Young Beef Research Articles

Diet-induced changes in bacterial communities in the jejunum and their associations with bile acids in Angus beef cattle

BackgroundThe small intestine, while serving as the main absorption organ, also possesses a unique bacterial environment and holds the critical function of conversion of primary bile acids. Bile acids are, in turn, able to regulate bacterial composition and promote the growth of bacteria that convert primary bile acids to secondary bile acids. However, in beef cattle, few studies have explored the influence of diets on jejunal bacterial communities and examined its relationships with bile acids. Here, we examined the impact of grain- and grass-based diets on jejunal and fecal bacterial communities’ composition and investigated possible association of bacterial features with bile acids.ResultsWe demonstrated that the influences of diets on intestinal bacteria can be observed in young beef cattle after weaning. A significantly higher level of microbial diversity was documented in feces of grass-fed cattle comparing to grain-fed cattle. Top 20 important genera identified with random forest analysis on fecal bacterial community can be good candidates for microbial biomarkers. Moreover, the jejunal bacteria of adult Angus beef cattle exhibited significant differences in microbial composition and metabolic potential under different diets. Global balances and bacteria signatures predictive of bile acids were identified, indicative of the potential association of bacterial features with bile acids.ConclusionsThe findings from this study provided novel insights into the relationships between jejunal bacteria and bile acids under different diets in Angus beef cattle. Our results should help us gain a better understanding of potential health benefits of grass-fed beef.

Growth and Development Patterns of the Skeleton in Simmental and Cross Young Beef Bulls

The age-related carcass-morphology and composition changes and the growth and development patterns of the axial and peripheral skeleton systems and the bones composing them in the Simmental and crossbred young beef bulls have been studied. In order to carry out the survey, the young bulls were divided into three groups of 15 animals each. The first (control) group included the purebred Simmental young bulls. The second (experimental) group was formed of the halfbred and crossbred young stock produced by crossbreeding between the Simmental cows and the Simmental beef bulls of German selection. The third (experimental) group was composed of the crosses of Simmental cows with Charolais bulls. The Charolais crosses had more energy for growth. Thus, their liveweights comprised 431.9, 523.4, and 620.6 kg at the ages of 12, 15, and 18 months, respectively, which were 7.8, 7.5, and 10.2% more than that in their peers of the maternal breed. The crossbred young stock in both groups was distinct for carcass morphology and composition, reaching a more advanced level of the carcass flesh-coverage mass in all the age intervals when compared that to the purebred Simmentals. The age-related changes in the absolute and relative masses of the young-bull carcass bones are caused by different intensities specific to bone growth in the axial and peripheral skeleton systems. For instance, the intensity of bone growth in the axial skeleton system tended to increase in the postnatal period, while the bone growth rates of the peripheral skeleton system decreased. Irregularity in developing the indicated skeleton systems is caused by different intensities specific to growth of certain bones and their complexes. The highest growth rate is usually typical for ribs and the vertebral column, while the slowest growth rate is most common for extremitas thoracica and extremas pelvina. The bone growth rates for the limb proximal structures generally exceed that for the distal bone structures. The age-related differences in the growth rates of certain skeleton structures can cause some changes in ratios between the linear body measurements of the young bulls.

Мясная продуктивность бычков разных экстерьерно-конституциональных типов

Мясная продуктивность бычков разных экстерьерно-конституциональных типов

To what extent does the composition of batches formed at the sorting facility influence the subsequent growth performance of young beef bulls? A French observational study

