荒漠草原放牧与舍饲对滩羊屠宰性能与肉品质的影响

为探究荒漠草原放牧与舍饲对滩羊屠宰性能和肉品质的影响,本研究将39只3月龄滩羊公羔分为荒漠草原放牧组(GZ)、限时放牧4 h补饲组(TG)和舍饲组(SF)3组,测定滩羊的屠宰性能与肉品质指标.结果显示:SF组滩羊的宰前活重、胴体重、屠宰率、净肉率和肉骨比显著优于TG组,TG组滩羊除肉骨比和净肉率外,显著优于GZ组(P<...     

Fatty acid profile and carcass characteristics in castrated and uncastrated hair lambs

The aim of this study was to investigate the effects of castration on carcass characteristics and fatty acid profile of visceral fat and meat from lambs. Eighteen six-month-old Santa Inês male lambs (18.9?±?2.4 kg of body weight (BW)) were used. Animals were assigned to two treatments according to their sexual condition: uncastrated (U) or castrated (C). During a 98-day experimental period, animals were kept on an Andropogon gayanus grass pasture area of 1 ha and supplemented with 200 g/animal/day of concentrate mixture. Water and mineral salt were available ad libitum. The lambs were weighed fortnightly, and at the last day of the trial, they were slaughtered for evaluation of carcass characteristics and fatty acids profile of perirenal fat and longissimus lumborum muscle samples. Castrated lambs showed higher BW than U during most part of the experiment (p?<?0.05). Fat deposition was higher in C lambs as evidenced by their increased carcass fat cover. Meat from U lambs showed lower content of C_16:0 and higher polyunsaturated fatty acids (PUFA) (p?<?0.05) than that from C (U, 14.3 and C, 10.5%). Conjugated linoleic acid (CLA) content was not affected by castration (p?>?0.05) (U, 0.74 and C, 0.76%). The cis-9, cis-12 C_18:2n-6 (U, 10.6 and C, 6.86%) fatty acid and the PUFA:SFA (saturated fatty acids) ratio (U, 0.36 and C, 0.25) were higher in the muscle of U lambs (p?<?0.05), indicating that the meat from U animals may provide more benefits to human health than that of C.

     

The effects of diet,slaughter weight and docking on growth,carcass composition and meat quality of fat-tailed Barbarine lambs. A review

This review summarises the main factors that influence meat production and quality in fat-tailed Barbarine (FTB) lambs. As a general feature, FTB lamb's growth is moderate, and the average daily gain ranges between 100 and 350 g. The carcass being relatively fatty, carcass fat content varies from 10% to 32%; white fat and rose meat are often dominant in these carcasses. The meat fatty acid profile of this fat-tailed breed is similar to that of thin-tailed ones, with a prevalence of palmitic, stearic and oleic acids. The order of dissected adipose tissues accumulation, estimated by allometry coefficients, is in agreement with observations in thin-tailed sheep. However, tail fat allometry coefficient is closer to kidney fat values rather than to the subcutaneous one. Concerning effects of feed level, growth of FTB lambs fed silage is higher than those fed oat hay. With moderate concentrate supply, FTB lambs' growth is more pronounced on pasture diet than on the feedlot (FL) diet. Furthermore, at similar slaughter weights, carcasses of lambs fed pasture diet have less tail and carcass fat than those from lambs fed FL diet (5% and 18% vs. 9% and 24% for grazing and FL lambs, respectively). No difference in fat colour, fat firmness or cooked meat flavour is observed between carcasses obtained at different slaughtering weight (i.e. from 25 to 35 kg). The tail docking of FTB improved lambs' growth particularly before weaning. Its effect on carcass composition and fat proportion depends on stage of slaughtering and type of fattening diet. For suckled lambs (4 months), the docking resulted in the lower carcass fat weight (and proportion), while for fattened lambs, carcass composition was similar for all types of lambs. Overall, FTB lambs always grow slower than Noire de Thibar lambs. This is particularly pronounced during the fattening phase. Then, for FTB breed, the possibilities to obtain heavy carcasses are at risks of fat accumulation, 22.8% vs. 14.4% for FTB and Noire de Thibar thin-tailed lambs, respectively. However, the main advantage of FTB breed is that adults are well adapted to food scarcity and may produce lambs even under harsh conditions.     

