Genetic associations between age at first calving and heifer body weight and scrotal circumference in Nelore cattle

P>Age at first calving (AFC) measures the entry of heifers into the beef cattle production system. This trait can be used as a selection criterion for earlier reproductive performance. Using data from Nelore cattle participating in the `Program for Genetic Improvement of the Nelore Breed` (PMGRN-Nelore Brazil), bi-trait analyses were performed using the restricted maximum likelihood method, based on an AFC animal model and the following traits: female body weight adjusted to 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted to 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. The heritability estimates for AFC ranged from 0.02 +/- 0.02 to 0.04 +/- 0.02. The estimates of additive direct heritabilities (with standard error) for BW365, BW450, SC365, SC450, SC550 and SC730 were 0.36 +/- 0.07, 0.38 +/- 0.07, 0.48 +/- 0.07, 0.65 +/- 0.07, 0.64 +/- 0.07 and 0.42 +/- 0.07, respectively, and the genetic correlations with AFC were -0.38, -0.33, 0.10, -0.13, -0.13 and 0.06, respectively. In the herds studied, selection for SC365, SC450, SC550 or SC730 should not cause genetic changes in AFC. Selection based on BW365 or BW450 would favor smaller AFC breeding values. However, the low magnitude of direct heritability estimates for AFC in these farms indicates that changes in phenotypical expression depend mostly on non-genetic factors.

Attaching and effacing lesions in the large intestine of an eight-month-old heifer associated with Escherichia coli O26 infection in a group of animals with dysentery

Escherichia coli O26:K60, with genetic attributes consistent with a potentially human enterohaemorrhagic E coli was isolated from the faeces of an eight-month-old heifer with dysentery. Attaching and effacing lesions were identified in the colon of a similarly affected heifer examined postmortem, and shown to be associated with E coli O26 by specific immunolabelling.

Additive genetic relationships between scrotal circumference, heifer pregnancy, and stayability in Nellore cattle

Scrotal circumference data from 47,605 Nellore young bulls, measured at around 18 mo of age (SC18), were analyzed simultaneously with 27,924 heifer pregnancy (HP) and 80,831 stayability (STAY) records to estimate their additive genetic relationships. Additionally, the possibility that economically relevant traits measured directly in females could replace SC18 as a selection criterion was verified. Heifer pregnancy was defined as the observation that a heifer conceived and remained pregnant, which was assessed by rectal palpation at 60 d. Females were exposed to sires for the first time at about 14 mo of age (between 11 and 16 mo). Stayability was defined as whether or not a cow calved every year up to 5 yr of age, when the opportunity to breed was provided. A Bayesian linear-threshold-threshold analysis via Gibbs sampler was used to estimate the variance and covariance components of the multitrait model. Heritability estimates were 0.42 +/- 0.01, 0.53 +/- 0.03, and 0.10 +/- 0.01, for SC18, HP, and STAY, respectively. The genetic correlation estimates were 0.29 +/- 0.05, 0.19 +/- 0.05, and 0.64 +/- 0.07 between SC18 and HP, SC18 and STAY, and HP and STAY, respectively. The residual correlation estimate between HP and STAY was -0.08 +/- 0.03. The heritability values indicate the existence of considerable genetic variance for SC18 and HP traits. However, genetic correlations between SC18 and the female reproductive traits analyzed in the present study can only be considered moderate. The small residual correlation between HP and STAY suggests that environmental effects common to both traits are not major. The large heritability estimate for HP and the high genetic correlation between HP and STAY obtained in the present study confirm that EPD for HP can be used to select bulls for the production of precocious, fertile, and long-lived daughters. Moreover, SC18 could be incorporated in multitrait analysis to improve the prediction accuracy for HP genetic merit of young bulls.

