Charolais Cross Research Articles

Brahman and Brahman crossbred cattle grown on pasture and in feedlots in subtropical and temperate Australia. 3. Feed efficiency and feeding behaviour of feedlot-finished animals

The objective of this experiment was to quantify differences in feed efficiency and feeding behaviour of 470 heifers and steers by Brahman, Belmont Red, Santa Gertrudis, Angus, Hereford, Shorthorn, Charolais and Limousin sires mated to Brahman dams. Animals were bred in subtropical Queensland and finished in a temperate New South Wales feedlot. Animals averaged 598 days of age and 425.8 kg at the start of the feed intake test period. Sire breeds did not differ for eating rate, feed conversion ratio or relative growth rate. Generally, higher daily feed intakes (DFI) corresponded with higher average daily gains (ADG). Straightbred Brahmans fed the most frequently (16.6 ± 0.8 sessions/day; P < 0.05) but spent the least time eating of all breeds (67.4 ± 2.7 min/day; P < 0.001). Least squares means for Brahman, Belmont Red, Santa Gertrudis, Angus, Hereford, Shorthorn, Charolais and Limousin sired progeny, respectively, for residual feed intake (RFI; P < 0.05) were 0.02 ± 0.16, 0.14 ± 0.13, –0.10 ± 0.23, 0.54 ± 0.17, –0.27 ± 0.18, 0.29 ± 0.18, –0.46 ± 0.16 and –0.21 ± 0.13 kg/day, and for ADG (P < 0.001) were 1.06 ± 0.05, 1.17 ± 0.04, 1.52 ± 0.08, 1.47 ± 0.06, 1.46 ± 0.06, 1.46 ± 0.06, 1.35 ± 0.06 and 1.38 ± 0.05 kg/day. While straightbred Brahmans did not differ from all other sire breeds for RFI, their lower appetite relative to crossbred contemporaries resulted in the lowest DFI (P < 0.001) and lowest ADG (P < 0.001) overall. Angus sired crosses were the least efficient feeders and spent the most time eating, consumed the most feed and had the highest RFI, but were not significantly different to Santa Gertrudis and Shorthorn crosses for these traits. Angus sired crosses spent 24.1 and 15.4 min/day more time eating (P < 0.001) than straightbred Brahmans and Charolais crosses, and consumed 35 and 13% more feed (P < 0.001) respectively. Charolais sired crosses were the most feed efficient with the lowest RFI and intermediate DFI, and did not differ significantly from the highest ranking sire breeds for ADG or Kleiber ratio. While Belmont Red crosses did not differ from all breeds for RFI, they had significantly lower DFI than British and Santa Gertrudis crosses resulting in lower ADG (P < 0.001) relative to these sire breeds. Therefore, selection of Charolais, Hereford, Limousin and Santa Gertrudis sire breeds would result in the most feed efficient (low RFI) crosses with Brahman without any sacrifice in ADG.

Performance and meat quality of native and continental cross steers grazing improved upland pasture or semi-natural rough grazing

There is growing interest in the environmental benefits of grazing by cattle, yet little information is available regarding the levels of production that might be achieved on semi-natural rough grazing (SNRG). The overall aim of this research was to assess the performance of native and ‘improved’ breeds of cattle when grazing grass/clover swards and SNRG in order to explore potential genotype × nutritional environment interactions. This paper reports the findings of three experiments conducted over three years. The first experiment assessed the performance of autumn-born Welsh Black (WB) and Charolais cross (CX) cattle aged approximately 9 months when grazing ryegrass/white clover-dominated improved permanent pasture (PP) and Molinia caerulea-dominated SNRG. Both genotype and pasture type had significant effects on liveweight gain, with growth rates higher for WB steers than CX steers ( P < 0.001) and higher on the improved pasture than on the SNRG ( P < 0.001). The second experiment was conducted the following summer when the steers were 20 months old and evaluated the effects of breed and pasture type on subsequent finishing performance, carcass composition, meat quality, flavour and fatty acid composition. Genotype had no effect on liveweight gain during the grazing period, but pasture type again had a highly significant effect on growth rate ( P < 0.001). Carcass conformation was good and similar for both breeds. Pasture type had a greater effect on fatty acid composition of the meat than did breed. Likewise, genotype had no effect on meat colour or stability, whereas pasture type affected both. Loin steaks from the SNRG-grazed animals had significantly more vitamin E than those from PP-grazed animals ( P < 0.001) and this was reflected in lower lipid oxidation (TBARS) after simulated retail display ( P < 0.001). The third experiment assessed the performance of spring-born Welsh Black and Limousin cross steers aged 14 months when grazing PP and SNRG. Again only pasture type had a highly significant effect on growth rate ( P < 0.001). Measurements made during the first two experiments using automatic behaviour recorders indicated that pasture type influenced grazing behaviour to a greater degree than breed, and sward measurements found no between-breed differences in utilisation of M. caerulea. Overall the results indicate that the type of sward grazed has a greater influence on animal performance and meat quality than breed type when beef cattle are produced in Less Favoured Areas.