Self-Regulation of Supplemental Feed Intake by Grazing Dairy Cows and its Effect on Animal Performance

Abstract

Grazing Norwegian Red dairy cows were offered one of two roughage supplements ‘baled silage (S) or ryegrass (R)’ on an ad libitum basis for a limited period daily. A third group received concentrate (C). Milk and FCM yields were significantly (P<0.05) influenced by treatment (23.65 and 22.81, 23.20 and 22.05 and 22.58 and 22.73 kg d^?1, for S, C and R, respectively). Milk composition was unaltered. The cattle offered ryegrass consumed significantly (P<0.05) more supplementary feed and less pasture, and spent less time grazing and more time ruminating than the other two groups. Cattle with high initial yields, despite higher intakes of both pasture and supplement, had reduced liveweight gains and a faster decline in milk production in comparison with low yielders.     

Fatty acid profile of plasma,muscle and adipose tissues in Chilota lambs grazing on two different low quality pasture types in Chiloé Archipelago (Chile)

There is no information about the effect of different pasture types on tissue fatty acid profiles of a native rustic lamb breed of the Chiloe Archipelago, the Chilota. Eight Chilota lambs were grazed on a ‘Calafatal’ pasture (CP), a typical secondary succession of Chiloé Archipelago (Chile) and eight Chilota lambs were located to graze on naturalized pasture (NP) of Chiloé. Botanical, chemical and lipid composition of the two types of pastures and of different lamb tissues (muscle, subcutaneous – and tail adipose tissues) and plasma were performed. Both pasture types induced high n‐3 polyunsaturated fatty acids (PUFA) and CLAcis‐9,trans‐11 proportions in Chilota meat. Thus, in muscle, Chilota lambs grazing CP showed higher sum PUFA, sum n‐6 PUFA proportion and n‐6/n‐3 PUFA ratio compared with Chilota lambs grazing NP. In tail fats of Chilota lambs grazing CP significantly higher proportions of 18:3n‐3, sum saturated fatty acids, sum PUFA, n‐3 and n‐6 PUFA were detected compared with Chilota lambs grazing NP. Feeding of different pasture types (CP vs. NP) caused significant differences in fatty acid composition of muscle and the two fat depots in Chilota lambs, but also point to tissue‐specific responses of de novo synthesized fatty acid deposition in the tissues.     

Growth performance and meat characteristics of hair lambs grazing stargrass pasture without supplementation or supplemented with concentrate containing different levels of crude protein

Abstract

Forty crossbreed hair lambs (19.1 kg body weight; 8 months of age) grazing on a Cynodon plestoctachyus pasture without supplementation or supplemented with 300 g of concentrate containing different levels of crude protein (CP) were randomly assigned to treatments defined as follows: control (without supplementation); CP130 (concentrate 130 g CP/kg), CP150 (concentrate 150 g/kg), CP170 (concentrate 170 g/kg), and CP190 (concentrate 190 g CP/kg). Lambs fed supplements had higher final body weight (BW), total gain, average daily gain (ADG), total dry matter intake (DMI), total tract digestion, and carcass dressing than lambs in control treatment. Final BW, total gain, ADG, total DMI, feed conversion, and total tract digestion were improved linearly as protein level in concentrate increased. Meat of lambs fed supplements was lighter, redder, and less yellow than meat of lambs in control treatment. It is concluded that supplementation improved ADG, feed conversion, carcass dressing, and meat color.     

