Evidence of genotype by environment interaction for reproductive and maternal traits in beef cattle

Disentangling the Multidimensional Relationship between Livestock Breeds and Ecosystem Services

Simple Summary

Livestock breeds represent the diversity of livestock animals. They participate in the delivery of ecosystem services (ES), i.e., the benefits to humans provided by nature. In recent years, the contribution of livestock breeds to ES has received attention in livestock research. Additionally, there is increasing interest in integrating this knowledge into policies to make agriculture more sustainable. In this work, we elaborate on livestock breed characteristics that are key to the study of livestock breed contributions to ES. Thus, we explore the natural and human factors that have produced livestock breeds as ecologically and culturally mediated entities. In addition, we review the different roles of livestock breeds as biodiversity components. Finally, we examine how livestock breeds participate in livestock system heterogeneity. By integrating these aspects, we might better understand how livestock breeds provide and modulate ES provision and, therefore, how to improve breed conservation and livestock policies toward more sustainable farming.

Abstract

There is an increasing interest in assessing livestock breed contributions to ecosystem services (ES) and including this knowledge in decision making. However, this task has been limited due to the complexity of the multidimensional relationship between livestock diversity and ecosystem services. In this work, we elaborate on the livestock breed characteristics central to developing a comprehensive approach to livestock breed inclusion in the ecosystem services framework. Thus, we explore the multidimensional nature of livestock breeds, i.e., as eco-cultural entities, biodiversity components, and drivers of livestock system heterogeneity and functioning. First, anthropogenic and natural factors have acted jointly to develop breeds as eco-cultural entities. This fact represents an opportunity to move toward farming system sustainability by Nature-Based Solutions and Nature’s Contribution to People paradigms. Second, livestock breeds are components of biodiversity, and as such, can be framed as goods, as final ecosystem services, and as regulators of ecosystem processes. Third, livestock breeds contribute to livestock system heterogeneity and resilience. By integrating these aspects, we might better understand how livestock breeds provide and modulate ecosystem service provision and, therefore, how to improve breed conservation and livestock policies toward farming system sustainability.

Genetic analysis of novel phenotypes for farm animal resilience to weather variability

BACKGROUND

Climate change is expected to have a negative impact on food availability. While most efforts have been directed to reducing greenhouse gas emissions, complementary strategies are necessary to control the detrimental effects of climate change on farm animal performance. The objective of this study was to develop novel animal resilience phenotypes using reaction norm slopes, and examine their genetic and genomic parameters. A closely monitored dairy goat population was used for this purpose.

RESULTS

Individual animals differed in their response to changing atmospheric temperature and a temperature-humidity index. Significant genetic variance and heritability estimates were derived for these animal resilience phenotypes. Furthermore, some resilience traits had a significant unfavourable genetic correlation with animal performance. Genome-wide association analyses identified several candidate genes related to animal resilience to environment change.

CONCLUSIONS

Heritable variation exists among dairy goats in their production response to fluctuating weather variables. Results may inform future breeding programmes aimed to ensure efficient animal performance under changing climatic conditions.

Selection for increased muscling is not detrimental to maternal productivity traits in Angus cows

The aim of the present study was to assess the effect of selection for increased muscling on maternal productivity of a temperate beef cow herd. Cows of predominantly Angus breeding were selected using visual muscle score (1–15 scale, where 1 = lightest and 15 = heaviest muscling) into low- and high-muscled animals, and mated to Angus bulls with low or high muscularity. Initially, low-muscled cows were mated to low-muscled bulls to create the Low line, and high-muscled bulls and cows were mated to create the High line. On discovering that some High cattle carried the myostatin (821 del11) gene, a second High line was created to distinguish between cattle with no copies of the myostatin gene (High line) and those with one copy (HighHet line). Data from 12 breeding cycles, consisting of 2003 joining records, and 1713 resulting weaning records were analysed to assess maternal productivity. Cows from the three lines were similar in weight (547, 548 and 550 kg, P = 0.9), but varied in body composition – from Low to High to HighHet cows, muscling traits increased and fatness traits decreased (all P < 0.001). Compared with Low cows, High cows had a 4.4 units higher muscle score, 10% higher eye muscle area and 21% less fat, and HighHet cows had a 7.1 units higher muscle score, 17% higher eye muscle area and 45% less fat. There were no significant effects of selection for increased muscling on live birth or weaning rates, or weaning weight (all P > 0.1). Dystocia levels of Low and HighHet maidens or cows did not differ significantly, but High maidens or cows had less dystocia (P = 0.013). Low, High and HighHet cows weaned 218, 225 and 216 kg of calf/cow joined.year, indicating similar maternal productivity.

