New Directions for Accelerated Lambing
Brian Magee
Cornell University
August 1983

Five years ago the Cornell University Dorset flock was started on the CAMAL System (Cornell Alternate Month Accelerated Lambing). On paper it seemed like a good approach to maximizing lamb production from Dorsets. Every other month the ewes were exposed to a ram and alternate months the ewes lambed. The ewes were given a chance to lamb on a 6, 8 or 10 month interval. Unlike a three in two years scheme, the ewes were given several chances to lamb on an accelerated schedule before they returned to once a year lambing.

It became apparent in the first year that one problem with the CAMAL system was the difficulty encountered in predicting stages of pregnancy for proper feeding. It was even more difficult to predict which breeding period would result in pregnancy for effective flushing. In order to solve these problems of pre-partum and pre-breeding feeding, I devised what Dr. Hogue calls the MAGEE system of accelerated lambing. Instead of alternate lambing and breeding periods, the lambing of one portion of the flock coincides exactly with the breeding of another portion of the flock. In this way the entire flock can be managed as a unit throughout most of the year. Flushing and pre-partum feeding can be accomplished on a flock basis and sorting out pre-partum ewes can be postponed until quick sorting by palpation of the udder is possible.

The shortest interval between lambings on the MAGEE system is 7.2 months with a second chance at 9.7 months. There are 5 lambings yearly instead of 6 with the CAMAL System and a ewe can achieve 5 lambings in 3 years if she completes the cycle perfectly. The numbered superscripts in Table 1 plot the sequence of a perfect set of 5 lambings in 3 years. A ewe's failure to rebreed at one of the 5 breeding periods would result in a lifetime pattern of two 7-2 month intervals followed by one 9.7 month interval, which is exactly 3 lambings every 2 years. Therefore a ewe does not have to be perfect to achieve a respectable accelerated schedule. For that matter, a shepherd might wish to lamb only 3 times in one year. By following the schedule in upper case letters in Table 1, two sets of lambing and breeding periods would still coincide for ease of management. This variation of 3 lambings in 2 years also allows the possibility of an extended lactation during the peak summer pasturing season.

As can be seen in Table 1, August 8 has been chosen to start the first breeding period. This fits our teaching and research needs and is also our best guess for optimal performance of our Dorsets. One may choose to start the first breeding and lambing period on any other day of the year and then space the start of each succeeding breeding one-half sheep gestation (73 days) apart to fit the year exactly.

Ewes on the CAMAL System were first exposed to the ram during their 56 day lactation period and for the second time one to five weeks postweaning. On the MAGEE System all lambs are weaned one week before the first breeding period so that the stress of lactation is usually shorter than on the CAMAL System.

During the winter, spring and summer breeding periods a fertile ram is put with the ewes for 30 days. For the October-November breeding, a 20 day breeding period has proven to be long enough. In the August-September breeding period, I have had success synchronizing the breeding of Finnsheep naturally by exposing the ewes to a teaser ram (vasectomized) for the first 10 days of the breeding period and then replacing the teaser with a fertile ram for the last 20 days. The last two years my Finns have bred within a three day period and lambing in January has only lasted for one week.

A marker is put on the ram's brisket during all breeding periods so that the first ewes bred are well-marked on the rump. Two weeks later the color is changed so that rebreeding can be detected. Little or no remarking means the ram is doing his job. If there are many ewes being marked for a second time, one should put a new ram in with the ewes. Having an active fertile ram is an absolute necessity. Because of genetic variation, the widespread use of hormones and light therapy, there is no guarantee that a fall born ram will breed in the spring or summer. I test rams by keeping a monthly record of the scrotal circumference. If the circumference recorded during the fall decreases by one inch or more in either the spring or summer, then I don't use the ram.

The temptation to extend the breeding period for longer than 30 days should be strongly resisted. Remember the ram will be back with the ewes in 45 days. Extending the breeding period may pick up young ewes cycling for their first time yet by waiting for a later cycle, at the next breeding period the young ewe may be more fertile. I also cull spring born ewe lambs not cycling by 10 months of age for meat while they are still lambs.

Feeding the flock over an extended lambing is inefficient and long lambing periods do not optimize labor efficiency. Instead of just making it through another lambing (the feeling often expressed by once a year lambing shepherds), a short lambing period can be enjoyable and any problems will be more likely remedied instead of forgotten before the next lambing.

Cash flow can be more even on a successful system and money made on one crop can be reinvested for a second return in the same year.

Table 2 compares the last year's performance of September lambing Cornell Dorsets on the CAMAL System with the first year's performance of August-September lambing Cornell Dorsets on the MAGEE System. It can be seen that lower lambing percentage on the CAMAL System offset slight gains made in shortening the lambing interval to produce an unimpressive 166% annual lamb crop. The next year on the MAGEE System, a shortened interval coupled with an increase in lambing percentage increased yearly lambing rates substantially. The increase in annual lambing percentage of mature Finn sheep on a 7.2 month interval is even more dramatic.

It is true that some Dorset and Finn sheep flocks are approaching these respective lambing rates with once a year lambing. It is not likely that those Dorset flocks are weaning a 225% lamb crop from the ewes and even less likely that a Finn flock lambing once a year is weaning a 435% lamb crop from the ewe annually.

The ewe that gestates on summer pasture and lactates on fall pasture can produce several lambs which often sell for a premium at Christmas time. This ewe has generated a greater profit for her owner than could normally be realized from the sale of many spring born lambs.

For the skeptic or critic of accelerated lambing who feels it is not possible or unnatural to expect a ewe to lamb continuously in less than a 12-month interval, it might be pointed out that the native Criollo sheep of Ecuador and Columbia lamb naturally every 7 months. They have the advantage of a constant day length which is probably the most difficult obstacle to overcome at our latitude. Yet my experience with this new system makes me optimistic for the possibilities of successful accelerated lambing operations that require no artificial light or hormone therapy. Careful attention to a few important details of feeding, breeding and management will go a long way in releasing the tremendous production potential many of our sheep have in store for us.