Gender status effect on carcass and meat quality traits of feedlot Angus × Nellore cattle

The study evaluated the effect of gender status on carcass and meat quality of feedlot Angus × Nellore cattle. A total of 176 cattle, 20 months old, were confined for 190‐days and assigned to four treatments: bulls, immunocastrated, steers, and heifers. Bulls had greater rib eye area and HCW (p = 0.0001). Heifers had increased fat thickness (p = 0.0001). Steers and heifers had higher marbling scores (p = 0.0001). There was interaction between gender and aging time for Warner‐Bratzler Shear Force (p = 0.0002), L* (p = 0.0118), and b* (p = 0.0113) values of beef. The sensory panel results showed that beef from bulls had the lowest consumer overall acceptance (p = 0.0278). Especially, regardless tenderness, steers and immunocastrated beef were considered tender, independent of aging time. Beef produced by heifers, steers, and immunocastrated is considered to be of higher quality than bulls. Thus, it is may be an interesting alternative to produce high‐quality beef than bulls, to attend the consumer demand for high‐quality products. Additionally, the low fatty acids n6 levels and low n6:n3 ratio, high levels of CLA, MUFAs, and oleic acid suggests that the heifer meat is favorable for human health.     

亚麻籽对育肥牛肉品质及脂肪酸的影响

本试验旨在研究亚麻籽对育肥牛肉品质及脂肪酸的影响。选择体重接近的西门塔尔杂交牛32头,采用单因素试验设计,随机分为4组,每组8头,其中试验Ⅰ组(对照组)、Ⅱ组、Ⅲ组和Ⅳ组牛饲喂亚麻籽的比例分别占精料0%,5%,10%和15%。结果表明,1)各试验组屠宰率,净肉率与对照组比较无显著差异(P>0.05),背膘厚度显著提高(P＜0.05),试验Ⅳ组的背膘厚度比对照组显著提高了57.75%,牛肉中脂肪含量显著提高(P＜0.05); 2)日粮中添加亚麻籽显著降低育肥牛宰后24和48 h剪切力(P＜0.01)和pH(P＜0.01);3)日粮中添加亚麻籽使肉牛背最长肌中多不饱和脂肪酸(PUFA)显著提高(P＜0.01)。日粮中添加亚麻籽可以改善胴体品质,优化了肉牛肌肉的脂肪酸组成,特别是显著增加了PUFA含量。综合分析,亚麻籽在育肥牛日粮中的适宜饲喂比例为精料的10%～15%。     

Effect of regular walking exercise on glucose tolerance and insulin response to i.v. glucose infusion in growing beef steers

The purpose of the present paper was to investigate the effect of regular walking exercise on glucose tolerance and insulin response to i.v. glucose infusion in growing beef steers. Four crossbred beef steers walked on a treadmill during a 6 week exercise period (1.2 km/h, 1 h/day and 5 days/week). The changes in plasma glucose and insulin levels following glucose infusion were analyzed immediately prior to (bodyweight: 260.4 ± 24.2 kg) and after (295.7 ± 30.1 kg) the exercise period. The basal levels of plasma glucose (86.4 vs. 82.0 mg/dL, P = 0.040) and insulin (24.5 vs. 14.3 μU/mL, P = 0.016) were significantly lower after the exercise period. Further, the increase in the levels of plasma glucose (420.4 vs. 280.8 mg/dL, P < 0.001) and insulin (94.5 vs. 73.1 μU/mL, P = 0.028) following the glucose infusion decreased after the exercise period. The area under the curve of plasma glucose (108.8 vs. 62.9 mg/dL per min, P < 0.001) and insulin (53.6 vs. 29.7 μU/mL per min, P = 0.018) indicated more rapid clearance of exogenous glucose and less insulin secretion for glucose clearance after the exercise period. These results suggest that regular exercise improves glucose tolerance, with lower insulin response to glucose infusion in growing steers, as observed in rodents and humans.     

Genetic relationships between meat quality traits and fatty acid composition in Japanese black cattle

Genetic parameters were estimated to investigate the relationships between meat quality traits and fatty acid composition from 11 855 Japanese Black cattle. The meat quality traits included beef marbling score (BMS), beef color score, firmness of beef (FIR), texture of beef (TEX) and beef fat color score (BFS). The data on fatty acid composition included oleic acid and monounsaturated fatty acids (MUFA) contents, the ratio of MUFA to saturated fatty acids (MUS) and the ratio of elongation. The heritability estimates for meat quality traits ranged from moderate (0.30) to high (0.72). The strong genetic correlations between them were useful for simultaneous genetic improvement. In addition, high heritability estimates of fatty acid composition, ranging from 0.60 to 0.63, indicated that they could also be improved genetically. The genetic correlations of fatty acid composition with BMS, FIR and TEX were weak and negative. In contrast, positive and stronger genetic correlations were found between BFS and fatty acid composition, in particular, related to the level of unsaturation (0.77 and 0.79 for MUFA and MUS, respectively). This implies that improving the level of unsaturation makes fat darker (more yellow) and thus requires balancing with BFS.     