Identification of Quantitative Trait Loci Affecting Cattle Temperament

In addition to its potential contribution to improving animal welfare, the study of the genetics of cattle behavior may provide more general insights into the genetic control of such complex traits. We carried out a genome scan in a Holstein x Charolais cross cattle population to identify quantitative trait loci (QTL) influencing temperament-related traits. Individuals belonging to the second-generation of this population (F(2) and backcross individuals) were subjected to 2 behavioral tests. The flight from feeder (FF) test measured the distance at which the animal moved away from an approaching human observer, whereas the social separation (SS) test categorized different activities which the animal engaged in when removed from its penmates. The entire population was genotyped with 165 microsatellite markers. A regression interval mapping analysis identified 29 regions exceeding the 5% chromosome-wide significance level, which individually explained a relatively small fraction of the phenotypic variance of the traits (from 3.8% to 8.4%). One of the significant associations influencing an FF test trait on chromosome 29 reached the 5% genome-wide significance level. Eight other QTL, all associated with an SS test trait, reached the 1% chromosome-wide significance level. The location of some QTL coincided with other previously reported temperament QTL in cattle, whereas those that are reported for the first time here may represent general loci controlling temperament differences between cattle breeds. No overlapping QTL were identified for the traits measured by the 2 different tests, supporting the hypothesis that different genetic factors influence behavioral responses to different situations.

Identification of QTL controlling distress at social separation in cattle

Modern cattle management systems involve animals’ separation from penmates for procedures such as weighing, measuring and blood-sampling. This separation can result in distress in some individuals. Environmental and genetic factors are known to control the variability observed in behavioural responses of different individuals. We carried out a genome scan in a Holstein x Charolais cross population to identify QTL influencing temperament-related traits. One of these tests was the social separation test (SS test), which was designed to measure animals’ fearfulness to social separation (Ball et al., 2002). We present here the results obtained for the traits scored in the SS test performed in the heifers of the second-generation of this population.

The effect of genotype on fattening and body development traits of young cattle

Differences in demonstration of fattening and traits of body development in young cattle from three genotype groups are investigated: Domestic Simmental breed (G1) and its crosses F1 gen. With Limousine (G2) and Charolais breed (G3). Sample included total of 96 heads, 32 in each group. The greatest body mass at birth was realized by Charolais crosses (41,8 kg) and the lowest calves of domestic Simmental breed (40,5 kg), significance of differences established was at the level of p&lt;0,05. Genotype had significant effect (p&lt;0.01) on body mass and age at the end of fattening, as well as average life daily gain. Charolais and Limousine crosses at the ages of 446 and 443 days achieved higher body masses at the end of fattening (621 kg and 590 kg) compared to Domestic Simmental breed (477 days and 579 kg). The effect of genotype on traits of body development was highly significant (p&lt;0.01) for all traits except height to rump (p&lt;0.05). The highest values of height to withers and rump (131,8 cm and136,1 cm) and cannon circumference (23,1 cm), and the lowest for breast depth (70,8 cm) and breast girth (198,9 cm) were realized by young cattle of Domestic Simmental breed. The most favourable body development from the commercial aspect was realized by Charolais crosses with the highest determined values of breast depth (74,5 cm), carcass length (157,7 cm) and breast girth (202,5 cm). Limousine crosses are characterized by the lowest height to withers and rump (126,7 cm and 134,3 cm), the lowest values of carcass length (155,3 cm) and cannon circumference (21,9 cm), whereas in regard to breast depth (73,5 cm) and girth (202,1 cm) they take intermediary position. .