The effect of genotype × environment interactions on biological efficiency in beef cows

An experiment was conducted to examine the response of three genotypes of beef cows to contrasting levels of nutrition supplied from grazed pasture. Twenty-two Hereford × Friesian (HF), 20 Aberdeen Angus × Friesian (AF) and 24 Welsh Black (WB) spring-calving beef cows with their Charolais-cross calves were used in 4 years consecutively. During the summer grazing period they grazed permanent pasture maintained at either 4 to 5 cm (short) or 7 to 8 cm (tall) sward surface height. Sward height treatment significantly (P < 0·001) affected cow and calf live-weight gain (0·498 v. 0·041 (s.e.d. 0·0405) kg/day and 1·12 v. 0·90 (s.e.d. 0·021) kg/day for cow and calf live-weight gain on the tall and short swards respectively). The live-weight gains of the HF and WB cows were similar, but the AF cows gained less weight on the tall sward and lost weight on the short sward. Calf live-weight gain reflected cow milk yield, with the calves from HF and AF cows having similar live weight gains (1·06 and 1·02 kg/day respectively) and those from WB cows having lower gains (0·95 kg/day; P < 0·001). The effect of sward height on calf live-weight gain was greatest in the WB-born calves because of the lower milk yield from WB cows. Body chemical composition changes of cows were predicted from live weight and body condition score, using prediction equations derived from separate groups of cows which were slaughtered at a range of body compositions for determination of chemical composition. Energy balances, calculated from changes in chemical composition, showed the AF cows to have the lowest energy balances with the WB cows the highest. Calculation of energetic efficiency and land use efficiency of weaned calf production taking account of annual food requirements indicated that the HF cows were most efficient, and the WB cows least efficient. The effect of increasing nutritional environment (as represented by sward height treatment) was such as to increase energetic efficiency for all genotypes, but land use efficiency was increased for HF and AF cows, and decreased for WB cows. These results indicate the factors such as size of cows, milk yield potential and pattern of nutrient partitioning can influence energetic land use efficiency of weaned calf production, and that important interactions between genotype and nutritional environment can occur in different measures of efficiency.

The nature, scope and impact of genomic prediction in beef cattle in the United States

Artificial selection has proven to be effective at altering the performance of animal production systems. Nevertheless, selection based on assessment of the genetic superiority of candidates is suboptimal as a result of errors in the prediction of genetic merit. Conventional breeding programs may extend phenotypic measurements on selection candidates to include correlated indicator traits, or delay selection decisions well beyond puberty so that phenotypic performance can be observed on progeny or other relatives. Extending the generation interval to increase the accuracy of selection reduces annual rates of gain compared to accurate selection and use of parents of the next generation at the immediate time they reach breeding age. Genomic prediction aims at reducing prediction errors at breeding age by exploiting information on the transmission of chromosome fragments from parents to selection candidates, in conjunction with knowledge on the value of every chromosome fragment. For genomic prediction to influence beef cattle breeding programs and the rate or cost of genetic gains, training analyses must be undertaken, and genomic prediction tools made available for breeders and other industry stakeholders. This paper reviews the nature or kind of studies currently underway, the scope or extent of some of those studies, and comments on the likely predictive value of genomic information for beef cattle improvement.

Development of a software model to estimate daily greenhouse gas emissions of pasture-fed ruminant farming systems

A software model has been developed to estimate greenhouse gas emissions of pasture-fed ruminant farming systems. The model estimates on-farm emissions associated with livestock (sheep and beef), fertiliser, petrol, diesel and electricity. Carbon sequestration from native and exotic forestry is then included to produce an on-farm carbon footprint, in the form of carbon dioxide equivalents. This paper describes the livestock model, which has been designed to record the movement of animals within individual farm units according to defined livestock classes. Allowances are made for unrecorded deaths, by estimating the number of animals missing within a defined time period and spreading the deaths according to expected seasonal variation in mortality. The enteric methane and nitrous oxide emissions are predicted using a combination of customised growth and lactation curves, and internationally recognised formulae to predict nutrient energy requirements. Customised growth and lactation curves allow estimation of liveweights and energy requirements associated with maintenance, growth, pregnancy and lactation on a daily basis. Daily estimation of emissions reduces errors introduced by monthly or seasonal averaging of livestock numbers and liveweights. The model has been developed into a commercial application (Alliance Group hoofprint) for use by New Zealand sheep and beef farmers, and could be adapted for other international livestock farming operations.

