulls had similar fattening performances and beef traits, although the BB crossbreds were slightly more muscular. Otherwise, the BB-sired heifers exceeded the PIEM-sired heifers in growth rate (1.12 vs. 0.98kg/d), feed efficiency (0.129 vs. 0.121kg/kg DM), increases in muscle scores (1.45 vs. 0.98 SEUROP scores) and carcass yield (0.612 vs. 0.605), but not in fatness, retail cut proportions and meat quality traits. Sexual dimorphism is, therefore, less distinct in BB than in PIEM crossbreds. In conclusion, BB sires are to be preferred for "product quality", and PIEM sires for "process quality", on account of welfare and ethical issues.

Different modes of food restriction and compensatory growth in double-muscled Belgian Blue bulls: animal performance, carcass and meat characteristics

Fifty double-muscled Belgian Blue bulls were divided into five groups. The first group (control, CG) was given, on an ad libitum basis, a fattening diet based on sugar-beet pulp. In G2 and G3, fattening was interrupted 103 and 187 days, respectively after the beginning of the experiment, by approximately a 2-month period of food restriction during which the animals received a maintenance ration. The last two groups, namely G4 and G5, received for about 4 months a limited amount of the restriction diet to support growth of 0·5 and 0 kg/day, respectively, before being fattened as CG. The average daily gain was 1·48 kg/day in CG v. 1·33, 1·30, 1·43 and 1·61 kg/day during the period of ad libitum feeding in G2, G3, G4 and G5. Higher nitrogen (N) balance during compensatory growth in G2, G4 and G5 (78·8, 81·0 and 74·6 v. 53·3 g N per day in CG, P < 0·001) resulted mainly from a higher efficiency of N retention. In G3, however, compensatory growth was characterized by lower N digestibility and efficiency of N retention. Muscle proportion in the carcass was higher in G3 while fat plus connective tissue proportion was lower (P < 0·05). Muscle pH values in CG were lower than in the other groups (P < 0·01) but ether extract values were higher. The intramuscular fat of G2 and G3 was characterized by higher proportions of polyunsaturated fatty acids.

Phase-feeding to optimize performance and quality of Belgian Blue double-muscled bulls

To optimize performance and carcass quality of Belgian Blue double-muscled bulls four phased feeding regimens were evaluated. All diets were offered ad libitum and consisted of 650 g concentrates and 350 g maize silage per kg dry matter (DM). Total period was divided into three phases (ca. 360 to 460, 460 to 570 and 570 to 680 kg). All four groups received the same maize silage but the different energy and protein densities were applied using different concentrates. During the three phases, the negative control (NC) group constantly received a diet with a low protein and a moderate energy density; the second group (DP) received with each phase diets with decreasing protein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high protein density and the last group (DPIE) received diets which decreased in protein and increased in energy density.

The NC group grew significantly slower during the first interval (1·37 v. 1·62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third period IE had the slowest growth. The NC group needed 21 and 20 days more than the DP and DPIE groups, respectively, to reach the same slaughter weight. The NC group had the lowest DM intake during the first interval, the IE group during the third interval. No significant differences (P > 0·05) were found for food conversion, when expressed as DM or NEF (net energy for fattening). IE had the worst protein conversion while NC had the best, with the two other groups being intermediate.

The only important significant difference concerning carcass quality was the improved dressing proportion of the IE and DP groups. Although significant, differences in the fat content of the m. longissimus thoracis are of minor importance. These results proved that for Belgian Blue double-muscled bulls, protein density of the diet can be decreased with increasing live weight, while energy should be increased to give optimal performance.