To meet the demands of the beef cattle sector in France, weaned beef calves are transported to sorting facilities and sorted into batches composed of animals of similar body weight (BW) before the beginning of the fattening period. This procedure aims to facilitate animal management. However, it leads to practices that affect animal welfare, health and performance, such as transporting weaned beef calves over long distances and mixing animals originating from different cow/calf farms. In contrast, other potentially beneficial practices, such as pre-weaning vaccination against bovine respiratory diseases (BRD), are seldom taken into consideration when batches are formed. This observational study, based on field data from 15,735 Charolais bulls, aimed to investigate which criteria should be favored for batch constitution by quantifying the effect of batch characteristics on the growth performance of young bulls during the fattening period. Clustering analysis was used to group young bulls exhibiting similar batch characteristics and define batch types. Associations between batch characteristics/batch types and individual growth performance/homogeneity of growth performance (mean and standard deviation (SD) of average daily gain (ADG) and fattening period duration) were studied using linear mixed models. The mean BW and the percentage of animals vaccinated against BRD before weaning were positively associated with ADG (+35 g/d for each additional 50 kg and +28 g/d for a high percentage of vaccinated animals, P < 0.05). In contrast, transportation distance was negatively associated with ADG (−12 g/d for each additional 120 km travelled). Mixing animals and BW homogeneity did not affect growth performance (P > 0.05). Only the mean BW and mixing animals negatively influenced the homogeneity of ADG (P < 0.01). The clustering analysis revealed that batches with the most BW heterogeneity, the least mixing, the shortest transportation distance and a high percentage of pre-weaning animals vaccinated against BRD had better growth performance compared to batches with the opposite characteristics (+61 g/d, P < 0.001). Our results suggest that major improvements of growth performance of fattening young bulls could be obtained by minimizing transportation distance, providing vaccination programs against BRD before weaning, and maintaining groups from the same cow/calf farm instead of constituting groups of animals with similar BW at the beginning of fattening.

Forage potential of corn intercrops for beef cattle diets in northwestern Alberta

AbstractIntercropping systems involving cereals with legumes provide several advantages such as elevated forage yield and improved forage nutritive value. This study was designed to assess viability of corn (Zea mays L.) intercrops to improve the forage crude protein (CP) of corn forage for beef cattle production. A corn monocrop (C‐M) was compared with seven corn intercrops (five annual legumes, a non‐legume crop (radish (Raphanus sativus L.), C‐RA) and an annual crop mixture (ACM)). The corn forage dry matter (DM) yield was significantly improved (P &lt; .05) for C‐M than all intercrops. Of the seven intercrops, only corn‐radish intercrop (C‐RA) produced significantly lower total forage DM yield (corn + companion) than C‐M. Of the seven corn intercrops, only corn‐hairy vetch (Vicia villosa Roth) (C‐HV) and corn–annual crop mixture (C‐ACM) had significantly (P &lt; .05) improved forage CP and digestible CP than C‐M. Both C‐HV and C‐ACM exceeded the CP recommendations for mature beef cattle and also had adequate CP for young (growing and finishing calves) beef cattle, thereby eliminating the need for protein supplementation during the feeding of either C‐HV or C‐ACM beef cattle. Forage minerals were not significantly affected (P &gt; .05) by corn intercrops. Forage total digestible nutrients (TDN) was significantly (P &lt; .05) influenced by intercrops and varied from 65.9‐71.2%. Results indicate that selected corn intercrops can improve nutritive value of forage for beef cattle production.

Identification of the production system of beef cattle by the stable isotope analysis

Abstract: The objective of this work was to evaluate the potential of the stable isotope technique to characterize beef cattle production systems in tropical conditions. For this, carbon and nitrogen stable isotopes were identified in non-defatted and defatted bovine muscles. A total of 45 cattle were evaluated in three production systems: pasture, conventional feedlot, and young beef bull feedlot (n = 15 per system). Samples from the Trapezius cervicis, Longissimus dorsi, and Semitendinosus muscles were collected to determine the isotopic composition of δ13C and δ15N. The isotopic data of the δ13C and δ15N of non-defatted and defatted muscles were subjected to the principal component analysis (PCA) and to the discriminant analysis (DA). The PCA allowed separating the three production systems based on the results obtained for the non-defatted and defatted muscles. A correct global classification rate of 100% and a cross-validation rate of 100% were obtained with the DA. The carbon and nitrogen isotopic ratio of non-defatted and defatted muscles allows for the precise identification of beef cattle production systems in tropical conditions.

