P. L. Greenwood

Long-term consequences of birth weight and growth to weaning on carcass, yield and beef quality characteristics of Piedmontese- and Wagyu-sired cattle

Cattle sired by Piedmontese or Wagyu bulls were bred and grown within pasture-based nutritional systems followed by feedlot finishing. Effects of low (mean 28.6 kg, n = 120) and high (38.8 kg, n = 120) birth weight followed by slow (mean 554 g/day, n = 119) or rapid (875 g/day, n = 121) growth to weaning on carcass, yield and beef quality characteristics at about 30 months of age were examined. Low birth weight calves weighed 56 kg less at 30 months of age, had 32 kg lighter carcasses, and yielded 18 kg less retail beef compared with high birth weight calves. Composition of carcasses differed little due to birth weight when adjusted to an equivalent carcass weight (380 kg). Calves grown slowly to weaning were 40 kg lighter at 30 months of age compared with those grown rapidly to weaning. They had 25 kg smaller carcasses which yielded 12 kg less retail beef than their counterparts at 30 months of age, although at an equivalent carcass weight yielded 5 kg more retail beef and had 5 kg less fat trim. Neither low birth weight nor slow growth to weaning had adverse effects on beef quality measurements. No interactions between sire-genotype and birth weight, or growth to weaning, were evident for carcass, yield and beef quality traits. Although restricted growth during fetal life or from birth to weaning resulted in smaller animals that yield less meat at about 30 months of age, adverse effects on composition due to increased fatness, or on indices of beef quality, were not evident at this age or when data were adjusted to an equivalent carcass weight.

Myofibre characteristics of ovine longissimus and semitendinosus muscles are influenced by sire breed, gender, rearing type, age and carcass weight

The objective of this study was to determine the extent to which sire breed (Merino, primarily a wool-producing breed, and Poll Dorset, primarily a meat-producing breed), gender (castrate and ewe), rearing type (single- or multiple-reared), age (4, 8, 14 and 22 months) and carcass weight influence ovine (n = 204) myofibre characteristics. In Merino-sired sheep, the relative area (% of total myofibre area) of type 2X myofibres was lower and of type 2A myofibres higher in the longissimus lumborum (longissimus) muscle than in Poll Dorset-sired sheep. Female sheep had a higher relative area of type 2X and a lower relative area of type 2A myofibres than castrate sheep in the longissimus muscle. The percentage of type 2A myofibres increased and of type 2X myofibres decreased in the longissimus between 4 and 22 months of age. Type 1 myofibres in the semitendinosus muscle were more prevalent and type 2X myofibres less prevalent in Merino than in Poll Dorset-sired sheep. The percentage of type 1 myofibres was lower in female than in castrate sheep. Age-related effects on semitendinosus myofibre characteristics varied with gender, sire breed and rearing type. Influences of rearing type on myofibre characteristics were evident in the semitendinosus muscle at younger ages, but did not persist to 22 months of age. The greatest increases in myofibre cross-sectional areas occurred between 8 and 14 months of age in the longissimus muscle, and between 14 and 22 months of age in the semitendinosus muscle. Carcass weight significantly influenced cross-sectional area of type 2A, 2AX and 2X myofibres in longissimus and semitendinosus muscles. It is concluded that influences of sire breed, gender, rearing type, age and carcass weight on ovine myofibre percentages varies between longissimus and semitendinosus muscles. Furthermore, the pattern of postnatal myofibre growth differs between these muscles.

Future research priorities for animal production in a changing world

This paper reports the outcomes from an International Workshop on ‘Animal Production in a Changing World’ held in Clermont-Ferrand (INRA-Theix, France) on 9–10 September 2009 in which 35 participants from 15 different countries participated. The main objective was to discuss the main challenges within the livestock sector: its environmental impact and role in global climate change; balancing the need for increased production of animal products coupled with a lower footprint and addressing societal needs in terms of product quality for the consumer. Five key lectures presented the main drivers of animal agriculture: population growth, environmental impact, mitigation and adaptation options, efficiency of production and quality of animal products. The key lectures highlighted the synergies between research needs and strategies dedicated to improving food quality and safety and those devoted to decreasing the environmental impact of ruminant livestock production. After the lectures two discussion groups were set up to discuss the main research priorities in relation to reducing environmental footprint and improving product quality. The main remarks from the group working on product quality were that the existing knowledge is not fully applied, the priorities with regards to quality differ between developing and developed countries and that, as one component in assessing food quality, an environmental index needs to be established taking into account carbon footprint, water and energy use. The discussion within the group working on environmental issues highlighted the importance of focusing on whole life cycle analysis in the mitigation area, while the adaptation strategy should be based on selection for profitable animals under different production systems. In summary, a fundamental shift in designing our production systems is required to help ensure present needs for animal products are met without compromising future generations.

