Michael G. Keane

Breeding objectives for beef cattle in Ireland

Abstract Breeding objectives for beef cattle in Ireland were derived and used to define selection sub-indexes. The intention of the sub-indexes was to simplify selection decisions by commercial bull and semen buyers for situations where all of the resulting progeny are slaughtered, or when some female progeny are kept as replacement breeding cows. Separate sets of economic values for calving ease and gestation length are proposed for use in separate calving sub-indexes depending on whether dairy cows or beef cows are to be mated. Proposed economic values for calf quality, growth, calving and reproduction sub-indexes were assumed to be independent of the breed of cow to be mated. It was also recommended that separate total indexes for dairy cow and beef cow matings be constructed as simple linear functions of the sub-indexes.

Beef production from Holstein–Friesian bulls and steers of New Zealand and European/American descent, and Belgian Blue×Holstein–Friesians, slaughtered at two weights

Abstract Various strains of Holstein–Friesian cattle have been imported into Ireland in recent years. The objective of this study was to evaluate for beef production the male progeny of New Zealand (NZ) and European/American (EU) Holstein–Friesians, and Belgian Blue×Holstein–Friesians (BB). The NZ animals were imported from New Zealand as embryos which were implanted into Irish heifers. The EU animals were the progeny by artificial insemination (AI) of high genetic merit Irish cows and high genetic merit European/North American-bred bulls. The BB animals were the progeny both by AI and natural mating of Belgian Blue bulls and Holstein–Friesian cows on commercial farms. A total of 96 spring-born male cattle (32 per genotype) were reared from calfhood to slaughter. They spent their first summer together at pasture and they were then blocked on weight to a 3 genotypes (NZ, EU and BB)×2 production systems (bulls and steers)×2 slaughter weights (550 and 630 kg) factorial experiment. After slaughter, carcasses were measured and the ribs joint was dissected into subcutaneous fat, intermuscular fat, muscle and bone. For NZ, EU and BB, respectively, mean daily gains from arrival to slaughter were 773, 822 and 850 (S.E.D. 9.8) g, mean carcass weights per day from arrival were 425, 459 and 528 (S.E.D. 3.8) g, mean kill-out proportions were 496, 508 and 554 (S.E.D. 2.8) g/kg and mean carcass weights were 284, 302 and 339 (S.E.D. 3.0) kg. Carcass conformation score, carcass fat score, fat depth and m. longissimus area did not differ significantly between NZ and EU, but BB had higher values for carcass conformation and m. longissimus area and lower values for the fatness indicators. Compared with NZ, EU had more muscle and bone and less fat in the ribs joint, while BB had more muscle and less fat and bone than the dairy strains. Bulls had significantly higher slaughter and carcass weights per day from arrival than steers and also had a higher proportion of muscle and a lower proportion of fat in the ribs joint. Delaying slaughter increased slaughter and carcass weights but there was no significant effect on ribs joint composition. It is concluded that EU were slightly superior to NZ for beef production and BB were considerably superior to both dairy strains. Rearing as bulls rather than as steers improved carcass traits and retaining animals to a heavier slaughter weight improved carcass compactness with little effect on rib joint composition.

A comparison of Friesian-Holstein, Piemontese×Friesian-Holstein and Romagnola×Friesian-Holstein steers for beef production and carcass traits