Exterior Features and Productive Qualities of Young Beef Cattle of Various Genotypes

The article describes the issues of comparative assessment of economic and biological features and productive qualities of beef cattle bred in Western Kazakhstan. The authors present norms and rations for feeding young animals of different genotypes. The results of studying the exterior features, body weight and average daily gain of Kazakh Whiteheaded breed and foreign Hereford and Aberdeen Angus breeds are presented. The authors conduct a comparative analysis of body weight and average daily gain of young animals of different breeds grown in the semi-desert zone of Western Kazakhstan. It has been found that during the growing period from 8 to 15 months, the average daily gain of body weight of the Hereford breed was 658.1 g for bull calves and 587.1 g for heifers, of the Aberdeen Angus breed – 603.8 g and 500.9 g respectively and of the Kazakh Whiteheaded breed – 758.8 g and 561.1 g respectively.

Fattening of Young Beef Cattle on Hay Diets

The article presents the results of studies on the use of hayfood rations from perennial legumes prepared in packaging film for feeding young cattle. The diets of feeding young cattle are balanced according to the main elements of nutrition, which made it possible to obtain average daily gains at the level of 10220–1244 grams. The nutritional value of the diets was almost the same in the groups and amounted to 9.33–9.39 energetic feed unit. It was found that animals treated with alfalfa and goat senator digested dry matter better by 7.83 and 3.4 %, crude protein by 5.41 and 1.87 %; crude fat by 19.89 and 4.67 %, crude fiber by 16.46 and 14.10 % compared with calves receiving clover hay, respectively. Using silage diets from these crops improves energy metabolism. The coefficient of productive use of metabolic energy by animals of the 3rd experimental group was 43.91 %, which is 5.15 % more than in the 1st experimental group, by 8.60 % from the 2nd experimental group. Animals of the 3 experimental groups were characterized by a higher slaughter yield, in comparison with other groups. The cost of feed per unit of increase in live weight of animals in group 2 was 9.19 energetic feed unit, which is 0.9 energetic feed unit and 1.73 energetic feed unit less than in 1 and 3 groups.

Effects of rumen-protected oil supplementation on finishing grazing beef cattle.

The objective of this study was to evaluate the effects of rumen-protected oil (soybean and palm oil) in supplements for beef cattle during the fattening phase in pastures on the intake and digestibility of nutrients, animal performance, and carcass characteristics. Forty-eight noncastrated male Nellore cattle (15 ± 2months and 389.5 ± 20kg of body weight) were used in a completely randomized design to evaluate the following treatments: protein-energy supplement (PES) without rumen-protected oil (control: CO), PES containing palm rumen-protected oil (PRPO), PES containing soybean rumen-protected oil (SRPO), and PES containing a mixture of soybean and palm rumen-protected oil (SPRPO). The study lasted 112days, and there was a decrease in crude protein intake (P < 0.05) and an increase in ether extract intake (P < 0.05) when rumen-protected oil was included in the supplements. In comparison to the palm rumen-protected oil supplement, the soybean rumen-protected oil supplement promoted a lower average daily gain (ADG) (P < 0.05); however, regardless of the rumen-protected oil source, an increase in the fat thickness of the subcutaneous tissue was observed. In addition, there was no difference in carcass gain (P > 0.05) regardless of oil source. Rumen-protected oil is a tool to increase the finishing of pasture-finished young beef cattle in the dry season.

