The Research Column

Microbial contamination is generally associated with the presence of microbial biofilms attached to the inner surfaces of tanks, pipes and milk processing lines.

As carbon dioxide, methane is a potent greenhouse gas (GHG), but when it comes to ruminant livestock and climate change there are many other characteristics which need to be considered. The important ones are: (1) it stays in the atmosphere only for about 12 years versus 1000+ years for carbon dioxide; (2) it is derived from atmospheric carbon such as carbon dioxide; (3) it is part of the biogenic (photosynthetic) cycle, and (4) it eventually returns to the atmosphere as carbon dioxide, which means it is recycled carbon.

Numerous studies have shown the negative effects of heat stress during the dry period on dairy cow performance during the subsequent lactation. Exposure of cows to heat stress during the dry period is associated with compromised mammary cell formation and decreases in milk yield in the subsequent lactation. Moreover, a greater incidence of postpartum disorders and lower reproductive performance are associated with exposure of cows to heat stress during the dry period. Dry period heat stress also decreases dry matter intake and body weight, gestation length, and calf weight.

Heat stress has been estimated to cost the dairy industry in the United States more than $900 million annually due to production losses. The main contributors to heat stress are temperature, humidity, and the temperature-humidity index (THI). A THI of 68 to 72 has been reported to induce heat stress in cows and decrease milk production. Prior research has been conducted on heat abatement measures in free stall barns with sprinklers, evaporative cooling, and fan design.

The gastrointestinal tract is highly sensitive to a large number of internal variables in the lifecycle of dairy cows. The hindgut is susceptible to acidosis, much like the rumen, but due to a variety of physiological and structural differences, it is less capable of tolerating acidosis than the rumen, resulting in increased permeability to antagonistic compounds and repartitioning of energy to support an immune response. By improving gut integrity and function, less energy is repartitioned, thereby saving energy for productive purposes.

In last month’s column, I touched on the use of Saccharomyces cerevisiae fermentation products (SCFP) during the transient phase; the emphasis being on on performance, blood biomarkers, rumen fermentation, and ruminal bacteria population.

Four multi-lactation dairy cows in early lactation and subsequently in late lactation were fed two diets for 28 days in a changeover design that provided, within the same stage of lactation, similar amounts of rumen fermentable feed with either high (HS) or low starch (LS). All diets had similar dietary crude protein and rumen-undegradable protein content. Amino acid profiles were similar to that of casein.

Discipline: body condition score; Keywords: body reserve status, fat, hormonal changes, pregnancy, metabolic disorders.

Research in this context was reviewed by J.R.Roche and coworkers in a paper published in the Journal of Dairy Science, Volume 92, pages 5769 to 5801. The title of the paper is: Body condition score and its association with dairy cow productivity, health, and welfare.

Discipline: mastitis; Keywords: dry cow therapy, Staphylococcus aureus, antibiotics, re-infection,teat sealant.

 In a large study this question was addressed in two papers: in the first paper the preventive effect of various dry cow measures on new infections were investigated and in the second paper the cure of existing infections. These studies are unique in the sense that a highly powerful statistical method, called meta-analysis, was used which enable scientists to pool research data from various studies conducted in different circumstances and synthesize a highly reliable result which for all practical purposes can be considered correct to implement. The titles of the respective papers published by T. Halasa and co-workers in the Journal of Dairy Science, Volume 92 of 2009, page 3134 to 3149 and page 3150 to 3157 are: Meta-analysis of dry cow management for dairy cattle. Part 1. Protection against new intramammary infections and Part 2. Cure of existing intramammary infections.

Discipline: lactation management; Keywords: reproduction, model, MDP, daily information, economic implications.