Search

Background: We investigated breed and gender variations in the compositions of long-chain (≥ C20) omega-3 polyunsaturated fatty acids (LC omega-3 PUFA), fat melting point (FMP) and intramuscular fat (IMF) contents in biopsy samples of the M. longissimus dorsi muscle of grazing beef cattle. The hypothesis that biopsy compositions of health-beneficial LC omega-3 PUFA, FMP and IMF in a pasture-based production system will vary with breed, was tested. Muscle biopsies were taken from 127 yearling pasture-based Angus, Hereford, and Wagyu heifers and young bulls exclusive to the Australian Bowen Genetics Forest Pastoral breeding stud averaging 12 ± 2.43 months of age and under the same management routine. Results: Breed had a significant influence on IMF, FMP, and the compositions of oleic acid, α-linolenic acid (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA), docosapentaenoic (DPA), and total EPA + DHA + DPA in the M. longissimus dorsi muscle biopsies (P ≤ 0.03). The Wagyu breed had the highest (11.1%) and Hereford the lowest (5.9%) IMF (P = 0.03). The reverse trend was observed in FMP values where the Hereford breed had the highest (55 °C), Angus intermediate (46.5 °C), and Wagyu the lowest (33 °C) FMP. The Wagyu and Angus breeds had similar oleic fatty acid (18:1n-9) content, while the Hereford breed had the lowest (P < 0.01). The highest ALA, DPA, total EPA + DHA, total EPA + DHA + DPA and total ALA + EPA + DHA + DPA contents were detected in the Wagyu breed (P ≤ 0.03). The Hereford had similar EPA and DPA contents to the Angus (P ≥ 0.46). Total EPA + DHA + DPA contents in Wagyu, Angus, and Hereford were 28.8, 21.5, and 22.1 mg/100g tissue (P = 0.01), respectively. Sex was an important source of variation that influenced LC omega-3 PUFA composition, FMP and IMF, where yearling heifers had higher IMF (11.9% vs 5.3%), lower FMP (33°C vs 37°C), and higher LC omega-3 PUFA than bulls. Conclusion: All the results taken together indicate that the Wagyu breed at 28.8 mg/100g tissue, was the closest to meeting the Australia and New Zealand recommended source level threshold of 30 mg/100g tissue of health-beneficial ≥ C20 omega-3 FA content. Since gender was a significant determinant of LC omega-3 PUFA composition, IMF content and FMP, it should be factored into enhancement strategies of healthy meat eating quality traits in grazing cattle. These findings also suggest that the Bowen Genetics Forest Pastoral beef cattle studs are important sources of LC omega-3 PUFA that can be used to cover the deficit in these health claimable fatty acids in Western diets. [ABSTRACT FROM AUTHOR]

Dairy heifers in New Zealand are typically naturally mated by Jersey bulls to produce low-value non-replacement offspring sold for slaughter a few days after birth. Producing a beef-sired calf from a dairy heifer will increase the value of these calves for beef production but may compromise the subsequent career of the animals, in terms of milk production, rebreeding success, health, or survival of the heifer. This study aimed to determine the impact of low birthweight Angus and Hereford bulls versus breed-average Jersey bulls on the reproduction and production traits of first-calving dairy heifers. The experiment included 304 heifer-calf pairs over 2 years. Calves sired by Angus and Hereford bulls were 3.5–4.4 kg and 3.7–6.8 kg heavier than Jersey-sired calves and had a 4.2% and 9.3% incidence of assistance at birth for normally presented calves over the 2 years, respectively. No normally presented Jersey-sired calves were assisted. There was no difference in body condition score, pre-calving live weight, milk production, pregnancy rate, inter-calving interval, re-calving day, and 21-day re-calving rate of heifers mated to the different breeds of bulls. The results indicate that the Angus and Hereford bulls with low birthweight and high direct calving ease estimated breeding values (EBV) can be used to produce calves of greater value than Jersey-sired calves without impacting dairy heifer production. However, a small increase in assistance at calving could be expected. [ABSTRACT FROM AUTHOR]

• Male-sexed semen can increase numbers of heavier and faster-growing male offspring • Artificial insemination is not commonly practised in extensive beef cow herds • Sexed semen increased breeding costs by up to 91% compared with natural mating only • Increased income from heavier, male offspring did not justify the higher breeding costs • Male-sexed semen was not profitable for the extensive beef cow herd modelled Male-sexed semen can be used in beef cow herds to increase the number of heavier and faster-growing male offspring. The use of sexed semen requires artificial insemination (AI) which has limited use in extensive beef systems due to practical constraints and the additional breeding costs incurred. The objective of this study was to use bio-economic simulation modelling to predict the profitability of using sexed semen via fixed time AI for a New Zealand hill country farm system based around a beef cow herd. When modelling self-replacing Angus herds male-sexed Simmental semen was utilised across 43% of mixed-age cows then follow up Simmental bulls were used for subsequent natural mating. To generate replacement Angus heifers, first time calvers and remaining mixed-age cows were bred with unsexed Angus semen and then naturally bred with Angus bulls if they did not conceive. All mixed-age cows in an AngusxHolstein-Friesian herd with a bought-in replacements policy were bred with male-sexed Simmental semen followed by Simmental bulls. First time AngusxHolstein-Friesian calvers were bred with unsexed Angus semen followed by Angus bulls. Sire breed was assumed to have the same effects on offspring production regardless of use through AI or natural mating. Herds using sexed semen were assumed to undergo synchronised fixed-time AI which resulted in a more condensed calving spread and 3% heavier average weaning weights due to calves being predominantly male and on average seven days older. Total breeding costs were higher for herds using sexed semen via AI at NZD 135-166 /cow compared with NZD 67-102 /cow for herds using only natural mating. Increases in breeding costs were relatively larger than any additional income for all herds using sexed semen via AI, resulting in lower COS (cash operating surplus) compared with herds using all-natural mating. The COS of using sexed semen via AI were 14% (COS = NZD 280 /ha) and 9% (COS = NZD 405 /ha) lower than all-natural mating using Simmental sires for the purebred Angus (COS = NZD 325 /ha) and AngusxHolstein-Friesian crossbred (COS = NZD 444 /ha) cow herds, respectively. It appears producing more fast-growing male calves through use of sexed semen via AI is not currently an economically feasible option for beef producers under extensive production systems. Future analysis could include benefits of access to higher genetic merit sires as the combination of superior genes and more male offspring may be more profitable than all-natural mating. [ABSTRACT FROM AUTHOR]