The 13C bicarbonate dilution technique to determine energy expenditure in young bulls validated by indirect calorimetry

We explored the applicability of the 13 C bicarbonate dilution technique for determination of energy expenditure (EE) in young bulls in comparison to whole body indirect calorimetry (IC). Twelve bulls of a F2 German Holstein x Charolais cross (4.5 months, 332 ± 16 kg BM) received a diet providing 1000 kJ ME d − 1 kg BM − 0.75 and 4.3 g crude protein d − 1 kg BM − 0.75 . Bulls were housed in respiration chambers and received an intravenous bolus of NaH 13 CO 3 (A: 3 μmol kg BM − 1 ( n = 2), B: 7 μmol kg BM − 1 ( n = 4), C: 17.5 μmol kg BM − 1 ( n = 6), 99 at.% 13 C) into the jugular vein to measure EE. Simultaneously, EE was determined by IC. After the 13 C administration blood samples and breath gas were collected from the animals in the respiration chamber during a 24-h period (7.00–7.00 h). The recovery of 13 C in breath CO 2 (% of 13 C dose) was irrespective of NaH 13 CO 3 dose (A: 69.7 ± 2.7%, B: 70.5 ± 4.5%, C: 75.0 ± 4.9%; P > 0.05). Only small amounts of 13 C were excreted in urine (3.4 ± 2.6%) and feces (2.0 ± 1.3%). The EE determined by the 13 C bicarbonate method using breath and blood 13 C recovery rates as correction factors was not different from that measured by IC (816 ± 81 [blood] or 827 ± 101 [breath] vs. 820 ± 90 kJ d − 1 kg BM − 0.75 ). Bland–Altman analysis showed a 95% confidence interval for EE of ± 99 and ± 109 kJ d − 1 kg BM − 0.75 based on blood and breath 13 C recovery, respectively. In conclusion, the 13 C bicarbonate dilution method is appropriate to obtain reliable estimates of EE in young bulls using blood CO 2 or breath CO 2 under standardized experimental conditions, i.e. in the fasting state.

Diskospondylitis and umbilical abscessation in a calf

DISKOSPONDYLITIS is a rare vertebral disease in cattle thatmost often results from the haematological spread of bacter-ial infection; it has a guarded prognosis and the treatmentoptions are limited. This short communication describes acase of diskospondylitis in association with umbilical absces-sation in a calf.A 16-week-old,male neutered Charolais cross calf was pre-sented with a four-week progressive history of stiff gait and anabnormal posture when recumbent. The calf was the smallestof a springborn group. On clinical examination, the calf had asubjectively short neck and pain was elicited on palpationaround the caudal cervical region. The calf had a weak gait,with the right limbs more severely affected than the left, anddragged the right forelimb; it was also observed to have diffi-culty rising from recumbency. A neurological examinationrevealed proprioceptive deficits in both forelimbs, and tetra-paresis.A grade II/VI heart murmur was also detected.Routinehaematological and biochemical analyses were performed;these revealed a mild hypomagnesaemia (0·42 mmol/l, refer-ence range 0·65 to 1·39 mmol/l),and a high red blood cell (