Abstract Recently the Italian Piemontese and Romagnola beef breeds have been imported into Ireland. The objective of this study was to evaluate the progeny of these breeds from Friesian-Holstein dairy cows for beef production. A total of 120 spring-born steers comprised of 40 Friesian-Holsteins (FR), 40 Piemontese×Friesian-Holsteins (PM) and 40 Romagnola×Friesians-Holsteins (RO), born in 2 consecutive years, were reared from calfhood to slaughter at ∼2 years of age. Calves were artificially reared indoors and spent their first summer at pasture towards the end of which they were castrated. They were housed during the first winter and subsequently spent their second summer at pasture. At the start of the second winter they were assigned to a 3 (FR, PM, RO breed types)×2 (low and high feeding levels)×2 (short and extended finishing periods) factorial experiment. The low (L) and high (H) feeding levels were 3 and 6 kg concentrates per head daily, respectively, with grass silage ad libitum. The short (S) and extended (E) finishing periods were 124 and 207 days, respectively. After slaughter, the pistola hind quarter was separated into subcutaneous and intermuscular fats, bone and muscle. For the breed types as listed, mean values for carcass weight per day from arrival, kill-out proportion, carcass conformation score and carcass fat score were 434, 435, and 453 (S.E.D. 7.6) g, 519, 547 and 538 (S.E.D. 3.7) g/kg, 2.1, 2.9 and 2.9 (S.E.D. 0.12), and 4.0, 3.4 and 3.8 (S.E.D. 0.11), respectively. For FR, PM and RO, pistola weight as a proportion of carcass side weight was 447, 462, and 466 (S.E.D. 2.5) g/kg, pistola muscle proportion was 642, 716 and 687 (S.E.D. 4.1) g/kg, and pistola fat proportion was 165, 115 and 137 (S.E.D. 4.0) g/kg, respectively. Compared with L, the H feeding level increased carcass weight and improved carcass conformation but otherwise had few effects on carcass traits. Compared with S, the E finishing period increased carcass weight and all measures of carcass fatness. Allometric growth coefficients relative to carcass side weight for the hind quarter, the distal pelvic limb, the lumbar joint and the ribs joint were all 1.0. It is concluded that the Piemontese and Romagnola beef breeds are suitable for crossing on Friesian-Holstein dairy cows and the progeny are suited to Irish steer beef production systems. Productivity and carcass merit of these beef crosses are superior to those of Friesian-Holsteins. While live and carcass growth rates were higher for RO than PM, both had similar estimated muscle growth rates.

The value of muscular and skeletal scores in the live animal and carcass classification scores as indicators of carcass composition in cattle.

The objective was to determine the relationship of muscular and skeletal scores taken on the live animal and carcass conformation and fat scores with carcass composition and value. Bulls (n = 48) and heifers (n = 37) of 0.75 to 1.0 late-maturing breed genotypes slaughtered at 16 and 20 months of age, respectively, were used. At 8 months of age (weaning) and immediately pre-slaughter, visual muscular scores were recorded for each animal and additionally skeletal scores were recorded pre-slaughter. Carcass weight, kidney and channel fat weight, carcass conformation and fat scores, fat depth over the longissimus dorsi muscle at the 12th (bulls) or 10th (heifers) rib and carcass length were recorded post-slaughter. Each carcass was subsequently dissected into meat, fat and bone using a commercial dissection procedure. Muscular scores taken pre-slaughter showed positive correlations with killing-out rate (r ≈ 0.65), carcass meat proportion (r ≈ 0.60), value (r ≈ 0.55) and conformation score (r ≈ 0.70), and negative correlations with carcass bone (r ≈ -0.60) and fat (r ≈ -0.4) proportions. Corresponding correlations with muscular scores at weaning were lower. Correlations of skeletal scores taken pre-slaughter, carcass length and carcass weight with killing-out rate and the various carcass traits were mainly not significant. Carcass fat depth and kidney and channel fat weight were negatively correlated with carcass meat proportion and value, and positively correlated with fat proportion. Correlations of carcass conformation score were positive (r = 0.50 to 0.68) with killing-out rate, carcass meat proportion and carcass value and negative with bone (r ≈ -0.56) and fat (r ≈ -0.40) proportions. Corresponding correlations with carcass fat score were mainly negative except for carcass fat proportion (r ≈ 0.79). A one-unit (scale 1 to 15) increase in carcass conformation score increased carcass meat proportion by 8.9 and 8.1 g/kg, decreased fat proportion by 4.0 and 2.9 g/kg and decreased bone proportion by 4.9 and 5.2 g/kg in bulls and heifers, respectively. Corresponding values per unit increase in carcass fat score were -11.9 and -9.7 g/kg, 12.4 and 9.9 g/kg, and -0.5 and -0.2 g/kg. Carcass conformation and fat scores explained 0.70 and 0.55 of the total variation in meat yield for bulls and heifers, respectively. It is concluded that live animal muscular scores, and carcass conformation and fat scores, are useful indicators of carcass meat proportion and value.