Protection against bovine respiratory syncytial virus in calves vaccinated with adjuvanted modified live vaccine administered in the face of maternal antibody

Bovine respiratory syncytial virus (BRSV) is major viral contributor to bovine respiratory disease (BRD). BRD is a major cause of morbidity and mortality in all classes of cattle but particularly young beef and dairy calves. Passive antibodies not only help protect the calf against infection, but may interfere with the immune responses following vaccination. The purpose of this study was to evaluate the efficacy of an adjuvanted modified live virus (MLV) vaccine in the presence of well-defined maternal passive immunity. Calves were vaccinated at approximately 1 month of age and challenged ~90 days later when BRSV systemic antibodies were ≤1:4. Body temperature was lower at 6 and 7 days post challenge and other clinical signs were also lower in the vaccinates. Nasal viral shed was 3–4 times lower in the vaccinated animals as measured by virus isolation and polymerase chain reaction (PCR) and peaked 5 days post challenge compared to the controls (who peaked at days 6 and 7). On day 8 following challenge, animals were necropsied, and lung lobes were scored and tested for virus by PCR and indirect fluorescent assay (IFA). There was a 25-fold reduction in PCR virus detection in vaccinates and two of the vaccinated calves’ lungs were PCR negative. Only 29.4% of vaccinated calves were BRSV positive on IFA testing at necropsy, while 87.5% of control calves were BRSV positive. Vaccinated calves developed a mucosal BRSV IgA response with over 50% of the vaccinated calves having IgA prior to challenge and all vaccinated calves were positive following challenge. Additionally, vaccination stimulated the production of Interferon gamma (IFN-γ) in mononuclear cells to prime the immune system. This study established that an adjuvanted MLV vaccine could provide protection against BRSV as measured by clinical, virological, and pathological parameters while also activating both mucosal and systemic immunity.

Fatty acid composition of blood lipids of young beef cattle of different genotypes of CAPN1, GH, TG5, LEP genes

The results of genotyping of beef cattle (bull-calves of white-faced and Kazakh whiteheaded cattle) made it possible to establish the features of gene polymorphism ensuring meat efficiency (CAPN1, GH, TG5, LEP). Genotype carriers of selection significant alleles marking high efficiency and quality of beef are revealed. Superiority by body weight, daily average gains of homozygous (CAPN1CC GHLL TG5TT LEPTT) genotypes in comparison with alternative (CAPN1GG GHVV TG5CC LEPCC) genotypes was established in the selection of white-faced bull-calves by 13.2 and 14.9%, Kazakh white-headed – by 11.8 and 13.3%. The fatty acid composition of blood lipids of young white-faced, Kazakh white-headed cattle of different genotypes is defined. The features of fatty acid composition of blood lipids depending on pedigree and genotype of animals expressed by integrated indicators characterizing the intensity of biosynthesis of fatty acids are established: index of lipid saturation (ILS), index of lipid exchange intensity (ILEI), metabolism efficiency ratio of essential fatty acids (MER). The determined stable correlation of integrated indicators of lipid exchange intensity with body weight and daily average gains gives grounds for their use as biochemical test systems during lifetime assessment of young cattle breeding potential.

Histologic comparison of inflammatory cells in the penile and preputial epithelium of young vs mature beef bulls

There is evidence supporting clearance of the Tritrichomonas foetus in young bulls. The reasons for mature bulls becoming chronic carriers and resolution of venereal infections in young bulls have not been illuminated. It has been hypothesized that there is variation in the inflammatory response in the reproductive tract as the bull ages. Hence, the objectives of this study were to evaluate the immune cell population in the normal bovine penile and preputial epithelium and to examine any differences in cell populations between young and mature age groups. Our hypothesis was that there are significant differences in immune cell types within the penile and preputial epithelium and dermis of young versus mature bulls.

Cattle Review

Introduction: This edition of Cattle Review considers risk factors for negative energy balance in dairy cows, carriage of Pasteurellaceae in the airways of young beef cattle and the quantification of antibiotic use in Germen livestock.