20 EFFECTS OF DOSE OF ESTRADIOL BENZOATE AND PROGESTERONE IN PROSTAGLANDIN-TREATED BEEF HEIFERS

Estradiol and progesterone have been used to synchronize follicular wave emergence and ovulation in a two-dose prostaglandin (PGF)-based synchronization program (Martínez et al. 2004 Theriogenology 62, 363–372). However, it was observed that some heifers displayed estrus prior to the second PGF, suggesting that premature luteolysis may have occurred. An experiment was designed to determine the effects of dose of estradiol benzoate (EB) and/or progesterone (P) on follicular and luteal dynamics in a two dose PGF-based protocol in beef heifers. In two replicates, beef heifers (n = 28; Simmental, Hereford, and Charolais crosses, 350 to 450 kg) received 500 μg cloprostenol (Schering-Plough Animal Health, Pointe-Claire, PQ, Canada) on Day −7. On Day 0, heifers were randomly allocated to nine treatment groups to receive 0, 1, or 2 mg of EB and 0, 50, or 100 mg of P i.m. in canola oil in a 3 × 3 factorial design. A second PGF treatment was administered on Day 14. Ultrasonography was done once daily from Days −5 to 9, and every 12 h thereafter until ovulation. Blood samples were collected at 12-hour intervals from Day 0 to 5 for estradiol and FSH concentrations, and every 24 h for progesterone. The effects of EB and P and their interaction on corpus luteum (CL), follicles, and hormone profiles were analyzed by analysis of variance, and means were compared by LSD or Tukey's test. All variables were normally distributed (Wilk-Shapiro test and rankit plots). The day of follicular wave at the time of treatment tended to vary among groups (P = 0.08) and the diameter of the dominant follicle also differed (P &lt; 0.05). The interval from treatment to wave emergence was shorter (P &lt; 0.05) in heifers that received 2 mg EB (4.6 ± 0.3 d) than in those that did not receive EB (5.9 ± 0.6 d), while the 1 mg EB group (5.1 ± 0.6 d) was intermediate. The interval to wave emergence in the 2 mg EB group was the least variable (P &lt; 0.05). There was no effect of EB (P = 0.72) on the diameter of the CL at the time of the second PGF, but there was an effect of P treatment (P = 0.01). The variability of the interval from the second PGF to ovulation may have been influenced by treatment group but was statistically not significant (P &lt; 0.1). There was an effect of time (P &lt; 0.01) on plasma progesterone concentrations and a P × time interaction (P = 0.06) can also be assumed. Estradiol concentrations were affected by EB dose, time, and EB × time interaction (all P &lt; 0.01). FSH concentrations were modified by time (P &lt; 0.01). In summary, treatment with EB 7 days after a single injection of PGF affected follicular development, while P treatment at that time appeared to influence CL function.

Effect of aggregation of horn fly populations within cattle herds and consequences for sampling to obtain unbiased estimates of abundance.

Reanalysis of counts of horn fly, Hematobia irritans (L.), obtained from a variety of cattle herds indicated that aggregation of the flies within herds decreased as mean fly density increased. Aggregation was also related to the proportion of fly-resistant and fly-susceptible cattle in a herd. Herds were grouped according to their degree of horn fly aggregation. Low aggregation herds included larger framed Angus, Horned Hereford, Polled Hereford, and Red Poll breeds. Moderate aggregation occurred with Brahman, Charolais, small-framed Angus, mixed cows, and Hereford x Charolais cross. High aggregation occurred with Chianina and mixed herds. Relationships between the sample means and variances varied among aggregation groups. A resampling approach was used to determine the influence of random sampling of a herd on the proportion of horn fly population estimates within fixed percentages of the true mean. The proportion of sample means within +/- 5, 10, 15, and 20% of the true means varied with the proportion of the herd sampled, the mean and variance of fly density, and herd size. Recommendations for obtaining sample size to estimate fly density within a fixed percentage of the true mean are given.

Effect of forage/concentrate ratio and dietary coconut oil level on methane output and performance of finishing beef heifers

Intake, animal performance and methane (CH 4) output was investigated using 36 finishing Charolais cross heifers (mean starting weight 462 kg, S.D.±16) fed ad libitum over an 11-week period. Six dietary treatments were investigated in a randomised block design experiment with a factorial arrangement of treatments. The six experimental diets consisted of three forage/concentrate (F/C) ratios (0.65:0.35, 0.40:0.60 and 0.10:0.90) supplemented with two levels of coconut oil (0 or 350 g/day). Rumen protozoa numbers were significantly ( P<0.001) lower for diets containing coconut oil at the end of the trial. Reducing the F/C ratio resulted in significantly ( P<0.001) increased rates of live weight gain (LWG) and carcass gain (CG), but coconut oil had no effect on animal performance. Methane output in litres per day was significantly modified ( P<0.001) by both the F/C ratio and level of coconut oil. Maximal CH 4 output was recorded on the 0.40:0.60 diet, with coconut oil reducing daily CH 4 output regardless of the F/C ratio. Methane output per unit of animal product (per kg of LWG and carcass gain) was significantly reduced by lower F/C ratios and the dietary inclusion of coconut oil ( P<0.001 and P≤0.003, respectively). No significant ( P>0.05) interaction between the F/C ratio and coconut oil level was identified although coconut oil significantly reduced dry matter intake (DMI), CH 4 l/day and LWG on the 0.65:0.35 F/C ratio diet.

The effect of abrupt weaning of suckler calves on the plasma concentrations of cortisol, catecholamines, leukocytes, acute-phase proteins and in vitro interferon-gamma production.

