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Feeding the boar for optimal semen production

by 5m Editor
28 August 2006, at 12:00am

By JSR Genetics - While genetics play a role in the fertility of a breeding boar, nutrition is arguably the key factor for maintaining and/or promoting fertility. This article will consider a particular family of nutrients - lipids, also known as fat. The main roles of lipids are energy provision, as structural components of cells and as precursors of hormone-like molecules.

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Interest in the effect of specific lipids on male fertility has grown over the last 10 years. Many scientific reports have emphasized the importance of the omega-3 family of lipids, and have warned of their potential lack in the feeds of breeding animals. Key omega-3s are essential fatty acids, which cannot be synthesised by the animal, and therefore must be provided via the feed. Presently, most commercial feeds are grossly unbalanced, with about 36% of omega-6 to only 1% of omega-3 fats.

Omega-3s are a main structural component of the spermatozoa across many species (Table 1). Boar semen has a characteristically low content of omega-3, when compared to that of most other mammalian species. When boar feed is supplemented with a specific fish oil, a natural source of omega-3s, total omega-3 levels in spermatozoa rise from about 32% to a maximum of 44%.

Table 1: Proportion of main fatty acid (fat) families in spermatozoa of various species.
% of total fat Boar Ram Bull
Omega-6 33 6 14
Omega-3 32 62 56

Professor Strzezek1 has recently published an article on the effect of feeding fish oil to boars. His study considered numerous quality parameters of the freshly ejaculated semen and how this might affect storability of the spermatozoa. Amongst his findings, he confirmed an increase in the total sperm output in the ejaculates of the supplemented animals, an increased proportion of membrane intact spermatozoa and greater resistance of the acrosome (the envelope containing all the molecules that ensure that fertilising processes can occur). An improvement of the seminal plasma was also described, with an increased content of antioxidants, ensuring the protection of the aforementioned lipids as well as spermatozoa integrity during storage.

Darby Genetics of South Korea recently carried out a large on-farm trial involving 1160 sows and reported beneficial effects of inseminating semen from boars fed a specific fish oil supplement coupled with antioxidants. Farrowing rates increased by 6.4 % with an extra 0.7 piglets born alive; this corresponds to an extra 119 piglets per 100 services. Another advantage shown by this study was the increased total sperm number produced by the boars receiving the feed supplement, providing more AI bottles per collection. Similar results were also observed in large trials in countries around the world, therefore suggesting a global inadequacy in the feeding regime of breeding boars (Table 2).

Table 2: Trial results obtained in various countries. Sows were inseminated with an identical dose with semen from boars receiving a feed supplement, against those with semen from animals on a classic commercial feed.
Country Increase of FR Increase of BR Increase of BA / 100 services Number of sows
UK + 6 % + 0.3 + 81 4629
Spain + 6.2 % + 0.3 + 79 550
Germany + 2.3 % + 0.4 + 58 160
Poland + 4.7 % + 0.4 + 77 120
FR: Farrowing rate, BA: Born alive

(1) Strzezek and co-authors (2004). Effect of dietary supplementation with polyunsaturated fatty acids and antioxidants on biochemical characteristics of boar semen. Reproductive Biology; Volume 4, pages: 271-287.

Appeared in International Pig Topics

May 2006