The relationship between carcass characteristics,plasma hormones and metabolites in young fattening bulls

Six Belgian Blue bulls (double-muscled type) and six Friesian bulls were offered a fattening diet for 34 weeks. Plasma samples were obtained once a week and also every 20 min over a 24 h period, 7 weeks before slaughter.No differences were observed between the breeds in plasma glucose, urea and free amino nitrogen concentrations, while creatinine was significantly higher in the Belgian Blue bulls. Tri-iodothyronin, tetra-iodothyronin, insulin-like growth factor 1, insulin and testosterone concentrations were higher in the Holstein group. In contrast, the Belgian Blue bulls appeared to produce more growth hormone. The slaughter weight, carcass weight, dressing percentage and proportion of lean meat were significantly higher in the Belgian Blue group. The characteristics of muscle mass (carcass weight, dressing percentage and proportion of lean meat) were positively correlated with creatinine and with the total peak area or peak amplitude of growth hormone. The insulin concentration was positively correlated with the proportion of adipose tissue in the carcass and negatively correlated with the proportion of muscle. There were no correlations between the carcass characteristics and insulin-like growth factor 1 or testosterone. No further information was provided when the ratios of the hormones were correlated with carcass characteristics.     

Growth- and breed-related changes of muscle bundle structure in cattle

The objective of this study was to investigate the changes in muscle fiber bundles of cattle of different breeds during growth. Different numbers of muscle fibers are surrounded by connective tissue to form bundles macroscopically visible as meat fibers or meat grain, a common meat quality trait. To determine the influence of breed and age on morphological characteristics of muscle fiber bundles, 4 cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus, a typical beef cattle; Galloway, a smaller beef type; Holstein Friesian, a dairy type; and double-muscled Belgian Blue, an extreme type for muscle growth, were used. Between 5 and 15 bulls of each breed were slaughtered at 2, 4, 6, 12, or 24 mo of age, and slices of semitendinosus muscle were removed. Muscle structure characteristics were determined by computerized image analysis. During growth, the muscle cross-sectional area enlarged (P < 0.001) about 5-fold in double-muscled Belgian Blue bulls and about 4-fold in the other breeds. This was a result of the enlargement (P < 0.001) of primary bundles and muscle fibers. The bundle size was similar (P > or = 0.15) in bulls of German Angus and Galloway in all age groups and was doubled (P < 0.001) in double-muscled Belgian Blue animals from 4 mo of age on. The Holstein Friesian bulls had the smallest (P < 0.001) muscle fiber bundles at 24 mo of age. The number of muscle fibers per bundle and the number of bundles per muscle remained nearly constant (P > 0.05) during growth. This supports the existing view that the structure of the muscle is already fixed in prenatal life. The double-muscled Belgian Blue bulls showed a more than 2.5-fold greater (P < 0.001) number of muscle fibers per primary bundle compared with the other breeds investigated. The larger muscle fiber bundles led to a smaller amount of connective tissue per muscle area in double-muscled cattle. The coarser grain of meat in double-muscled Belgian Blue bulls and in older animals was not related to greater shear force values.     

Animal performance, plasma hormones and metabolites in Holstein and Belgian Blue growing-fattening bulls

Six Holstein (light-muscled type) and six Belgian Blue bulls (double-muscled type) were fed a finishing diet. Average daily gain was 1.36 kg for the Holstein bulls vs 1.24 kg for the Belgian Blue bulls (P less than .05). Holstein bulls consumed more feed (2.3 vs 1.8 kg/100 kg body weight, P less than .001) than the Belgian Blue bulls. The dressing percentage (55.4 vs 65.8%, P less than .001) and the proportion of muscle (56.1 vs 71.3%, P less than .001) in the carcass were less, whereas the proportions of adipose tissue (28.3 vs 15.4%, P less than .001) and bone (15.7 vs 13.4%, P less than .05) were higher in the Holstein bulls. Plasma creatinine determined in samples obtained once a week was lower (11.0 vs 20.3 mg/liter, P less than .001) in the Holstein bulls. In contrast, Holstein bulls tended to produce more triiodothyronine (2.3 vs 1.8 nM, P less than .10), tetraiodothyronine (71.9 vs 54.7 nM, P less than .10) and insulin-like growth factor I (IGF-I; 340 vs 205 ng/ml, P less than .20) than the Belgian Blue bulls. Growth hormone, insulin, IGF-I and testosterone were measured at 20-min intervals during two 24-h periods. In wk 6, Holstein bulls tended to produce more growth hormone than the Belgian Blues, as indicated by higher total peak area (3,185 vs 2,431 ng), peak amplitude (34.1 vs 22.6 ng/ml, P less than .10) and baseline (4.6 vs 3.3 ng/ml, P less than .20). In wk 27, the trends were opposite.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth- and breed-related changes of muscle fiber characteristics in cattle