The objective of this study was to examine the effect of abrupt weaning (inclusive of social group disruption and maternal separation) on the physiological mediators of stress and measures of immune function. Thirty-six male and 36 female calves (Limousin and Charolais crosses), habituated to handling, were blocked by sex, weight, and breed of dam and randomly assigned, within block, to either a control or abruptly weaned group. Animals were separated into the respective treatment groups at 0 h. Calves were bled at -168, 6 (males only), 24, 48, and 168 h after weaning, and the behavioral reaction of calves to handling was scored. Cortisol, catecholamine (not sampled at -168 h), acute-phase protein concentrations, and in vitro interferon-gamma production and neutrophil:lymphocyte ratio were measured. The effects of weaning, calf sex, time, and their respective interactions were described. Disruption of the established social group at 0 h increased (P < 0.001) the plasma cortisol concentration and neutrophil:lymphocyte ratio and decreased the leukocyte concentration (P < 0.001) and the in vitro interferon-gamma response to the mitogen concanavalin-A (P < 0.001) and keyhole limpet hemocyanin (P < 0.001) for weaned and control animals compared with -168 h. There was no effect of weaning or sex on the behavioral reaction of calves to handling. Plasma cortisol and adrenaline concentrations were not affected by weaning or sex. Plasma noradrenaline concentration was influenced by weaning x sex (P < 0.05) and time x sex (P < 0.05). The response increased for male calves with weaning and increased with each sampling time after weaning. For heifers, the response was not affected by weaning and plasma concentrations decreased at 168 h after weaning. There was no effect of weaning or sex on leukocyte concentration. The neutrophil:lymphocyte ratio increased after weaning (P < 0.01) and was affected by sex (P < 0.05). Weaning decreased (P < 0.05) the in vitro interferon-gamma response to the antigen keyhole limpet hemocyanin. There was a time x weaning x sex (P < 0.05) interaction for fibrinogen concentration but no effect of treatment on haptoglobin concentration. Abrupt weaning increased plasma cortisol and noradrenaline concentrations that were accompanied by attenuation of in vitro interferon-gamma production to novel mitogen and antigen complexes up to 7 d after weaning.

An assessment of several potential enrichment devices for feedlot cattle

The behavior of Charolais cross heifers kept in experimental feedlot pens (3 pens, N=10 per pen) was observed for frequency and duration of use of and percentages of animals interacting with, five environmental potential enrichment devices (PEDs) over a period of 22 days. The PEDs consisted of a scratching/rubbing walkway, a moveable scratching/rubbing device, a milk-scent releasing device, a lavender-scent releasing device and a control non-scented device. The scratching/rubbing devices had higher durations and frequencies of use than the scent devices ( P<0.05). Use of the scratching/rubbing walkway decreased in frequency and duration but this stabilized by day 16 ( P<0.05). Use of the moveable scratching/rubbing PED fluctuated but there were no differences between day 2 and day 22, the last day of the trial. The scratching/rubbing walkway and the moveable scratching/rubbing device were also used by more animals (75.0 and 75.8%) than the milk, lavender and blank-scent devices (50.0, 20.0 and 15.8%, pooled S.E.=3.98, P<0.05). Frequency and duration of use of the milk-scent and lavender-scent device was higher on day 2 than for the blank-scent device but there were virtually no differences between the three devices for the remainder of the trial. These results indicate that the scratching/rubbing devices are good environmental enrichment candidates while cattle quickly lost interest in the tested scent devices.

Shelf life and eating quality of beef from cattle of different breeds given diets differing in n-3 polyunsaturated fatty acid composition