Genetic parameters for carcass cut weight in Irish beef cattle.

The objective of this study was to estimate genetic parameters for the weights of different wholesale cuts, using an experimental and a commercial data set. The experimental and commercial data sets included 413 and 635 crossbred Belgian Blue, Charolais, Limousin, Angus, Holstein, and Simmental animals, respectively. Univariate analyses using a mixed linear animal model with relationships were undertaken to estimate the heritability of cold carcass weight, carcass conformation and fat, and the cut weights, whereas a series of bivariate analyses was used to estimate the phenotypic and genetic correlations between carcass weight, carcass conformation, carcass fat, and the major primal cuts. Heritability estimates for cold carcass weight in both data sets were moderate (>0.48), whereas heritability estimates for carcass conformation and fat grading were greater in the commercial data set (>0.63) than in the experimental study (>0.33). Across both data sets, heritability estimates for wholesale cut weight in the forequarter varied from 0.03 to 0.79, whereas heritability estimates of carcass cut weight in the hindquarter varied from 0.14 to 0.86. Heritability estimates for cut weights expressed as a proportion of the entire carcass weight varied from 0.04 to 0.91. Genetic correlations were strong among the different carcass cut weights within the experimental and the commercial studies. Genetic correlations between the weights of selected carcass cuts and carcass weight were moderate to high (minimum 0.45; maximum 0.88) in both data sets. Positive genetic correlations were observed in the commercial data set between the different wholesale cut weights and carcass conformation, whereas these were positive and negative in the experimental data set. Selection for increased carcass weight will, on average, increase the weight of each cut. However, the genetic correlations were less than unity, suggesting a benefit of more direct selection on high value cuts.

Predicting beef carcass meat, fat and bone proportions from carcass conformation and fat scores or hindquarter dissection

Equations for predicting the meat, fat and bone proportions in beef carcasses using the European Union carcass classification scores for conformation and fatness, and hindquarter composition were developed and their accuracy was tested using data from 662 cattle. The animals included bulls, steers and heifers, and comprised of Holstein-Friesian, early- and late-maturing breeds × Holstein-Friesian, early-maturing × early-maturing, late-maturing × early-maturing and genotypes with 0.75 or greater late-maturing ancestry. Bulls, heifers and steers were slaughtered at 15, 20 and 24 months of age, respectively. The diet offered before slaughter includes grass silage only, grass or maize silage plus supplementary concentrates, or concentrates offered ad libitum plus 1 kg of roughage dry matter per head daily. Following the slaughter, carcasses were classified mechanically for conformation and fatness (scale 1 to 15), and the right side of each carcass was dissected into meat, fat and bone. Carcass conformation score ranged from 4.7 to 14.4, 5.4 to 10.9 and 2.0 to 12.0 for bulls, heifers and steers, respectively; the corresponding ranges for fat score were 2.7 to 11.5, 3.2 to 11.3 and 2.8 to 13.3. Prediction equations for carcass meat, fat and bone proportions were developed using multiple regression, with carcass conformation and fat score both included as continuous independent variables. In a separate series of analyses, the independent variable in the model was the proportion of the trait under investigation (meat, fat or bone) in the hindquarter. In both analyses, interactions between the independent variables and gender were tested. The predictive ability of the developed equations was assed using cross-validation on all 662 animals. Carcass classification scores accounted for 0.73, 0.67 and 0.71 of the total variation in carcass meat, fat and bone proportions, respectively, across all 662 animals. The corresponding values using hindquarter meat, fat and bone in the model were 0.93, 0.87 and 0.89, respectively. The bias of the prediction equations when applied across all animals was not different from zero, but bias did exist among some of the genotypes of animals present. In conclusion, carcass classification scores and hindquarter composition are accurate and efficient predictors of carcass meat, fat and bone proportions.

