Genetic response to selection for weaning weight or yearling weight or yearling weight and muscle score in Hereford cattle: efficiency of gain, growth, and carcass characteristics

Herd-of-origin effect on the post-weaning performance of centrally tested Nellore beef cattle

The objective of a performance test station is to evaluate the performance of potential breeding bulls earlier in order to decrease the generation interval and increase genetic gain as well. This study evaluates the herd-of-origin influence on end-of-test weight (ETW), average daily weight gain during testing (ADG), average daily weight gain during the adjustment period (ADGadj), rib eye area (REA), marbling (MARB), subcutaneous fat thickness (SFT), conformation (C), early finishing (EF), muscling (M), navel (N) and temperament (T) scores, and scrotal circumference (SC) of Nellore cattle that underwent a performance test. We evaluated 664 animals that participated in the performance tests conducted at the Center for Performance CRV Lagoa between 2007 and 2012. Components of variance for each trait were estimated by an animal model (model 1), using the restricted maximum likelihood method. An alternative animal model (model 2) included, in addition to the fixed effects present in S1, the non-correlated random effect of herd-year (HY). A significant HY effect was observed on ETW, REA, SFT, ADGadj, C, and Cw (p < 0.05). The estimated heritability of all traits decreased when the HY effect was included in the model; also, the bull rank, in deciles, changed significantly for traits ETW, REA, SFT, and C. The adjustment period did not completely remove the environmental effect of herd of origin on ETW, REA, SFT, and C. It is recommended that the herd-of-origin effect should be included in the statistical models used to predict the breeding values of the participants of these performance tests.

Genetic association between body composition measured by ultrasound and visual scores in Brazilian Nelore cattle

The objective of this study was to evaluate the genetic variability of body composition traits measured by ultrasound, growth traits, and visual scores as well as their genetic associations in Nelore cattle. A total of 9,765, 13,285, 13,061, 12,811, 3,484, 3,484, 3,483, and 3,303 records of weight at time of ultrasound measure (W550), 12th-13th rib LM area (LMA), backfat thickness (BF), rump fat thickness (RF), visual scores for body structure (BS), finishing precocity (FP), muscling (MS), and sheath and navel characteristics (SN), respectively, were used. The model included contemporary group (defined as year and season of birth, sex, and management group) as a fixed effect and age of dam at calving and age of the animal (linear and quadratic effects) as covariates. The direct additive genetic effect was included as a random effect. The analyses also included 46,157 observations of BW adjusted to 120 d. The (co)variance components were estimated by the restricted maximum likelihood method using a multitrait animal model. Heritability estimates for W550, LMA, BF, RF, BS, FP, MS, and SN were 0.37 ± 0.030, 0.33 ± 0.03, 0.24 ± 0.02, 0.28 ± 0.03, 0.24 ± 0.04, 0.38 ± 0.05, 0.29 ± 0.05, and 0.38 ± 0.06, respectively. The estimated genetic correlations between visual scores and LMA were moderate and positive, ranging from 0.37 to 0.44. Similar results were obtained for the estimated genetic correlations between FP and MS with fat thickness measures (BF and RF). Low genetic correlations were estimated between SN and BS and between SN and the body composition traits, indicating that selection for body composition traits and BS will not affect sheath and navel size. The estimated genetic correlations between weight adjusted to 120 d of age (W120) and W550 and BS were high (0.87 and 0.91) and moderate with LMA (0.49 and 0.55), FP (0.37 and 0.41), and MS (0.47 and 0.55). The visual scores and ultrasound-measured body composition traits have enough genetic variation for selection purposes in Nelore cattle. Selection based on visual scores for body structure, finishing precocity and muscling should lead to desired changes in body composition albeit much more slowly than direct selection on those traits measured by ultrasound. Selection for heavier BW at early ages should lead to favorable changes in yearling LM area and visual scores.

