The Research Column

Lactation yield estimates standardized to common lactation lengths of 270 or 305 days are commonly used in management decisions and genetic evaluations. The use of such measurements to quantify the merit of individual cows fails to penalize cows that do not reach the standardized lactation length, or vice versa to reward cows that lactate for more than the standardized lactation length. The objective of a study by Dr M.

The nitrogen (N) use efficiency (conversion of feed N into milk N) of dairy cattle is poor, typically ranging from 25 to 35%. The unused feed N is excreted about equally via the faeces and urine, although the proportion depends on the crude protein (CP) level and the ratio of rumen degradable protein (RDP) to rumen undegradable protein (RUP) in the diet. The excreted N is lost at each stage of manure management (e.g., during collection, storage, and after land application) in several forms: ammonia (NH3), nitrous oxide (N2O) and nitrate.

Although limited in South Africa, many dairy cattle worldwide are still housed in tiestalls, meaning that they are tethered by the neck to individual stalls. On some farms, tied cattle are permitted seasonal access to pasture, but otherwise their movements are restricted compared with cows housed in freestall barns or other loose housing systems. The aim of the systematic review by Dr A Beaver and colleagues was to summarize the scientific literature pertaining to the welfare of tied dairy cattle through comparison with less-restrictive housing systems.

Oestrus detection has become more difficult over the years due to decreases in the oestrus expression of high-producing dairy cows, and increased herd sizes and animal densities. Through the use of hormonal synchronization protocols, also known as timed artificial insemination protocols, it is possible to alleviate some of the challenges associated with oestrus detection. However, timed artificial insemination masks cows’ fertility performance, resulting in a possibly biased comparison of treated animals and innately fertile animals.

In the study four milk production systems over three successive lactations and 20 cows per system during each lactation, were investigated. With winter calving-fully housed (WC-FH), Holstein cows were housed for the entire lactation and offered a complete diet consisting of grass silage, maize silage, and concentrates [approximately 50% forage on a dry matter (DM) basis].

Discipline: housing; Keywords: thermal protection, durable lying surfaces, behaviour, free-stall lying surface softness, culling.

Is there an advantage to having soft flooring material instead of concrete? A recent Danish study investigated whether this was indeed the case; reference: L.E. Ruud, K.E. Bøe and O. Østerås. Associations of soft flooring materials in free stalls with milk yield, clinical mastitis, teat lesions, and removal of dairy cows. Journal of Dairy Science (2010) Volume 93, pages 1578-1586

Discipline: lactation management; Keywords: metabolic diseases, correct feeding strategies, moderate energy, lactation length.

These questions were addressed in a study by Dr Silva-del-Rio and colleagues in a study published in 2010 in the Journal of Animal Science, Volume 88, pages 1048 to 1060. The title of the paper appropriately was Effects of twin pregnancy and dry period feeding strategy on milk production, energy balance, and metabolic profiles in dairy cows.

Discipline: milk powder; Keywords: heat-treatment, shelf life, pH , protein content, standardization material.

Discipline: effluent management; Keywords: reduced water intake, waste-water disposal, processing, cleaning processes.

Discipline: reproduction; Keywords: increased profit, improved overall efficiency, energy reserves, after calving ovulation, artificial insemination.