Influences of nutrition during pregnancy and lactation on birth weights and growth to weaning of calves sired by Piedmontese or Wagyu bulls

The aim of this study was to quantify the effects of nutrition during pregnancy and lactation on birth weight and growth to weaning of Piedmontese and Wagyu sired calves. This research was also conducted to provide animals for long-term studies on the consequences of growth early in life. During 2 breeding cycles, Hereford cows were managed within low or high pasture-based nutritional systems from about 80 days of pregnancy to parturition. During lactation, the calves and their dams remained on the low or high nutritional system or crossed over to the alternative system. From commencement of the nutritional treatment during pregnancy until parturition, and then during lactation, cows on low nutrition lost an average of 45 and 23 kg liveweight, respectively, and those on high nutrition gained 55 and 40 kg, respectively. Calves of Wagyu sires weighed less at birth (31.0 v 35.9 kg, s.e. = 0.31 kg) and weaning (182 v. 189 kg, s.e. = 2.26 kg) than those of Piedmontese sires. Calves of cows on low nutrition during pregnancy weighed less at birth than those of cows on high nutrition (32.5 v. 35.2 kg, s.e. = 0.32 kg). Low nutrition during pregnancy adversely influenced birth to weaning ADG (676 v. 759 g, s.e. = 9.2 g), weight gain (145 v. 160 kg, s.e. = 2.1 kg) and liveweight (177 v. 195 kg, s.e. = 2.3 kg) of calves at weaning. The nutritional system during lactation had greater effects on ADG (618 v. 816 g, s.e. = 9.2 g), weight gain (131 v. 174 kg, s.e. = 2.1 kg) and liveweight (164 v. 207 kg, s.e. = 2.3 kg) of calves at weaning than the nutritional system during pregnancy. Overall, the responses to the nutritional treatments were consistent for the progeny of both sire-genotypes.

Consequences of prenatal and preweaning growth for feedlot growth, intake and efficiency of Piedmontese- and Wagyu-sired cattle

Consequences of low (mean 28.0 kg, n = 77) and high (mean 38.4 kg, n = 77) birthweight followed by slow (mean 548 g/day, n = 75) or rapid (mean 859 g/day, n = 79) growth to weaning for feedlot growth, intake and efficiency from 26 to 30 months of age were determined in Wagyu × Hereford (n = 81) and Piedmontese × Hereford (n = 73) cattle. Cattle were selected for study based on birthweight and preweaning growth rate, from multi-modal distributions achieved by imposition of low or high maternal nutrition during pregnancy and lactation, with the objective of achieving as close as possible to a 30% difference in birthweight and a 2-fold difference in preweaning growth rate between progeny groups. High birthweight cattle entered the intake test 57 kg heavier, grew 100 g/day more rapidly, and ate 1.0 kg dry matter /day more than the low birthweight cattle. The high birthweight cattle tended to have a higher feed conversion ratio than low birthweight cattle, but net feed intake did not differ due to birthweight group. Cattle grown rapidly to weaning entered the intake test 29 kg heavier, grew at an equivalent rate, and ate 0.7 kg dry matter/day more than the cattle grown slowly to weaning. No differences in feed conversion ratio or net feed intake were observed between the preweaning groups. When assessed at the same liveweight, differences in dry matter intake and/or feed conversion ratio due to birthweight or preweaning growth were no longer apparent. Interactions between prenatal and preweaning growth, or between sire genotype and early-life growth, were not evident for feedlot growth, intake or efficiency. It is concluded that severely restricted growth during prenatal life or from birth to weaning results in cattle that are smaller and consume less feed at the same age as their well grown counterparts; however, long-term effects of growth during early life on efficiency of utilisation of feed are not evident.

