Thursday, October 10, 2019

Lamb Served in Dining Halls

For the second year in a row, the lamb from our comparison study of ram, wether, and short-scrotum lambs was served in the dining halls at the University of Maryland College Park. On October 2nd, a Harvest Festival was held to promote local food, including the lamb. Sliced leg of lamb and lamb burgers were served to students, faculty, and visitors.

Results: Growth and Carcass Data

This was the second year of a 2-year study comparing the growth and carcass characteristics of (intact) ram, wether, and short-scrotum lambs from a commercial sheep dairy in Maryland.

After weaning, lambs were grazed and fed for 107-d at the University of Maryland's Western Maryland Research & Education Center in Keedysville. At the end of the study, they were harvested to collect carcass data.  Data was collected on 21 rams, 25 wethers, and 18 short-scrotum lambs. 

Ram lambs had the heaviest final weights and highest ADG. The wether lambs had the lightest final weights and lowest ADG.  Short scrotum lambs were not statistically different from ram lambs. Ram lambs had the heaviest hot and cold carcass weights. Wethers had the lightest. Short scrotum lambs were intermediate.

A 4% pencil shrink was applied to the lambs to calculate dressing percentage. Dressing percentage was determined by dividing hot carcass weight (HCW) by "shrunk" live weight. Wether lambs had the highest dressing percentage. Ram and short scrotum lambs were not statistically different.

Rib eyes (REA) from the ram carcasses were largest. Wethers had the smallest rib eyes. Short scrotum lambs were intermediate. However, when adjusted to a common weight (of 100 lbs), there were no statistical differences in rib eye area among treatment groups.

Wethers produced the fattest carcasses, as evidenced by greater back fat (BF) and yield grade (YG). Short scrotum lambs had more back fat and higher yield grades than ram lambs, but the differences were not statistically significant. At the same time, none of the lambs carried excess back fat or internal fat.

Sex did not affect body wall thickness (BWT), percent kidney and heart fat (KH), or leg conformation score (LC). Ram carcasses yielded a higher percentage of boneless closely trimmed retail cuts (BCTRC) than wether lambs. Short scrotum lambs were intermediate. BCTRC is calculated using the following formula: 49.936 - (0.0848 x HCW) - (4.376 x BF) - (3.530 x BW) + (2.456 x REA).

Due to inadequate backfat, seven ram carcasses failed to quality for the USDA Choice grade, as there is a minimum requirement of 0.08 inches. Two short scrotum carcasses failed to grade. All of the wether carcasses graded Choice or above.  Despite the leanness of the carcasses, there was evidence of quality in all the carcasses: maturity, flank streaking, and conformation.

For the second year in a row, ram and short scrotum lambs demonstrated superior growth and carcass composition compared to wether lambs.

Wednesday, August 21, 2019

Testicle Dissection

At the time of harvest, five pairs of testicles were obtained from intact rams and five were obtained from short-scrotum rams. The testicles were sent to Virginia State University for dissection by Dr. Stephan Wildeus and Dr. Dahlia O'Brien.

The short-scrotum lambs had significantly smaller testes than the ram lambs: 108.9 vs. 291.2 g. The epididmymal weight was also smaller (17.7 vs. 53.8 g) in the short-scrotum lambs, as were the ratios of parenchyma: tunica and testis: epididymis).

Organ weights
 Sex No. Total testes, g Epididymal wt, g Parenchyma:
tunica ratio
Testis: epididymis
 Ram 5 291.2 53.8 9.79 5.50
 Short scrotum 5 108.9 17.7 7.76 6.32
Probability 5 <0.0012 <0.0027 0.1204 0.2594

The testicles from the intact ram lambs were smaller than last year by about 100 g. This may have accounted for the lower ejaculate quality of the intact rams. One of the short-scrotum rams had one testicle that was significantly larger than the other. Its testicle was also considerably larger than the other short scrotum rams (by over 50 g). 

Thursday, August 15, 2019

Background Information on 2019 Lambs

Sixty-four lambs were used to compare the growth, carcass, and reproductive characteristics of intact ram (n=21), short-scrotum (SC) ram (n=18), and wether lambs (n=25) . The lambs were single-sourced from the state's only licensed sheep dairy. The breed was East Friesian x Lacaune.

The oldest lamb was born on January 26. The youngest lamb was born on March 22. Upon arrival, the lambs ranged in age from 31 to 86 days and averaged 65.1 ± 17.4 days of age. The median age was 70 days. The median date of birth was February 11. Less than 2 days separated the average age of the rams, SC, and wethers.

