Agustín Ruíz-Flores

Genotype by climate interaction in the genetic evaluation for growing traits of Braunvieh cattle in Mexico

The objective of this study was to determine the magnitude of genotype by climate interaction (GCI) in the national genetic evaluation for weaning (WW) and yearling (YW) weights of Mexican Braunvieh cattle. The numbers of performance records and animals in the pedigree were 12,364 and 25,173 for WW, and 7,991 and 18,072 for YW, respectively. Performance records were clustered based on climatological variables into: dry tropic (DT), wet tropic (WT), and temperate (TE) climates. Animal models were used to estimate genetic parameters and predict breeding values in each of the climates. Bivariate analyses were carried out for pairwise combinations of climates on each trait, considering the same trait in different climates as a different trait. Criteria to evaluate GCI were genetic correlations (rg), correlations between predicted breeding values (rBV), and frequencies of coincidence (FC) in the ranking of the top 25 sires. Results of comparisons between pairs of climates were variable, depending on specific cases. For WW, the rg, rBV, and FC ranged from −0.36 to 0.84, −0.60 to 0.97, and 0.16 to 0.92, respectively; whereas for YW, they fluctuated between 0.23 and 0.99, 0.33 and 1.00, and 0.60 and 1.00, respectively. For both traits, the results suggest absence of GCI between DT and TE; however, GCI was detected in the other pairs of climates, where WT was involved. To maximize genetic progress, the joint genetic evaluation should be performed only for animals with performance data in DT and TE, whereas a separated evaluation is suggested for animals with performance records generated under WT conditions.

Genotype by feeding system interaction in the genetic evaluation of Jersey cattle for milk yield

Results of studies in dairy cattle about the magnitude of the genotype-environment interaction (GEI) are variable, depending on the definitions of genotype and environment. Therefore, the objective of this study was to determine the magnitude of the interaction of genotype and feeding system (confinement and grazing) in the Mexican genetic evaluation of Jersey cattle for milk yield. The number of lactations and animals in the pedigree used were 5122 and 18 432. An animal model and the MTDFREML program were used to estimate genetic parameters and predict genetic values of the animals. Bivariate analysis was carried out considering the performance of confined and grazing cows as two different traits. Three indicator variables were used to assess GEI: (i) magnitude of the genetic correlation coefficients, (ii) correlation between predicted breeding values and (iii) frequency of coincidence in the ranking of top sires. The magnitude of GEI depended on the choice of the indicator variable. The estimate of genetic correlation coefficient less than unity (0.76; P < 0.05) suggested the presence of biologically important GEI. The differences in phenotypic averages and variances between confinement and grazing systems seem to be the main causes for the genotype by environment interaction detected. However, the correlation coefficient between breeding values from confined and grazing animals (0.96) and the frequency of coincidence between breeding values of common sires within the top 100 in confinement and grazing (0.86) indicated low-to-moderate re-ranking of animals or top sires. In addition, the high correlations between predicted breeding values of Mexican genetic evaluation and the two environments (0.99 and 0.93 for confinement and grazing) indicated that for the two feeding systems, breeding values from national analyses could be safely used.

LEVEL OF ADOPTION OF QUALITY MANAGEMENT SYSTEMS INTO THE MEXICAN PORK INDUSTRY

This research studies the characteristics of the Mexican pork sector; adoption status of quality management systems, and product destinations. Ninety six percent of fifty enterprises have fully answered a questionnaire. Ninety percent are small and medium-sized, the rest are large-sized firms. Nineteen percent of them have totally adopted HACCP, sixty three percent are implementing or planning to do it, the rest have no plans to adopt it. Thirteen percent of the enterprises had ISO 9000. Thirty four percent of their sales go to supermarkets, 57% to other retail chains and 9% to exportation. Product destinations are mainly Central America, United States of America, Asia and Mexico. To improve efficiency and the quality of process it is necessary to implement HACCP. Besides, customers and legal requirements are the external factors, which result in this adoption. In the process of implementing, there are some problems, such as staff motivation and training. The results suggest that HACCP system operating is important for the Mexican pork industry. It also has relevant implications in domestic trade. It is necessary to encourage adoption of quality management systems in the sector.