AbstractTwo experiments were conducted with 32 Charolais cross steers (experiment 1) and 36 Holstein-Friesian and Welsh Black steers (experiment 2) to examine the effects of dietary n-3 polyunsaturated fatty acids (PUFA ) and breed on meat quality. Diets were comprised of grass silage and a concentrate (60 : 40 on a dry-matter basis). Lipid in the concentrate provided 30 g/kg diet dry matter derived from either linseed, fish oil or linseed/fish oil (experiment 1); and linseed or linseed/fish oil (experiment 2). These n-3 PUFA sources were compared with Megalac, a saturated fatty acid control, in both experiments. Diets were offered for 120 days (experiment 1) and 90 days (experiment 2). Measurements of meat quality included fatty acid composition, lipid oxidation and colour during retail display (i.e. shelf life parameters) and eating quality assessed by a trained taste panel. The samples examined were sirloin (longissimus) steaks and minced beef burgers produced from the forequarter muscles infraspinatus, supraspinatus and triceps brachii. The fatty acid results showed that linseed increased the proportion of 18 : 3 n-3 (a -linolenic acid) in neutral lipid of the burgers and approximately doubled it in the phospholipid. Increased synthesis of 20 : 4 n-3 and 20 : 5 n-3 also occurred, raising their levels in the phospholipid. Fish oil doubled the proportions of 20 : 5 n-3 and 22 : 6 n-3, with the linseed/fish oil results intermediate between linseed and fish oil. The Welsh Blacks in experiment 2 had higher proportions of 18 : 3 n-3 in neutral lipid and higher proportions of 18 : 3 n-3, 20 : 5 n-3 and 22 : 5 n-3 in phospholipid. This showed a clear genetic effect on fatty acid composition. The fish oil diet in experiment 1 greatly increased lipid oxidation during retail display in both overwrapped loin steaks and burgers packed in a modified atmosphere. Values for lipid oxidation in the burgers were much higher than in the steaks due to the intimate mixing of phospholipid fatty acids and prooxidants. Lipid oxidation was also greater in the linseed/fish oil samples than controls in both experiments but was similar in linseed and controls. Colour oxidation also proceeded more rapidly in the fish oil samples in experiment 1 and tended to be faster in the linseed/fish oil groups in both experiments. Eating quality was affected by diet in experiment 1 — the fish oil samples eliciting higher scores for ‘fishy’ and ‘rancid’ than controls and having lower ‘overall liking’ scores. Steaks from animals given the linseed diet (with high 18 : 3 n-3 proportions) had the highest ‘overall liking’ scores in experiment 1 but the cattle given linseed for the shorter time in experiment 2 were not different from controls. Despite their different PUFA profile in muscle, Welsh Blacks had similar eating quality scores to Holstein-Friesians which deposited more neutral lipid (marbling fat) in muscle.

Effect of breed type, sex, method of rearing, winter nutrition and subsequent grazing treatment on lifetime performance and carcass composition in a 20-month beef system: carcass characteristics

AbstractIn a lifetime study of spring-born cattle in a 20-month beef system the effects of production factors on carcass characteristics were examined using 302 serially slaughtered animals born in three consecutive years. A multifactorial design was used with three animal factors — maturity (early maturing Hereford crosses v. late maturing Charolais crosses), sex (heifer v. steer) and method of rearing (suckled calves v. bucket-reared calves). After an initial rearing period, feeding treatments were imposed during the subsequent winter period, followed by the imposition of two sward heights (low 6 to 8 cm and high 8 to 10 cm) during the subsequent grazing season. An initial representative group of 16 cattle was slaughtered at the start of the grazing season and most of the remaining cattle were subsequently slaughtered off grass at three randomly allocated slaughter times, on average 67, 110 and 154 days post turn-out. Interactions between the main production factors were not significant with the exception of slaughter date with winter feeding levels for fat in rib joint and weight of saleable meat, and slaughter date and sex for live weight, carcass weight and weight of saleable meat. Breed type, sex and method of rearing affected the weight of saleable meat off grass by 14·7, 14·8 and 5·6 kg respectively. The influence of the winter feeding treatments on the weight of saleable meat was small by the time the final group were slaughtered. Sward height had a transient effect on weight, condition and carcass composition, the effects becoming less evident as the grazing season progressed. The effect of delaying slaughter had the largest and most significant influence on carcass composition of all the production factors studied, although changes in body composition between slaughter dates were relatively slow.

Estimation of maintenance energy requirements of beef cattle and sheep

Metabolizable energy intake and heat production were measured in a series of calorimetry experiments carried out at the Agricultural Research Institute of Northern Ireland, Hillsborough, between 1993 and 1996 with beef cattle and sheep. A total of 75 estimates were made with cattle: 23 with Charolais cross steers; 16 with Simmental cross steers and 36 with Angus cross steers (450–628 kg liveweight). Fifty-six estimates were made with lambs: 24 with Blackface cross, eight with Suffolk cross and 24 with Texel cross (23–53 kg liveweight). The diets offered to both cattle and sheep contained proportionately 0·0–0·8 cereal-based concentrates, the remainder being grass silage. Linear regressions of energy retention (measured by calorimetry) against metabolizable energy intake were produced for the cattle and sheep studies. From these linear regressions an estimate of metabolizable energy required for maintenance (MEm) was obtained. For cattle, the derived MEm was 0·614 MJ/kg LW0·75 per day, and for sheep the derived MEm was 0·460 MJ/kg LW/kg LW0·75 per day. The estimates were proportionately 0·34 higher in cattle and 0·32 higher in sheep than the 1990 values of the UK Agricultural and Food Research Council.