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

Seventy six Belgian Blue (BB) bulls, with double-muscled conformation, were randomly allocated to six dietary treatments in a 2 × 3 factorial experiment. The treatments included low (N(L)=127 g CP/kg DM), medium (N(M)=153 g CP/kg DM) and high (N(H)=172 g CP/kg DM) levels of dietary protein in combination with low (E(L)=7.38 MJ ME/kg DM) and high (E(H)=8.03 MJ ME/kg DM) levels of dietary energy. Fatty acid composition was determined on total lipid samples of the M. longissimus thoracis of all animals and on the separated triacylglycerol and polar lipid fatty acid fractions of the medium-protein group. Dietary energy and protein levels influenced the carcass characteristics of BB bulls but the effects were small. Carcass fat cover score, carcass fat content and intramuscular fat content were slightly but significantly higher in the animals on the high versus the low energy diets. The overall intramuscular fat content was very low (<1%) and the overall polyunsaturated:saturated fatty acid ratio (0.39) high compared to normal figures for beef. The high versus the low dietary energy level increased the monounsaturated (P<0.001) and decreased the polyunsaturated (P<0.001) fatty acid proportion with no change in the saturated fatty acid proportion. This may have been due in part to the addition of beef tallow to increase the energy level of the diet. Concomitant shifts in the individual fatty acids included increased proportions of C14:0 (P<0.001), C16:0 (P<0.03), C16:1 (P<0.01), C18:1 (P<0.001) and decreased proportions of C18:2 (P<0.001) and C20:4 (P<0.001). Increasing dietary protein levels had inconsistent effects on the fatty acid profiles. The proportion of polar lipid fatty acids in the total fatty acids was 0.34 and 0.25 for the E(L) and E(H) group, respectively, in the Nm treatment group. Changes in fatty acid proportions of the triacylglycerol fatty acid fraction were similar to those seen in the total lipid fatty acids when related to dietary energy level, but no significant changes in the polar lipid fatty acid proportions were observed. Significant linear relationships were found between measures of carcass and muscle fatness and fatty acid proportions. With increasing muscle total fatty acid content, saturated and monounsaturated fatty acid proportions increased (r=0.38 and r=0.55, respectively, P<0.01) and the polyunsaturated fatty acid proportion decreased (r=-0.73, P<0.01). The diet had some effects but the relatively unsaturated intramuscular fatty acid composition was mainly related to the low total fat content of the BB animals.

Double-muscled and conventional cattle have the same net energy requirements if these are related to mature and current body protein mass, and to gain composition

The hypothesis tested in this paper is that double-muscled (DBM) and conventional cattle, considerably differing in body composition, have similar NE requirements when: a) NE(m) is scaled as a function of current (P(i)) and adult (P(m)) protein mass; and b) ME for gain (ME(g)) is estimated from protein (Pr) and lipid (Lr) retention and their partial ME use efficiencies, the k(p) and k(l) values, respectively. First, 2 databases were examined: 1 was developed combining well known literature information from comparative slaughter trials conducted on British beef steers; the other was based on a trial conducted using extremely lean DBM Piemontese bulls. From the first database, NE(m) was calculated to be 1.625 × P(i) ÷ P(m) × P(m)(0.73) (MJ/kg(0.73)). From the second database, the daily ME(g) was determined as 22.8 MJ × Pr ÷ k(p) + 38.74 MJ × Lr ÷ k(l), assuming (from prior reports) that k(p) = 0.20 and k(l) = 0.75. Thereafter, ME(m) was defined as ME intake minus ME(g), and, hence, NE(m) was predicted as 1.625 × P(i) ÷ P(m) × P(m)(0.73) (where 1.625 was the value obtained from the first dataset). The resulting k(m) (NE(m)/ME(m)) averaged 0.67. This k(m) value did not differ from that (0.65; P = 0.12) predicted by Garrett's equation, which uses dietary ME content as the only predictive variable. Second, the procedure was tested for the ability to detect effects on k(m) caused by increasing BW and dietary factors not estimable from the dietary ME content only. Data were gathered from a trial involving 48 DBM Piemontese bulls divided into 4 groups fed 1 of 4 diets differing in CP content (145 or 108 g/kg DM), with or without addition of 80 g/d of rumen-protected CLA (rpCLA). Bulls were examined at 3 consecutive periods of growth, corresponding to 365, 512 and 631 kg of average BW. All energy balance items were influenced by increasing BW, except k(m) (P = 0.61), in agreement with the expectation that NE(m) requirement depends on the degree of maturity (P(i)/P(m)) and the P(m)(0.73) of an animal, whereas k(m) reflects characteristics of the feed provided. The k(m) value was also influenced by the CP × rpCLA interaction (P = 0.013). We conclude that DBM and British beef steers have similar NE requirements when these are scaled as a function of P(i) and P(m), and gain composition, considering Pr, k(p), Lr and k(l). The proposed procedure will be useful to predict the energy requirements and feed use in cattle of different types that vary in BW, provided that body and gain compositions are known or accurately predicted.