Genetic analyses of cow lifetime production up to 12 mating years in crossbred beef cattle

A total of 1088 females of 14 breed groups (Angus and Hereford purebreds, and 12 first-cross groups) were evaluated over two locations for lifetime survival, numbers of calvings, numbers of calves weaned and cow lifetime records of calf survival. These traits are known to be related to a cow's lifetime productivity. The animals were part of the Ruakura Beef Breed Evaluation, designed to compare the growth and carcasses of steers, and the reproductive and maternal performance of females of different breed groups. Data were from 4 birth years of females and 11 breed-groups at location 1, and from 5 and 10 respectively at location 2, with seven breed-groups common to both locations. Females were first mated as yearlings. Culling at ages 2·5 to 4·5 years was based mainly on females that were non-pregnant on two occasions, whereas in subsequent years any non-pregnant female was culled. At location 1, there was a maximum possible number of mating years of 22 for females in the 1st birth year, declining to a maximum of 9 for those in the 4th birth year; for each age group at location 2 there was a maximum of 9 mating years. The average cow survival (number of mating years) was 7·26 (s.d. 3·02) at location 1 and 5·81 (s.d. 2·31) at location 2, with a coefficient of variation similar at both locations and averaging 0·41. The performances from the poorest to the best breed groups had a 1·5-fold range for number of mating years and a 1·8-fold range for number of calvings and number of calves weaned. The heritability of number of mating years (no. = 150 sire groups) was 0·13 (s.e. 0·08), number ofcalvings 0·11 (s.e. 0·08), number of calves weaned 0·15 (s.e. 0·08), and calf survival as a cow trait 0·027 (s.e. 0·018). This last heritability increased to 0·093 if adjustment was made to the underlying liability scale. There was no significant effect of breed of cow on number of mating years, nor on number of calves weaned per 100 calvings at either location, whilst the effect was significant for number ofcalvings and for number of calves weaned per cow (P < 0·10). The wide breed variation pointed to opportunities for selection among breeds, whilst the low heritabilities suggested that within-breed selection will be slow unless early indicator traits can be found.

Annual energy intake and the metabolic and reproductive performance of beef cows differing in body size and milk potential

The metabolic status and reproductive performance of four pure breeds of beef cow (small size and low milk potential, Aberdeen Angus; small size and high milk potential, Welsh Black; large size and low milk potential, Charolais; and large size and high milk potential, Simmental) were monitored during their first two parities. Heifers from each breed were allocated to one of two levels of annual energy intake relative to metabolic body weight (M075) (mean daily intakes equivalent to 705 and 820 kj/kg M0·75) in a factorial design. In the 1st year 64 heifers (eight per treatment) which had calved as a consequence of first or second service were selected for the experiment. In the 2nd year 40 of these animals (five per treatment) which held to first or second service remained on experiment. Animals were housed all year round and given diets designed to represent energy intakes while grazing during the summer and conserved feeding during the winter. Pregnancy was established in late July of each year using a combination of oestrous synchronization and artificial insemination. Blood samples were collected at monthly intervals from weaning in November until calving in May; three times weekly from calving until oestrous synchronization (11 weeks later); and fortnightly thereafter until weaning.

For the annual levels of dietary energy intake offered, two breeds (Welsh Black and Charolais) exhibited relatively high growth rates and had the longest post-partum anovulatory periods; and Charolais cows also had the poorest conception rates of all breeds. Relatively lean cows at calving (body condition score < 2·5 units) were sensitive, in terms of the duration of the anovulatory period, to live-weight loss during the early post-partum period, particularly when blood glucose levels were low, whereas relatively fat cows at calving (body condition score > 2·5 units) were not. The data suggest: (i) that mechanisms controlling the anabolic processes governing maternal growth are antagonistic towards those that control reproduction; and (ii) the catabolism of lean tissue rather than fat tissue during the early post-partum period is also antagonistic towards the mechanisms that govern reproductive function in cows.

Annual energy intake and the performance of beef cows differing in body size and milk potential

The accumulative effects of different levels of annual energy intake over the first two parities on four breeds of beef cow (small size and low milk potential, Aberdeen Angus; small size and high milk potential, Welsh Black; large size and low milk potential, Charolais; and large size and high milk potential, Simmental) were assessed for various production traits and calf performance. Heifers were allocated to each of two levels of annual energy intake relative to metabolic body weight (M0·75) (mean daily intakes equivalent to 705 and 820 kj M0·75) and for the next 2 years these animals (10 per breed) were continuously housed and given diets designed to represent energy intakes while grazing during the summer and conserved forage feeding during the winter. Changes in live weight and body composition were measured throughout both years and milk yield, milk composition and calf performance during both lactations.

