Michael J Drennan

Effect of transportation and weaning on humoral immune responses of calves

Transportation exposes cattle to stress and results in increased morbidity and mortality. An investigation was made of the effects of transport and another important stressor, weaning, on the immune function of calves by determining humoral immune responses to keyhole limpet haemocyanin (KLH). In a 2 x 2 factorial designed experiment, suckled calves were either (1) weaned at housing (day 0) and not transported, (2) weaned at housing and transported, (3) weaned while still at pasture nine to 13 days prior to housing and not transported or (4) weaned at pasture and transported. All calves were immunized with KLH at housing (day 0) and serum samples were collected subsequently to determine class and subclass anti-KLH antibody responses (IgG1, IgG2, IgA and IgM) by direct ELISA. Increased anti-KLH IgG1 and IgG2 concentrations were shown in calves that were weaned prior to housing and transported on day 10 (P < 0.05 and P < 0.01 respectively). Transported calves had increased IgG1 concentrations on day 20 (P < 0.05) compared with calves that were not transported. However, calves weaned at housing and not transported had increased IgA and IgM responses on day 30 compared with the other groups of calves (P < 0.05). This study shows that transportation and weaning affect the humoral immune responses of suckler calves and that the effects persist for several weeks. However, the effects of the treatments were not consistent for all antibody classes measured.

The value of muscular and skeletal scores in the live animal and carcass classification scores as indicators of carcass composition in cattle.

The objective was to determine the relationship of muscular and skeletal scores taken on the live animal and carcass conformation and fat scores with carcass composition and value. Bulls (n = 48) and heifers (n = 37) of 0.75 to 1.0 late-maturing breed genotypes slaughtered at 16 and 20 months of age, respectively, were used. At 8 months of age (weaning) and immediately pre-slaughter, visual muscular scores were recorded for each animal and additionally skeletal scores were recorded pre-slaughter. Carcass weight, kidney and channel fat weight, carcass conformation and fat scores, fat depth over the longissimus dorsi muscle at the 12th (bulls) or 10th (heifers) rib and carcass length were recorded post-slaughter. Each carcass was subsequently dissected into meat, fat and bone using a commercial dissection procedure. Muscular scores taken pre-slaughter showed positive correlations with killing-out rate (r ≈ 0.65), carcass meat proportion (r ≈ 0.60), value (r ≈ 0.55) and conformation score (r ≈ 0.70), and negative correlations with carcass bone (r ≈ -0.60) and fat (r ≈ -0.4) proportions. Corresponding correlations with muscular scores at weaning were lower. Correlations of skeletal scores taken pre-slaughter, carcass length and carcass weight with killing-out rate and the various carcass traits were mainly not significant. Carcass fat depth and kidney and channel fat weight were negatively correlated with carcass meat proportion and value, and positively correlated with fat proportion. Correlations of carcass conformation score were positive (r = 0.50 to 0.68) with killing-out rate, carcass meat proportion and carcass value and negative with bone (r ≈ -0.56) and fat (r ≈ -0.40) proportions. Corresponding correlations with carcass fat score were mainly negative except for carcass fat proportion (r ≈ 0.79). A one-unit (scale 1 to 15) increase in carcass conformation score increased carcass meat proportion by 8.9 and 8.1 g/kg, decreased fat proportion by 4.0 and 2.9 g/kg and decreased bone proportion by 4.9 and 5.2 g/kg in bulls and heifers, respectively. Corresponding values per unit increase in carcass fat score were -11.9 and -9.7 g/kg, 12.4 and 9.9 g/kg, and -0.5 and -0.2 g/kg. Carcass conformation and fat scores explained 0.70 and 0.55 of the total variation in meat yield for bulls and heifers, respectively. It is concluded that live animal muscular scores, and carcass conformation and fat scores, are useful indicators of carcass meat proportion and value.

Genetic parameters for carcass cut weight in Irish beef cattle.

