Red meat vs plant-based alternative
At this time of year when healthy eating is promoted heavily, with some advocating a plant-based diet, this paper is pertinent to the discussion. Red meat is a nutrient-dense food and a dietary staple for many. A new generation of plant-based meat analogues has been designed to mimic the experience of eating meat, but there is limited evidence about their digestive efficacy and nutritional quality.
Pham et al (2022) (Current Developments in Nutrition10.1093/cdn/nzac082) compared the postprandial digestive response of a single meal containing meat, including lamb, pasture-raised beef (pasture) or grain-finished beef (grain) with the response to a plant-based meat analogue, Beyond Burger. The primary outcome was the appearance of amino acids in plasma. Secondary outcomes included glucose and insulin levels, appetite assessment and anthropometry.
Thirty healthy men participated in a double-blinded randomised crossover trial. Following an overnight fast, each consumed one of the four test meals on four occasions separated by a washout period of at least 1 week,. The meal was a burrito-style wrap containing meat or plant-based meat analogues, vegetables, salsa, and seasonings in a flour tortilla. The amount of uncooked pasture, grain, lamb or plant-based meat analogue was 220 g. Venous blood samples were collected over 4 hours. Appetite and hunger status was scored with visual analogue scales.
Pre-meal amino acid concentrations in plasma did not differ by group. Postprandial amino acids peaked at 2–3 hours in all groups. The plant-based meat analogue meal produced significantly lower plasma concentrations of total, essential, branched-chain and non-proteogenic amino acids than the lamb, pasture or grain meals. There were no significant differences between meal groups in scores for hunger, fullness or cravings.
The authors concluded that meals containing red meat provided greater bioavailability of amino acids than those containing the plant-based meat analogue. Pasture vs grain origin of the beef had little influence on participants' postprandial digestive responses.
Sexed semen
The worldwide use of sexed semen in cattle has been reviewed by Seidel and Dejarnette (2022) (Animal Reproduction Science10.1016/j.anireprosci.2021.106841). Successful sorting of sperm based on the presence of the X- or Y-chromosome was reported in the early 1980s, with the first live births reported in rabbits in 1988. Subsequent development of technological efficiencies resulted in commercialization of sex-sorted semen to cattle producers in 2003–5.
At product launch, low throughput dictated that reasonable prices to the producer could only be accomplished with extremely low sperm number dosages. Furthermore, conception rates were 70–75% of those achieved by conventional unsorted product. Refinements in sorting equipment have resulted in reduced production costs, while modifications to other aspects of sperm processing and freezing have facilitated maintenance of a conception potential more like that of conventional semen.
More recently, strategic use of sex-sorted semen coupled with genomic technologies to identify superior females to satisfy replacement female needs has led to identification of a population of dairy cows from which replacements are not desired, leading to a tremendous increase in use of beef semen in dairy herds. Although the primary application of sexsorted semen is to accelerate genetic progress while enhancing biosecurity through in-house production of replacement animals, numerous other potential applications are evolving or are under consideration.
Further to the use of sexed semen in dairy herds, male-sexed semen can also be used in beef herds to increase the number of heavier and faster-growing offspring. However, the use of sexed semen requires artificial insemination which has limited use in extensive beef systems because of its practical constraints and additional breeding costs. The objective of the study by Farrell et al (2022) (Livestock Science10.1016/j.livsci.2022.105107) was to predict the profitability of using sexed semen via fixed time artificial insemination for a New Zealand hill farm system.
When modelling self-replacing Angus herds, male-sexed Simmental semen was used across 43% of mixed-age cows then follow up Simmental bulls were used. 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 Angus x Holstein-Friesian herd with a bought-in replacements policy were bred with male-sexed Simmental semen followed by Simmental bulls. First time Angus x Holstein-Friesian calvers were bred with unsexed Angus semen followed by Angus bulls.
Herds using sexed semen were assumed to undergo synchronised fixed-time artificial insemination which resulted in a more condensed calving spread and 3% heavier average weaning weights because calves were predominantly male and on average 7 days older. Total breeding costs were higher for herds using sexed semen via artificial insemination compared with herds using only natural mating. Increases in breeding costs were relatively larger than any additional income for all herds using sexed semen via artificial insemination compared with herds using all-natural mating.
It appears that producing more fast-growing male calves through use of sexed semen via artificial insemination is not currently an economically feasible option for beef producers under extensive New Zealand production systems.