108 Impacts of dam age and milk production on cow/calf profitability

Abstract Cow herd profitability can be greatly influenced by reproductive success, average age of herd, and genetic potential within the environment. Productivity is influenced by cow age with calf weaning weight, increasing from 2 to 5 yr of age in dams. With that in mind, increasing average age of the cowherd has the potential to increase cow/calf profitability. Culling cows before 5 yr of age negatively impacts production efficiency due to decreased calf weaning weight in younger cows and subsequently, increase replacement rate and costs. Therefore, reproduction in young cattle is important to overall economic efficiency within the cow herd and a driving factor in longevity. Due to decreased reproduction and offspring performance, young females have previously been considered an economic liability. The effect of increased average cow age within the herd along with increased pregnancy rate of young cows has shown to increase production efficiency by decreasing replacement rates and adding greater production potential with increased calf weaning weights. In young beef cows, partitioning nutrients away from lactational demands allows for nutrients to be utilized for cow growth and reproduction. An increase in selection for milk production has resulted in beef cows undergoing greater nutritional stress during early lactation, which ultimately reduces cowherd reproduction and efficiency. Although a big emphasis is placed on output traits, economic value of reproduction is 5 times greater than growth or maternal output traits in beef cattle. In addition, the value of the added milk production may not fully be captured, due to extensive environments with limited nutrients. Even in environments with greater feed resources, selection for milk production may led to a decrease in reproduction, production efficiency, and cowherd retention rate.

Relationship between feed efficiency and slaughter traits of French Charolais bulls.

Improving feed efficiency is of interest to French beef producers so as to increase their profitability. To enable this improvement through selection, genetic correlations with production traits need to be quantified. The objective of this study was to estimate the genetic parameters for growth, feed efficiency (FE), and slaughter performance of young beef bulls of the French Charolais breed. Three feed efficiency criteria were calculated: residual feed intake (RFI), residual gain (RG), and ratio of FE. Data on feed intake, growth, and FE were available for 4,675 Charolais bulls tested in performance test stations and fed with pelleted diet. Between 1985 and 1989, 60 among 510 of these bulls were selected to procreate one generation of 1,477 progeny bulls which received the same pelleted diet at the experimental farm in Bourges. In addition to feed intake, growth, and FE traits, these terminal bulls also had slaughter traits of carcass yield, carcass composition, and weight of visceral organs collected. Genetic parameters were estimated using linear mixed animal models. Between performance test bulls and terminal bulls, the genetic correlation of RFI was 0.80 ± 0.18; it was 0.70 ± 0.21 for RG and 0.46 ± 0.20 for FE. For carcass traits, RFI was negatively correlated with carcass yield (-0.18 ± 0.14) and muscle content (-0.47 ± 0.14) and positively with fat content (0.48 ± 0.13). Conversely, RG and FE were positively correlated with carcass yield and muscle content and negatively with fat content. For the three FE criteria, efficient animals had leaner carcass. For visceral organs (as a proportion of empty body weight), RFI was genetically correlated with the proportions of the 5th quarter (0.51 ± 0.17), internal fat (0.36 ± 0.14), abomasum (0.46 ± 0.20), intestines (0.38 ± 0.17), liver (0.36 ± 0.16), and kidneys (0.73 ± 0.11). Conversely, RG and FE were negatively associated with these traits. The high-energy expenditure associated with the high-protein turnover in visceral organs may explain this opposite relationship between FE and the proportion of visceral organs. Selection for final weight and RFI increased growth and FE in progeny, and also improved carcass yield and muscle content in the carcass. To conclude, determinations of growth and feed intake in performance test stations are effective to select bulls to improve their growth, FE, and muscle content in carcass.