Unravelling the complex interactions between genetics, animal age and nutrition as they impact on tissue deposition, muscle characteristics and quality of Australian sheep meat

The combined effects of age and genetics and Poll Dorset sire and growth path were studied in two separate experiments (n = 595 and 627, respectively). In the first experiment, containing genotype crosses typically used in Australia (Merino, Poll Dorset, Border Leicester) and sires selected for growth or muscling, sheep were slaughtered at 4, 8, 14 and 22 months. The second experiment used Poll Dorset sires selected for high muscling, fat or growth with progeny having two levels of nutrition postweaning. Border Leicesters expressed higher levels of carcass fat percentage and intramuscular fat and produced the heaviest carcass. Merinos had the lowest subcutaneous fat depth and highest carcass lean percentage when compared at the same age. The progeny of Poll Dorset sires selected for high muscling (PDm) expressed a shift toward glycolytic fibres relative to those from Merino sires, and PDm sires produced progeny with reduced spine and limb length and higher carcass muscle:mineral ratios, suggesting skeletal stunting. Genotype meat quality differences were minimal except that PDm sire topsides were tougher and Merinos produced higher pH meat. With age (4-22 months), lambs became heavier and fatter, fibres shifted towards oxidative and away from glycolytic, muscle myoglobin increased, the meat became darker and redder and tenderness declined. Early weaning had no effect on the time to reach slaughter weight, provided nutrition was not restricted. The sire genetics influence on the carcass composition far outweighed the effect of nutrition postweaning. Lambs on a restricted diet tended to have less acceptable meat quality but this was not evident in lambs from sires selected for high fatness. Sensory tenderness was improved and intramuscular fat was higher in lamb progeny from sires selected for high fatness.

Consequences of prenatal and preweaning growth for yield of beef primal cuts from 30-month-old Piedmontese- and Wagyu-sired cattle.

Cattle sired by Piedmontese or Wagyu bulls were bred and grown within pasture-based nutritional systems followed by feedlot finishing. Effects of low (mean 28.6 kg, n = 120) and high (38.8 kg, n = 120) birthweight followed by slow (mean 554 g/day, n = 119) or rapid (875 g/day, n = 121) growth to weaning on beef primal cut weights at ~30 months of age were examined. Cattle of low birthweight or grown slowly to weaning had smaller primal cuts at 30 months as a result of reduced liveweight and smaller carcasses compared with their high birthweight or rapidly grown counterparts. Hence they require additional nutritional and economic inputs to reach target market weights. At equivalent carcass weights (380 kg), cattle restricted in growth from birth to weaning yielded slightly more beef and were somewhat leaner than their rapidly grown counterparts, resulting in primal cuts being up to 4% heavier in the slowly grown compared with the rapidly grown cattle. Compositional differences due to birthweight were less apparent at the same carcass weight, although low birthweight cattle had a slightly (~2%) heavier forequarter and slightly lower (~1%) hindquarter retail yield, and less shin-shank meat (~2%) than high birthweight cattle, suggesting only minor effects on carcass tissue distribution. There were few interactions between sire genotype and birthweight or preweaning growth, and interactions between birthweight and preweaning growth were not evident for any variables. However, variability between cohorts in their long-term responses to growth early in life suggests other environmental factors during early-life and/or subsequent growth influenced carcass yield characteristics. Overall, this study shows that effects of birthweight and preweaning growth rate on carcass compositional and yield characteristics were mostly explained by variation in carcass weight and, hence, in whole body growth to 30 months of age.

Growth and carcass characteristics of Wagyu-sired steers at heavy market weights following slow or rapid growth to weaning

Two groups of Wagyu × Hereford steers grown slowly (slow preweaning group, n = 14, mean average daily gain = 631u2009g/day) or rapidly (rapid preweaning group, nu2009=u200915, mean average daily gain = 979u2009g/day) from birth to weaning were backgrounded on improved, temperate pasture to equivalent group liveweights (543 v. 548u2009kg, s.e. = 8.8u2009kg), then finished in a feedlot for 120 days. At weaning, the slow preweaning group was 79u2009kg lighter than the rapid preweaning group. They required an additional 43 days of backgrounding to reach the same feedlot entry weight as the rapid preweaning group. The slow preweaning group grew more rapidly during backgrounding (630 v. 549u2009g/day, s.e. = 13.7u2009g/day) but tended to grow more slowly during feedlotting (1798 v. 1982 g/day, s.e. = 74.9u2009g/day) than their rapid preweaning counterparts, with overall growth rates from weaning to feedlot exit not differing between the 2 groups (rapid 763 g/day v. slow 772u2009g/day, s.e. = 17.5u2009g/day). At slaughter, following the feedlot phase, carcass weights of the 2 groups did not differ significantly (rapid 430u2009kg v. slow 417u2009kg, s.e. = 7.2u2009kg). There was a tendency for the steers grown slowly to weaning to have a higher dressing percentage (57.6 v. 56.6%, s.e. = 0.33%), but there were no significant differences in carcass compositional characteristics between the 2 groups. The slow preweaning steers did have a greater eye muscle area than the rapid preweaning steers (106.6u2009v. 98.9 cm2, s.e. = 1.87) when carcass weight was used as a covariate. These findings demonstrate that cattle grown slowly to weaning have similar composition at slaughter as those grown rapidly during the same period when backgrounded on pasture to the same feedlot entry weight. Furthermore, marbling was not adversely affected by slow growth to weaning.