The objective of this study was to investigate the growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality. Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus as a beef type, Galloway as a hardy type, Holstein Friesian as a dairy type, and double-muscled Belgian Blue as an extreme type for muscle growth were used. Between 5 and 17 bulls of each breed were slaughtered at 0, 2, 4, 6, 12, 18, and 24 mo of age. Muscle fiber traits were determined and classified by computerized image analysis, and several measures of meat quality were also determined, including shear force value, meat color, and i.m. fat content. The postnatal growth of semitendinosus muscle in cattle was characterized by a nearly 10-fold increase of muscle fiber area from birth to 24 mo of age. In the first few months after birth, a transformation of type IIA fibers into IIB fibers was found, whereas type I fibers were nearly unaffected by age. The apparent total muscle fiber number of semitendinosus muscle did not increase during postnatal life. These results confirm that the fiber number is determined in embryonic development. Throughout the study, the double-muscled Belgian Blue (BBDM) bulls had almost twice the fiber number of the other breeds, emphasizing a more extensive hyperplasia of muscle fibers during embryonic development in BBDM compared with the other three breeds. The apparent number of type I fibers was, however, not affected by breed, which suggests that the additional fibers found in BBDM postnatally were type IIB and IIA fibers. We did not find significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM. Having pooled the four breeds, paler meat was related to a higher frequency of type IIB fibers, a lower area of type IIA and type I fiber, and a higher total muscle fiber number. These findings based on data of double muscling give us some hints for biological causes for the variation of meat quality. Further investigation, in particular within each breed, is necessary to identify the superior fiber traits for bovine meat production.     

Effect of energy restriction and re-alimentation in Belgian Blue double-muscled beef cows on digestibility and metabolites

Four groups of five non-lactating and non-pregnant Belgian Blue double-muscled (BBDM) cows were used to investigate the effect of energy level (E) on digestion, and blood and urine metabolites. The energy levels of the groups, applied indoors during a 140-day restriction period, were 100%, 90%, 80% or 70% of their energy requirements (E100, E90, E80, E70) respectively. Afterwards, animals grazed on the same swards for 203 days (re-alimentation period). Balance trials were conducted at the end of the restriction period (BT1) and at the end of the re-alimentation period (BT2). Blood was sampled at the end of these trials. Diets consisted of maize silage and straw (80/20 on a dry matter basis) and a mineral-vitamin premix, fed at the appropriate E during BT1, or maize silage and a mineral-vitamin premix, fed at 125% of the maintenance requirements, during BT2. Significant increases of the digestibility coefficients were found during BT1 when E decreased, resulting in a better net energy capture of 7% for E70 compared with E100 (p < 0.05). Slightly, but non-significantly higher digestibility coefficients were observed for decreasing E during BT2. Plasma concentrations of glucose and creatinine did not differ between treatments during BT1, while differences were found for triacylglycerols and alpha-amino nitrogen. A tendency for a linear increase was observed for non-esterified fatty acids with decreasing E. Differences in blood metabolite concentrations disappeared in BT2. Urinary creatinine excretion was not affected by E, while body nitrogen loss increased linearly with energy restriction in BT1. No differences were found during BT2, suggesting that non-lactating and non-pregnant BBDM cows are able to adapt to a cyclic change of body weight and body reserves. These data show that restricted cows mobilized body fat as well as body protein. It is concluded that the qualitative aspects of metabolism during energy restriction are comparable in double-muscled cows with those in non-double-muscled animals, although the magnitude of the effects may be different.     

