Results from the Second Year of the Lakeland Project

.By Cathy Gallivan, Susan Hosford, Tracy Hagedorn, Wade Meunier, Sunterra Meats, Mel Mathison, Lakeland College

Editor’s Note: The Lakeland Carcass Sire Project is a three-year project scheduled for completion March 2009. The results presented below are preliminary results from the second year of the project only; final conclusions about the terminal sire breeds used in the study will only be available at the end of the project.

The objective of this project is to compare the ability of five terminal sire breeds of sheep used in western Canada (Suffolk, Charollais, Canadian Arcott, Texel and Ile de France) to sire lambs that grow quickly and produce lean carcasses with a high yield of wholesale cuts.

In each year of the project, rams of these five breeds were mated to ewes in the Lakeland College commercial ewe flock. Lambs were born, weaned and fed to market weight at the college. From there they were transported to Sunterra Meats in Innisfail for slaughter, grading and processing into wholesale cuts.

Methods

As a result of a serious outbreak of sheep footrot in the college ewe flock in the winter and spring of 2006, the entire flock of mixed Suffolk, Dorset, Romanov and Rideau Arcott ewes was culled during the summer of 2006. The flock wasreplaced with a group of mature commercial white-faced range ewes of Rambouillet and Columbia breeding. Beginning on August 29, 2006, these new ewes were single-sire mated to 26 rams (representing the five terminal sire breeds in the study) from Alberta, Saskatchewan and Ontario. Every effort was made to acquire rams that were as unrelated as possible.

Lambs were reared from birth until slaughter on the college farm facility. After a period of approximately 48-72 hours in a claiming pen, ewes and lambs were removed to one of three large pens, where the lambs remained until they were shipped to slaughter. Male lambs were castrated in their first 48-72 hours. All lambs were identified with double RF ID tags (Allflex).

Lambs were weaned when the youngest lamb in the pen was 56 days old. Ewes were removed to another facility. The lambs were left in the pens, with they were already accustomed to.

From one week of age until slaughter, lambs had ad libitum access to a total mixed ration pellet (16% CP) and long-stem grass hay. Lambs were weighed at weaning and every two weeks thereafter.

Lambs were killed on six slaughter dates from June 18, 2007 to September 11, 2007. Live weights were taken two hours before transportation to Sunterra Meats, a journey of approximately four hours. At the processing plant, lambs were penned overnight with access to water and killed the next day, approximately 10 hours after arrival at the plant.

All of the carcasses in this project were graded by the same experienced grader. The GR measurement was taken at the 12th rib and a visual assessment for muscling at the leg, loin and shoulder was made. Carcasses were chilled overnight (about 15 hours) and processed the next morning.

From the cooler, each carcass was weighed on a cold weight scale, then cut and divided into three primal cuts: the shoulder, middle (rack and loin) and leg of the lamb. The leg was then further processed into a tunnel-boned leg, the middle into a rack, short loin and Alta rib, and the shoulder into a shank and a flat pack boneless shoulder. Each of these cuts were trimmed as required for sale, and the weights of each recorded. Excess fat was discarded until the ratio of lean to fat in the trim from each lamb was 70:30, and the weight of the trim weighed for each lamb.

Two hundred and sixty-three lambs born in 2007 were available for analysis. The lambs were sired by terminal sires of the Canadian Arcott (58), Charollais (41), Ile de France (64), Suffolk (53) and Texel (47) breeds. The majority of lambs were raised as twins (153) or singles (69), with 41 lambs reared artificially.

The MIXED procedure of SAS was used in the analysis. The model for all traits contained the fixed effects of sire breed, sex of lamb, type of rearing, and the pen the lamb was reared in. The sire of the lamb (within sire breed) was included as a random effect.

Weaning weight and hot and cold slaughter weights were adjusted to a common age of the lamb by the inclusion of lamb age as a covariate in the models for these traits.

Lambs were sent to slaughter on the first weigh date when their live weight exceeded 108 lb., in order to ensure a hot carcass weight of less than 60 lb., because of severe price penalties for carcasses over that weight. The postweaning growth rate of the lambs was therefore evaluated as the age at which a lamb was sent to slaughter. This trait was adjusted for the lamb’s actual slaughter weight by the inclusion of slaughter weight in the model as a covariate.

Carcass traits were adjusted to a common hot carcass weight by the inclusion of the hot carcass weight as a covariate in the models for these traits

Growth Traits

Least-squares means of weaning weight and age at slaughter are shown in Table 1. The average lamb born in 2007 was weaned at 47 days of age weighing 17.4 kg.

Breed of sire was a significant (P=.01) source of variation in weaning weight adjusted to a common weaning age. Lambs sired by Charollais and Suffolk rams were heavier at weaning than lambs sired by Ile de France or Texel rams. Canadian-Arcott sired lambs were intermediate between the two heavier and lighter breeds. Male and female lambs had weaning weights that were similar to each other. Weaning weight was significantly (P<.0001) affected by type of rearing. Lambs reared as singles, twins or artificially had weaning weights of 19.9 kg, 17.6 kg and 13.6 kg, respectively.

The average lamb born in 2007 was slaughtered at 139 days at a weight of 53.1 kg.

Breed of sire was a highly significant (P<.0001) source of variation for age at a common slaughter weight. Lambs sired by Texel rams reached slaughter weight later than lambs sired by any of the other four breeds. Ile de France-sired lambs reached slaughter weight later than lambs sired by Suffolk or Charollais rams. Male lambs went to slaughter 8.5 days earlier (P<.0001) than female lambs.

Type of rearing was also a significant (P<.01) source of variation; lambs reared as singles were slaughtered 5.6 days earlier than lambs reared as twins, which were slaughtered 13.4 days earlier than artificially-reared lambs.

Table 1. Least-squares means of weaning weights and ages at slaughter of lambs sired by five terminal sire breeds