As it was a dairy farm, the lambs were weaned at an early age, ~30 days. After weaning, they remained in the barn/dry lot until they were transported to the University of Maryland's Western Maryland Research & Education Center on April 22.

Birth weights ranged from 5.5 to 16.0 lbs. and averaged 11.5 ± 2.2 lbs. Birth weights were similar for ram, SC, and wether lambs. Birth type ranged from 1 to 3 and averaged 1.95 ± 0.55. The  median birth type was 2 (twin). Birth type was similar across treatment groups. Most of the lambs (87.5%)  had the same sire.

The lambs were weighed upon arrival. Starting weights ranged from 28.0 to 71.0 pounds and averaged 44.5 ± 10.6 lbs. The ram lambs were a little heavier than the wether lambs: 45.1
± 10.5 vs. 43.5 ± 10.9 lbs.  The SC were intermediate: 45.1 ± 10.9 lbs. 

Castrations were performed by 10 days of age. Every third lamb was left a ram, castrated, or made a short-scrotum.

Sex No. Start age, d Birth type Birth wt, lbs. Start wt, lbs. Same sire, #
Ram 21 66.4 2.00 11.6 45.1 19
SC 18 63.7 1.79 11.6 44.4 16
Wether 25 64.2 2.00 11.2 43.5 21
All 64 65.1 1.95 11.5 44.5 56

Compared to last year, this year's lambs were younger (11 days) and lighter (11 pounds).

All of these factors will be put into the statistical model to determine if they affected the outcome of the experiment. Last year, they did not.

4-H Pelt Project

The pelts (hides, skins) from the lambs in the comparison study of ram, wether, and short-scrotum lambs are being used in a 4-H Entrepreneurship Program, under the leadership of Ashley Travis, 4-H Youth Educator in Washington County, and Dr. Jesse Ketterman, Family & Consumer Sciences Educator for the Western Maryland Cluster.

The pelts were retrieved immediately after slaughter at Old Line Custom Meat Company (in Baltimore). They were salted generously and laid on top of each other for transport. Upon arrival to the Western Maryland Research & Education Center, the pelts were lightly salted again, re-stacked, and held overnight in a cooler.

The following day, the pelts were taken to the local fairgrounds where they were stretched out on wooden pelts and re-salted (even more generously). Pelts were trimmed to removed flesh and excess body parts.The pelts will be dried for approximately 2 weeks before being transported to Bucks County Fur Products, Inc. (in Quakertown, PA) for professionally tanning. Bucks County Fur specializes in the tanning of sheep, goat, and deer hides.

Youth will sell the finished pelts, hopefully for a profit, after expenses have deducted. As part of the entrepreneurship program, youth learned how to develop their own business plans. They will give oral presentations to share their business plans. The youth are mostly 12-13 years of age.

Pelts immediately after slaughter

Initial salting of pelts in the back of a pickup truck

Stacked and ready to go

Stretched and salted for drying

Ordinarily, pelts are a waste product of lamb production, unless producers decide to tan their own hides. For innovative producers, pelts are a way to add value to a lamb and increase the profitability of sheep rearing. Professionally tanned sheep hides can fetch good prices, especially if they are from large sheep (or lambs) with long, colorful fleeces.

In the past, pelts (especially those from unshorn fine wool lambs) had a significant value and were an important source of income for lamb processors. Currently, lamb pelts are selling for a low price and many processors simply discard them. The high value of the US dollar (against international currencies) is one reason given for their low commercial value.

Weekly Lamb Pelt Price Report

Wednesday, August 14, 2019

Fertility Testing

On August 6, the lambs were evaluated for fertility traits: libido (mating desire) and semen quantity and quality. The testing was done by Dr. Stephan Wildeus and Dr. Dahlia O'Brien from Virginia State University. Youth participating in the 4-H Research Academy assisted with data collection.

Each lamb was put in a pen with two mature ewes for 5 minutes. The ewes had previously been treated with CIDRs so that they would be in estrus (heat) at the time of testing. Two pens (8 ft. x 8 ft). were set up side-by-side. Reproductive behaviors were observed and recorded. The time to first service was measured in seconds.

Evaluating libido in male lambs

Intact males (rams) and short-scrotum rams exhibited similar mating behavior (libido), with no statistical differences. The only observed mating behavior in the wethers was sniffing, but it was less than ram and SC lambs.