Meta-analysis: effects of exogenous fibrolytic enzymes in ruminant diets

ABSTRACT There are unknown interactions between supplements of exogenous fibrolytic enzymes (EFE) and the cell walls of feedstuff in ruminal conditions. The quantitative effects of using EFE in ruminant diets were evaluated using meta-analysis. Records (586) were extracted from 74 journal articles from a list of published papers (2000–2012). Statistical analyses were performed considering fixed [type of forage-based diet, forage-to-concentrate ratio (F:C ratio) and primarily enzyme activities in the EFE], and random effects [Experiment(Article)]. In dairy cows fed high-forage (F:C ≥50%), the supplementation of primarily mixtures of cellulases and xylanases (Cel:Xyl: 1:4–1:1) increased milk production and milk composition of legume-based diets, and primarily xylanases (Xyl) EFE improved those variables of grass-based diets. In F:C <50% grass-based diets, Cel:Xyl improved the average daily gain (ADG) and feed conversion [FC:DM intake (DMI)/ADG] of beef cattle. DMI of dairy cows was not affected by EFE supplementation, but EFE improved the DMI of beef cattle. EFE effects were inconsistent in sheep productive performance variables. Cellulases (Cel) and Xyl enhanced in vivo dry matter (DM) digestibility (DMD) in low-forage (F:C <50%) grass-based diets. In F:C ≥50% legume-based diets, EFE enhanced the in situ DM disappearance (ISDMD), and mainly Cel:Xyl improved the in situ neutral detergent fibre (NDF) disappearance (ISNDFD), but there were no effects in those variables in F:C ≥50% grass-based diets. Regardless of the type of ruminal liquid (RL) or forage, in F:C ≥50% diets, in vitro DM degradability (IVDMD) was improved mainly by Cel, but fibre degradability only was improved by Cel:Xyl when sheep RL was used for in vitro evaluations. Overall, EFE could improve the productive performance of dairy cows and beef cattle, but the response depends upon the proper mixture of Cel and Xyl according to the diet composition. Abbreviations: ADF: acid detergent fiber; ADG: average daily gain; A:P: acetate:propionate ratio; BW: initial body weight; Cel:Xyl: cellulases:xylanases; DM: dry matter; DMD: in vivo dry matter digestibility; DMI: dry matter intake; EA: enzyme activities; EFE: exogenous fibrolytic enzymes; F: type of forage; FC: feed conversion; F:C: forage-to-concentrate ratio; ISDMD: in situ dry matter disappearance; ISNDFD: in situ neutral detergent fiber disappearance; IVADFD: in vitro acid detergent degradability; IVDMD: in vitro dry matter degradability; IVNDFD: in vitro neutral detergent fiber degradability; NDF: neutral detergent fiber; VFA: in vitro volatile fat acids

Screening genetic diseases prevalence in Braunvieh cattle

Heritable abnormalities can cause a reduction in productive performance, structural defects, or death of the animal. There are reports of hereditary abnormalities in Braunvieh cattle from several countries, but no evidence was found on their existence in Mexico. In this study, 28 genes associated with hereditary diseases were screened with the GGP-LD 30K array (GeneSeek®) in 300 Mexican registered Braunvieh animals. Allelic frequencies of the markers associated with illness were obtained for the following: citrullinaemia, spinal dysmyelination, spinal muscular atrophy, Brows Swiss fertility haplotype 2, congenital muscular dystonia, epidermolysis bullosa, Pompes, maple syrup urine, syndactyly, Weaver syndrome, crooked tail, deficiency of uridine monophosphate synthase, hypotrichosis, Marfan syndrome, and weak calf syndrome. The allelic frequency values were low for all the analysed loci (from 0.0015 to 0.0110), with exception of syndactyly (0.4145). Although homozygous animals for these genetic conditions were detected, no physical or physiological abnormalities associated with the clinical form of the diseases were observed in the sampled animals. Markers associated with a crooked tail, deficiency of uridine monophosphate synthase, hypotrichosis, Marfan syndrome, and weak calf syndrome were absent. The studied Mexican Braunvieh population does not present clinical or subclinical effects for ten diseases in homozygous animals. However, since the assessed animals are considered as breeding stock, the monitoring of carrier animals might be periodically necessary.

Potential influence of κ-casein and β-lactoglobulin genes in genetic association studies of milk quality traits

Objective From a review of published information on genetic association studies, a meta-analysis was conducted to determine the influence of the genes κ-casein (CSN3) and β-lactoglobulin (LGB) on milk yield traits in Holstein, Jersey, Brown Swiss, and Fleckvieh. Methods The GLIMMIX procedure was used to analyze milk production and percentage of protein and fat in milk. Models included the main effects and all their possible two-way interactions; not estimable effects and non-significant (p>0.05) two-way interactions were dropped from the models. The three traits analyzed used Poisson distribution and a log link function and were determined with the Interactive Data Analysis of SAS software. Least square means and multiple mean comparisons were obtained and performed for significant main effects and their interactions (p<0.0255). Results Interaction of breed by gene showed that Holstein and Fleckvieh were the breeds on which CSN3 (6.01%±0.19% and 5.98%±0.22%), and LGB (6.02%±0.19% and 5.70%±0.22%) have the greatest influence. Interaction of breed by genotype nested in the analyzed gene indicated that Holstein and Jersey showed greater influence of the CSN3 AA genotype, 6.04%±0.22% and 5.59%±0.31% than the other genotypes, while LGB AA genotype had the largest influence on the traits analyzed, 6.05%±0.20% and 5.60%±0.19%, respectively. Furthermore, interaction of type of statistical model by genotype nested in the analyzed gene indicated that CSN3 and LGB genes had similar behavior, maintaining a difference of more than 7% across analyzed genotypes. These results could indicate that both Holstein and Jersey have had lower substitution allele effect in selection programs that include CSN3 and LGB genes than Brown Swiss and Fleckvieh. Conclusion Breed determined which genotypes had the greatest association with analyzed traits. The mixed model based in Bayesian or Ridge Regression was the best alternative to analyze CSN3 and LGB gene effects on milk yield and protein and fat percentages.

IMPLEMENTATION OF HACCP IN THE MEXICAN POULTRY PROCESSING INDUSTRY

Hazard Analysis and Critical Control Point (HACCP) is a safety and quality management tool used as major issue in international and domestic trade in food industry. However, detailed information on costs and benefits of HACCP implementation is needed to provide appropriate advice to food processing plants. This paper reports on the perceptions of costs and benefits by the Mexican poultry processing plants and sale destinations. The results suggest that the major costs of implementing and operating HACCP within poultry processing plants are record keeping and external technical advice. The main benefit indicated by the majority of processing plants is a reduction in microbial counts. Over 39% of poultry production is sent to nation-wide chains of supermarkets, and less than 13% is sent to international markets. It was concluded that the adoption of HACCP by the Mexican poultry processing sector is based on the concern to increase and keep the domestic market, rather than to compete in the international market.