Relationship between leptin content, metabolic hormones and fat deposition in three beef cattle breeds

The aim of the study was to determine if cattle breeds differing in their carcass characteristics also differ in the profiles of their leptin and metabolic hormones. Three breeds, Belgian Blue (BB) (n = 12), Limousin (L) (n = 12) and Aberdeen Angus (AA) (n = 12) with varying ability to deposit fat and protein were compared. Blood, muscle and subcutaneous (SC) adipose tissue were sampled. Animal performance, carcass and meat characteristics were determined as well as plasma leptin concentration, leptin gene expression in SC adipose tissue, leptin-receptor gene expression in SC adipose tissue and plasma concentration of insulin, tri-iodothyronin (T3), thyroxin (T4) and cortisol. The BB bulls showed the lowest values of leptin gene expression (P < 0.05). Values of plasma leptin concentration and of leptin-receptor gene expression tended to be lower in BB than in the other breeds. For a similar amount of adipose tissue (after normalisation), BB bulls showed a higher ratio of plasma leptin (P < 0.05), whereas normalised leptin gene and leptin-receptor gene expressions did not significantly differ between breeds. Belgian Blue bulls also differed in their metabolic hormone profile, tending to show lower values of insulin, T3 and T4 than the two other breeds. Cortisol levels were significantly lower (P < 0.05) in BB than in L and AA animals.     

Economic and production consequences of liver fluke disease in double-muscled fattening cattle.

The frequency of liver fluke disease in fattening units was determined by the analysis of random faeces samples issued from 1,513 Belgian White Blue bulls aged from 5 to 7 months and weighing from 200 to 300 kg. 12.5% of the investigated bulls were positive for liver fluke disease. These bulls were spread over 56.5% of the investigated fattening units. Furthermore the infestation rate varied from 0 to 33.3% inside the fattening units. In order to assess the economic consequences of bovine fascioliasis in double-muscled cattle and the beneficial effects of a treatment against such a disease, a trial including 30 Belgian White Blue bulls, weighing 365 +/- 9 kg and aged from 10 to 12 months, was conducted in a selected fattening unit. On the basis of faecal examinations, the 30 animals were subdivided in negative (group A; n = 10) and positive animals (n = 20) for fascioliasis, the latter being either treated with nitroxinil (group B; n = 10) or not (group C; n = 10) on day 0 of this trial which was conducted during 75 days. The daily body gains in group C (1.661 +/- 0.140 kg) were significantly lower than those in group A (1.975 +/- 0.120 kg). On the other hand there was no significant difference between the daily body gains registered in group B (1.960 +/- 0.085 kg) and A. The estimated financial loss, due to flukes and accounted on a 75 day-period, averaged 2,748 Belgian Francs per bull in group C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth- and breed-related changes of marbling characteristics in cattle

The objective of this study was to investigate the growth- and breed-related changes of marbling characteristics in cattle. Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus, as a typical beef cattle; Galloway, as a smaller, environmentally resistant beef cattle; Holstein-Friesian, as a dairy-type cattle; and double-muscled Belgian Blue, as an extreme type for muscle growth, were used. These 4 breeds were expected to have differences in muscle development and i.m. fat deposition. Between 5 and 15 bulls of each breed were slaughtered at 2, 4, 6, 12, or 24 mo of age. Marbling characteristics were determined and classified in LM and semitendinosus muscle by computerized image analysis. Among breeds, differences appeared in the quantity, structure, and distribution of the marbling flecks in both muscles. The deposition of fat in the double-muscled Belgian Blue bulls remained substantially inferior to that of the other breeds, up to the age of 24 mo. Marbling in German Angus bulls particularly showed larger (P < 0.05) marbling fleck areas. Galloway cattle had the greatest (P < 0.05) number and the most regular (P < 0.05) distribution of the marbling flecks in young animals. Furthermore, for marbling characteristics in Holstein-Friesian animals, a great number and slightly finer structure were observed compared with the other breeds investigated. Postnatal growth-related changes of marbling in LM were characterized by as much as a 40-fold increase in the number of marbling flecks from 2 to 24 mo of age but also by up to a 4-fold enlargement in the area of the marbling flecks. The structure of marbling flecks was determined by 2 development trends. On the one hand, the marbling flecks became larger (P < 0.05), and the structure became coarser, which was reflected by an increasing (P < 0.01) proportion of long marbling flecks as well as an increasing (P < 0.01) maximum skeleton line length. On the other hand, continually new small, round marbling flecks appeared. This caused a decrease (P < 0.01) in the proportion of the 3 largest marbling fleck areas. The distribution of the marbling flecks became more regular (P < 0.05) with increasing proportion and number of marbling flecks. The results suggest that hyperplasia of adipocytes plays an important role in marbling during growth of muscle in cattle.     