Genetic associations between age at first calving and heifer body weight and scrotal circumference in Nelore cattle

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Genetic parameters and relationships of heifer pregnancy and age at first calving with weight gain, yearling and mature weight in Nelore cattle

The objectives of the current study were to investigate the additive genetic associations between heifer pregnancy at 16 months of age (HP16) and age at first calving (AFC) with weight gain from birth to weaning (WG), yearling weight (YW) and mature weight (MW), in order to verify the possibility of using the traits measured directly in females as selection criteria for the genetic improvement of sexual precocity in Nelore cattle. (Co)variance components were estimated by Bayesian inference using a linear animal model for AFC, WG, YW and MW and a nonlinear (threshold) animal model for HP16. The posterior means of direct heritability estimates were: 0.45 +/- 0.02; 0.10 +/- 0.01; 023 +/- 0.02; 0.36 +/- 0.01 and 0.39 +/- 0.04, for HP16, AFC, WG, YW and MW, respectively. Maternal heritability estimate for WG was 0.07 +/- 0.01. Genetic correlations estimated between HP16 and WG, YW and MW were 0.19 +/- 0.04; 0.25 +/- 0.06 and 0.14 +/- 0.05, respectively. The genetic correlations of AFC with WG, YW and MW were low to moderate and negative, with values of -0.18 +/- 0.06; -0.22 +/- 0.05 and -0.12 +/- 0.05, respectively. The high heritability estimated for HP16 suggests that this trait seem to be a better selection criterion for females sexual precocity than AFC. Long-term selection for animals that are heavier at young ages tends to improve the heifers sexual precocity evaluated by HP16 or AFC. Predicted breeding values for HP16 can be used to select bulls and it can lead to an improvement in sexual precocity. The inclusion of HP16 in a selection index will result in small or no response for females mature weight. (C) 2011 Elsevier B.V. All rights reserved.

Genetic correlations between heifer subsequent rebreeding and age at first calving and growth traits in Nellore cattle by Bayesian inference

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Additive genetic relationships between scrotal circumference, heifer pregnancy, and stayability in Nellore cattle

Scrotal circumference data from 47,605 Nellore young bulls, measured at around 18 mo of age (SC18), were analyzed simultaneously with 27,924 heifer pregnancy (HP) and 80,831 stayability (STAY) records to estimate their additive genetic relationships. Additionally, the possibility that economically relevant traits measured directly in females could replace SC18 as a selection criterion was verified. Heifer pregnancy was defined as the observation that a heifer conceived and remained pregnant, which was assessed by rectal palpation at 60 d. Females were exposed to sires for the first time at about 14 mo of age (between 11 and 16 mo). Stayability was defined as whether or not a cow calved every year up to 5 yr of age, when the opportunity to breed was provided. A Bayesian linear-threshold-threshold analysis via Gibbs sampler was used to estimate the variance and covariance components of the multitrait model. Heritability estimates were 0.42 +/- 0.01, 0.53 +/- 0.03, and 0.10 +/- 0.01, for SC18, HP, and STAY, respectively. The genetic correlation estimates were 0.29 +/- 0.05, 0.19 +/- 0.05, and 0.64 +/- 0.07 between SC18 and HP, SC18 and STAY, and HP and STAY, respectively. The residual correlation estimate between HP and STAY was -0.08 +/- 0.03. The heritability values indicate the existence of considerable genetic variance for SC18 and HP traits. However, genetic correlations between SC18 and the female reproductive traits analyzed in the present study can only be considered moderate. The small residual correlation between HP and STAY suggests that environmental effects common to both traits are not major. The large heritability estimate for HP and the high genetic correlation between HP and STAY obtained in the present study confirm that EPD for HP can be used to select bulls for the production of precocious, fertile, and long-lived daughters. Moreover, SC18 could be incorporated in multitrait analysis to improve the prediction accuracy for HP genetic merit of young bulls.

[Hyena disease in a Brown Swiss heifer]

A heifer with developmental skeletal disorder was presented to the ruminant clinic of the University of Berne. Abnormal long bone growth and a wobbling gait were the main clinical signs. All long bones were examined radiologically, several parameters of body size were measured and the results were compared to the measurements of a healthy control animal. Haematology and blood chemistry were normal. Based on the poor prognosis the animal was slaughtered. The final diagnosis of hyena disease was based on the characteristic growth disturbances in the caudal parts of the body, giving the animal a hyena-like appearance. For the first time a case of hyena disease is reported in Switzerland.

[Heifer breeding farms as a source for spreading the BVD virus?]