Effect of mixed feeds containing different levels of olive cake on fattening performance,carcass, meat quality and fatty acids of lambs

In this study, the effects of diet including different levels of olive cake were investigated on the fattening performance, blood parameters, certain slaughtering traits, and carcass quality of lambs. Thirty-six male lambs were used in the experiment. The lambs were randomly assigned to three groups with 12 lambs each. Groups included control, 12.5 and 25% olive cake (OC). The mixed feeds were offered ad libitum. All lambs were also allowed to consume alfalfa hay (83.8 g DM/animal/day). The experiment lasted for a period of 56 days. The effect of different levels of olive cake was not found different in fattening performance values of lambs in 0–56 days (P > 0.05). Carcass weight, pH, and yield were not different (P > 0.05). While the values of color parameters, cooking loss, tenderness, and ether extract level of longissimus dorsi muscle (MLD) was not found different (P > 0.05), it was determined that the levels of olive cake increased the water-holding capacity of meat (P < 0.05). Furthermore, although the levels of olive cake were shown to decrease total n-3 and total saturated fatty acids (Σ SFA), they also increased total n-6, n-6/n-3 ratio, total monounsaturated fatty acids (Σ MUFA), and total polyunsaturated fatty acids (Σ PUFA) were not different (P > 0.05).     

Comparison of characteristics of lambs fed concentrate or grazed on ryegrass to traditional or heavy slaughter weights. I. Production, carcass, and organoleptic characteristics

The objectives of this study were to determine the effects of finishing lambs on concentrate (C) or by grazing ryegrass forage (F) to slaughter end weights of 52 (N) or 77 kg (H) on carcass characteristics and organoleptic properties. This experiment included 64 Targhee x Hampshire lambs (average BW = 24 +/- 1 kg) in a 2 x 2 x 2 factorial arrangement of treatments to compare wethers vs. ewes, C vs. F, and N vs. H slaughter weights. No interactions (P > 0.10) were observed between gender and other main effects. Hot carcass weight and dressing percent were greater (P < 0.001) for C- than for F-fed lambs. Backfat thickness also was greater (P < 0.001) for lambs fed C than for those fed F. Moreover, USDA lean quality score and USDA yield grades were higher (P < 0.001) for C- than for F-fed lambs, as well as for lambs slaughtered at H vs. N market weights. There was a higher (P < 0.005) incidence of off odors and off flavors in cooked muscle from F- vs. C-fed lambs, and also from H vs. N slaughter-weight lambs. The heavy C-fed lambs had juicier (P < 0.001) meat than other treatment combinations. Cooked meat from C-fed lambs received higher (P < 0.001) overall acceptability scores. Concentrate-finished lambs produced fatter carcasses and more palatable meat than forage-finished lambs; however, forage finishing allowed for slaughter at heavier weights without excessive fat deposition.     

Carcass traits and meat quality of Texel lambs raised in Brachiaria pasture and feedlot systems

Our hypothesis suggests an improvement in carcass and meat quality of pasture‐finished animals by introducing concentrate feed into diets. This study aimed to evaluate the effect of different levels of protein‐energy supplementation on carcass and meat characteristics of Texel lambs raised on Brachiaria pastures, and compare the results with those obtained from confined animals. Thirty 2‐month‐old intact lambs were divided into five treatments: pasture with mineral supplementation, pasture containing daily supplies of 0.8, 1.6, and 2.4% BW protein‐energy supplementation, and confinement (reference treatment). All animals were slaughtered 104 days after the beginning of the experiment. Lambs submitted to 1.6% and 2.4% BW supplementation presented similar characteristics to animals kept in confinement and were superior to animals treated with 0 or 0.8% of BW supplementation levels (p < .05). Increases of subcutaneous fat thickness were verified for 0.0, 0.8, 1.6, 2.4% BW, and confinement treatments, being respectively of 0.25, 0.74, 1.61, 1.69, and 1.98. Conversely, treatments had no influence on meat physical‐chemical characteristics, being all considered moderately soft, juicy (tender), and with mild tastes and odors. Lambs raised on Brachiaria pastures have high‐quality meat, but more protein‐energy supplementation is needed to be an alternative for the feedlots for young animals.     