Cardio-pulmonary function values in double-muscled cattle during muscular exercise

Eleven double-muscled calves of the Belgian White and Blue breed and eleven Friesian calves have been investigated at rest, during exercise on a treadmill (11% incline; speed 1.3 m.sec^-1) and 10 and 30 minutes after the end of this exercise. Blood gases and acid-base status were determined in mixed venous and arterial blood sampled from the pulmonary and the carotid artery respectively. Expired gases were collected in a balloon. The time of collection, volume of expired gases and fractional O₂ and CO₂ concentrations in expired gases were measured.In double-muscled calves, inadequate oxygen intake and carbon dioxide elimination were demonstrated by the increase in the carbon dioxide tension (PaCO₂) and in the hydrogen ion concentration [H⁺]_a and the decrease in the oxygen tension (PaO₂) in arterial blood during exercise. In Friesian calves, an adequate increase in oxygen intake occurred and no acidosis was recorded. A metabolic acidosis explained by only a 1.5-fold increase in the cardiac output and by the small increase in haemoglobin concentration was recorded in double-muscled calves.It was concluded that some aspects of the cardio-pulmonary and metabolic responses to exercise in double-muscled calves can be related to their inability to greatly increase their O₂ consumption.     

Effects of crossbreed pregnancies on the abortion risk of Neospora caninum-infected dairy cows

Previous studies have shown that the use of beef bull semen significantly reduces the rate of abortions due to Neospora caninum in artificially inseminated (AI) seropositive dairy cows. In addition, certain beef breeds could be more resistant to N. caninum infection and abortion than others. The aim of the present study was to determine whether different crossbreed pregnancies, those derived from Limousin, Charolais, Piedmontese or Belgian Blue semen, carry different risks of abortion in Neospora-infected dairy cows. The effects of possible interactions between maternal levels of N. caninum antibodies and the different breed crosses were also evaluated. The study was performed on five commercial Holstein–Friesian dairy herds in Northeast Spain with previously confirmed diagnoses of N. caninum infection in aborted foetuses. The study population was comprised of 1115 pregnancies: 633 pregnancies recorded after AI using Holstein–Friesian semen from 18 bulls and 482 after AI using beef semen from 27 bulls (304 inseminations using semen from Limousin bulls, 191 from Belgian Blue bulls, 89 from Piedmontese bulls and 49 from Charolais bulls). Abortion rates were 32.2% (155/482) and 15.2% (96/633) for seropositive cows inseminated with Holstein–Friesian and beef breed semen, respectively. Logistic regression analysis revealed the herd and the interaction between maternal N. caninum antibody titre and the different crossbreeds as significant factors affecting the abortion rate. Lowest abortion rates, similar to that shown by seronegative animals in the analysed herds (3.2%, 239/7432), were observed in dams AI using Limousin semen that had low (<30 relative index (RI) units) N. caninum antibody titres (2.1% abortion, 3/145) and these cows were used as reference. Compared to the cows used as reference, cows with low N. caninum antibody titres (<30 RI units) showed a similar risk of abortion when inseminated with Piedmontese or Charolais bull semen, but higher risk of abortion when inseminated with Holstein (17.9 times) or Belgian Blue (7.2 times) bull semen. All cows with high N. caninum antibody titres (≥30 RI units) had a higher risk of abortion, ranging from 8.9 times (cows inseminated with Limousine semen) to 37.8 times (cows inseminated with Piedmontese semen), compared to the cows used as reference. In conclusion, different crossbreed pregnancies carried different abortion risks in Neospora-infected dairy cows. The use of beef bull semen dramatically reduced the risk of abortion in dairy cows, especially if Limousin breed semen was used. Moreover, this reduction was found to be dependent on the N. caninum antibody titre such that the lowest incidence of abortions was recorded in Limousin semen inseminated cows with low antibody titres. Insemination of Neospora-seropositive cows with beef bull semen could both reduce the risk of abortion and avoid breeding replacements for infected cattle.     