Effect of concentrate feeding pattern in a grass silage/concentrate beef finishing system on performance, selected carcass and meat quality characteristics

Steers were offered grass silage ad libitum and 6.4 kg concentrates daily for 126 days or silage ad libitum for 35 days, followed by concentrates ad libitum (Experiment 1). Steers were offered grass silage ad libitum and 6 kg concentrates daily for 154 days, concentrates ad libitum or grass silage ad libitum for 112 days followed by concentrates ad libitum (Experiment 2). All treatments received the same total concentrate allowance. In Experiment 1, there was no difference in any measurement of meat quality. In Experiment 2, ad libitum concentrate feeding per se, decreased redness and increased shear force of muscle at 2 days post-mortem. Delaying concentrate feeding decreased fat yellowness, decreased shear force at 7 and 14 days post-mortem and increased muscle redness at 14 days post-mortem. Modifications of the beef production system examined had minor effects on beef quality which are unlikely to be of commercial significance.

Fatty acid composition of M. Longissimus dorsi from Holstein–Friesian steers of New Zealand and European/American descent and from Belgian Blue × Holstein–Friesian steers, slaughtered at two weights/ages

Our objective was to determine the effect of breed (B) and slaughter age/weight on the fatty acid composition, particularly the conjugated linoleic acid (CLA) concentration of beef. Two strains of a dairy breed [Holstein-Friesian (HF) (n=16 steers/strain)] and a late-maturing breed [Belgian Blue×Holstein-Friesian (BB) (n=16 steers)] were used. The HF strains were either of New Zealand (NZ) or European-American (EU) descent (selected in a grazed grass or a high concentrate nutritional environment, respectively). Animals were grown from calves to either a light (L; 560kg) or heavy (H; 630kg) target slaughter weight. Samples of M. longissimus dorsi were collected post-slaughter, lipids were separated into neutral (NL) and polar (PL) fractions, and fatty acid composition determined by gas-chromatography. The total fatty acid concentration and the concentrations of cis9, trans11 CLA, total CLA, MUFA and SFA in total intramuscular lipids were lower and the P:S ratio higher for BB than NZ or EU which did not differ. These differences largely reflected the changes in NL. The C18 desaturase index was higher for NZ than EU but EU did not differ from BB. Increasing slaughter weight/age increased the total fatty acid concentration and the concentrations cis9, trans11 CLA (P=0.06), total CLA (P=0.06), trans11 C18:1, MUFA and SFA and the C18 desaturase index and decreased the P:S ratio. The n-6:n-3 PUFA ratio was similar at the lighter slaughter weight/age for the three breeds/strains but increased for NZ and EU with increasing slaughter weight/age but was not affected in BB. It is concluded that the CLA concentration largely reflected muscle fatness but that increasing slaughter weight/age differentially affected the n-6:n-3 PUFA ratio of beef from early and late-maturing cattle.

Proteomic profiling of bovine M. longissimus lumborum from Crossbred Aberdeen Angus and Belgian Blue sired steers varying in genetic merit for carcass weight.