Effect of liveweight gain of pregnant 15-month-old Angus heifers on the milk intake of their first calves and the liveweight of their first and second calves

Nutritional methods of manipulating birthweight of calves would be useful to beef cattle farmers as a tool for managing dystocia, particularly in 2-year-old heifers. This experiment examined the impact of liveweight gain during pregnancy on birthweight, liveweight to weaning, body dimensions and milk intake of the calves, as well as subsequent liveweight and maternal performance of the heifers. Treatments were high (1.22 ± 0.12 kg/day; H) or moderate (0.56 ± 0.11 kg/day; M) liveweight gain for 10 days before conception, and moderate liveweight gain (0.54 ± 0.30 kg/day; M) or liveweight loss (–0.11 ± 0.30 kg/day; L) for the first trimester (93 days) of pregnancy. HL heifers delivered calves that were lighter absolutely and relative to postpartum liveweight of the heifers than the HM, MM or ML heifers. The 8–15% reduction in birthweight could have a substantial impact on incidence of dystocia, but mechanisms for the reduction were unclear. Liveweight gain treatments had no effect on body dimensions or milk intake of the calves. MM and HM calves were heavier during the rearing period than ML calves. There was no effect of treatment on days to calving or inter-calving interval between first and second calves. Conception rate at the third joining period was not different among treatments. The liveweight gain treatments applied achieved a reduction in birthweight and generally had only minor effects on the subsequent performance of the heifers.

Collective and individual functions of leptin receptor modulated neurons controlling metabolism and ingestion

Two known types of leptin-responsive neurons reside within the arcuate nucleus: the agouti gene-related peptide (AgRP)/neuropeptide Y (NPY) neuron and the proopiomelanocortin (POMC) neuron. By deleting the leptin receptor gene (Lepr) specifically in AgRP/NPY and/or POMC neurons of mice, we examined the several and combined contributions of these neurons to leptin action. Body weight and adiposity were increased by Lepr deletion from AgRP and POMC neurons individually, and simultaneous deletion in both neurons (A+P LEPR-KO mice) further increased these measures. Young (periweaning) A+P LEPR-KO mice exhibit hyperphagia and decreased energy expenditure, with increased weight gain, oxidative sparing of triglycerides, and increased fat accumulation. Interestingly, however, many of these abnormalities were attenuated in adult animals, and high doses of leptin partially suppress food intake in the A+P LEPR-KO mice. Although mildly hyperinsulinemic, the A+P LEPR-KO mice displayed normal glucose tolerance and fertility. Thus, AgRP/NPY and POMC neurons each play mandatory roles in aspects of leptin-regulated energy homeostasis, high leptin levels in adult mice mitigate the importance of leptin-responsiveness in these neurons for components of energy balance, suggesting the presence of other leptin-regulated pathways that partially compensate for the lack of leptin action on the POMC and AgRP/NPY neurons.

Parámetros y tendencias genéticas para características de crecimiento en el ganado criollo colombiano Romosinuano

Se estimaron los parámetros genéticos para características de crecimiento en un núcleo de bovinos de la raza criolla Romosinuano que forman parte del Programa de Conservación del Centro de Investigación Turipaná, localizado en el Valle del Sinú (Córdoba, Colombia). Fue utilizado un modelo animal univariado para las características productivas de ‘peso al nacimiento’ (PN), ‘peso al destete’ (PD, ajustado a los 270 días), ‘peso a los 16 meses’ (P16m), ‘ganancia diaria de peso al destete’ (GPD) y ‘ganancia diaria de peso a los 16 meses’ (GP16m). Se obtuvieron valores de heredabilidad total medios (0,28; 0,43 y 0,38 para PN, PD, P16m, respectivamente); así mismo, se obtuvo un valor medio para GPD (0,42) y un valor bajo para GP16m (0,20). Los valores de heredabilidad directa siempre fueron mayores que los valores de heredabilidad materna y la correlación entre efectos directos y maternos presentó valores negativos consistentemente. Los valores genéticos anuales promedio para los efectos directos presentaron siempre una tendencia creciente a diferencia de los efectos maternos que mostraron una tendencia decreciente, con excepción del PN. Los resultados muestran valores de heredabilidad aceptables para los parámetros mencionados, mientras la tendencia indica un progreso genético leve pese a ser un núcleo de conservación cuyo objeto es preservar la variabilidad genética.  

Genetic parameters for six measures of length of productive life and three measures of lifetime production by 6 yr after first calving for Hereford cows1