Quantitative analysis of performance, carcass and meat quality traits in cattle from two Australian beef herds in which a null myostatin allele is segregating

Two Australian beef cattle herds, in which selection for muscularity was a primary objective, were used in this study to identify bovine myostatin (MSTN) mutations associated with increased muscling, and to assess associations between genotype and performance, carcass and meat quality traits. One was a research herd (herd A) established from Angus × Hereford cows, and comprised a high and low muscle selection line. The other (herd B) was a commercial beef enterprise with cattle of Angus and Charolais origin. Sequencing of the MSTN coding region and flanking splice junctions in an initial sample of 34 animals from both herds identified the 821 del11 mutation as well as six other polymorphic sites. The nucleotide 374–50C > T polymorphism in intron 1 was found to be in linkage disequilibrium with the 821 del11 mutation, with both variants confined to the high muscle selection line in herd A. No other variants were exclusive to either of the two herd A selection lines. The effect of the 821 del11 mutation was further investigated in a total of 803 cattle from both herds. A relatively high prevalence of 821 del11 heterozygotes (herd A 16%; herd B 23%) was found and heterozygotes had significant advantages in eye muscle area and muscle score over their wildtype counterparts, and did not differ in meat quality. Retail beef yield from steers was higher for the 821 del11 heterozygotes from herd A (67.0 v. 63.5%) and herd B (71.8 v. 68.6%), relative to homozygous wildtype contemporaries, demonstrating the benefits of incorporating single null MSTN alleles into breeding programs.

Eastern grey kangaroo (Macropus giganteus) myofibres. 2. Characteristics of eight skeletal muscles

The myofibre characteristics of eight skeletal muscles of economic importance, comprising six muscles from the upper hindlimb, one from the lumbar and one from the sacral region, from five eastern grey kangaroos (Macropus giganteus) were determined. Differential staining of myosin heavy chains allowed myofibres to be classified as Types 1 (slow oxidative), 2A (fast oxidative-glycolytic) and 2X/2B (fast glycolytic), as well as the intermediate or transitional Types 2C (Type 1–Type 2A intermediate) and 2AX/B (Type 2A–Type 2X/2B intermediate). The m. psoas minor had a higher area comprising Type 1 myofibres (41.4%) relative to total myofibre area than did any of the other muscles studied (each <5%). This was due to the m. psoas minor having a higher percentage (31.9%) and larger average cross-sectional area (CSA; 4211 µm2) of Type 1 myofibres. Type 2X/2B myofibres comprised over 70% of the relative area in the mm. semimembranosus, semitendinosus and gluteus medius, compared with 34.2% in the m. psoas minor, with the other muscles intermediate. The proportion of Type 2A myofibres ranged from 19.1% (m. gluteus medius) to 34.6% (m. caudal dorsolateral sacrocaudalis) of the relative myofibre area. The m. caudal dorsolateral sacrocaudalis had the largest average myofibre CSA and the m. adductor the smallest (5539 and 2455 µm2, respectively). Among the intermediate myofibre types, Type 2AX/B myofibres were more prevalent (range 4.3%–13.0% of myofibres) than Type 2C myofibres (≤0.5%). Overall, the correlations between carcass weight and the percentage and relative areas of myofibres were positive for Type 2A and negative for Type 2X/2B myofibres. The results provide a detailed characterisation of myofibres in kangaroo skeletal muscles of economic importance. Furthermore, they enhance our understanding of factors influencing kangaroo muscle structure and post-mortem metabolism and provide potential indicators of eating quality of kangaroo meat.