Effects of corn grain particle size and treated soybean meal on carcass and meat quality characteristics of beef steers finished on a corn silage diet

Thirty-nine steers were distributed into a 2 x 2 factorial arrangement of treatments to determine the effect of corn grain particle size (cracked [CC] vs ground [GC] corn) and soybean meal treatment (solvent extracted soybean meal [SS] vs lignosulfonate treated soybean meal Soypass™ [SP]) on carcass and meat quality traits. When CC diet was supplemented with SS carcass quality grade score tended to decrease (P=0.09). GC had no effect on meat quality, while SP only increased the intramuscular fat content when added to CC (P=0.01). The CC diet supplemented with SP increased the proportion of saturated fatty acids (P=0.01). Despite the positive effects on carcass quality, the lack of improvement in meat quality and the more saturated fatty acid profile would not justify the use of processed corn or treated soybean meal in the finishing diet of steers.

Effects of dietary protein level in the early fattening period on free amino acids and dipeptides in the blood and Longissimus thoracis muscle in Japanese Black steers

The effects of crude protein (CP) concentration in feed using soybean meal as its source in the early fattening period on the levels of free amino acids (FAAs) and dipeptides in the blood, and the levels in the M. longissimus thoracis after slaughter were studied in Japanese Black steers. Sixteen steers were divided into four groups and given feed with a CP content of 12, 14, 16, or 18% of dry matter (DM) from 10 to 20 months old, and they were fed with the same level of CP (13.5-13.9% of DM) until slaughter at 30 months of age. There was no significant difference in the weight gain, carcass weight or marbling score between the groups. Concerning the serum FAA and dipeptide contents at 20 months of age, the alanine, tyrosine and tryptophan levels decreased, while the carnosine (Car) level increased, with increases in the CP level in the feed. Although there were no significant differences in the FAA contents of the Longissimus thoracis muscle between the groups, the Car content decreased with increases in the feed protein level.

Effect of breed body size and the muscular hypertrophy gene in the production and carcass traits of concentrate-finished yearling bulls

To examine the extent of the effect of muscular hypertrophy character in beef of northern-Spanish breeds, animal performance and carcass characteristics of 152 finishing steers from 5 genotypes were studied: 32 yearling bulls from a rustic Asturiana de la Montaña (AM) breed, 96 yearling bulls from Asturiana de los Valles (AV) breed, divided in 3 groups depending on the presence of the gene responsible for double-muscling (i.e., 32 AV mh/mh, 32 AV mh/+, 32 AV +/+), and 24 yearling bulls from AM x AV cross were used. Each genotype was composed of 8 animals per year (4 animals per pen) for 4 yr, except for the AM x AV genotype, which was only evaluated in the last 3 yr of the experiment. All animals were fed indoors with concentrate meal and barley straw ad libitum. Average daily gains in AV animals (1.41 kg/d) were greater (P < 0.01) than in AM (1.12 kg/d), whereas AM x AV were intermediate (1.29 kg/d) to these. No significant differences (P = 0.604) in ADG were found among the 3 AV genotypes. Longer fattening periods (P < 0.001) were taken for AM animals to reach acceptable BW at slaughter. Double-muscled animals (AV mh/mh) were found to have the best feed efficiencies when expressed as G:F (P < 0.001). However, residual feed intake calculated on a daily basis showed a greater efficiency in AV mh/mh and AM than in other genotypes. Carcasses from double-muscled animals had greater BW, yield, conformation and compactness index, and less fat cover than the other genotypes (P < 0.001). Carcasses from AM breed were the lightest and had the worst conformation, whereas those from AM x AV generally presented intermediate characteristics between AV and AM. Double-muscled animals had the greatest LM weight and area. The sixth-rib dissection revealed a greater percentage of muscle (84.6%) and decreased percentages of subcutaneous fat (1.1%), intermuscular fat (4.7%), bone (8.5%), and other tissues (1.2%) in AV mh/mh compared with other genotypes. Water-holding capacity was greatest in AM and least in AV mh/mh. In conclusion, double-muscled AV bulls would provide the greatest economic returns at intensive feeding systems because of their greater efficiency, reduced feeding costs, greater carcass weight and conformation, and greater lean yields, though some LM characteristics (reduced fat content and water-holding capacity) could negatively affect the sensory attributes of the meat compared with other genotypes with greater fatness.

Targets and procedures for altering ruminant meat and milk lipids

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.