One of our biggest challenges was coming up with a creative project; I mean, how many times have you seen the old experiment where you plant three bean seeds and give them different types of water and measure the differences in growth?
I realized we'd never been very methodical about tracking the growth rates of our sheep; heck, we didn't even have a scale for weighing them. After some thought as the the experiment's design, and an investment in a scale, we were ready for the first lambs to be born. Once they started arriving, HFB and I went out every single night and weighed each one. It was a bit of a hassle, but I came to enjoy spending the time with him --- and teaching him how to use Microsoft Excel to record the data about each lamb and then track the results. We did this for several weeks, until we felt we had enough data for analysis. I transferred the numbers to SPSS, and showed him how to do some basic analysis of variance (ANOVA). And the best part about that was it allowed me to introduce him to more of what I do in my professional work.
Anyhow, here is his final report (the tables didn't paste nicely, so I had to re-type the numbers here...even so, I'm not happy with the formatting. Blame Blogger):
We live on a farm and raise sheep for meat. I wanted to know more about why some lambs grow bigger and faster than others. For this reason, I chose to do a lamb-weighing project for my science report.
I decided to test two hypotheses on the way lambs grow. First, we’ve seen that male sheep tend to be more aggressive than female sheep. As a result, they might take more milk and therefore grow faster. Secondly, some of our lambs are singles, others are twins, and a few are triplets. This makes a difference because each ewe has the same amount of milk, but not the same number of lambs. I hypothesize that the singles would be biggest, then twins, while the triplets are smallest.
Beginning in late March when the first lambs were born, we weighed each lamb every day in the evening. We recorded each of these weights in a spreadsheet. Five females and eleven males were born, and of these sixteen, there were two singles, eight twins, and six triplets.
The results of the analysis prove one hypothesis and show the other one to be false. I did this by subtracting the birth weight from its final weight and dividing by the number of days old the lamb was. I also computed this average daily weight gain for various types of lambs. These figures are detailed in the table below.
Weight Gain By Lamb Types
Starting Weight Avg. Daily Gain
Males 7.5 .47
Females 7.0 .51
Singles 7.1 .53
Twins 7.8 .49
Triplets 6.8 .41
As the table shows, the females’ average daily weight gain was essentially the same as that of the males’. However, singles do gain more than twins, and twins do gain more than triplets. (See the table above.) The singles gained a little more than half a pound (0.53) per day, the twins about half a pound (0.49), and the triplets gained just over two-fifths of a pound (0.41).
Something interesting happened with the triplets. We had two sets. One of those triplets died on day 8. Now we had one set of triplets and the two others became twins. Before the death, both sets grew at exactly the same rate, 0.38 lbs. per day. After the death, the triplets continued growing like triplets, but the new set of “twins” began growing like twins (0.47 lbs. per day).
Impact of Reducing Triplets to Twins
Nera's Triplets Licorice's Triplets
(All Survived) (One Died on Day 8)
Days 1-8 .38 .38
Days 9-14 .38 .47
In conclusion, the amount of food lambs get is very important. A lamb’s growth is affected most by how much food it gets, and not as much as by if it’s male or female. Triplets are good because we have one more lamb, However, if all three triplets must share one ewe’s milk, they don’t reach their growth potential. From this I conclude that next year, if we have triplets, we should give them some extra feed to make up for the lack of milk.