Productivity of crossbred dairy cows suckling their calves for 12 or 24 weeks post calving

An experiment on restricted suckling of crossbred dairy cows was conducted at the Livestock Research Centre, Tanga in northeast Tanzania. Thirty-six Bos taurus (Holstein Friesian and Jersey) x Bos indicus (East African Zebu) cows were allocated alternately as they calved to suckling their calves for either 12 or 24 weeks after calving. Cows grazed improved pastures and were offered 4 kg concentrate daily. Milking occurred twice daily by hand; calves were allowed to suck residual milk for 30 min following each milking. Calves were also allowed access to grazing and were offered a maximum of I kg concentrate daily to 24 weeks of age. Weaning age had no significant effect on lactation milk yield for human consumption, the mean (SE) yield being 1806 (102.0) L and 1705 (129. 1) L for 12- and 24-week weaning, respectively. Cows from the two treatments suffered similar losses of live weight and body condition score during lactation and neither group had returned to the original body condition score 40 weeks following calving. Post-partum anoestrous intervals were prolonged. Although not significant, cows suckling calves to 24 weeks had a mean interval to first oestrus extended by 38 days compared with cows suckling calves to 12 weeks. The mean (SE) daily live weight gains of the calves to 52 weeks were 263 (14.1) g/day and 230 (18.1) g/day for calves weaned at 12 and 24 weeks, respectively, such that 12-month weights were 119 (5.6) kg and 110 (7.3) kg, respectively. Twelve-week-weaned calves consumed more concentrate (p < 0.05) from 13 to 24 weeks than did 24-week weaned calves. Calculation of residual milk consumption removed by calves from birth to 12 weeks indicated that it accounted for 28% of total yield. No benefits in cow and calf performance and welfare were found to justify prolonging the suckling period to 24 weeks.

MALDI MS

Matrix-assisted laser desorption/ionization (MALDI) is a key technique in mass spectrometry (MS)-based proteomics. MALDI MS is extremely sensitive, easy-to-apply, and relatively tolerant to contaminants. Its high-speed data acquisition and large-scale, off-line sample preparation has made it once again the focus for high-throughput proteomic analyses. These and other unique properties of MALDI offer new possibilities in applications such as rapid molecular profiling and imaging by MS. Proteomics and its employment in Systems Biology and other areas that require sensitive and high-throughput bioanalytical techniques greatly depend on these methodologies. This chapter provides a basic introduction to the MALDI methodology and its general application in proteomic research. It describes the basic MALDI sample preparation steps and two easy-to-follow examples for protein identification including extensive notes on these topics with practical tips that are often not available in the Subheadings 2 and 3 of research articles.

The mammalian cell cycle: an overview

In recent years, we have witnessed major advances in our understanding of the mammalian cell cycle and how it is regulated. Normal mammalian cellular proliferation is tightly regulated at each phase of the cell cycle by the activation and deactivation of a series of proteins that constitute the cell cycle machinery. This review article describes the various phases of the mammalian cell cycle and focuses on the cell cycle regulatory molecules that act at each stage to ensure normal cellular progression.

Cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors: detection methods and activity measurements

The cyclin/cyclin-dependent kinase (Cdk) complexes and the Cdk inhibitors (CDKI) are crucial regulators of cell cycle progression in all eukaryotic cells. Using rat cardiac myocytes as a model system, this chapter provides a detailed account of methods that can be employed to measure both cyclin/Cdk activity in cells and the extent of CDKI inhibitory activity present in a particular cell type.