Utilization of Frozen Thawed Semen in Large Black Pigs; Growth and Carcass Characteristics of Large Black Pigs Fed Diets Supplemented With or Without Alfalfa
In recent years conservation of minor livestock breeds has been faced with numerous challenges attributed to decreasing national herd sizes, as well as differences in reproduction and growth. One such minor swine breed, the Large Black pig (LB), is increasingly attractive to small farmers due to their foraging abilities and carcass characteristics. Therefore, the LB pigs have been used in niche pork production systems which market pasture-raised pork products. The LB breed is critically endangered, maintaining a registered breeding population of less than 400 animals, with increasing prevalence of inbreeding and genetic drift. Therefore, the LB breed could benefit from a genetic importation to increase genetic diversity in a national herd with rapidly decreasing animal numbers. A genetic importation would require frozen semen to be brought in from another country for use in breeding U.S. pigs. Frozen-thawed semen (FTS) presents challenges for swine due to the reduced motile sperm cells which negatively impacts fertility. Therefore, the present study evaluated the utilization of FTS in a genetic importation for the LB pig.
A genetic importation occurred in 2016 where semen from the United Kingdom was used on various farms in the U.S. but resulted in zero piglets born. Therefore, 16 LB sows were donated to Purdue University for research into improving estrous and ovulation synchronization to facilitate FTS utilization. Four breeding replicates were performed where following 14 days of Matrix feeding, OvuGel® was administered at 144 h following last Matrix feeding (LMF) or 96 h in post-weaned sows and two FTS inseminations occurring at: 30 and 36 h, 17 and 23 h, 24 and 30 h, and 24 and 32 h after OvuGel® for replicates 1-4, respectively. Approximately 2.64±0.3 billion motile sperm cells per insemination were utilized in replicates 1-3 with American LB FTS, with replicate 4 utilizing 0.34±0.03 billion motile sperm cells of imported FTS. Follicle diameter (P=0.260), ovulation within 48 h of OvuGel® (P=0.411), and weight prior to breeding (P=0.681) did not influence conception rate, however expression of estrus was determined to significantly influence conception rate (P=0.043). Seventy-five LB piglets were weaned across the first three breeding replicates, with parity 2 sows observed to have larger litter sizes than parity 1 sows (P=0.066).
Large Black and Duroc-sired (DS) crossbred pigs from replicates 1 and 2 farrowing were fed corn and soybean meal based finishing diets supplemented with (FIB) or without alfalfa and wheat middlings (CON). Following 6 dietary phases through finishing, 25 LB and 25 DS pigs were slaughtered at similar ages for digestive organ dissection and carcass measurements. Loin muscles were evaluated for fresh pork quality and instrumental color and tenderness. LB pigs had a reduced ADG (P<0.0001) and G:F (P<0.0001) compared to DS pigs. Pigs fed FIB resulted in reduced ADG (P=0.020) and reduced G:F (P=0.007). At slaughter LB pigs were 26.4 kg lighter than DS pigs (P<0.0001), and pigs that were fed FIB had lighter live weights (P=0.002) than pigs fed CON. LB pigs had 28.5±1.3 cm2 smaller longissimus muscle area (P<0.0001), yielding 2.0 cm more 10th rib back fat than DS pigs (P<0.0001). CON pigs had heavier HCW (P<0.0001) than FIB pigs, however FIB pigs had greater percent lean (P=0.015). LB pigs had significantly reduced percent lean than DS pigs (P<0.0001). LB pigs had loins with reduced drip loss (P=0.009) and cooked shear force values (P<0.0001). Overall, the growth and carcass composition of the pigs was most affected by genotype, and to a lesser extent than the type of diet fed.
In conclusion, the genetic importation of LB semen was successful as ½ blood piglets were created for dispersal into the U.S. LB herd. Improvements in FTS utilization in this heritage breed contributed to the successful creation of live-born pigs. Additionally, growth and carcass information was obtained for LB breeders to use in understanding and marketing of this heritage breed of pigs.