The objective of this study was to estimate genetic parameters for the weights of different wholesale cuts, using an experimental and a commercial data set. The experimental and commercial data sets included 413 and 635 crossbred Belgian Blue, Charolais, Limousin, Angus, Holstein, and Simmental animals, respectively. Univariate analyses using a mixed linear animal model with relationships were undertaken to estimate the heritability of cold carcass weight, carcass conformation and fat, and the cut weights, whereas a series of bivariate analyses was used to estimate the phenotypic and genetic correlations between carcass weight, carcass conformation, carcass fat, and the major primal cuts. Heritability estimates for cold carcass weight in both data sets were moderate (>0.48), whereas heritability estimates for carcass conformation and fat grading were greater in the commercial data set (>0.63) than in the experimental study (>0.33). Across both data sets, heritability estimates for wholesale cut weight in the forequarter varied from 0.03 to 0.79, whereas heritability estimates of carcass cut weight in the hindquarter varied from 0.14 to 0.86. Heritability estimates for cut weights expressed as a proportion of the entire carcass weight varied from 0.04 to 0.91. Genetic correlations were strong among the different carcass cut weights within the experimental and the commercial studies. Genetic correlations between the weights of selected carcass cuts and carcass weight were moderate to high (minimum 0.45; maximum 0.88) in both data sets. Positive genetic correlations were observed in the commercial data set between the different wholesale cut weights and carcass conformation, whereas these were positive and negative in the experimental data set. Selection for increased carcass weight will, on average, increase the weight of each cut. However, the genetic correlations were less than unity, suggesting a benefit of more direct selection on high value cuts.

The relationship of live animal muscular and skeletal scores, ultrasound measurements and carcass classification scores with carcass composition and value in steers

This study examined the relationship of muscular and skeletal scores and ultrasound measurements in the live animal, and carcass conformation and fat scores with carcass composition and value using 336 steers, slaughtered at 2 years of age. Live animal scores and measurements were recorded at 8 to 12 months of age and pre-slaughter. Following slaughter, each carcass was classified for conformation and fatness and the right side dissected into meat, fat and bone. Carcass conformation scores and fat scores were both measured on a continuous 15-point scale and ranged from 2.0 to 12.0 and from 2.8 to 13.3, respectively. Pre-slaughter muscular scores showed positive correlations (P < 0.001) ranging from 0.31 to 0.86 with carcass meat proportion, proportion of high-value cuts in the carcass, conformation score and carcass value, significant negative correlations with carcass fat (r = -0.13) and bone (r = -0.81) proportions, and generally low non-significant relationships with the proportion of high-value cuts in meat and carcass fat score. Pre-slaughter ultrasound muscle depth and carcass conformation score showed similar correlations with carcass traits to those using the pre-slaughter muscular scoring procedure. Pre-slaughter ultrasound fat depth showed positive correlations (P < 0.001) with carcass fat proportion (r = 0.59) and fat score (r = 0.63), and significant negative correlations (-0.23 to -0.50) with carcass meat and bone proportions, high-value cuts in the carcass and in meat, and carcass value. Pre-slaughter skeletal scores generally showed poor correlations ranging from -0.38 to 0.52 with the various carcass traits. Corresponding correlations (-0.26 to 0.44) involving records collected at 8 to 12 months of age were lower than those using pre-slaughter records. A one-unit increase in carcass conformation score increased carcass meat proportion and value by 11.2 g/kg and 5.6 cents/kg, respectively. Corresponding values for fat score were -8.2 g/kg and -5.1 cents/kg. In conclusion, both pre-slaughter live animal scores/measurements and carcass classification scores, explained an appreciable amount of the total variation in carcass meat, fat and bone proportions and carcass value, and a moderate amount of the variation in proportion of high-value meat cuts in the carcass.

Predicting beef carcass meat, fat and bone proportions from carcass conformation and fat scores or hindquarter dissection