• Beef-dairy crossbred cows sourced from the dairy industry can be farmed as a breeding herd for beef production. • Beef-dairy cows have been observed as lighter than Angus cows while weaning heavier calves. • Feed demand, productivity, and profitability of these breed options were compared using bio-economic modelling. • Beef-dairy herds were 8% to 79% more profitable, depending on offspring sale policies and sire breed choice. • Numbers of breeding cows may reduce to levels which are impractical in this system with fixed feed supply on hill country. Beef-dairy crossbred cows (such as Angus-Friesian) have lighter mature cow weights while weaning heavier calves compared with cows in a typical self-replacing New Zealand Angus breed herd. The objective of this study was to quantify the potential profitability of farming an Angus-Friesian cow herd through modelling the potential changes in cattle numbers, feed demand, production, and beef enterprise economics. The Angus-Friesian cow herd was simulated as purchasing all replacement heifers and was modelled with different sire breeds (Angus or terminal such as Charolais or Simmental) and offspring sale policies (sold at weaning at six months of age or at 27 months of age). Total annual cattle feed demand was maintained at the same level for all modelled scenarios. Angus-Friesian herds had 8% to 79% higher beef enterprise cash operating surplus (COS) compared with the self-replacing Angus herd (COS = NZD 255/ha). For the Angus-Friesian herds, selling all offspring prime (direct to slaughter) at 27 months of age resulted in 20% to 59% higher COS than selling all offspring store (sold at weaning) at weaning at six months old. Utilising terminal breed sires with the Angus-Friesian herd resulted in 10% to 12% higher COS compared with using Angus sires when selling all offspring store at weaning, due to the heavier sale weights and resultant higher per head sale values. However, when selling all offspring prime at 27 months of age the utilisation of Angus sires resulted in 10% to 11% higher COS than using terminal sires, as the lighter weights and thus total feed demand was lower for offspring born to Angus sires allowing for a greater breeding cow numbers (and therefore numbers of offspring sold). Scenarios in which offspring were retained on-farm until 27 months of age increased total feed demand of cattle destined for sale, necessitating reductions in breeding cow numbers to as low as 60% of the base system level, which may inhibit farmers' ability to manage pasture quality. Farmers considering a change to an Angus-Friesian crossbred herd of breeding cows can include the potential herd numbers, feed demand, production, and economic changes predicted in this analysis in their decision making, as well as the practicalities of the explored strategies for designing their farm system. [ABSTRACT FROM AUTHOR]

• Using terminal sires in a beef cow herd increases sale prices and feed demand per animal sold. • Selling more of cattle direct to slaughter necessitated reductions in cow herd numbers. • Selling more cattle direct to slaughter was the most economically beneficial strategy explored. • Price premiums and higher weaning rates were also economically beneficial. • These management options can be implemented concurrently in a beef cow herd. New Zealand farmers can choose to breed a proportion of their beef cow breeding herd with terminal breed sires to produce heavier offspring to sell for higher per head prices. However, the heavier weights of terminal offspring also increase their feed demand which may necessitate cow herd size reductions in a system with a fixed feed supply. This study used a bio-economic, system dynamics model to simulate cattle numbers, production, and beef enterprise cash operating surplus (COS) for a self-replacing beef suckler herd of Angus breed cows bred with only Angus sires to produce purebred offspring or a proportion of cows bred with European breed terminal sires (such as Charolais or Simmental). The herd was also modelled with varying calf weaning rates (84 or 90%), with offspring sales occurring either at weaning or at 27 months of age, and in a secondary analysis, with or without price premiums for sales of cattle of at least 75% Angus breed. Total annual beef feed demand was maintained at 40% of total farm feed supply (total farm area of 530 ha) in all scenarios, with the remainder consumed by the on-farm sheep flock. Beef enterprise COS was therefore divided by the beef herd proportion of farm area (212 ha) to derive a per ha COS value. Herd replacement rate was first modelled at 22% allowing for 43% of cows to be bred with terminal sires with a weaning rate of 84%. With a weaning rate of 90% the replacement rate was 18% allowing 60% of cows to be bred with terminal sires. The base scenario with a herd weaning rate of 84% using only Angus sires had a COS of NZD 255 /ha. Relative to the base scenario, use of terminal sires increased COS by the largest amount (COS = NZD 317 /ha), Angus premiums increased COS by a lower amount (COS = NZD 307 /ha), and the higher weaning rate of 90% increased COS by a slightly lesser amount (COS = NZD 302 /ha). Alternatively, these strategies could be implemented concurrently, which was predicted to have the highest COS at NZD 381/ha. These results can inform farmer decision making and farmers can consider the relative profitability potential and practicality of the explored strategies for their breeding herd. [ABSTRACT FROM AUTHOR]