Animals from each of the four breeds gained weight but lost body condition during their first two parities in a manner that was dependent on their annual level of dietary energy intake. Welsh Black cows grew more than Aberdeen Angus cows and Charolais cows more than Simmental cows so that, by weaning during the second parity, the rank order of live weights between breeds was Charolais > Simmental > Welsh Black > Aberdeen Angus. Welsh Black and Simmental cows produced higher yields of milk (7·9 and 8·7 kg respectively) than Aberdeen Angus and Charolais cows (6·5 and 5·7 kg respectively; P < 0·001). Calves from the two large breeds grew more quickly than those from the two small breeds (1·13 v. 0·99 kg/day; P < 0·01) and calf performance was influenced by milk consumption. Biological efficiency, defined as weight of calf at weaning per GJ metabolizable energy (ME) on an annual basis, increased as annual energy intake decreased and tended to be higher for large breeds on 33 GJ ME per year than for small breeds on the same level of annual energy intake (7·19 v. 6·75). The complex means by which the different breed types interacted with their nutritional environment is discussed.

Profitability of calving heifers at 2 compared with 3 years of age and the effect of incidence of assistance at parturition on profitability

There is potential to increase the profitability of beef-breeding cows in New Zealand by calving heifers for the first time at 2 instead of 3 years of age; however, calving at this earlier age is often associated with an increase in assistance at calving. This study used a simulated farm system within the Grazing Systems Model to estimate the profitability of calving heifers at 2 years of age with various incidences of assistance at calving. Annual profit from the beef cattle herd was greater for primiparous 2-year-old heifers than for 3-year-old primiparous heifers when the incidence of assisted calving in 2-year-old heifers was less than 89%. Replacement rate increased with increased assistance at parturition. These results indicated that a considerable gain in profitability could be made by calving heifers for the first time at 2 instead of 3 years of age, and further gains could be made in herds already calving heifers at 2 years of age by reducing the incidence of assistance at calving.

Estimation of genotype×environment interactions for growth, fatness and reproductive traits in Australian Angus cattle

The magnitude of genotype × environment interactions (G × E) were estimated for growth, real time ultrasound scanned carcass and reproductive traits in Angus cattle. Traits measured in the states of Victoria and Queensland were assumed as different traits and the genetic correlations between them were estimated. Estimated heritabilities across states were similar for all traits. However, additive genetic variances of fat depth at the P8 (rump) site for bulls (BP8), intramuscular fat percent at the 12/13th rib for bulls (BIMF) and heifers (HIMF) were significantly different between states. Estimated genetic correlations across states for direct genetic effects were high for growth traits and ranged from 0.89 to 1.00. For the maternal genetic effects the correlations across states ranged from 0.66 to 0.87. The across state correlations for scanned traits were also high. The exception was for BIMF (0.65), where measurement procedures were observed to influence the result. The genetic correlation between the states increased to 0.94 when the records of bulls with low IMF value were removed. For reproductive traits, the estimated genetic correlations ranged from 0.97 to 1.00. These results indicated little evidence of G × E for growth, ultrasound scanned carcass and reproductive traits of Angus cattle from Victoria and Queensland. Combining performance data across states in a national genetic evaluation is appropriate and it is expected that the progeny of Angus cattle would rank similarly across states.

Dystocia in beef heifers: a review of genetic and nutritional influences

Breeding beef heifers for the first time at 15 months of age has potential to increase the efficiency of the beef breeding-cow herd. An increased incidence of dystocia in heifers calving at 2 years of age, compared to mature cows, is a major reason many farmers in New Zealand have not adopted the practice. The predominant type of dystocia affecting 2-year-old heifers is feto-maternal disproportion, a condition in which the fetus is too large relative to the size of the heifer's pelvis. Reducing birthweight of the calf is a means of reducing the incidence of dystocia. Birthweight and length of gestation are determined by genotype of the calf, maternal genetic effects and environmental effects. Bulls with low estimated breeding values for birthweight have been selected for mating heifers; however, the positive genetic correlation between birthweight and mature weight meant that the progeny of these bulls tended to be lighter at finishing, making them less desirable in the beef industry. The genotype of the dam also plays a role in determining the risk of dystocia; the maternal ability of the dam to nurture the fetus influences birthweight, and the dam's genetic potential for growth influences the size of her pelvic area. Heavy heifers tend to produce high birthweight calves, counteracting the reduction in the incidence of dystocia resulting from the larger pelvis in larger heifers. Manipulating feeding level during pregnancy offers an alternative method for manipulating the birthweight of calves. Little is known about the effects of nutrition in early gestation on placental development or birthweight of calves. No differences in the birthweight of calves have been observed in response to variation in feeding in mid-pregnancy, and variable responses in birthweight and the incidence of dystocia to feeding in the third trimester of pregnancy have been reported. Differences in birthweight have not always resulted in differences in the incidence of dystocia, primarily due to differences in liveweight of the heifer also induced by feeding regimens. Variability in the incidence of dystocia in response to feeding level in the third trimester of pregnancy makes it difficult to make recommendations for the feeding of heifers at this stage of gestation. More research is needed into the effects of nutrition in early gestation on fetal and placental development in cattle.