Influence of genetic markers on the feeding behavior of yearling bulls

Background: The search for gene and marker effects on economically important traits is aimed not only to understanding the genetic architecture of complex traits but also to applying the information to breeding schemes. Objective: To analyze the effect of two temperament-related SNPs (rs109576799 located in the DRD3 gene, and rs43696138 in the HTR2A gene) on feeding performance of Mexican beef cattle. Methods: One hundred and thirty-six young beef bulls were included in a centralized feed efficiency performance test based on residual feed intake (RFI), with 20 d for adaptation and 70 d of feed efficiency testing. In addition to feeding traits, temperament was assessed at the beginning of the trial using pen score (PS) and exit velocity (EV). All animals were genotyped with two markers located in the HTR2A and DRD3 genes, and an association analysis was conducted between these genotypes and the measured traits. Results: For Brangus breed, a significant association was obtained between average daily gain (ADG; p=0.019), and the rs43696138 marker, resulting in higher gains for homozygous genotype GG (1.69 ± 0.04 kg), when compared to the heterozygous genotype GA (1.54 ± 0.04 kg). Conclusion: The previously reported association of these markers with temperament was not confirmed in the evaluated breeds; however, the rs43696138 marker showed an effect on a feeding performance trait. Further studies are needed to determine the effect of this and other markers on both RFI and temperament.

Effects of postpartum fat supplementation and source on the reproductive performance of lactating young beef cows grazing cool-season grass pastures

ABSTRACT Objective The objective was to evaluate the effects of fat supplementation and source on reproductive performance of young lactating Angus beef cows grazing cool-season grass (CSG) pastures. Materials and Methods Over 3 yr, 36 second- and third-calving, lactating (38 ± 1.5 d postpartum) Angus cows (554 ± 15.5 kg of BW) were assigned randomly to 9 paddocks (4 cows per paddock) of CSG pastures. Each paddock was assigned randomly to a nonsupplemented control (CON) or 2 supplemented (SUP) treatments in which cows received 300 g/cow per day of supplemental fat (ether extract) from a canola seed–based (CAN) or flaxseed-based (FLX) pellet for 42 d before start of the breeding period. Data were analyzed as a randomized complete block design contrasting the effects of fat supplementation (CON vs. SUP) and fat source (CAN vs. FLX). Results and Discussion Results indicate that cows in CON had greater (P = 0.01) forage utilization and tended (P = 0.08) to have greater estimated forage DMI compared with cows in SUP, whereas no difference (P ≥ 0.76) was observed between CAN and FLX treatments. By the end of the trial, all treatments resulted in positive ADG, maintained or increased BCS and s.c. fat thickness, and reduced serum nonesterified fatty acid concentrations with no difference (P ≥ 0.20) among treatments. No differences (P ≥ 0.12) were observed for pregnancy rate, calving distribution, and calving-to-calving interval. The failure to find treatment differences in growth and reproductive performance is likely a result of greater-than-expected nutrient content (CP: 12.5 ± 2.5%; TDN: 56.5 ± 2.9%) of CSG pastures and similar nutritional status across treatments. Implications and Applications These results indicate that prebreeding fat supplementation and source had no beneficial effects on reproductive performance of young, lactating Angus beef cows grazing good quality CSG pastures.

The effects of age and gender (bull vs steer) on the feeding behavior of young beef cattle fed grass silage.

ObjectiveThe objective of this study was to determine the effects of age and gender (bull vs steer) on feeding behavior parameters in young beef cattle fed grass silage.MethodsThe study was conducted on 180 young beef cattle at 7 to 18 mo of age. The experimental materials comprised 90 bulls produced by commercial crossing of Polish Holstein-Friesian cows with Charolais, Limousin and Hereford bulls (30 animals of each breed) and 90 steers of the same genotypes. The animals had ad libitum access to grass silage; the concentrate was fed separately, in feed stations. They received 28 g dry matter of concentrate per kg of metabolic body weight per day. Bunk visit data and silage intake for all experimental animals were recorded individually using the Roughage Intake Control system (5 feed bunks per 15 animals).ResultsAge and gender (bull vs steer) exerted significant effects on the feeding behavior of young beef cattle. The frequency of bunk visits and meal frequency decreased, whereas the feeding rate of silage, and the average duration and size of a single meal increased with age (p<0.01). Bunk attendance and meal frequency were higher (p<0.01) in steers than in bulls (49.1 vs 37.4 visits/d, and 8.63 vs 7.99 meals/d, respectively). Daily feeding time was longer in steers than in bulls (102.3 vs 100.3 min/d, respectively), but the feeding rate of silage was lower in steers, and their meals were smaller in size and shorter in duration (p<0.01). Daily silage dry matter intake was higher (p<0.01) in bulls than in steers (4.62 vs 4.47 kg/d, respectively).ConclusionThe results of this study indicate that age and gender (bull vs steer) exerted significant effects on the feeding behavior of young beef cattle.

