Evaluation of estimated genetic merit for carcass weight in beef cattle: Blood metabolites, carcass measurements, carcass composition and selected non-carcass components

In Ireland, a new beef genetic index has been developed. Growth rate is expressed as expected progeny difference for carcass weight (EPD_CWT) and is estimated on an across-breed basis. Cross-breeding of dairy cows with both Aberdeen Angus and Belgian Blue beef sires is widely practised. The objective of this study was to compare blood metabolites, slaughter traits and carcass composition of progeny from Holstein–Friesian dairy cows and Aberdeen Angus (AA), Belgian Blue (BB), Friesian (FR) and Holstein (HO) sires. The AA and BB sires were selected, within breed, to be of either high (H) or low (L) estimated genetic merit for carcass weight. A total of 170 male progeny from spring-calving cows and 42 sires (10 AA, 13 BB, 7 FR and 12 HO) were artificially reared indoors and managed together until the end of their second grazing season when they were assigned to either a Light (560 kg) or Heavy (620 kg) slaughter weight. Blood metabolite concentrations were measured six times throughout life and feed intake was recorded during the first and second winter. Carcass measurements and selected non-carcass components were recorded after slaughter and the right side of each carcass was dissected into lean, fat and bone. Differences in blood metabolite concentrations amongst genetic groups were negligible although there were some effects of the prevailing level of nutrition. M. longissimus area scaled for carcass weight was 0.220, 0.221, 0.260, 0.255, 0.212 and 0.208 (SE 0.004) cm²/kg for AAH, AAL, BBH, BBL, FR and HO, respectively. Carcass measurements scaled for carcass weight were greater for L, AA, HO and the dairy strains than for H, BB, FR and the beef breeds, respectively. There was no effect of estimated genetic merit for carcass weight on carcass composition. Statistically significant interactions between genetic merit and beef breed existed for some traits with the genetic merit effect largely evident for AA only. BB and the beef breeds had more lean, less fat and more high value lean in the carcass than AA and the dairy strains, respectively. It is concluded that genetic group had little effect on blood metabolite concentrations but there were some feeding level effects. Estimated genetic merit for carcass weight affected carcass weight, m. longissimus area and carcass measurements scaled for carcass weight but the effects were confined to AA. There were large effects of beef breed and dairy strain on carcass composition.     

经人工授精传播的猪病及其预防措施

猪人工授精技术（Artificial insemination,AI）已在集约化养猪生产国中得到了广泛应用。人工授精是一种将优秀基因引入母猪群中的非常有效的工具,并能够将疾病传播的风险降至最小。然而,受到病原体污染的精液对生产实际的危害是巨大的。在已经从公猪精液中检测到的微生物中,大部分是非致病性的,但有一些是有名的病原体,如猪繁殖与呼吸综合症病毒,这部分病原体能给养猪业造成重大的经济损失。精液受到微生物的污染可能是由于公猪全身性感染和/或泌尿生殖道感染所致,或可能发生在精液采集、处理和存储过程中。这会导致精液品质下降,胚胎或胎儿死亡,以及受体母猪的子宫内膜炎和全身性感染和/或发病。用于从精液中分离细菌和病毒的常规技术因受多种原因的影响并不总是能获得理想的结果,这些原因包括所用技术缺乏敏感性和检测速度慢、对检测结果难以进行解释。近年来,PCR技术得到了普遍的应用,它们具有很高的敏感性,能很快获得检测结果,并且适合对大样本的检测。防止通过人工授精传播疾病的最佳方法是使用无特定病原体的公猪、对它们及其精液进行定期检测以及维持极高的生物安全水平。其它方法则应该侧重于利用合适的抗菌剂对精液进行处理,以及重点减少在采集、处理和存储过程中精液所受到的污染。     

Effect of dietary modification of muscle long-chain n-3 fatty acid on plasma insulin and lipid metabolites, carcass traits, and fat deposition in lambs