Effects of rearing system on meat quality,fatty acid and amino acid profiles of Hu lambs

To determine the effects of early rearing system on meat quality traits, fatty acid and amino acid profiles of meat, 48 Hu lambs were selected and randomly divided into four treatments: control lambs were ewe‐reared from birth to 60 days of age (ER), while treatment lambs were segregated from their dams at 10, 20 and 30 days of age, then artificially reared with milk replacer until 60 days of age (EW10, EW20 and EW30, respectively). All lambs had no access to the milk replacer or their dams from 61 to 90 days. Creep feed was supplied ad libitum to all lambs from 15 to 90 days of age. Artificially reared lambs (EW10, EW20 and EW30) had higher (p < .05) creep feed intake, average daily gain, slaughter weight, hot carcass weight, meat ether extract content, bright meat color (lightness and yellowness) than ewe‐reared lambs. The content of unsaturated fatty acids and monounsaturated fatty acids in EW10 and EW20 were greater (p < .05) than that in ER, whereas the proportions of saturated fatty acids in EW10 and EW20 were lower than that in ER (p < .05). The percentages of C18:0, C18:2, C18:3 and the ratio of polyunsaturated fatty acids and saturated fatty acids of artificially reared lambs were greater than ewe‐reared lambs (p < .05). The meat proportions of leucine, alanine and proline were higher (p < .05) in artificially reared lambs than ewe‐reared ones. Finally, the artificially reared system increased meat production and changed the fatty acid and amino acid profiles of meat, and it would be appropriate to rear Hu lambs artificially from 10 days with milk replacer.     

Vitamin and trace element supplementation in grazing dairy ewe during the dry season: effect on milk yield,composition, and clotting aptitude

A study was carried out to evaluate the influence of vitamin and trace mineral supplementation on milk production and composition in grazing dairy ewes during the dry season. Ewes (n = 50) were assigned at weaning to blocks and treatments. Ewes were daily conducted (8 h/day) on a pasture based on Italian ryegrass (Lolium multiflorum). At fold, ewes received a basal diet composed by ad libitum oat hay and a definite amount of a pelleted concentrate. Dietary treatments included: (1) the control concentrate containing background of vitamin and trace mineral only, and (2) the experimental concentrate containing the premix supplement (10 g/kg of dry matter). Vitamin and trace mineral supplementation did not affect ewes’ body weight. Milk, fat- and protein-corrected milk, fat percentage, and clotting properties were improved in ewes fed supplemented concentrate. There was a week × treatment interaction (P < 0.05) for yield of milk and corrected milk that was greatest at peak production in ewes fed the premix. Our findings indicate that in grazing dairy ewe, the dietary vitamin and trace mineral supplementation during dry season led to an increase of milk production and quality, with positive improvement in milk clotting aptitude.     

The fatty acid composition of muscle fat and subcutaneous adipose tissue of pasture-fed beef heifers: influence of the duration of grazing

Our objective was to determine the effect of the duration of grazing before slaughter on the fatty acid composition of muscle fat and s.c. adipose tissue (SAT) of beef heifers. Sixty crossbred Charolais heifers (n = 15 per treatment) were assigned randomly to one of four dietary treatments: 45 animals (Treatments 1, 2, and 3, respectively) were housed at the beginning of the experiment, and 15 (Treatment 4) were fed at pasture. Two groups of 15 heifers were moved to pasture 40 d (Treatment 2) and 99 d (Treatment 3) before slaughter, respectively, resulting in preslaughter grazing periods of 0, 40, 99, or 158 d for Treatments 1, 2, 3, and 4, respectively. Before grazing the predominantly perennial ryegrass pasture, animals were housed and offered grass silage ad libitum and 3 kg of concentrate diet (650 g of grass silage/kg of total DMI). After slaughter, the fatty acid profile of the neutral (NL) and polar lipid (PL) fractions of muscle fat from the LM and the total lipids from SAT were analyzed by gas chromatography. Duration of grazing showed a quadratic tendency on mean carcass weight (P = 0.08), but did not affect growth (P = 0.27) or the lipid content (P = 0.13) of the LM. Increasing the duration of grazing led to a linear increase (P < 0.001) in the concentration (on fresh-tissue basis) of CLA in muscle fat (from 11.80 to 17.75 mg/100 g of muscle in NL, and from 0.52 to 0.82 mg/100 of g muscle in PL) and in SAT (from 3.98 to 10.23 mg/g of SAT; P < 0.001), and increased the concentration of C18:1trans-11 in both muscle fat fractions (P < 0.001) and in SAT (P < 0.001). In the total muscle lipids, the polyunsaturated to saturated fatty acid ratio (P:S) increased from 0.12 to 0.15 with increased duration of grazing following a linear (P < 0.05) and cubic pattern (P < 0.05). Increasing the duration of grazing led to a linear decrease in the n-6:n-3 ratio of muscle fat from 2.00 to 1.32 (P < 0.001), and from 2.64 to 1.65 in the SAT lipids (P < 0.001), mainly as a consequence of the increased concentration of C18:3n-3. It is concluded that muscle fat and SAT fatty acid profile was improved from a human health perspective by pasture feeding, and that this improvement depended on the duration of grazing.     

