Optimizing weaning strategies of dairy replacement calves

The question addressed is when pre-weaning calves housed individually can be grouped successfully without increasing stress and the incidence of disease. This research by Drs Bach in colleagues was published in The Journal of Dairy Science, Volume 93 of 2010, pages 413 to 419. The title of the paper is: Optimizing weaning strategies of dairy replacement calves.

It is generally recommended to keep calves individually housed and provide them with milk or milk replacer twice daily. The main purpose for housing the calves individually is to prevent the spread of diseases and facilitate the control of starter intake. However, in large herds labour costs to do that is a factor and therefore the practice of grouping calves and offering them milk replacer by automatic feeding system has become a practice; but obvious at a risk of higher incidence of disease. On the other hand exposure to pathogens would build calf immunity, which may be favourable to selecting healthy and fit replacement heifers.

In order to manage these objectives a general recommendation in the US is to keep the calf in individual housing for a further week, presumably to make it stronger and with better immunity, before housing it in a group. However, this practice has not been scientifically tested and therefore one of the objectives in this study was to evaluate whether allowing calves to remain individual for an additional six days after weaning was beneficial in terms of improving performance and preventing respiratory problems. The second objective was to evaluate the effect on performance and incidence of diseases of moving calves into groups before weaning at two different ages.

Objective 1 was studied with 320 female Holstein calves with measurements animal performance, whether more robust and healthy and if the additional six days housed individually would assist the calf to reach a target weight of 115kg at an earlier age. The 320 calves were assigned to two treatments: 1) allowing them to remain individually housed for an additional six days after weaning, or 2) moving them immediately after weaning to a different pen, forming groups of eight contemporaneous calves. Objective 2 was studied with 240 female Holstein calves divided into one of two treatments: (a) individually housed until 56 days of age and then moved to groups of eight contemporaneous calves in super hutches of 6 × 3m, or (b) moved to the super hutches after 49 days. All calves were weaned at 70 days of age.

The results showed that calves moved to groups immediately after weaning reached the target weight six days earlier and they experienced a lesser incidence of respiratory problems than those grouped six days after weaning. Calves grouped at 49 days of age had a greater average daily gain and weight at 56 days of age as a result of a greater total solid feed intake compared with those grouped at 56 days of age. Calves grouped at 56 days, however, had a greater average daily gain between 56 and 64 days of age (the week following grouping for the calves in the 56-day treatment) than those grouped at 49 days of age. Overall, the proportion of calves affected by a respiratory problem during the total experimental period did not differ between treatments, but those calves grouped at 49 days of age had a lower number of respiratory cases than those grouped at 56 days of age.

It was concluded that moving calves from individual housing to group housing immediately after weaning is preferable to waiting an additional six days. In addition, moving calves from individual housing to group housing at 49 days of age and starting to reduce milk replacer offering once grouped is preferable to starting to reduce milk replacer while calves are still individually housed.