去势对西门塔尔牛牛肉品质的影响

为分析去势对17~21月龄西门塔尔牛牛肉品质的影响,本研究选取50头健康的、16月龄的西门塔尔公牛,进行药物驱虫后,依据体重进行配对试验设计,设置去势组和未去势组,每组25头,同一阶段饲喂相同饲粮,试验期150d。结果表明,与未去势组相比,去势极显著提高了牛肉的肌红蛋白含量(P0.01),极显著降低了背最长肌的pH(P0.01),显著提高了牛肉的大理石花纹、脂肪、干物质、油酸和单不饱和脂肪酸含量和MUFA/SFA、MUFA/PUFA比值(P≤0.05);去势具有降低牛肉硬脂酸含量的趋势(0.05P≤0.10)。上述结果说明:去势能提高17~21月龄西门塔尔牛牛肉的大理石花纹等级,改善牛肉的色泽,增加牛肉脂肪和干物质含量,提高牛肉中油酸和单不饱和脂肪酸的含量。在生产中,在1.5岁左右对西门塔尔公牛去势,可达到改善牛肉品质的目的。     

Effects of parent‐of‐origin models with different pedigree information on beef carcass traits and fatty acid composition in Japanese Black cattle

Genomic imprinting should be considered in animal breeding systems to avoid lead in bias in genetic parameter estimation. The objective of this study was to clarify the effects of pedigree information on imprinting variances for carcass traits and fatty acid composition in Japanese Black cattle. Carcass records [carcass weight, rib eye area, rib thickness (RT), subcutaneous fat thickness and beef marbling score (BMS)] and fatty acid composition were obtained for 11,855 Japanese Black feedlot cattle. To estimate and compare the imprinting variances for the traits, two imprinting models with different pedigree information [the sire–dam gametic relationship matrix (Model 1) and the sire–maternal grandsire (MGS) numerator relationship matrix (Model 2)] were fitted. The ratio of the imprinting variance to the total additive genetic variance for RT (6.33%) and BMS (19.00%) was significant in Model 1, but only that for BMS (21.09%) was significant in Model 2. This study revealed that fitting the sire–MGS model could be useful in estimating imprinting variance under certain conditions, such as when restricted pedigree information is available. Furthermore, the present result suggested that the maternal gametic effects on BMS should be included in breeding programmes for Japanese Black cattle to avoid selection bias caused by imprinting effects.     

A 90‐day adaptation to a high glycaemic diet alters postprandial lipid metabolism in non‐obese horses without affecting peripheral insulin sensitivity

High glycaemic feeds are associated with the development of insulin resistance in horses. However, studies that evaluated the effect of high glycaemic feeds used horses that either ranged in body condition from lean to obese or were fed to increase body condition over a period of months; thus, the ability of high glycaemic feeds to induce insulin resistance in lean horses has not been determined. This study evaluated the insulin sensitivity of 18 lean horses fed a 10% (LO; n = 6), 20% (MED; n = 6) or 60% (HI; n = 6) non‐structural carbohydrate complementary feed for 90 days. Although both the MED and HI diets increased insulinaemic responses to concentrate feeding in relation to the LO diet (p > 0.05), neither induced insulin resistance, as assessed by glucose tolerance test, following the 90‐day feeding trial. Interestingly, the post‐feeding suppression of plasma non‐esterified fatty acids was less pronounced in HI‐fed horses (p = 0.054) on days 30 and 90 of the study, potentially indicating that insulin‐induced suppression of adipose tissue lipolysis was reduced. As insulin‐resistant animals often have elevated plasma lipid concentrations, it is possible that altered lipid metabolism is an early event in the development of insulin resistance. The effects of high glycaemic feeds that are fed for a longer duration of time, on glucose and lipid metabolism, should be investigated further.     