Relationship of rumen fill and fermentation to diurnal and seasonal variation of herbage intake in dairy cows grazed on perennial ryegrass pasture

To clarify the effect of digesta weight in the reticulorumen on diurnal and seasonal fluctuations in herbage intake, six ruminally cannulated, non‐lactating dairy cows were grazed on perennial ryegrass/white clover pasture during morning and evening sessions in spring and autumn. The digesta weight of fresh matter, dry matter (DM) and fiber in the reticulorumen at the beginning and the end of each grazing session was lower in spring than in autumn (P < 0.01). Although the digesta weight was similar between the sessions at the beginning of grazing, it was greater for the evening than for the morning at the end of grazing (P < 0.01). The large particles proportion in the digesta was lower for the morning than the evening (P < 0.01), and it was lower in spring than in autumn (P < 0.01). The concentrations of volatile fatty acids in rumen fluid were generally higher in spring compared with autumn. The herbage DM intake during the evening was greater compared with the morning in both seasons (P < 0.01). However, there was no difference in herbage DM intake between seasons. The results showed that the rumen digesta fill was not the sole factor explaining diurnal and seasonal variation of herbage intake in grazing dairy cows.     

Effect of increased concentrate allotment before evening grazing on herbage intake,nitrogen utilization and rumen fermentation in dairy cows grazed on perennial ryegrass pasture

Two experiments were conducted to elucidate the effect of increased concentrate allotment before evening grazing on herbage intake, nitrogen utilization and rumen fermentation in dairy cows. In experiment 1, nine lactating cows were grazed in the morning and evening sessions (2.5 h each). The cows were allocated to treatments of three concentrate allotment levels before the evening grazing session by altering proportions to daily total offered; 25%, 50% and 75%. Daily herbage dry matter intake quadratically decreased with increasing the concentrate allotment levels (P < 0.05). Nitrogen utilization was similar among treatments. To investigate diurnal changes in rumen fermentation, a second experiment was conducted where six ruminally cannulated non‐lactating dairy cows grazed in the morning and evening sessions (3 h each) were subjected to the same treatments as experiment 1. Total volatile fatty acid concentration in the rumen linearly increased with increasing the concentrate allotment levels throughout the pre‐evening grazing session to the post‐morning grazing session (P < 0.01). The results indicate that dairy cows reduce daily herbage intake but do not alter nitrogen utilization with increasing concentrate allotment before evening grazing. © 2016 Japanese Society of Animal Science     

Estimation of energy intake from heart rate and energy expenditure in sheep under confinement or grazing condition

We studied the feasibility of using heart rate (HR), or energy expenditure (EE), calculated as HR multiplied by O₂ pulse – the amount of O₂ delivered to the body at every heartbeat – to estimate individual intake of metabolisable energy (MEI) in lambs. HR was automatically recorded every 20 min during 48 h, and averaged daily (HRmean), in eight confined lambs fed with 1 kg of concentrate (C), 600 g of concentrate and 400 g of vetch hay (CH), or concentrate ad libitum (CC) or grazing lush green alfalfa (A). O₂ pulse was measured for 10 min a.m. and p.m., using an open-circuit respiratory system, simultaneously with HR measurements. Dietary treatments and time of measurement did not affect O₂ pulse significantly. Diurnal lowest HR (HRmin) was found at night for all treatments, and highest HR (HRmax) was recorded between 1000 to 1200 in all treatments but CC. Diurnal HRmean was lowest in CH and highest in CC (P<0.04), the other treatments being intermediate. HRmin was the highest in CC (P<0.02). Rumination was associated with lower HR than grazing, idling being intermediate (P<0.001). Diurnal HRmean, but not EE, was significantly related with ME intake in confinement (R²=0.17, P<0.05), or at pasture (R²=0.55, P<0.01), and not accurately enough for predictive purposes (R.S.D. 100 to 130 MJ kg⁻¹ BW^0.75). This low accuracy was probably more related with large individual variation, and with environmental effects on HR, than with lack of linearity between MEI and HR, because group means of MEI were well related with HRmean or EE (R²=0.99 and R²=0.97, respectively).     