Equations for predicting the meat, fat and bone proportions in beef carcasses using the European Union carcass classification scores for conformation and fatness, and hindquarter composition were developed and their accuracy was tested using data from 662 cattle. The animals included bulls, steers and heifers, and comprised of Holstein-Friesian, early- and late-maturing breeds × Holstein-Friesian, early-maturing × early-maturing, late-maturing × early-maturing and genotypes with 0.75 or greater late-maturing ancestry. Bulls, heifers and steers were slaughtered at 15, 20 and 24 months of age, respectively. The diet offered before slaughter includes grass silage only, grass or maize silage plus supplementary concentrates, or concentrates offered ad libitum plus 1 kg of roughage dry matter per head daily. Following the slaughter, carcasses were classified mechanically for conformation and fatness (scale 1 to 15), and the right side of each carcass was dissected into meat, fat and bone. Carcass conformation score ranged from 4.7 to 14.4, 5.4 to 10.9 and 2.0 to 12.0 for bulls, heifers and steers, respectively; the corresponding ranges for fat score were 2.7 to 11.5, 3.2 to 11.3 and 2.8 to 13.3. Prediction equations for carcass meat, fat and bone proportions were developed using multiple regression, with carcass conformation and fat score both included as continuous independent variables. In a separate series of analyses, the independent variable in the model was the proportion of the trait under investigation (meat, fat or bone) in the hindquarter. In both analyses, interactions between the independent variables and gender were tested. The predictive ability of the developed equations was assed using cross-validation on all 662 animals. Carcass classification scores accounted for 0.73, 0.67 and 0.71 of the total variation in carcass meat, fat and bone proportions, respectively, across all 662 animals. The corresponding values using hindquarter meat, fat and bone in the model were 0.93, 0.87 and 0.89, respectively. The bias of the prediction equations when applied across all animals was not different from zero, but bias did exist among some of the genotypes of animals present. In conclusion, carcass classification scores and hindquarter composition are accurate and efficient predictors of carcass meat, fat and bone proportions.

The influence of the basal diet on the effects of yeast culture on ruminal fermentation and digestibility in steers

The effects of dietary inclusion of yeast culture (Yea-Sacc) on rumen fermentation and digestibility in vivo were examined. In a Latin square experiment with 30-day periods, four rumen fistulated steers were offered 0 or 10 g yeast culture per animal daily in a low quality (4 kg barley straw plus 2.5 kg barley/soyabean meal mixture per day) (L) or high quality (2 kg barley straw plus 8 kg barley/soyabean meal mixture per day) (H) diet. The diets were offered in two feeds at 08:00 h and 16:00 h with no refusals. Rumen samples were withdrawn on 2 days per period at 08:00 (before feeding), 12:00, 16:00, 20:00 and 24:00 h. Mean rumen pH, liquid outflow rate, molar acetate proportion and the acetate to propionate ratio were lower (P < 0.001) and the concentrations of total volatile fatty acids (VFA), ammonia and bacterial nitrogen and molar proportions of butyrate and isoacids were higher (P < 0.001) on Diet H. Rumen ammonia concentration was not affected when yeast was included in Diet L but was reduced (P < 0.05) when yeast was added to Diet H. Inclusion of yeast culture in Diet L decreased (P < 0.05) VFA 4 h after the second feed, but inclusion of yeast culture in Diet H increased (P < 0.1) VFA subsequent to the second feed. Degradability of cotton was lower on Diet H, but unaffected by yeast culture. In a replicated Latin square experiment with 34-day periods, 12 non-fistulated steers were offered the experimental diets. Digestibility of dry matter, organic matter and crude protein (CP) were higher (P < 0.001) and acid detergent fibre lower (P < 0.05) on Diet H. Digestibility of CP was decreased (P < 0.05) when yeast was included in Diet L, but not affected when yeast was added to Diet H. It is concluded that dietary inclusion of yeast culture had a small influence on rumen fermentation parameters and in vivo digestibility, but that its effect on nitrogen metabolism appeared to be dependent on the nitrogen content of the basal diet.

Rumen and blood variables in steers fed grass silage and rolled barley or sugar cane molasses-based supplements

The effects on rumen fermentation and blood metabolites when barley or cane molasses were offered as isoenergetic and isonitrogenous supplements at 610 g kg−1 of total dietary dry matter (DM) intake were studied in steers fed grass silage. Six rumen fistulated steers were used in a 2 (supplements) × 2 (periods, 28 days duration) cross-over experiment. The animals were offered 35.2 g supplement DM and 22 g silage DM kg−1 bodyweight0.75 daily at 08:30 and 16:30. Rumen fluid samples were collected from all animals on Days 27 and 28 of each period before the morning feed and 1, 2, 3, 6, 8, 9, 10, 14 and 24 h thereafter. Blood samples were collected from each steer on Day 26, before the morning feed and 1 and 3 h thereafter. Mean rumen pH (6.9 vs. 6.9), concentration of total volatile fatty acids (71.2 vs. 71.7 mmol−1) and molar proportion of propionate (15.8 vs. 16.6) were similar for both supplements. The molasses-based supplement resulted in a lower (P < 0.01) rumen concentration (mg dl−1) of ammonia-N (5.6 vs. 9.3) and l-lactate (26.2 vs. 49.3), and as proportions of total volatile fatty acids, lower (P < 0.01) acetate (58.4 vs. 66.5) and higher (P < 0.01) butyrate (23.0 vs. 14.0) than the barley-based supplement. Type of supplement did not affect the concentration of haemoglobin in blood. Plasma glucose concentration was higher (P < 0.01) before the morning feed and mean plasma urea-N was lower (P < 0.06) in animals offered the molasses-based supplement. Sampling time significantly affected all blood metabolites and rumen fermentation variables measured. It is concluded that under the conditions of this study, plasma glucose and urea-N concentrations and the pattern of rumen fermentation differed between barley and molasses-based supplements to grass silage.