In a previous study we showed that feeding fish meal significantly increased muscle long chain n-3 fatty acids (FA) and hot carcass weight. In this study we compared the effect of fish meal and fish oil on increasing muscle long-chain FA. We also investigated whether the increase in carcass weight was due to the effect of dietary enrichment of muscle long-chain n-3 FA on muscle membrane phospholipids and(or) to rumen by-pass protein provided by fish meal. Forty crossbred ([Merino x Border Leicester] x Poll Dorset) wether lambs between 26 and 33 kg BW were randomly assigned to one of five treatments: 1) basal diet of oaten:lucerne chaff (Basal); 2) Basal + fish meal (9% DM) = FM; 3) Basal + fish oil (1.5% DM) with protected sunflower meal (9% DM ) = FOSMP; 4) Basal + fish oil (1.5% DM) = FO; or 5) Basal + protected sunflower meal (10.5% DM) = SMP. Daily intake of ME (9.60 - 10.5 MJ ME/d) and CP (150 to 168 g/d) in all treatments was kept similar by varying the ratio of oaten:lucerne chaff and by feeding the animals at 90% ad libitum intake. Blood samples were collected at the start of the experiment and on the day (d 42) prior to slaughter. Lambs were then slaughtered at a commercial abattoir. At 24 h postmortem carcass traits were measured and longissimus thoracis muscle taken for analysis of FA of phospholipid and triglyceride fractions. Lambs fed FO and FOSMP showed a marked increase in muscle longchain n-3 FA (P < 0.001) and a reduction in magnitude of the rise in insulin concentration (P < 0.001) after feeding compared with lambs fed Basal and SMP diets. Lambs in FM had a moderate increase (P < 0.001) in muscle long-chain n-3 FA content. Compared with Basal diet, both plasma total cholesterol (P < 0.02) and high-density lipoprotein cholesterol (P < 0.001) levels were greater in SMP and less in FO and FOSMP treatments. The i.m. fat content was reduced (P < 0.05) in FM and FO treatments, but carcass weight was increased only with fish meal (P < 0.03). Adding SMP to FO produced muscle with an intermediate level of i.m. fat, whereas muscle long-chain n-3 FA, i.m. fat, and insulin concentration were unchanged with SMP treatment. These results indicate that an increase in carcass weight in FM may be due to the supply of ruminally undegraded protein. They also suggest that fish oil along with fish meal can increase long-chain n-3 FA content in phospholipid of muscle membrane. This may be associated with reduced i.m. fat content and altered insulin action and lipoprotein metabolism.     

Predicting behavioral changes associated with age-related cognitive impairment in dogs

OBJECTIVE: To monitor the progression of age-related behavioral changes in dogs during a period of 6 to 18 months and to determine whether signs of dysfunction in any of 4 behavioral categories can be used to predict further impairment. DESIGN: Age-stratified cohort study. ANIMALS: 63 spayed female and 47 castrated male dogs 11 to 14 years of age. PROCEDURE: Data were collected from randomly selected dog owners who were interviewed by telephone twice at a 12- to 18-month interval; data were included if the dog had lived > or = 6 months between interviews. The interview focused on signs of impairment in the following behavioral categories: orientation in the home and yard, social interactions with human family members, house training, and the sleep-wake cycle. Dogs were determined to have impairment in 0 behavioral categories (on the basis of < or = 1 sign for each category), impairment in 1 category (> or = 2 signs of dysfunction in that category), or impairment in > or = 2 categories. RESULTS: Between interviews, 22% (16/73) of dogs that did not have impairment in a category at the time of the first interview developed impairment in that category by the time of the second interview. Forty-eight percent (13/27) of dogs that had impairment in 1 category at the time of the first interview developed impairment in > or = 2 categories by the time of the second interview and were significantly more likely to develop impairment in > or = 2 categories, compared with dogs that initially had impairment in 0 categories. Dogs with 1 sign of dysfunction in orientation were significantly more likely to develop impairment in that category, compared with dogs that had 0 signs of dysfunction in orientation. CONCLUSIONS AND CLINICAL RELEVANCE: Age-related behavioral changes in dogs are progressive. Clinicians should consider trying to predict which dogs are most likely to become progressively impaired during the subsequent 6 to 18 months.     

Spike glycoprotein cleavage recognition site analysis of infectious bronchitis virus.

