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Immunocastration and DDGS Effects on Pig Carcases

21 February 2013

Kansas Swine Day 2012

Although immunocastrating pigs led to lower carcase yields, the pigs had a better feed conversion, according to research by M. D. Asmus, M. D. Tokach, S. S. Dritz, J. L. Nelssen, R. D Goodband, and J. M. DeRouchey in a paper published for the K-State Swine Day.

A total of 1,360 pigs (PIC 337 × 1050, initially 53.0 lb) were used in a 125-d study to determine the effects of dried distillers grains with solubles (DDGS) withdrawal post-immunocastration (IC; Improvest, Pfizer Animal Health, Kalamazoo, MI) on growth performance and carcase fat quality of growing-finishing pigs. Pens of pigs were randomly allotted by initial weight and gender (barrows or IC) to 1 of 3 dietary treatments with 8 replications per treatment for a total of 48 pens with 27 to 29 pigs per pen. Treatments were arranged in a 2 × 3 factorial with the main effects of gender (barrow or IC) and diet (0% DDGS throughout, 30% DDGS throughout, or 30% DDGS through d 75 then withdrawn to 0% to d 125). Boars were injected with Improvest on d 39 and 74 of the study. Dietary treatments were corn-soybean meal– based diets and fed in 5 phases. No gender × diet interactions (P > 0.18) were observed except for a tendency for F/G (P < 0.07) during the second phase (d 25 to 53), when 1 of the 2 barrow groups fed 30% DDGS had an increase in ADFI resulting in poorer F/G. For the entire period before the second Improvest injection (d 0 to 74), barrows tended (P < 0.08) to have increased ADG (1.98 vs. 1.95 lb) and increased (P < 0.001) ADFI (4.32 vs. 3.91 lb) but were less efficient (P < 0.001) than boars (2.19 vs. 2.01). During the same time period, pigs fed 30% DDGS had reduced (P < 0.002) ADG and poorer feed efficiency.

For the period after the second Improvest injection until the first marketing event (d 74 to 107; 33 d after the second dose), IC pigs had increased (P < 0.01) ADG (2.29 vs. 2.10 lb), similar ADFI (6.92 vs. 6.81 lb), and were more efficient (P < 0.001; 3.02 vs. 3.25) than barrows. From d 0 to 107, IC pigs had improved (P < 0.03) ADG (2.05 vs. 2.01 lb), F/G (2.34 vs. 2.52), and lower ADFI (4.80 vs. 5.06 lb) than barrows. The inclusion of 30% DDGS regardless of withdrawal or gender did not influence ADG or ADFI but did worsen (P < 0.001) feed efficiency.

For the period after the second Improvest injection to the end of the trial (d 74 to 125; 51 d after the second dose), IC pigs had increased (P < 0.01) ADG (2.29 vs. 2.10), ADFI (7.09 vs. 6.82), and were more efficient (3.09 vs. 3.25) than barrows. Overall (d 0 to 125), IC pigs had improved (P < 0.003) ADG (2.07 vs 2.02) and F/G (2.44 vs. 2.58) and lower ADFI (5.05 vs. 5.22) than barrows. The inclusion of 30% DDGS regardless of withdrawal or gender again did not influence ADG or ADFI but worsened (P < 0.001) feed efficiency.

carcase yield was lower (P < 0.001) for IC pigs than barrows regardless of dietary DDGS or withdrawal strategy. Pigs fed 30% DDGS throughout had decreased (P < 0.001) carcase yield; however, withdrawing DDGS from the diet on d 74 was effective at fully recovering the yield loss, returning values similar to that of pigs fed the control diet throughout. carcase fat iodine values (IV) were consistently higher (P < 0.001) regardless of fat depot or harvest time when 30% DDGS were included in the diet. The withdrawal strategy was successful at lowering (P < 0.003) IV when compared to feeding DDGS throughout; however, it was not successful (P < 0.001) at fully lowering IV to values similar to pigs fed the control diet throughout. Iodine value of the jowl (P < 0.07), loin (P < 0.02), and clear plate (P < 0.003) tended to be or were greater for IC pigs than barrows on d 107, but differences in IV between IC and barrows disappeared by d 125. Similar to previous studies, withdrawing DDGS from the diet before harvest can improve carcase fat quality (IV) and recover yield loss, but F/G was still poorer regardless of withdrawal strategy.

Overall, immunocastrates had reduced carcase yields, but they also had reduced ADFI and improved ADG, which led to improved feed efficiency. Although the use of Improvest can increase IV of fat depots when pigs are harvested at a shorter interval after the second injection, extending the feeding duration after the second injection returns IV to values similar to barrows. Another interesting observation is the magnitude of changes in fatty acid profile or IV between the different fat depots in relationship to rations, genders, and days after second injection with the immunocastrated barrows exhibiting larger changes than the contemporary physically castrated barrows.

Further Reading

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December 2012

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