Effects of supplemental conjugated linoleic acids (CLA) on fresh and post‐thaw sperm quality of Holstein bulls

This study was designed to investigate the effects of feeding‐protected conjugated linoleic acid (CLA) on the semen production and sperm freezability in Holstein bulls. Twelve bulls were randomly assigned to two groups (n = 6 per group). Bulls received the normal diet (control group) or the normal diet top‐dressed with 50 g of CLA (treated group) for 10 weeks. The control group received 40 g/day calcium soap of fatty acid. Fresh and post‐thaw semen quality was assessed on ejaculates collected at the 0, 4, 6, 8 and 10 week of supplementation. Semen evaluations including sperm concentration, motion characteristics (subjective and computer‐assisted), viability (Eosin–Nigrosin), membrane integrity (hypo‐osmotic swelling test) and abnormality were conducted. Semen volume, sperm concentration and total sperm output were not affected by dietary treatment (p > .05). The proportion of spermatozoa with abnormal morphology in fresh semen significantly increased (p < .05) in the CLA‐fed group compared to control group. Also, in CLA‐fed group, the proportion of post‐thaw spermatozoa with abnormal morphology at week 10 of trial was significantly higher in CLA than control group (p < .05). Progressive motility tended to be increased in the CLA‐fed group, although dietary supplementation did not affect other CASA parameters or viability in fresh and frozen‐thawed sperm. In this study, CLA supplementation had little positive effect on fresh or post‐thaw sperm quality of Holstein bulls.     

荷斯坦牛和西门塔尔牛冻精品质及其体外受精后早期胚胎发育的比较研究

为探讨荷斯坦牛和西门塔尔牛冻精的精液品质及体外受精后胚胎发育能力的差异,利用目测法、低渗膨胀法和考马斯亮蓝染色法评估了荷斯坦牛和西门塔尔牛冻精的活力、质膜完整率和顶体完整率,并比较了二者冻精体外受精后胚胎的卵裂率和囊胚率。结果表明,荷斯坦牛和西门塔尔牛冻精的活力(30.4%和27.2%)、质膜完整率(41.96%和36.22%)和顶体完整率(77.02%和73.02%)均无显著差异(P>0.05),但荷斯坦牛冻精体外受精后的卵裂率(57.5%和48.6%)和囊胚率(30.3%和23.2%)显著高于西门塔尔牛冻精(P<0.05)。提示,不同品种公牛精液体外受精后的发育能力有显著差异(P>0.05)。     

Estimation of endogenous levels of osteopontin,total antioxidant capacity and malondialdehyde in seminal plasma: Application for fertility assessment in buffalo (Bubalus bubalis) bulls

This study was attempted to identify subfertile bulls by quantifying the endogenous levels of osteopontin (OPN), total antioxidant capacity (TAC) and malondialdehyde (MDA) in seminal plasma of buffalo bulls. On the basis of conception rate, buffalo bulls were classified into two groups: high‐fertile (conception rate >50%) and subfertile bulls (conception rate <40%). A total of 100 ejaculates (10 ejaculates from each bull) were collected through artificial vagina method. The concentration of OPN, TAC and catalase (CAT) of high‐fertile bulls was found to be higher (p < .05) than that of subfertile bulls. Further, MDA level in seminal plasma was found to be lower (p < .05) in high‐fertile bulls compared with subfertile bulls. The fertility status had no effect on the superoxide dismutase (SOD) concentration in seminal plasma of both the groups. The levels of OPN (r = .678, p = 0.013) and TAC (r = .648, p = .042) were found to be positively correlated with bull fertility and the level of MDA (r = ?.718, p = .019) was found to be negatively correlated with bull fertility. However, the fertility of bulls was not found to be significantly correlated with SOD, CAT and sperm motility. In conclusion, seminal OPN, TAC and MDA tended to be more realistic in identification of subfertile bulls from breeding herds.     

Effect of health status on fattening performance in young crossbred polish Holstein‐Friesian × Limousin Bulls and steers

The aim of this study was to determine the effect of disease incidence on selected parameters of cattle fattening performance and carcass quality, and the fatty acid profile of beef. The experimental materials comprised 16 bulls and 16 steers, Polish Holstein‐Friesian × Limousin crossbreeds (including 10 healthy and six treated animals of each category). At 5 weeks of age, bloodless castration was carried out using a rubber elastrator. The calves were fed milk replacer provided in automatic feeding stations. Until 540 days of age, the animals were fattened in an Animal Research Laboratory equipped with the Roughage Intake Control (RIC) system (Insentec, the Netherlands). In comparison with healthy (untreated) bulls and steers, sick (treated) animals had lower average body weight at 180 days of age, by 37 kg (P ≤ 0.05) and lower average final body weight at 540 days of age, by 56 kg (P ≤ 0.05). Sick animals were characterized by lower feed intake and worse feed efficiency (not statistically significant differences). Hot carcass weight reached 318 kg in healthy animals and 258 kg in treated bulls (P ≤ 0.05). In treated steers, the percentage of lean meat and bones in the three‐rib section was higher and the percentage of fat was lower, compared with their healthy counterparts (P ≤ 0.01). There was a category × health status interaction for carcass tissue composition. There were no significant influences of type of sickness on analyzed traits. In comparison with healthy steers, intramuscular fat of Musculus longissimus dorsi (MLD) from treated steers had significantly (P ≤ 0.05) higher concentrations of polyunsaturated fatty acids (n‐6 and n‐3) and a lower content of conjugated linoleic acid.     

