This week's summary is following on with the theme of youngstock management and rearing.
Dairy farms from nine areas in New Zealand were used for this study on calf and colostrum management practices and potential associations with the transfer of immunity from colostrum.
Key Points
Risk factors that were important in studies overseas were not identified as important in this New Zealand study.
Total protein concentrations were higher in calves from farms with a smaller herd size (600 or less cows) than farms with a larger herd size (more than 600 cows).
Factors affecting how well a cow can feed her calf may have a greater impact on failure of passive transfer (FPT) than the management of calves once they reach the rearing shed.
What is failure of passive transfer (FPT)?
It is constantly drilled into us how important feeding good-quality, 1st-milking colostrum to newborn calves is. This is because calves are born with what is called a naive immune system, so are born with a very limited ability to fight off disease.
They can get immunoglobulins (and other goodies) from their mum's colostrum (1st milk/gold colostrum), but, their ability to absorb immunoglobulins declines up to 24 hours after birth.
Simply put, when calves do not get enough immunoglobulins they are said to have failure of passive transfer (FPT).
To help calves get the best start possible, remember the 3Q's of colostrum management - Quickly, Quantity and Quality!
The figure below shows the apparent absorption of IgG from first feeding colostrum to calves at either 6, 12, 24, 36 or 48 hours old. As can be seen in the graph below, there is a sharp decline over the first 24 hours in the calf's ability to absorb IgG from colostrum.
This does not mean that there is no point in feeding good quality colostrum to 24-hour-old calves, it just means that they require much more milk and/or a greater IgG concentration in that feed in order to absorb sufficient IgGs.
In our pasture-based system, where there are a lot of cows calving in a short period of time, it is often not practical or feasible to ensure all calves are fed within a few hours of being born. One recommendation is to pick up calves twice per day or more. In an Australian study, picking up calves more frequently reduced the proportion of calves with failure of passive transfer (FPT).
Survey results:
The majority (65.3%) of farms surveyed in this study picked up calves once per day or less often, whereas, 19.8% picked up calves once or twice and 14.9% two or more times a day.
Interestingly, there was approximately a 50:50 split on what was done if a calf had just been born at the time of pick-up; with 48.5% leaving the calf with the dam and 51.5% picking it up anyway. Unfortunately the data wasn't split by how the previous question was answered which would have helped the interpretation of this answer. If calf pick-up occurred once per day or less, we would hope the newborn would be picked up rather than left for a further 24 hours or more!
At the time of first feeding (once in the calf shed), 27% of respondents tube fed all calves and 42% tube fed calves if they needed it (calf not sucking), as shown in the graph below (Figure 2). This 42% was made up of farmers who used group feeders (13/42) or individual feeders (29/42) at this first feed. Only 1% of respondents did not feed additional colostrum to what the calf would have got from it's dam. The last group always fed calves with a group feeder (18%) or with an individual teat (13%).
The majority of respondents (blue in figure 3 below) fed between 2 and 2.5L of colostrum in the first 24 hours, closely followed by 3-4L (purple). 10% of respondents fed 5L or more and only 1% fed no colostrum over the first 24 hours.
The concentration of IgGs in colostrum declines after the cow has calved. Therefore, collecting calves and milking the cows soon after calving is recommended to provide colostrum of high quality. As can be seen in figure 4 below, 24 hours after calving there was approximately 50% of the IgG concentration that was present at calving.
Only 1 farm reported that the average time from calving until first milking was less than 6 hours. 37.6% of farms reported between 6-12 hours after calving, whereas, the majority (61.3%) of farms reported between 12-24 hours as the average time from calving until first milking.
Only 7% of respondents never pooled first-milking colostrum from different cows, whereas, 27% sometimes did and 66% always pooled first-milking colostrum.
Interestingly, 16% of respondents pooled first-milking colostrum with that of cows from later milkings to feed to newborn calves. 12% sometimes did and 72% never did. It is recommended to pool colostrum from milkings 2 to 8 for calves older than 24 hours, but to feed first milking colostrum to the newborns.
42% of respondents did not think that they would have failure of passive transfer (FPT) diagnosed in their calves.
The reasons why they thought they would not have FPT were:
“they had good procedures in place to get good quality colostrum to the calves” (29/42)
“calves were happy and healthy” (4/42)
“calves were kept on the mother to get colostrum” (3/42)
“they did not know what FPT was” (2/42)
they had done prior testing (1/42)
no reason given (3/42)
57% of respondents did think that they would have FPT diagnosed in their calves
The reasons why included:
an understanding of the limitations of the timing of picking up calves
weather influencing feeding behaviour
variations in quality of colostrum
that not all calves will feed off their mother
On farms where respondents thought they might have FPT diagnosed, these herds had between 5-66% of calves diagnosed with FPT. On the farms where they didn't think they would have any the range varied from 7-80% of calves.
Furthermore, the mean concentrations of total protein (as a measure of FPT) in the serum of calves was not different between farms where respondents thought they would have calves with FPT (60.3 g/L) in comparison with those that thought they would not have FPT (59.5 g/L).
What farm level factors influenced total protein/FPT in calves?
Many farm level factors were tested to see what influenced total protein concentration in the serum of calves. For full list refer to the paper and/or supplementary tables below.
Of these factors tested only 2 were deemed to be significant enough to include.
These were; region and herd size.
Region
Concentrations of total protein were lower in calves from farms in Otago and Southland (56.2 g/L and 56.9 g/L; purple in figure 5) compared to calves on farms in the Far North (62.6 g/L; blue in figure 5). The authors hypothesized that this could be associated with low environmental temperatures at birth for those herds in the south.
Herd size
Herds with more than 600 cows had lower total protein concentrations in calves than herds with 600 or less cows. Those with more than 600 cows had 58.3 g/L of total protein and was 61.3 g/L for those with 600 cows or less.
What colostrum quality factors influenced total protein/FPT in calves?
As with farm level factors, there were many colostrum quality factors tested to see what influenced total protein concentration in the serum of calves.
These included:
time from calving until colostrum given by farmer
the volume of colostrum provided in the first 24 hours
the method of colostrum feeding (tube, individual, group feeder etc.)
number of feeds in the first 24 hours
colostrum pooled from other cows
For this study there was no association found between any of the measures of colostrum quality and concentrations of total protein in serum of calves.
The way in which this study was completed may be a reason why there was no association found. Particularly, all calves were more than 24 hours old at the time of sampling and the colostrum sampled was collected on the same day as the calves blood samples were collected. Therefore, the colostrum tested was not the colostrum fed to the calves that were blood sampled.
Further from that, the survey was taken at the end of the calving season which may have reduced how accurate some of the answers were compared with if the survey was done during calving.
It is possible that the key factors likely to influence total protein concentrations and FPT in dairy calves are the speed with which calves are able to feed from their dam, and the volume and quality of colostrum that they consume prior to being collected. The authors hypothesized that intake of colostrum by the calf from its dam is likely to have a bigger impact on concentrations of total protein in serum than anything that is done in the rearing shed.
As this study was a survey, they were not able to measure the time from birth until the first feed or the quality/quantity of colostrum in that first feed. This definitely shows that we need more research done on these first few hours for NZ calves in order to better understand factors that affect FPT.
Lastly, DairyNZ has put together a "Calf Care Toolkit" survey that gives you a chance to level-up your calf care. I highly recommend checking it out, even if its just to reconfirm how great you are!
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Full paper: