Increased yearling weight as a proportion of 21-month weight was associated with increased milk production in dairy heifers

The carbon footprint of young-beef cattle finishing systems in the Eastern Plains of the Orinoco River Basin of Colombia

Introduction

Previous research has shown increased productivity amongst sown grass pastures compared to native savanna pastures by year-round grazing for fattening of adult and young Brahman (Bos indicus)-bred cattle in the well-drained native savanna ecosystem of the Colombian Orinoquía. But there is limited information on the carbon footprint (CF) of commercial young-Brahman heifers and steers reared throughout life on well-managed Brachiaria decumbens Stapf pastures.

Methods

The present study characterized growth, lifetime enteric methane (CH4) emissions, carcass carbon dioxide equivalent (CO2-eq) CH4 efficiency intensities (i.e., emissions per kg of product), and estimated the overall CF of young cattle grazing B. decumbens pastures subject to a range of daily liveweight gains (DLWGs; 0.428 – 0.516 kg) and fattening framework (405 – 574 kg). Weaning data from seven consecutive calving seasons in a commercial Brahman breeding herd continuously grazed on B. decumbens were integrated with a Microsoft Excel® dynamic greenhouse gas emission (GHGE) simulation of stockers-yearlings, and seven fattening, and processing scenarios.

Results

The model predicted that heifers subject to low and high DLWGs (0.428 vs 0.516 kg) and steers (0.516 kg) may be successfully fattened without supplementation assuming that animals had access to a well-managed grass pasture. Depending on the fattening strategy, kg CO2-eq CH4/kg edible protein values ranged from 66.843 to 87.488 ± 0.497 for heifers and from 69.689 to 91.291 ± 0.446 for steers.

Discussion

Assuming that forage on offer is at least 1,500-2,000 kg of dry matter/ha during the rainy season, all the simulated systems showed potential for C neutrality and net-zero C emission when considering GHGEs from the soil, pasture, and animal components vs the estimated soil C capture over seven seasons. However, under a more optimistic scenario, these beef systems could accomplish substantial net gains of soil C, over the period for which field data are available. Overall, this study projects the positive impact of the design of plausible fattening strategies on grasslands for improving cattle productivity and reducing emission intensities with concomitant increases in technical efficiency.

Low Birthweight Beef Bulls Compared with Jersey Bulls Do Not Impact First Lactation and Rebreeding of First-Calving Dairy Heifers—A Case Study in New Zealand

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.