Palatability of Beef Strip Loin Steaks Representing Various Marbling and Maturity Levels from Grain-Fed Beef

This study compared palatability traits of beef strip loin steaks with varying marbling scores from young and mature grain-fed beef. Strip loins (n = 150) were selected from grain fed cattle representing ten treatments with the following USDA marbling scores: Slightly Abundant or greater (SLAB+), Moderate or Modest (MD/MT), Small (SM), Slight (SL), and Traces or Practically Devoid (TR/PD) from young “A” maturity carcasses (Y) and mature “C” or greater maturity carcasses (M). Subprimals were fabricated into 2.5-cm steaks at 21 d postmortem and stored frozen until further analysis. Consumer (n = 120) sensory panelists evaluated cooked steaks for tenderness, juiciness, flavor liking, and overall liking. Trained panelists (n = 15 sessions) evaluated each sample for initial and sustained juiciness, initial and sustained tenderness, flavor intensity, and off-flavor intensity. For all traits, consumer and trained panelists’ scores generally decreased with decreasing marbling score, regardless of maturity. According to consumers, maturity had no effect on juiciness or flavor liking within each marbling score, except flavor liking of SLAB+ was greater (P &lt; 0.05) for young than mature carcasses. Conversely, young carcasses had greater tenderness scores than mature within all marbling categories except SM, which translated to greater overall liking of MD/MT, SL, and TR/PD of young compared to their mature counterparts (P &lt; 0.05). Trained panelists detected very few differences between young and mature samples within their respective marbling score; however, M-MD/MT had lower initial and sustained tenderness coupled with greater off-flavor intensity than Y-MD/MT (P &lt; 0.05). Mature samples with SLAB+ and MD/MT marbling were rated greater than or equal to Y-SM for all traits, indicating the presence of marbling from feeding a grain diet prior to harvest may elicit a similar eating experience to young beef by offsetting negative palatability traits often associated with mature beef.

Impacts of residual feed intake and pre-natal diet on reproductive potential of bulls

Our objective was to determine effects of genetic potential for residual feed intake (RFI) and pre-natal diet on post-natal growth and reproductive development of bulls. Twenty-five bull calves with a divergent potential for RFI were produced by mating purebred Angus heifers (60) categorised as high or low RFI and inseminated with semen from high or low RFI bulls. From 30 to 150 days of gestation, half the heifers (balanced for RFI across treatments) in each RFI category were fed to gain 0.7 or 0.5 kg/day (~100% and 75% of recommended feed intake; designated normal- and low-diet, respectively). Birthweights of bull calves (n = 25) did not differ significantly among treatment groups (P ≥ 0.1). However, there was a tendency (P &amp;lt; 0.1) for a maternal diet*time interaction for bull weights, with bulls from low pre-natal diet fed heifers growing faster between 10 and 16 months of age than bulls from normal pre-natal diet fed heifers. Furthermore, high-RFI bulls had a larger scrotal circumference (P &amp;lt; 0.01) and attained puberty (P &amp;lt; 0.05) earlier than low-RFI bulls. Other testes measures, including paired testes volume, epididymal sperm reserves, daily sperm production and total sperm production, were not significantly different among treatment groups (P ≥ 0.1). High RFI bulls tended (P &amp;lt; 0.1) to have better average sperm motility than low RFI bulls. However, sperm morphology, viability and chromatin damage were not different (P ≥ 0.1). In summary, young beef bulls with low RFI had smaller testis, delayed onset of puberty (~1.7 months) and tended to exhibit lower progressive motility compared with high RFI bulls. Pre-natal diet had no direct influence on male reproductive development, nor did it interact with RFI of bulls.