  Sex No. Sniff Butt Kick Flehmen Mount Service Time
  Ram 21 3.54a 0.10a 1.59a 0.47a 1.50a 1.30a 217
  Short scrotum 18 3.46a 0.05a 0.73ab 0.42a 1.24a 0.45ab 244
  Wether 25 1.33b 0a 0b 0b 0b 0b na
0.0001 n.s. 0.0039 0.0039 0.0410 0.0060 n.s.
Data with different subscripts are statistically different. n.s. = non-significant

Observed behavior was similar between pens (ewes) and indicated that teaser ewes in both pens displayed estrus adequately, with the only statistical difference being for kicks.

  Pen No. Sniff Butt Kick Flehmen Mount Service Time
  A 32 2.98 0.06 1.21 0.36 1.15 0.64 214
  B 32 2.58 0.04 0.33 0.23 0.67 0.53 247
Probability 0.389 n.s. 0.0252 n.s. n.s. n.s. n.s.
n.s. = non-significant

Using an estrus ewe, semen was collected from lambs with an artificial vagina (AV). Samples were obtained from seven ram lambs and seven short-scrotum lambs. The semen was evaluated on-site.

Ejaculates from SC (L) and ram lamb (R).
Intact and short-scrotum rams produced similar ejaculate volumes; there was no statistical difference. The semen from rams had 45.0% mobility, whereas the semen from the short scrotum rams had only 5.7% mobility. The semen from the rams had a greater concentration of sperm cells: 1.52 billion per ml vs. only 0.049 billion per ml for the short-scrotum rams.

  Sex No. Volume, ml Mobility, % Concentration, b/ml
  Ram 6 0.56a 45.0a 1.52a
  Short scrotum 6 0.49a 5.7b 0.049b
0.5566 0.0089 0.0152
Data with different subscripts are statistically different. n.s. = non-significant

Unlike last year, some sperm cells were observed in the ejaculates of short-scrotum rams. Some sperm mobility was also detected. A possible reason is that the short-scrotum procedure was done when the lambs were older (unlike last year), as some of the short-scrotum rams had noticeable scrotums.

Sperm mobility and concentration was less for the intact rams, as compared to last year. This may be because they weren't as far along in pubertal development. Age will be added to the statistical model.

The preliminary conclusion is that the short-scrotum rams would not work for breeding. However, there is no guarantee that they could not impregnate females.This differs from last year, when SC were deemed infertile, based on semen evaluation.

Tuesday, August 13, 2019

Raw Carcass Data

Lambs were harvested on August 8 at Old Line Custom Meat Company in Baltimore. Carcasses were evaluated on August 12. Carcass data was obtained from 64 lambs: 21 rams, 18 short-scrotum (SC) rams, and 25 wethers. The carcasses were split between the 12th and 13th ribs to expose the longissimus dorsi.

Ram 21 122.7 63.0 51.2 0.083 0.529 3.01 2.47 2.24 13.0 1.23 49.75
Short-scrotum 18 119.7 60.7 50.6 0.100 0.514 2.83 2.38 2.14 12.4 1.40 49.48
Wether 25 112.1 58.6 52.3 0.142 0.558 2.71 2.45 2.28 12.6 1.82 49.04
ALL 64 117.7 60.6 51.5 0.111 0.536 2.84 2.44 2.23 12.7 1.51 49.40
These are raw data. It is not known if observed differences are statistically significant.

Ribbed carcasses

Shrunk live weight (SLW)
SLW was calculated by multiplying the (final) August 7 weight by 0.96. SLW ranged from 88.1 to 152.4 lbs. and averaged 117.7 ± 14.3 lbs. Rams were heaviest: 122.7 ± 15.8 lbs. Wethers were lightest: 112.1 ± 12.7 lbs. SC were intermediate: 119.7 ± 12.3 lbs.

Hot carcass weight (HCW)
HCW was determined immediately after slaughter. For the 64 lambs, HCW ranged from 42.0 to 79.0 lbs. and averaged 60.6 ± 8.0 lbs. Rams were heaviest: 63.0 ± 8.9 lbs. Wethers were lightest: 58.6 ± 7.1 lbs. SC were intermediate: 60.7 ± 7.7 lbs.

Carcasses were weighed after chilling. Cold carcass weight (CCW) ranged from 40.0 to 76.0 lbs. and averaged 58.3 ± 7.9 lbs. Cold shrinkage ranged from 1.4 to 7.4 percent and averaged 3.8 ± 1.4%. CCW was not used in any calculations.

Dressing percentage (DP)
DP is the percent of live animal that ends up in the carcass. It was determined by dividing HCW by SLW. For the 64 lambs, DP ranged from 47.7 to 55.2 percent and averaged 51.5 ± 1.7%.  Wethers had the highest dressing percentage: 52.3 ± 1.6%. SC were lowest: 50.6 ± 1.8% Rams were intermediate: 51.2 ± 1.6%.