Development of DNA markers for improvement of meat quality in a Japanese Black cattle population in Hyogo Prefecture

The polymorphisms associated with economic traits in livestock animals provide useful information as genetic indicators for breeding improvement. Over the last two decades, several DNA markers have been developed in Japanese Black cattle; however, the effect of these markers differs across populations due to differences in their genetic structures and backgrounds. As such, there is a need to verify the effectiveness of these markers in each population. This review summarizes the effectiveness of previously reported markers on carcass traits and the development of novel DNA markers in a Japanese Black cattle population in Hyogo Prefecture. As result of genome wide association studies and resequencing analyses, two novel significant markers associated with meat quality-related traits (beef marbling and fatty acid composition) were developed. These findings will lead to the identification of responsible genes and polymorphisms and contribute to the development of novel DNA markers for numerous traits in various cattle populations.     

Basal levels and responses to glucose infusion of plasma glucose and insulin in beef steer before and after the end of the growing phase on pasture

We examined the effect of grazing during the growing phase on plasma glucose and insulin behavior at the end of the growing phase and at the early stage of the subsequent fattening phase in beef steers. From 13 to 45 weeks of age (growing phase), crossbred beef steers were grazed with minimal supplement (group G: n = 5) or housed while being fed on hay and concentrate (group H: n = 5). Following this phase, both groups were housed for finishing (fattening phase). At the end of the growing phase, group G showed faster plasma glucose disappearance after intravenous glucose infusion, with a smaller plasma insulin response, compared with group H. At the third week of the fattening phase, group G still showed higher glucose tolerance, although they experienced abrupt changes in nutritional and environmental factors. The results suggest that grazing during the growing phase probably improves the glucose tolerance and insulin response to glucose infusion in steers compared with animals that were housed during the corresponding period, and the improved properties may persist at least a few weeks after the commencement of fattening.     

Changes in molecular species composition of triacylglycerol in subcutaneous fat from beef cattle during fattening

The composition of the molecular species of triacylglycerols (TG) in subcutaneous fat biopsied from Japanese Black steers was studied during the fattening period. An analysis of the fatty acid (FA) composition of the TG showed that palmitic, palmitoleic, stearic and oleic acids were the major FA, together accounting for over 80% of the total FA. The concentrations of C14:0, C16:0 and C18:0 decreased between 10 and 30 months of age, while those of C16:1 c9 and C18:1 c9 increased during the fattening period. The major molecular species among more than 40 compounds were palmitoyl‐dioleoyl‐glycerol (POO) and dipalmitoyl‐oleoyl‐glycerol (PPO). POO showed the highest concentration during the fattening period. The levels of palmitoyl‐oleoyl‐linoleoyl glycerol and some tentatively identified molecular species increased during the fattening period, while the levels of tripalmitoyl, dipalmitoyl‐stearoyl‐glycerol, palmitoyl‐distearoyl and palmitoyl‐stearoyl‐oleoyl‐glycerol decreased with growth. A comparison of the experimental values of TG molecular species with theoretical values derived from the experimental FA contents showed that the FA distribution in TG was non‐random. TG synthesis favors the formation of TG molecular species containing at least one C16 FA, rather than three C18 FA.     

Effects of pre‐operative administration of medetomidine on plasma insulin and glucose concentrations in healthy dogs and dogs with insulinoma

ObjectiveTo investigate the effect of medetomidine on plasma glucose and insulin concentrations in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery.AnimalsTwenty–five dogs with insulinoma and 26 healthy dogs.MethodsIn dogs with insulinoma, medetomidine (5 μg kg^?1) was randomly included (n = 12) or omitted (n = 13) from the pre–anesthetic medication protocol, which typically contained an opioid and an anticholinergic. Healthy dogs received medetomidine (5 μg kg^?1; n = 13) or acepromazine (0.04 mg kg^?1; n = 13) plus an opioid (morphine 0.5 mg kg^?1) and an anticholinergic (atropine 0.04 mg kg^?1) as pre–anesthetic medications. Pre–anesthetic medications were given intramuscularly. Plasma glucose and insulin concentrations were measured before (sample 1) and 30 minutes after pre–anesthetic medication (sample 2), and at the end of surgery in dogs with insulinoma or at 2 hours of anesthesia in healthy dogs (sample 3). Glucose requirement to maintain intra–operative normoglycemia in dogs with insulinoma was quantified and compared. Data were analyzed with anova and Bonferroni post–test, t–tests or chi–square tests as appropriate with p < 0.05 considered significant. Data are shown as mean ± SD.ResultsMedetomidine significantly decreased plasma insulin concentrations and increased plasma glucose concentrations in healthy dogs and those with insulinoma. These variables did not change significantly in the dogs not receiving medetomidine. In the dogs with insulinoma, intra–operative glucose administration rate was significantly less in the animals that received medetomidine compared to those that did not.ConclusionsPre–anesthetic administration of medetomidine significantly suppressed insulin secretion and increased plasma glucose concentration in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery.Clinical relevanceThese findings support the judicious use of medetomidine at low doses as an adjunct to the anesthetic management of dogs with insulinoma.     