Milk production, milk fatty acid composition and conjugated linoleic acid (CLA) content in dairy ewes raised on feedlot or grazing pasture

To evaluate milk production and milk fatty acid (FA) composition and conjugated linoleic acid (CLA) content, 75 Sicilo-Sarde ewes were used on three dietary treatments during 89 days. Two groups were conducted on rotational grazing in separate pastures of green barley grass (GB group) or perennial ryegrass (RG group) and receiving daily 300 g of concentrate/ewe. A third group was conducted in feedlot (FL group) on oat hay and silage and receiving 500 g of the same concentrate per ewe per day. Milk production did not differ among GB and RG pasture treatments (617 ml/day) but it was higher (p < 0.01) than FL one (363 ml/day). Milk fat and protein content were higher for ewes in FL than for ewes raised on both pasture treatments (88.8 and 56.7 vs. 74.5 and 54 g/kg for fat and protein, respectively). However, fat and protein yields were higher for pasture groups than FL one. The palmitic, oleic, miristic, stearic, and caprinic acids were dominant for all regimens. Short-chain FA (C4:0–C10:0) did not differ among all treatments. The medium chain FA content was significantly higher in milk fat from FL group. Conversely, the long chain ones increased for grazing groups. Milk from pasture groups had a higher C18:3 proportion than that from FL sheep (4.5 vs. 2.7 g/1000 g). The CLA content was significantly (p < 0.001) higher for grazing groups than for FL one (7.3 and 10.3 for GB and RG, respectively, vs. 2.4 g/1000 g for FL). Pasture-based diets increased the concentrations of long-chain unsaturated FA and desirable FA in milk fat.     

放牧时间对羊肉多不饱和脂肪酸沉积及氧化稳定性的影响

分析不同放牧时间对羊肉抗氧化性能的影响。选择40只乌珠穆沁去势公羔,按照体重和出生月份接近的同质原则随机分成5个处理组:舍饲组(0H,对照),放牧2 h组(2H)、放牧4 h组(4H)、放牧8 h组(8H)和放牧12 h组(12H)。舍饲组圈养,4个放牧组在清晨6:00出牧,依组次分别在8:00、10:00、14:00和18:00归牧。试验期102 d,预试期15 d,正式期87 d。放牧试验结束后,从各组挑选体重接近的6只屠宰,取背最长肌,测定多不饱和脂肪酸(PUFA)和抗氧化物浓度。结果表明,1)放牧时间显著影响羊肉中抗氧化物的浓度。舍饲组的丙二醛(MDA)含量显著(P<0.001)高于4个放牧组,且4个放牧组之间差异不显著。放牧4~12 h组的谷胱甘肽过氧化物酶(GSH-Px)显著(P=0.020)低于舍饲组,但其超氧化物歧化酶(SOD)显著(P<0.001)高于舍饲组。总抗氧化能力(T-AOC)在各组间差异不显著。2)放牧时间与羊肉中的MDA、SOD水平呈二次曲线关系,MDA先降低,至放牧10 h后升高,SOD先升高,至放牧10 h后降低;GSH-Px水平与放牧时间呈负线性关系,放牧时间越长其值越低。3)放牧4,12 h组的PUFA和高度氧化多不饱和脂肪酸(HP-PUFA)均显著高于放牧2 h和舍饲组(P<0.01)。PUFA和HP-PUFA沉积量与抗氧化物浓度之间关系密切。绵羊每天放牧2~10 h,可以改善羊肉的氧化稳定性,防止PUFA氧化,从而延长高品质羊肉的保质期。     