Gestational, Periparturient and Preweaning Growth Traits of Holstein versus Gir × Holstein F1Crossbred Dairy Calves Born to Holstein dams

The objectives of this study were to assess the gestational, periparturient and preweaning growth traits of Holstein vs Gir × Holstein (G × H F₁) crossbred dairy calves. Holstein cows (n=64) pregnant with Holstein (H × H) calves (bulls, n=16; heifers, n=18) or G × H (bulls, n=8; heifers, n=22) calves were sampled from 60 days of gestation through calving for serum progesterone (P₄) and in utero placentome sizes, and at parturition for calving ease scores (CES), calf vigour scores (CVS), and placental characteristics. Post-calving calf measures included birth weight (day 0) and body weight (kg), hip width (HW), body length (BL), wither height (WH), hip height (HH) and heart girth (HG) through 42 days of age. Serum IgG and calf vital function tests (respiration rate (RR), heart rate (HR), rectal temperature (RT) and fecal scores) were recorded on days 1, 3, 7 and 14 of age (a.m. and p.m.). Serum gestational P₄ was higher (p<0.05) for cows with H × H than G × H calves. Placentome measurements in utero were greater (p<0.01) for H × H calves than for G × H calves, while at parturition placental characteristics did not differ (p0.10). Gestation length, CES and CVS also did not differ (p0.10) between H × H and G × H calves. Calf RR and HR were higher (p<0.05) for H × H than G × H calves at both a.m. and p.m., while RT, fecal scores and serum IgG did not differ (p0.10) between H × H and G × H calves. Birth weight did not differ (p0.10) between H × H and G × H calves within sex. Moreover, bulls did not differ (p0.10) in any of the growth measures between H × H and G × H calves, whereas H × H heifers at days 28 and 42 of age were greater (p<0.05) in all growth traits than G × H heifers. Nevertheless, the relative change in growth measures over time (days 0 to 42) did not differ (p0.10) between H × H and G × H calves. While subtle differences in gestational, early growth and vital function characteristics were observed, these data suggest very similar developmental profiles between H × H and G × H calves.     

Plasma leptin, feed intake and body fat accumulation in fattening castrated male and female lambs

The main objective of this study was to investigate the relationships between changes in plasma leptin concentration and feed intake or bodyweight in female and castrated male lambs with fattening. Four female and four castrated male lambs were used and were fed roughage and concentrate supplemented with beef tallow ad libitum for 28 weeks. Although the feed intake and bodyweight increased with fattening in both the castrated male and female lambs, they decreased at 24–28 weeks in the female lambs. At the end of fattening, the crude fat content in the muscle (loin) of the female lambs was significantly higher than in the castrated male lambs (P < 0.05), while the crude protein content in the loin and fillet meat was higher in the castrated male than in the female lambs (P < 0.05). The plasma leptin concentration showed high values at a later stage of fattening (P < 0.05). In the female lambs the plasma insulin concentration increased at a later stage of fattening (P < 0.05) and was positively correlated (P < 0.0001, r = 0.78) with plasma leptin. Plasma metabolites (glucose, nonesterified fatty acid, total cholesterol and triglyceride) concentrations were also changed with fattening. Plasma total cholesterol was positively related to plasma leptin, more closely in the female than in the castrated male lambs (in females, r = 0.63, P < 0.001; in males, r = 0.38, P < 0.01). The accumulation of body fat was probably accelerated by the consumption of a lot of concentrate feed supplemented with treated beef tallow and by the stimulation of insulin with fattening. Consequently, the plasma leptin concentration increased, especially toward the end of the fattening period. The decrease in feed intake and bodyweight after the 24th week of fattening was possibly caused by an increase in leptin that is involved in the homeostatic regulation of body energy by regulating appetite.     