It is well known that, in Switzerland, communal grazing of livestock on alpine pastures plays an important role in the spread of BVD virus. Analogously, we might expect that the communal raising on farms specialising in raising heifers of animals born on different farms would also favour the spread of BVDV. This study investigated whether a persistently infected (PI) breeding heifer kept on this type of farm over a period of 26 months would put the other animals at risk of being infected.The PI-animal was in contact with 75 heifers (here defined as contact animals) on this farm. Thirty-two of the contact animals that were probably pregnant (animals at risk of giving birth to a PI-calf) were moved to 8 different breeding farms (here defined as farms at risk). On these 8 farms, 246 calves were found to be at risk of being infected with BVDV. We examined 78 calves and investigated whether the move of the pregnant animals from their original farm had permitted the virus to spread to these 8 other farms.The contact animals had a seroprevalence of 92% and the animals at risk a seroprevalence of 100%. Only one PI-animal was found on the farms at risk.This BVD infection, however, occurred independently of the PI-breeding animal. Seropositive calves were found only on 2 farms. This study did not provide any proof for a spread of BVDV with the PI-breeding animal as a source; likewise, no persistent infection was proven to exist on the farms at risk. This result is likely to be representative for the endemic situation of BVD in Switzerland. Thus, PI-animals present on heifer raising farms infect calves well before servicing. Hence, no new PI-animals are generated, and the infection becomes self-limiting. When we reconstructed the animal movements between the farms and determined the animals to be examined with the aid of the Swiss national animal traffic database (TVD) we found the data of 37% of the heifers to be incomplete and failed to successfully establish the whereabouts of 3 animals.

Jackson County Heifer Development Project Summary

The heifer development project was a five year project conducted on the site of the former Jackson County Farm north of Andrew, Iowa, for four years and on an area producer’s farm for the fifth year. Heifers arrived around December 1 each year and the average number of heifers each year was 43 with a low of 37 and high of 47. After a 30+ day warm-up period the heifers were put on a 112-day test from early January to late April. They were fed a shelled corn and legume-grass hay ration consisting of between 13% and 14% crude protein and a range of .44 to .58 megacal/pound of NEg over the five years. During the 112-day test heifers gained 1.86, 1.78, 1.5, 1.63 and 2.2 pounds per day, respectively, for years 1992 through 1996. The actual average breeding weight was less than the target weight in three years by 5, 12 and 22 pounds and exceeded the target weight in two year by 17 and 28 pounds. Estrus synchronization used a combination of MGA feeding and Lutalyse injection. Heifers were heat detected and bred 12 hours later for a three-day period. On the fourth day, all heifers not bred were mass inseminated. Heifers then ran with the cleanup bull for 58 days. The average synchronization response rate during the project was 79%. The overall pregnancy rates based on September pregnancy averaged 92%. The five year average total cost per head for heifer development was $286.18 or about $.85 per day. Feed and pasture costs averaged 61% of the total costs.

Jackson County Heifer Development Project Update

The heifer development project took place the past four years on the site of the former Jackson County Farm north of Andrew, Iowa. Heifers arrived around December 1 with 38 heifers delivered for 1992, 44 for 1993, 46 for 1994, and 47 for 1995. After a 30+ day warm-up period, the heifers were put on a 112-day test from early January to late April. They were fed a shelled corn and legume-grass hay ration consisting of between 13% and 14% crude protein and .48, .58, .44, and .54 megacal/pound of NEg respectively for the years 1992 - 1995. During the 112-day test heifers gained 1.86, 1.78, 1.5, and 1.63 pounds per day respectively for years 1992 through 1995. The 1995 heifers averaged 853 pounds at breeding (22 pounds under target weight). This compares with previous years in which the breeding weight was less than target weight in two years by 5 and 12 pounds and exceeded the target weight in one year by 17 pounds. Estrus synchronization used a combination of MGA feeding and Lutalyse injection. Heifers were heatdetected and bred 12 hours later for a three-day period. On the fourth day, all heifers not bred were mass inseminated. Heifers then ran with the cleanup bull for 58 days. The synchronization response rate in 1995 was 83%, which compares with the three year previous average of 77%. The overall pregnancy rates based on September pregnancy exams were 94.6% in 1992, 93% in 1993, 91% in 1994, and 91.5% in 1995. Development costs for the 326 days in 1995 totaled $269.14 per heifer. This compares with the average of $286. 92 for the three previous years. The four-year average total cost per head for heifer development was $282.48, or about $.84 per day. Feed and pasture costs represented 58% of the total costs, or $.49 per day.