The effect of individual liveweight and condition of beef cows on their reproductive performance and birth and weaning weights of calves

AIM

To examine of the influence of liveweight (LW), condition (CS) and age of dam on inter-calving interval (ICI), date of calving, days from joining to calving, and birth and weaning weights of calves.

METHODS

LW and CS were measured in a herd of mixed-aged (3-8 years) Hereford x Friesian beef cows on four occasions, annually, over a 3-year period from joining (the date bulls were introduced into the herd at the start of a restricted breeding season) in November 2000 to weaning in March 2004. The four dates of weighing and condition-scoring were joining (November), weaning (March), winter (June), and pre-calving (August). Calves were tagged, identified to their dam, and weighed within 24 h of birth, and at weaning. Date of calving, ICI and days from joining to calving were determined.

RESULTS

The CS and LW of cows varied between years. LW increased in cows up to 6 years of age. Three-year-old cows had a longer ICI than older cows. Change in CS and LW from winter to pre-calving and pre-calving to joining were negatively correlated with ICI for younger cows but not for cows > or = 5 years (CS) and 6-8 years (LW) old. No difference in CS or LW precalving was evident between cows that subsequently became pregnant compared with non-pregnant cows, although cows that became pregnant gained more condition from pre-calving to joining than non-pregnant cows. Pregnant cows were heavier and had higher CS at joining than non-pregnant cows.

CONCLUSIONS

Young cows, up to second-mating as 3-year-olds, would benefit from separate nutritional management from older cows, to ensure ICI and days to conception are kept at targeted levels. In addition, increasing CS from pre-calving to joining and higher LW and CS at joining resulted in higher pregnancy rates.

Breakdown in correlations during laboratory evolution. I. Comparative analyses of Drosophila populations

We provide evidence from comparisons of populations of Drosophila that evolutionary correlations between longevity and stress resistance break down over the course of laboratory evolution. Using 15 distinct evolutionary regimes, we created 75 populations that were differentiated for early fecundity, longevity, starvation resistance, desiccation resistance, and developmental time. In earlier experiments, selection for postponed aging produced increases in stress resistance, whereas selection for increased stress resistance produced increases in longevity. Direct estimates of correlations also indicated an antagonistic relationship between early fecundity on one hand and longevity or stress resistance on the other. Laboratory evolution of extreme values of stress resistance, however, led to a breakdown in these evolutionary relationships. There was no evidence that these significant changes in correlation resulted from genotype-by-environment interactions or inbreeding. These findings suggest that correlations between functional characters are not necessarily durable features of a species, and that short-term evolutionary responses cannot be extrapolated reliably to longer-term evolutionary patterns.

Understanding maternal contributions to fertility in recipient cattle: development of herds with contrasting pregnancy rates

Causes of variation amongst recipients within a herd in their ability to initiate and maintain pregnancy is largely unknown. In order to develop an experimental resource to understand the biology of recipient reproductive performance, each of 155 contemporary yearling heifers received 2 in vitro-produced embryos on 6 separate occasions during a 26-month period. Sixty days after transfer, pregnancy and the number of foetuses were determined ultrasonically and then pregnancies were terminated and the process was repeated. Heifers were ranked on their aggregate pregnancy rate performance, and the highest (High) and lowest (Low) 25 were retained. Mean pregnancy rates of all recipients ranged from 0.20 to 0.67 depending on transfer occasion. The mean +/- s.e. pregnancy rate of the High and Low sub-herds were 0.76+/-0.04 vs. 0.11+/-0.03, respectively (P<0.001), with 55% and 37% of this difference due to differences in Day 25 return to oestrus rates and losses between Day 25 and Day 35, respectively. We suggest that failure in the mechanism involved in maternal recognition of pregnancy was a major cause of the difference between the two sub-herds. These sub-herds are a unique experimental resource for understanding the early pregnancy process in cattle.