The effect of differing forage:concentrate ratio and restricting feed intake on the energy and nitrogen utilization by beef cattle

Six Charolais cross steers (mean live weight 459 kg) were used in a partially balanced changeover design experiment with four 4-week periods. The energy and nitrogen utilization by cattle offered diets differing in forageiconcentrate ( F: C) ratio, but of equal metabolizable energy intake (MEI), were measured. The three diets were (1) high digestibility (D) grass silage offered ad libitum; (2) low D silage offered ad libitum and supplemented with sufficient concentrates to provide the same MEI as (1); (3) high D silage supplemented with the same F: C ratio as (2) and with intake restricted to the same MEI as (1) and (2). These three diet types were offered at two levels of energy intake, the higher level of energy intake having been achieved by adding further concentrates to diets 1 to 3. Gross energy intake (GEI) and faecal, urinary and methane outputs and heat productions were measured in respiration chambers for three days at the end of each period. When values were adjusted to equal MEI across the three diets, animals offered the restricted diet produced significantly less methane, expressed as a proportion of GEI ( P < 0.001), than those offered the other two diets. However, there was no difference in energy retention or the efficiency of utilization of energy for growth between the three diet types used in this study.

Effects of diet and slaughter endpoint on carcass composition and beef quality in Charolais cross steers

One hundred and eight Charolais cross steers were used to compare forage versus grain feeding as affected by slaughter endpoint on carcass composition and palatability attributes of beef. Diets included a 97% alfalfa silage ration or 68% high moisture corn, 25% alfalfa silage ration from start of test to finish or a ration of 97% alfalfa silage from start of test to day 42 of the trial followed by the 68% high moisture corn ration until slaughter. Cattle were slaughtered at either 4, 7, or 10 mm ultrasound backfat. Grain feeding increased (P = 0.01) average daily gain and decreased (P = 0.01) days to finish, while carcass weight and grade fat were similar (P &gt; 0.10) between diets. Palatability attributes were generally unaffected by diet with the exception of slightly less (P = 0.09) beef flavour and more (P = 0.01) off flavour in forage-fed beef versus grain-fed beef. Higher (P = 0.01) concentrations of linolenic acid and lower (P = 0.09) concentrations of oleic acid in forage-fed beef may be partially responsible for diet differences in flavour. As slaughter endpoint increased from 4 to 7 mm backfat, average daily gain, days to finish, and carcass weight increased (P = 0.01). Palatability attributes assessing juiciness and flavour did not differ (P &gt; 0.10) between slaughter endpoints. Beef from cattle slaughtered at 10 mm backfat was rated higher (P &lt; 0.05) for softness, tenderness, and chewiness than beef from cattle slaughtered at 4 and 7 mm finish. Slaughter endpoint effects on "tenderness" attributes may partially explain why less tender beef is entering the marketplace. Key words: Beef cattle, alfalfa, grain, palatability, shear, fatty acids

Eating quality of beef from different sire breeds

AbstractThree hundred and eight cattle, comprising steers and heifers from continental and British crosses were finished on an 18-month beef production system at Warren Farm, Lambourn, Berkshire and slaughtered across a range of fatness levels. The eating quality of roasting joints (semimembranosus.) and sirloin steaks (longissimus thoracis et lumborumj was evaluated and the chemical composition of the lean tissue was taken on a subset of the samples. Results suggested that the greatest differences between the breeds was in the joints. There were significant (P &lt; 0·01) differences in the lipid, moisture and collagen contents of the lean tissue of the joints from the different sire breeds. The Belgian Blue sire progeny had significantly lower lipid content than the Charolais or Aberdeen Angus crosses, and significantly lower collagen content than the Aberdeen Angus cross. In addition joints from Belgian Blue crosses were more tender than joints from other breed crosses. Although the lipid and moisture contents of the steaks from different sire crosses were significantly different there was no evidence of differences in eating quality. Perhaps surprisingly there were no significant relationships between the eating quality and chemical composition between or within breed. Irrespective of breed, carcass fatness influenced the juiciness of both the joints and the steaks although the response was different for continental crosses and British crosses and depended on carcass sex. Over and above this response, steer meat was generally more juicy than heifer meat.

