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  • Gibraltar Farm

Lamb Growth

This year we tried to better understand the change in weight gain of the lambs. Previous years we saw that growth slowed at a certain point, this raised many questions such as:

  • Is it related to the age of the lambs?

  • Does it vary by gender?

  • Does rainfall influence growth?

  • How does temperature impact growth?

This year we were better prepared to look into how the weight gain of the lambs changed. Well, that was until we had a very wet spring and summer, not to mention the coccidia that came with all the wet weather. And now it seems like we are going to have a warm start to fall.

In a 100% forage/grass based management system the lambs and ewes only get nutrients from what they graze and the free choice minerals that we provide. We mainly sell grass finished lambs (wholesale) so getting good consistent growth is very important to our bottom line. We cannot supplement with grain and the grazing season is only so long, lambs that do not make weight/condition cannot be sold at a premium, they will end-up at a sale barn.

I doubt if we can make any conclusions from what we saw this year, it seems like coccidia had a big impact and there's no way to separate the coccidia impact from the observation. With that said, it is still an interesting graph. Lets have a look at it.

Click on the image to view a larger PDF of the graph.

Let me explain what we are looking at ...

We looked at 58 ewe lambs and 45 ram lambs that we had weights for over about a 160 day period. The x axis is the number of days since 4/17/2017, this is the first date when we weighed all the lambs that we are looking at. The y axis on the left represents the average weight of a lamb (lb.) or the maximum temperature (Fahrenheit) for the day, this depends on which series you are looking at. The y axis on the right is the amount of rainfall we had on a specific day in inches.


  • Max Temperature: Maximum temperature in Degrees Fahrenheit for the day (y axis on the left)

  • Ewe Lamb Avg. Weight: Average weight (lb.) of an ewe lamb when weighed (y axis on the left)

  • Ram Lamb Avg. Weight: Average weight (lb.) of a ram lamb when weighed (y axis on the left)

  • Rainfall: Amount of rainfall on each day in inches (y axis on the right)


  • Weaned: Lambs were weaned 79 days after 4/17/2017 (Some of the ram lambs were close to 100 days and started to reach reach sexual maturity, we had to get them away from the adult ewes)

  • Confirmed Coccidia: Our first set of fecal samples confirmed that we had a coccidia problem. This was 90 days after 4/17/2017.

  • Treated Coccidia: We started treating for coccidia 102 days after 4/17/2017

  • Separate Ewes & Rams: Ewe lambs and ram lambs were separated and started grazing pastures of different quality, this was 125 days after 4/17/2017.


  1. Ram lambs grew faster than ewe lambs. The growth started to diverge well before weaning. They followed a similar pattern even as the gap was widening.

  2. We had a huge spike in growth after separating ewe lambs and ram lambs. We are not sure if the separation (ram lambs were getting preoccupied with ewe lambs) or the change of weather was responsible for the growth spike. There's also coccidia which we started treating, the treatment might have worked initially before coccidia started increasing again. I think we can be sure that it was not pasture, the ram lambs were on pastures that were better than that of the ewe lambs.

  3. We got a lot of rain and it is interesting to see how maximum temperatures buildup until there's a big drop again. There's a drop scheduled for later this week when our maximum goes back down to 60 again.

For now we are not making any conclusions. We realized that we needed to be better prepared to manage coccidia next year (if it is a wet year again). We will do the same again next year, hopefully with fewer extremes and no coccidia, the goal is to understand when we are not getting a good return for the pastures used.

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