Effects of feeding dried distillers grains with solubles (DDGS) on meat quality at the late stage of the fattening period of Holstein steers

Feeding dried distillers grains with solubles (DDGS) during the late stage of the fattening period of Holstein steers was studied in regard to the influence on meat quality. Sixteen Holstein steers approximately 18 months old were used in this study. Eight animals were fed commercial concentrated feed for the entire fattening period. The other eight animals were fed 15% DDGS in the concentrated feed for 3 months before slaughtering. The moisture, ether extract and crude protein from both groups was approximately the same. The thiobarbituric acid reactive substance (TBA) value of storage for 7 days at 5°C from the animals fed DDGS showed a tendency to be lower (P = 0.059). The change in the TBA value during storage was also lower for the animals not fed DDGS (P < 0.05). There were no differences in the subcutaneous fat color between the two groups. The a*(measure of redness) and b*(measure of yellowness) of the M. longissimus from the animals fed DDGS showed a tendency to be lower (P = 0.051, 0.070). The fatty acid composition of the M. longissimus, subcutaneous and perirenal fat were not widely influenced by the feeding of DDGS. It is suggested that feeding 15% DDGS during the late stage of the fattening period for Holstein steers reduced the oxidation of the beef.     

Plasma testosterone and LH responses to LHRH in double-muscled bulls treated with trenbolone acetate and zeranol

Twenty-four double-muscled Belgian White Blue bulls were assigned, according to body weight, to two groups with and without treatment with anabolic agents. Implants containing 140 mg trenbolone and 36 mg zeranol (Forplix) were inserted sc on the upper face of the ear flap. Plasma concentrations of testosterone and luteinizing hormone (LH) were determined at d 0, 30 and 60 of the experimental period. Mean testosterone levels at d 0 for treated and controls were, respectively, 2.1 and 1.7 ng/ml during the 10-h sampling period. At d 30 and 60, testosterone levels were strongly depressed in implanted bulls (.2 ng/ml) as compared with 2.5 and 1.7 ng/ml in control bulls (P less than .001 at d 30 and P less than .01 at d 60). Average plasma LH concentrations were identical in the two groups at d 0 and 60 (1.1 and 1.5 ng/ml, respectively), but showed a slight decrease at d 30 in the treated group (P less than .10). The pulsatile character of LH and testosterone profiles was abolished by the Forplix treatment. Luteinizing hormone-releasing hormone (LHRH) injection at d 0 was followed in both groups by an immediate and sharp increase in plasma LH concentrations. The LH response reached a maximal value between 20 to 40 min postinjection and then declined rapidly. On the contrary, Forplix treatment strongly reduced LH and testosterone responses to LHRH stimulation in treated animals. Average daily gain and feed to gain ratios were 1.087 +/- .127 and 7.52 +/- .32 kg, respectively, for the control bulls and 1.335 +/- .092 and 6.24 +/- .24 kg for the Forplix-treated bulls, thus clearly showing a beneficial effect of Forplix treatment.     

Oral administration of L-citrulline changes the concentrations of plasma hormones and biochemical profile in heat-exposed broilers

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 ± 1°C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3′-triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.     

Differential Expression of IGF Family Members in Heat‐Stressed Embryos Produced In Vitro from OPU‐Derived Oocytes of Nelore (Bos indicus) and Holstein (Bos taurus) Cows

The IGF system is related to embryo quality. We aim to determine the effect of the heat stress on the mRNA expression of IGF1 and IGF2, IGFR1 and IGFR2, IGFBP2 and IGFBP4, and PAPPA in in vitro production (IVP) blastocysts from Nelore and Holstein after ovum pick up (OPU) to better understand the differences between these breeds. Oocytes from four Nelore and seven Holstein were collected in six OPU sessions. Following in vitro maturation and fertilization using six Nelore or Holstein sires, embryos were divided into control (cultured at 39°C) and heat stress (HS; exposed to 41°C for 9 h). Blastocysts were submitted to RNA extraction. The IGF1 expression was higher in blastocysts under HS in both breeds, and the expression of IGFBP2 and IGFBP4 was higher in Holstein blastocysts under HS. The high PAPPA expression and the low expression of IGFBP2 and IGFBP4 are associated with a more efficient degradation of IGFBPs, which results in greater IGF bioavailability in Nelore blastocysts and may contribute to the superior HS tolerance in Nelore, when compared to Holstein.