The spike glycoprotein of infectious bronchitis virus (IBV), a coronavirus, is translated as a precursor protein (So), then cleaved into two subunits (S1 and S2) by host cell serine proteases. In this study, we compared the cleavage recognition site of 55 IBV isolates to determine if the cleavage recognition site sequence, which consists of five basic amino acid residues, correlates with host cell range, serotype, geographic origin, and pathogenicity as it does in orthomyxoviruses and paramyxoviruses. The most common cleavage recognition site observed (33 of 55 viruses) was Arg-Arg-Ser-Arg-Arg, representing at least 11 different serotypes. Thus, cleavage recognition site does not appear to correlate with serotype. We also determined that cleavage recognition site sequence does not correlate with pathogenicity because attenuated and pathogenic isolates (different passages of the same virus) contain identical cleavage recognition site sequences. In addition, nephropathogenic strains had the same cleavage recognition site sequence as many nonnephropathogenic isolates. Cleavage recognition site sequence does correlate with viruses in different geographic regions, which may be an important characteristic to examine in epidemiologic studies. An IBV monoclonal antibody neutralization-resistant mutant (NR 18) had an unusual substitution of Ile for Arg at the fourth position, giving the sequence Arg-Arg-Ser-Ile-Arg, which likely prevents cleavage and, thus, destroys the conformationally dependent monoclonal antibody binding epitope. Six residues on the amino-terminal side of the cleavage recognition site are conserved in 31% of the isolates and consist of only one or two basic amino acids. Thus, the number of basic residues around the cleavage recognition site does not appear to correlate with increased cleavability, host cell range, and increased virulence as it does with envelope glycoproteins in orthomyxoviruses and paramyxoviruses.     

Multiplex polymerase chain reaction for distinguishing Taylorella equigenitalis from Taylorella equigenitalis-like organisms.

It is difficult to distinguish isolates of Taylorella equigenitalis, the cause of contagious equine metritis, from a T. equigenitalis-like organism isolated from asymptomatic donkeys and horses. Although T. equigenitalis is responsible for a severe, contagious disease of the reproductive tract of equids, the T. equigenitalis-like organism, although contagious, does not appear to produce disease. Because of the economic consequences of correctly distinguishing isolates of these 2 microorganisms, a polymerase chain reaction (PCR)-based assay was developed that will distinguish isolates of T. equigenitalis from the T. equigenitalis-like microorganism. The primers used in the PCR assay were designed to amplify unique regions of the gene encoding the 16S ribosomal RNA.     

The effects of several supplementation frequencies on forage use and the performance of beef cattle consuming dormant tallgrass prairie forage

Two experiments were conducted to quantify the impact on forage use and performance of varying supplementation frequency of cattle consuming forage diets across a range of frequencies. In both experiments, a common supplement was used that contained a relatively high concentration of CP (43%) and was fed at the following frequencies: 1) 2 d/wk; 2) 3 d/wk; 3) 5 d/wk; and 4) 7 d/wk. In Exp. 1, 120 Hereford x Angus cows (BW = 537 kg) grazing winter tallgrass-prairie range were supplemented at the various frequencies from December 7 until calving (average calving date = 3/7/99). All treatments provided the same quantity of supplement on a weekly basis (12.74 kg, as-fed) but divided the amount delivered on a given day equally among the number of supplementation events for that treatment. Less BW was lost from December 7 through calving (linear effect, P = 0.02) as frequency of supplementation increased, but the magnitude of difference in weight change was relatively small. Body condition responded similarly through early February (linear effect, P = 0.02), although treatment effects were not as distinct at calving (cubic effect, P = 0.11). In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 257 kg) were blocked by weight and assigned to one of the four frequencies of supplementation. Steers were offered tallgrass prairie hay (73.5% NDF, 4.8% CP) ad libitum and were supplemented at a rate (relative to BW) similar to that of the cows in Exp. 1. Increasing frequency of supplementation increased (linear effect, P < or = 0.02) forage OM intake, OM and NDF digestion, and digestible OM intake. However, the most prominent differences in forage OM intake tended (cubic effect, P = 0.07) to occur with the two extreme frequencies of supplementation. In conclusion, forage use was improved with an increased frequency of supplementation, but the impact on performance is not likely to be large unless extreme differences in frequency occur.     

Seroprevalence of Ornithobacterium rhinotracheale infection in commercial laying hens in the north central region of the United States.

This study was the first to examine the seroprevalence of Ornithobacterium rhinotracheale (ORT) within a commercial egg layer population. Serum samples collected from egg production companies were examined by serum plate agglutination test (SPAT) and outer membrane protein-based enzyme-linked immunosorbent assay (ELISA). Results show that 90% of layer flocks were positive by SPAT and 100% by ELISA. Of the pullet flocks examined, 43% and 52% were positive by SPAT and ELISA, respectively. Our study indicates that the prevalence of ORT antibody is high in the commercial layer population, suggesting that this respiratory pathogen can easily spread through multiple-age layer farms from older flocks to newly housed pullet flocks.