Effects of pre‐weaning dietary substitutions on plasma insulin and glucose profiles in primiparous sows

The objective of this study was to investigate the effects of substituting 1 kg of a standard lactation diet with 1 kg of a sugar‐rich (15.75 DE MJ/kg) or fat‐rich (23.85 DE MJ/kg) diet during late lactation on blood glucose and insulin changes in primiparous sows. During a 4‐week lactation period, 21 primiparous sows were fed to appetite with a standard lactation diet (14.10 DE MJ/kg). At 9 days before weaning, sows were assigned to a control (C, n = 7), fat (F, n = 6) or sugar (S, n = 8) treatment. During the treatment period (from 8 days before weaning until weaning), 1 kg of the lactation diet was substituted with 1 kg of a sugar‐rich or fat‐rich diet for S and F sows. At 3 days before weaning, serial blood samples were collected for a total of 228 min around feeding to establish pre‐ and postprandial plasma glucose and insulin concentrations. Preprandial plasma glucose and insulin concentrations did not differ between treatments (p > 0.05); however, mean plasma glucose and insulin concentrations were higher for S compared to F (p < 0.05) and intermediate for the C sows. Postprandial plasma concentrations of glucose and insulin were higher for the S sows than for C and F sows (p < 0.05). Sow body weight loss during late lactation did not differ between treatments (p > 0.05). The results from our study suggest that a sugar‐enriched diet during the last week of lactation elevates circulating glucose and insulin concentrations and may potentially improve post‐weaning fertility in primiparous sows.     

Effect of mixing dietary fibre (purified lignocellulose or purified pectin) and a corn meal on glucose and insulin responses in healthy horses

The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post‐prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consisted of a 10‐day acclimatization to the diet (fed once per day); during this time, the horses were fed 1.2 kg hay/100 kg BW/day. Blood was collected after each acclimatization period before and after the test meal was fed, without any hay. The increase in plasma glucose and insulin, peak values, and area under the curves were similar for all diets. The present findings suggest that adding purified soluble or insoluble fibre to a corn meal does not affect post‐prandial glucose and insulin responses in healthy horses. Feeding strategies for horses with a high energy requirement should include a starch reduction per meal, rather than the addition of purified fibre.     

Effect of a genetic polymorphism in SREBP1 on fatty acid composition and related gene expression in subcutaneous fat tissue of beef cattle breeds

Sterol regulatory element-binding factor 1 (SREBP1) plays an important role in the lipogenesis which affects fatty acid (FA) composition in backfat and consequently influences beef nutritional quality. This study analyzed the association of 84 bp-indel, both short (S) and long (L) alleles in intron 5 of SREBP1, with FA composition and gene expression of SREBP1 in backfat of northern Spanish beef breeds (Pirenaica, Salers and Holstein-Friesian). Phylogenetic analysis suggests that 84 bp-indel of ruminants is a highly conserved region compared with those in the full-length sequence of intron 5 or mRNA of SREBP1 among species. Overall, higher content of polyunsaturated FAs was observed in SL genotype compared to LL genotype of 84 bp-Indel (p < .05). In particular, in Pirenaica, SL genotype was associated with a higher content of stearic (18:0), α-linolenic (18:3n-3) acid, and total n-3 content (p < .05). However, the gene expression of SREBP1 did not differ among genotypes of 84 bp-Indel (p > .05).     

Stimulatory effect of plasma samples from fattening cattle on adipogenesis‐related gene expression in preadipocyte cells

It is desirable to produce beef with high levels of monounsaturated fatty acids (MUFA), as this is related to fat softness and palatability. However, the physiology of MUFA synthesis in bovine fat during the fattening process remains to be established. In this study, in order to elucidate the relationship between plasma components and the fatty acid composition of intramuscular fat, we investigated the effect of plasma obtained from fattening cattle on the messenger RNA (mRNA) expressions of the adipogenesis‐related gene in a clonal bovine intramuscular preadipocyte line (BIP cells). The mRNA expressions of stearoyl‐CoA desaturase, adipocyte Protein 2, peroxisome proliferator‐activated receptor gamma and sterol regulatory element‐binding protein 1 in BIP cells were significantly higher following treatment with those plasma samples collected from the cattle with the highest diaphragmatic unsaturated fatty acids to saturated fatty acids ratio (US/S). Furthermore, the concentration of nonesterified fatty acid (NEFA) in the plasma samples had an inverse correlation with carcass diaphragmatic US/S. These results indicate that cattle with a low ratio of US/S in fat may be discriminated from the population of fattening cattle before slaughter by measuring the effect of their plasma on gene expression in BIP cells as well as their plasma concentration and composition of NEFA.     