Back fat (BF)
A metal ruler was used to measure BF. For the 64 lambs, BF ranged from 0.05 to 0.25 inches and averaged 0.111 ± 0.046 inches. The median BF was 0.100 inches. Wether lambs were the fattest: 0.142 ± 0.047 inches. Rams were the leanest: 0.083 ± 0.029 inches. SC lambs were intermediate: 0.100 ± 0.034 inches.

Body wall thickness (BWT)

A metal ruler was used to measure BWT.  BWT is a measurement across the lean, bone and fat of the lower rib, five inches from the midline of the carcass. Differences in carcasses are due primarily to fat. For the 64 lambs, BWT ranged from 0.30 to 1.00 inches and averaged 0.536 ± 0.125 inches. BWT was greatest for wether lambs: 0.558 ± 0.137 inches. It was lowest for SC: 0.514 ± 0.125 inches. Rams were intermediate: 0.529 ± 0.103 inches.

A nice one

Rib eye area (REA)

A plastic grid was used to measure the area of the rib eye muscle (REA; 20 dots=1 in²). For the 64 lambs, REA ranged from 2.10 to 4.05 square inches and averaged 2.84 ± 0.38 in².  The median REA was also 2.85 in². Rams had greater REA than wether lambs:  3.01 ± 0.40 in² vs. 2.71 ± 0.37 in². SC were intermediate: 2.83 ± 0.30 in².

Adjusted rib eye area (CWT)
Rib eye measurements were adjusted to a common weight (100 lbs.). For the 64 lambs, CWT ranged from 1.73 to 3.83
in² and averaged 2.44 ± 0.38 in². Rams and wethers had similar CWT: 2.47 ± 0.32 and 2.45 ± 0.48 in², respectively. CWT was lowest for SC: 2.38 ± 0.32 in².

Percent kidney and heart fat (KH)
KH is a measure of the (internal) fat around the organs. 
It was subjectively evaluated and expressed as a percentage of carcass weight. For the 64 lambs, KH ranged from 1.0 to 3.5 percent and averaged 2.23
± 0.79%. SC lambs had the lowest KH: 2.14 ± 0.80 percent. Ram and wether lambs were similar: 2.24 ± 0.82 and 2.28 ± 0.78%, respectively.

Leg conformation (LC)

LC is another measure of carcass muscling. It was subjectively evaluated using numbers that correspond to USDA quality grades. For the 64 lambs, LC ranged from 10 (low Choice) to 15 (high Prime) and averaged 12.7 ± 1.3. Rams had superior LC: 13.0 ± 1.5. Wethers had slightly higher LC than SC lambs: 12.6 ± 1.2 vs. 12.4 ± 1.3.
Chris Anderson measuring back fat and body wall thickness

Yield grade (YG)
YG (1-5) reflects the quantity of "retail" cuts that can be expected from a lamb carcass. YG is calculated solely from BF using the
following formula:  (back fat x 10) + 0.4.  Rams had the lowest YG: 1.23 ± 0.29. Wethers had the highest: 1.82 ± 0.47. SC were intermediate: 1.40 ± 0.34. The marketplace tends to prefer lambs that are YG 2-3. YG 1 carcasses may be discounted.

Percent boneless, closely trimmed retail cuts (BCTRC)
BCTRC is very meaningful because it represents the predicted portion of the carcass that is salable product. It is calculated using the following formula:  49.936 - (0.0848 x HCW) - (4.376 x BF) - (3.530 x BW) + (2.456 x REA)*. BCTRC ranged from 45.51 to 52.90 and averaged 49.40 ± 1.33%. It was highest for ram lambs (49.75 ± 0.98%) and lowest for wethers 49.04 ± 1.57%). SC were intermediate: 49.48 ± 1.25%

Quality grade
Quality grades indicate the expected eating satisfaction of lamb. There are four USDA quality grades: Prime, Choice, Good, and Utility. Quality grades are determined by three factors: maturity, flank streakings, and conformation. Flank streakings are the fat deposits on the flank muscles. In addition, carcasses must have at least 0.08 inches of BF to qualify for the Choice grade. Eight ram carcasses (38.1%) failed to meet the minimum requirement. Three SC carcasses (16.7%) lacked sufficient BF for the Choice grade. All of the wether carcasses were graded Choice or Prime.

*Source: Scott Greiner, Lamb Carcass Evaluation, Virginia Tech

Lamb Served in Dining Halls

For the second year in a row, the lamb from our comparison study of ram, wether, and short-scrotum lambs was served in the dining halls at t...