The effect of road transport in comparison to a novel environment on the physiological, metabolic and behavioural responses of bulls.

The objective was to investigate the effect of 18 h road transport with a 12h mid-journey rest period in comparison to the exposure of bulls to a novel environment on physiological, metabolic and behavioural responses of beef bulls. Thirty Charolais sired crossbred beef bulls (mean 486.0, s.d. 57.0 kg) were assigned by live weight to one of the two treatments, transport (T) (9h+9h) (n=15) and not-transported (NT) (n=15) on day 0. The bulls were transported at a spatial allowance of 1.3m(2)/animal by road for 9h, unloaded and rested for a 12h rest period, re-loaded and transported for a further 9h journey by road followed by a 2h rest period on the transporter, then unloaded and rested in a lairage for 24h with access to hay and water. Plasma albumin and urea concentrations increased (P<0.05) after the first 9h journey with values returning to baseline at the end of the 24h recovery period. There was a transient increase in haematocrit% in T and NT at sampling time points corresponding to the completion of the first 9h journey. Bulls spent longer time lying (P<0.05) during the first 9h journey compared with the percentage time spent lying during the second 9h journey. Differences in live weight, behaviour, and some blood variables show that transport is more stressful for bulls than being subjected to a novel environment and management, and while some biological variables returned to baseline values, others require a longer time (plasma haptoglobin, total protein, glucose and NEFA concentrations). Thus, the effective recovery of bulls exposed to an 18 h transport journey by road would suggest that a rest period of at least 24h with access to feed and water is required before further transport.

Live animal measurements, carcass composition and plasma hormone and metabolite concentrations in male progeny of sires differing in genetic merit for beef production.

In genetic improvement programmes for beef cattle, the effect of selecting for a given trait or index on other economically important traits, or their predictors, must be quantified to ensure no deleterious consequential effects go unnoticed. The objective was to compare live animal measurements, carcass composition and plasma hormone and metabolite concentrations of male progeny of sires selected on an economic index in Ireland. This beef carcass index (BCI) is expressed in euros and based on weaning weight, feed intake, carcass weight and carcass conformation and fat scores. The index is used to aid in the genetic comparison of animals for the expected profitability of their progeny at slaughter. A total of 107 progeny from beef sires of high (n = 11) or low (n = 11) genetic merit for the BCI were compared in either a bull (slaughtered at 16 months of age) or steer (slaughtered at 24 months of age) production system, following purchase after weaning (8 months of age) from commercial beef herds. Data were analysed as a 2 × 2 factorial design (two levels of genetic merit by two production systems). Progeny of high BCI sires had heavier carcasses, greater (P < 0.01) muscularity scores after weaning, greater (P < 0.05) skeletal scores and scanned muscle depth pre-slaughter, higher (P < 0.05) plasma insulin concentrations and greater (P < 0.01) animal value (obtained by multiplying carcass weight by carcass value, which was based on the weight of meat in each cut by its commercial value) than progeny of low BCI sires. Regression of progeny performance on sire genetic merit was also undertaken across the entire data set. In steers, the effect of BCI on carcass meat proportion, calculated carcass value (c/kg) and animal value was positive (P < 0.01), while a negative association was observed for scanned fat depth pre-slaughter and carcass fat proportion (P < 0.01), but there was no effect in bulls. The effect of sire expected progeny difference (EPD) for carcass weight followed the same trends as BCI. Muscularity scores, carcass meat proportion and calculated carcass value increased, whereas scanned fat depth, carcass fat and bone proportions decreased with increasing sire EPD for conformation score. The opposite association was observed for sire EPD for fat score. Results from this study show that selection using the BCI had positive effects on live animal muscularity, carcass meat proportion, proportions of high-value cuts and carcass value in steer progeny, which are desirable traits in beef production.