The effect of spreading sodium bicarbonate over the surface of grass silage on the intake of grass silages by beef cattle

Ten silages were obtained from farms in Northern Ireland. They were selected on the basis of either low pH (< 3.7) or perceived low intakes on the farms. The silages were offered to 100 Charolais cross steers, either with or without the addition of sodium bicarbonate, in a two-period changeover design experiment. The sodium bicarbonate was spread over the surface of the silage at a rate of 250 g per steer day −1. Each period was of a 2-week duration. Dry matter intakes (kg day −1 and g kg −1 liveweight (LW) 0.75) were recorded daily, with intakes on the second week of each period being used in the statistical analysis. Silage dry matter intakes with (+) and without (−) dietary addition of sodium bicarbonate were: 6.27 and 6.16 (SEM = 0.122) kg day −1; 65.8 and 64.7 (SEM = 1.29) g kg −1 LW 0.75. The lack of a significant effect of dietary addition of sodium bicarbonate on the intake of low pH silages suggests that sodium bicarbonate spread over the surface of the silage has no beneficial effect, in terms of intake, with silages of this type.

The response of bovine granulosa cells to different gonadotrophins in culture.

Previous studies with bovine granulosa cells cultured in vitro indicated that follicle-stimulating hormone (FSH) stimulated differentiation and progesterone production of granulosa cells in a dose-dependent manner, this was due mainly to an increase in the number of differentiated cells. The objectives of the present study were to investigate (1) whether the response of bovine granulosa cells in culture to luteinising hormone (LH) and equine chorionic gonadotrophin (eCG) was similar to the response to FSH, and (2) whether granulosa cells derived from different cattle breeds responded similarly to gonadotrophin stimulation. Pairs of ovaries were recovered postmortem from Charolais (38) and Hereford (41) crossbred post-pubertal heifers, and granulosa cells were aspirated from 5-8 mm follicles. In two simultaneous experiments, granulosa cells (2-3 x 10(5) viable cells) were cultured with different gonadotrophins (oFSH or oLH in Experiment 1; oFSH or eCG in Experiment 2). Cell culture was for 4 days at 37 degrees C in a humidified atmosphere of 5% CO2 in air in 1 ml of serum-free culture medium. Progesterone production, total DNA and the protein content of granulosa cells on Day 4 of culture were determined. Log10 data were analyzed by analysis of variance and multiple linear regression. In Experiment 1, both FSH and LH stimulated progesterone production (ng microgram-1 DNA) and protein content (microgram microgram-1 DNA) of granulosa cells in a dose-dependent manner (P < 0.01). The relative potencies of FSH to LH (milli micron/milli micron) were found not to be different from unity. In Experiment 2, progesterone production and the protein content of granulosa cells were stimulated by both FSH and eCG in a dose-dependent manner (P < 0.001). The progesterone response curves (log/log) were linear up to 1-10 milli microns FSH and 1-10 iu eCG, and were Y = 1.67 + 0.093 FSH and Y = 1.60 + 0.091 eCG for progesterone production. Calculated on a milli micron/iu basis, FSH was found to be 5.8 times more potent than eCG (P < 0.05) in terms of stimulating progesterone production. Granulosa cells derived from Hereford crosses were more sensitive (P < 0.001) than those from Charolais crosses to gonadotrophin stimulation (31 and 42 times for FSH and eCG, respectively, in terms of progesterone production, and 4.8 and 3.1 times for FSH and eCG, respectively, in terms of protein content). The response curves for both FSH and eCG were similar within each breed. The slopes of the progesterone response curves, and the protein responses were similar for all the gonadotrophins. In conclusion, these results imply that FSH; LH and eCG have similar effects on the differentiation and progesterone production of bovine granulosa cells from 5-8 mm follicles cultured in vitro. Furthermore, granulosa cells from different breeds cultured in vitro had different sensitivities to gonadotrophin stimulation.