Bovine skeletal muscle is a tissue of significant value to the beef industry and global economy. Proteomic analyses offer the opportunity to detect molecular mechanisms regulating muscle growth and intramuscular fat accumulation. The current study aimed to investigate differences in protein abundance in skeletal muscle tissue of cattle from two breeds of contrasting maturity (early vs. late maturing), adiposity, and muscle growth potential, namely, Belgian Blue (BB) × Holstein Friesian and Aberdeen Angus (AA) × Holstein Friesian. Twenty AA (n = 10) and BB (n = 10) sired steers, the progeny of sires of either high or low genetic merit, expressed as expected progeny difference for carcass weight (EPDcwt), and bred through AI, were evaluated as 4 genetic groups, BB-High, BB-Low, AA-High, and AA-Low (n = 5 per treatment). Chemical composition analysis of M. longissimus lumborum showed greater protein and moisture and decreased lipid concentrations for BB-sired compared with AA-sired steers. To investigate the effects of both sire breed and EPDcwt on M. longissimus lumborum, proteomic analysis was performed using 2-dimensional difference gel electrophoresis followed by mass spectrometry. Proteins were identified from their peptide sequences, using the National Center for Biotechnology Information (NCBI) and Swiss-prot databases. Metabolic enzymes involved in glycolysis (glycogen phosphorylase, phosphoglycerate mutase) and the citric acid cycle (aconitase 2, oxoglutarate dehydrogenase) were increased in AA- vs. BB-sired steers. Expression of proteins involved in cell structure, such as myosin light chain isoforms and troponins I and T, were also altered due to sire breed. Furthermore, heat shock protein β-1 and peroxiredoxin 6, involved in cell defense, had increased abundance in muscle of AA-sired relative to BB-sired steers. Protein abundance of glucose-6-phosphate isomerase, enolase-3, and pyruvate kinase was greater in AA-sired animals of High compared with Low EPDcwt. Changes in the expression of these proteins were supported by gene expression analysis using quantitative real-time PCR. This information will aid in our understanding of genetic influences controlling muscle growth and fat accumulation and could contribute to future breeding programs to increase lean tissue gain of beef cattle.

Effect of sire breed and genetic merit for carcass weight on the transcriptional regulation of the somatotropic axis in longissimus dorsi of crossbred steers.

The somatotropic axis plays an important role in postnatal growth, development, and differentiation of skeletal muscle. The aim of this study was to examine the effect of sire breed and sire EPD for carcass weight (EPD(cwt)) on the expression of components of the somatotropic axis in LM of beef cattle at slaughter. Crossbred Aberdeen Angus (AA; n = 17) and Belgian Blue (BB; n = 16) steers born to Holstein-Friesian dams and sired by bulls with either high (H) or low (L) EPD(cwt) were used in the study. Thus, there were 4 genetic groups [i.e., BBH (n = 8), BBL (n = 8), AAH (n = 8), and AAL (n = 9)]. Blood samples were collected via jugular venipuncture at regular intervals for analysis of plasma concentrations of IGF-1 and insulin. Total RNA was isolated from LM collected at slaughter, and the mRNA expression of IGF-1, IGF-2, their receptors (IGF-1R; IGF-2R), 6 IGFBP, acid labile subunit (ALS), and GH receptor (GHR) was measured by real-time reverse-transcription quantitative PCR. There was no effect of either sire breed or EPD(cwt) on concentrations of circulating IGF or insulin (P > 0.05). Gene expression of IGF-1R and IGFBP3 was upregulated in AA (P < 0.001) compared with BB, whereas IGF-1 was upregulated in H compared with L animals (P < 0.01). Correlation analysis indicated moderate positive associations between gene expression of IGFBP3 and IGF-1 (r = 0.54; P < 0.001) and IGF-1R (r = 0.48; P < 0.01). In addition, correlation analysis revealed that mRNA expression of IGFBP3 was moderately negatively associated with LM area per kilogram of carcass weight (r = -0.40; P < 0.05). Greater gene expression of IGF-1 and reduced transcript abundance of IGFBP3 in muscle may have a role in increased muscle growth potential in steers during the finishing period. These data will contribute to a better understanding of the molecular control of muscle growth at a tissue level in cattle.