Genetic parameters for length of productive life given the opportunity (LPL/O), measured as days between first calving and disposal conditioned on one of six opportunity groups, L1 through L6 (e.g., L2 is length of productive life in days given the opportunity to live 2 yr after first calving), and lifetime production (LP), measured as the number of calves born (NB), number of calves weaned (NW), and cumulative weaning weight (CW) by 6 yr after first calving, were estimated using records of 1,886 Hereford cows from a selection experiment with three selected lines and a control line. Weaning weights were adjusted to 200 d of age and for sex and age of dam. Estimates of heritability and genetic and environmental correlations were obtained by restricted maximum likelihood with bivariate animal models, with year of birth of cow as a fixed effect and direct genetic and residual as random effects. Genetic trends were estimated by regressing means of estimated breeding values by year of birth and line on birth year. Estimates of heritability (SE) for LPL/O ranged from 0.05 (0.01) to 0.15 (0.03). Estimates of genetic correlations (SE) among LPL/O ranged from 0.74 (0.14) to 1.00 (0.00), and estimates of environmental correlations ranged from 0.67 (0.05) to 0.98 (0.01). Estimates of heritability (SE) for NB, NW, and CW were 0.17 (0.05), 0.21 (0.06), and 0.18 (0.01). Estimates of genetic correlations (SE) among NB, NW, and CW ranged from 0.96 (0.02) to 0.99 (0.01). Estimates of environmental correlations (SE) ranged from 0.93 (0.01) to 0.99 (0.01). Estimates of genetic correlations for L6 with NB, NW, and CW were near 1.00 (0.09). Estimates of environmental correlations (SE) ranged from 0.57 (0.03) to 0.60 (0.03). Estimates of genetic change per year (SE) for L6 were low for all lines and ranged from -3.53 (2.09) to 4.63 (2.11) d/yr. Genetic trends for NB and NW were negligible for all lines. Genetic trends for CW were low and ranged from -2.81 (1.67) to 3.29 (1.76) kg/yr. Differences in genetic trends between selected lines and control were not significant (P > 0.05). Estimates of environmental trends (SE) over all lines were -104.00 (25.48) d/yr, -0.26 (0.02) calves/yr, -0.25 (0.02) calves/yr, and -55.10 (15.63) kg/yr, for L6, NB, NW, and CW, respectively. Selection for LPLIO or LP could be successful in a breeding program, but may be relatively slow due to the low magnitude of heritability and extended generation interval.

Number of calves born, number of calves weaned, and cumulative weaning weight as measures of lifetime production for Hereford cows1

Genetic parameters for lifetime production for cows with the opportunity to produce from 2 through 7 yr of age, as measured by the number of calves born (NB2, ..., NB7), the number of calves weaned (NW2, ..., NW7), and cumulative weaning weight (CW2, ..., CW7), were estimated using data from 3,064 Hereford cows from a selection experiment with a control line (CTL) and three lines selected for weaning weight (WWL), yearling weight (YWL), and an index of yearling weight and muscle score (IXL). Weaning weights were adjusted to 200 d of age and for sex and age of dam. Estimates of heritability and genetic and environmental correlations were obtained by restricted maximum likelihood with bivariate animal models, with year of birth of the cow as a fixed effect and direct genetic and residual as random effects. Genetic trends were estimated by regressing means of estimated breeding values by year of birth and line on birth year. Estimates of heritability (SE) for opportunity groups of 2 to 7 yr of age ranged from 0.08 (0.03) to 0.16 (0.05) for NB; from 0.05 (0.02) to 0.16 (0.05) for NW; and from 0.06 (0.02) to 0.16 (0.05) for CW. Estimates of genetic correlations (SE) among NB traits ranged from 0.60 (0.14) to 1.00 (0.00), and estimates of environmental correlations (SE) ranged from 0.67 (0.02) to 0.99 (0.00). For NW, estimates of genetic and environmental correlations ranged from 0.98 (0.11) to 1.00 (0.00) and from 0.65 (0.02) to 0.99 (0.00), respectively. Estimates of genetic correlations (SE) among CW traits ranged from 0.94 (0.08) to 1.00 (0.00). Estimates of environmental correlations (SE) ranged from 0.66 (0.02) to 0.99 (0.00). Estimates of genetic correlations for NB2 with all definitions of NW ranged from 0.47 (0.18) to 0.71 (0.12), and with all definitions of CW ranged from 0.55 (0.16) to 0.80 (0.11). Estimates of genetic correlations between NW2 and all definitions for CW ranged from 0.95 (0.02) to 0.99 (0.06). Estimates of annual genetic (SE) change were negligible for NB2, NB6, NW2, and NW6 for all lines. Estimates of annual genetic (SE) change for CW2 were 0.85 (0.11), 0.79 (0.14), 0.51 (0.10), and 0.52 (0.18) kg/yr, and for CW6 were 5.01 (1.25), 2.64 (1.75), 3.67 (1.16), and 3.33 (2.37) kg/yr for WWL, YWL, IXL, and CTL, respectively. Selection for lifetime production as measured by NB, NW, or CW could be effective but would be relatively slow due to low estimates of heritability and to increased generation intervals.