Effects of fat supplementation on plasma glucose,insulin and fatty acid analysis in ponies maintained on a forage‐based diet

The objective of this study was to observe how fat incorporated into an equine forage‐based diet through supplementation altered levels of plasma glucose, insulin and fatty acids. Five Shetland/Hackney cross pony mares were fed alfalfa pellet diets top dressed with commercially available vegetable oil (blend of soya bean, canola and corn oils) at 0%, 5%, 10% or 15% of diet. Ponies were randomly assigned one of four diets to start, with a 14‐day adjustment period between transitioning to another one of the four diets. Ponies were gradually adapted to the new diet within the 14‐day period before a five‐day trial period. Each pony received all four diets by the end of the study. Each trial was a five‐day period with a three‐day sample collection. Blood samples for each collection week were taken 0, 30, 60, 90, 120, 150, 180, 210, 240 and 270 min and at 5, 6, 7, 8, 9 and 10 hr post‐feeding. Excess fat did not impact plasma glucose (p > .1), nor did it affect blood plasma insulin concentration. While there was no time alteration found for plasma fatty acid concentration (p > .1), C14:0 increased when ponies were fed 0% fat and C18:2 decreased when ponies were fed 0% fat. Plasma fatty acids (% of total FA) were higher in C18:0, C18:1, C18:2 and C20:1 in the added fat diets (p < .1). These findings suggest the amounts reported in this study of fat supplementation on a forage‐based diet did influence the fatty acid analysis within the pony, but did not negatively impact blood glucose and insulin concentrations.     

Effect of supplemental β‐carotene compared to retinyl palmitate on fatty acid profile and expression of mRNA from genes involved in vitamin A metabolism in beef feedlot cattle

To examine the effects of dietary β‐carotene (βC) or retinyl palmitate (RP) on fatty acid (FA) profile and mRNA expression, samples were collected from 24 Angus‐cross calves that were allotted to four treatments consisting of RP supplemented at 2200 IU/kg, and synthetic β‐carotene (SβC) supplemented at one, five or 10 times RP. Longissimus muscle (LM) cis‐9, trans‐11 conjugated linoleic acid was greater in RP compared to SβC1X (P = 0.04). The polyunsaturated:saturated FA increased linearly (P = 0.04) in the LM as dietary SβC increased. Expression of βC oxygenase 2 (βCO2), an enzyme that cleaves β‐carotene, was greater in the LM for SβC1X compared to RP and decreased linearly as SβC increased (P ≤ 0.02). Peroxisome proliferator activated receptor γ (PPARγ) expression in the LM increased in SβC1X compared to RP (P = 0.03); however, PPARγ and retinoic acid X receptor α (RXRα) expression decreased linearly (P = 0.02) in the LM with increasing SβC. Retinoic acid receptor α (RARα) expression tended (P = 0.10) to decrease linearly in the LM with increased SβC. In conclusion, SβC supplementation increased mRNA expression of some lipogenic genes in the LM, but increasing dietary SβC inhibited their expression and tended to increase polyunsaturated FA.     

Choice of attractive conditions by beef cattle in a Y-maze just after release from restraint: Effect of sheep

To provide useful information on how to moderate post‐handling stress, Angus heifers (n = 157) were individually allowed to enter a choice area after 2 min of restraint in a crush and to choose between two pens. After the animal had chosen a pen, free access was given to both test pens and the choice area for a further 5 min. The behaviors during choice and after the first choosing were observed. In experiment 1, each heifer was given one of the following choices: pen with three familiar heifers (peers) versus pen with six sheep (sheep; n = 30); peers versus the bare pen (bare; n = 30); sheep versus bare (n = 30). When the choice combination was peers versus bare, more heifers than expected by chance chose the peers pen (χ² = 4.80; P < 0.05). However, when one of the other choice combinations was given, there was no significant difference between the number choosing a pen and the expected value. After the first choice, more heifers entered the peers pen than the bare pen (P < 0.05) or the sheep pen (P < 0.10). In experiment 2, another 67 heifers were given one of the following choices: peers versus pen with a novel object (NO; n = 19); sheep versus NO (n = 22); bare versus NO (n = 26). There was no significant difference between the number of heifers choosing a pen and the expected value in any choice combination. However, more heifers entered the peers pen than the NO pen (P < 0.01). It is concluded that sheep were not as attractive as peers, but sheep were not fearful animals for cattle.