Herbage intake and ruminal digestion of dairy cows grazed on perennial ryegrass pasture either in the morning or evening

This study aimed to clarify diurnal fluctuations of herbage intake, ruminal fermentation of herbage carbohydrates and proteins, and digesta particulate weight in the rumen of grazing dairy cows. Six ruminally cannulated, non‐lactating dairy cows were grazed on perennial ryegrass/white clover pasture either in the morning (04.00 to 08.00 hours) or the evening (16.00 to 20.00 hours). Cows grazed in the evening spent more time (P < 0.01) and consumed more herbage (P < 0.01) compared with cows grazed in the morning. Higher (P < 0.05) daily mean concentrations of total volatile fatty acid, propionate and n‐butyrate in rumen fluid were observed for cows grazed in the evening compared with cows grazed in the morning. Although cows grazed in the evening ingested more crude protein compared with cows grazed in the morning, no significant difference in NH₃‐N concentration in rumen fluid was observed between them. The ratio of purine‐derivative concentration to creatinine concentrations was higher (P < 0.01) in the urine of cows grazed in the evening than in cows grazed in the morning. These results clearly indicated that evening grazing was advantageous for dairy cows compared with morning grazing, in terms of ruminal fermentable energy intake and nitrogen utilization efficiency.     

Effects of nutritional level of concentrate‐based diets on meat quality and expression levels of genes related to meat quality in Hainan black goats

The present study investigated the effects of the nutritional levels of diets on meat quality and related gene expression in Hainan black goat. Twenty‐four goats were divided into six dietary treatments and were fed a concentrate‐based diet with two levels of crude protein (CP) (15% or 17%) and three levels of digestive energy (DE) (11.72, 12.55 or 13.39 MJ/kg DM) for 90 days. Goats fed the concentrate‐based diet with 17% CP had significantly (P < 0.05) higher average daily gains (ADG) and better feed conversion rates (FCR). The pH _24h value tended to decrease (P < 0.05) with increasing DE levels. The tenderness of Longissimus dorsi muscle (LD) and Semimembranosus muscle (SM) reduced with increasing CP levels (P < 0.05). With increasing DE levels, tenderness was increased (P < 0.05). The heart fatty acid‐binding protein (H‐FABP) mRNA expression levels in LD and SM increased with increasing DE levels (P < 0.05), but decreased with increasing CP levels (P < 0.05). The calpastatin (CAST) and μ‐calpain mRNA expressions levels in LD and SM were affected significantly (P < 0.05) by CP and DE levels in the diet. Therefore, the nutritional levels of diets affect meat quality and expression levels of genes associated with meat quality in Hainan black goats.     

自然放牧方式下欧拉羊羊肉中矿物元素、脂肪酸及氨基酸含量分析

为研究典型草原放牧欧拉羊体肌肉中矿物元素、脂肪酸和氨基酸的含量,本试验随机选取同一群体18月龄欧拉羊羯羊20只,测定欧拉羊体重、屠宰性能及背最长肌中矿物元素、脂肪酸、胆固醇、维生素E及氨基酸含量。结果表明:群体中体重在40 kg以下(LW组)占25%,40~50 kg(MW组)占45%,50 kg以上(HW组)占30%;HW组屠宰率、净肉率和眼肌面积均显著高于MW组和LW组;肌肉中铁含量为7.76~8.07 mg/100g,锌含量为10.06~10.74 mg/100g,HW组背最长肌锰含量显著低于LW组;胆固醇含量为36.57~43.43 mg/100g,n-6/n-3为2.12~2.21,HW组胆固醇含量及单不饱和脂肪酸与饱和脂肪酸的比值(M/S)显著高于MW组和LW组;维生素E含量丰富,为0.31~0.40 mg/100g,各组间差异不显著;3组的氨基酸相对含量差异不显著。综上可知,青海地区天然放牧的欧拉羊肌肉中铁、锌等矿物元素及维生素E含量较高,体重在50 kg以上维生素E含量更高且屠宰性能更好。天然放牧的欧拉羊肌肉中n-6/n-3比值较低,更符合人类健康的需求。