Nutrition: Should we go full boar on vitamins?

Thursday, October 1, 2009

Recent Canadian research indicates that, while vitamin supplements increase the amount of vitamins available for the animal, they had no significant effects on sperm production or semen quality 

by JANICE MURPHY

The major goal of commercial AI units is to produce large quantities of high quality semen as efficiently as possible. A long list of factors influence the quantity and quality of semen a boar produces, including breed, age, frequency of collection, season and nutrition. Researchers and breeders alike anticipate that a better understanding of the effects of these factors can eventually improve the efficiency of AI units.

In many species, feeding diets with supplemental vitamins leads to increased semen quality, quantity, or both. In boars, research has shown that a diet supplemented with selenium and vitamin E improves sperm quality. Researchers have also observed that adding extra vitamin E increased the concentration of spermatozoa in boar semen, and the addition of water-soluble and fat-soluble vitamins increased semen production during periods of intensive collection.

Considering all factors, it is generally accepted that collecting semen two to three times per week offers the best scenario for boars. The effect of collection frequency on semen quantity and quality, however, differs widely across studies. In general, greater collection frequencies are considered to be detrimental to semen quality.

Researchers at the Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada and Laval University recently assessed the relevance of increasing the daily allowance of vitamins on vitamin status and semen characteristics of boars under both controlled and commercial conditions. Two separate experiments evaluated the efficiency of a vitamin supplement to help boars cope with an intensive semen collection schedule.

In the first experiment, 39 boars were allocated to two dietary treatments – a control diet with a vitamin premix that provided concentrations similar to the industry average reported in a 1993 survey carried out by BASF, which exceeded National Research Council recommendations; and the control diet supplemented with extra fat-soluble and water-soluble vitamins (Tables 1 and 2).

The boars received three kilograms of feed daily, top-dressed with the vitamin premix at a rate of 50 grams. They averaged 136 kilograms bodyweight at the beginning and ended the experiment at 270 kilograms. Within each treatment, boars were put through two regimens of semen collection frequency over a 12-week period – three times per two weeks (3/2) and three times per week (3/1).

All boars were then intensively collected (daily) for two weeks, followed by a four-week resting period, during which time the boars were collected two times per week. The collection frequencies were then reversed, and the same procedure was followed until the end of the intensive collection period.

A second experiment was conducted under typical conditions at a commercial AI stud. In this experiment, 213 boars were distributed randomly, according to their age and sperm production (mature boars), to one of two dietary treatments – a basal diet with a vitamin premix used by the facility; and a basal diet supplemented with the control premix and vitamins used in experiment 1 (Tables 1 and 2). This experiment assessed 117 pre-pubertal boars (eight months old) and 96 mature ones (15 to 20 months old). All boars were collected two times per week over a six-month period.

Typical measurements of ejaculate and sperm quality were assessed – sperm concentration, volume and total number of sperm per ejaculate, subjective motility, morphology – and blood samples were collected throughout both experiments to assess metabolic vitamin status.

In the first experiment, vitamin concentrations in blood and seminal plasma increased in the supplemented boars but were not affected by collection frequency. Supplementing with vitamins did not affect sperm production or quality, although semen volume increased during the 12-week periods for treated boars. The 3/1 boars produced fewer doses per ejaculate but their cumulative sperm production for the 12-week periods increased by 19 per cent compared to 3/2 boars.

It is generally recognized that boars subjected to a high semen collection frequency have poor semen quality. In this experiment, there were no significant differences in motility or morphology of sperm between the 3/1 and 3/2 boars during the 12-week periods.

Motility did decrease during the intensive semen collection periods, when boars were collected daily for 14 days, but morphology was not affected. The researchers questioned whether a chronic increase in collection frequency (3/1 vs. 3/2) was stressful enough to affect semen quality, compared to an acute increase such as daily for 14 days.

During the intensive collection periods, sperm production decreased during the first week but then stabilized. However, sperm production, semen concentration, and volume all increased over the course of the rest period. In control boars, sperm concentration was greater for boars collected 3/2 than 3/1, whereas it was the opposite for treated boars.

All vitamins measured in seminal plasma and sperm decreased during intensive semen collection. It was anticipated that more vitamins would transfer over to the sperm as the frequency of ejaculation increased. This was not the case and it appeared that the difference between 3/1 and 3/2 boars was not enough to affect the overall vitamin requirement of the animal, as no significant effects on the concentration of vitamins in the blood were evident.

It would seem reasonable to assume that the daily loss of vitamins was two times greater for boars collected 3/1 than for boars collected 3/2. However, the results showed that the vitamin levels in blood plasma were unaffected by collection frequencies. The simple explanation for this is that the quantities of vitamins in seminal plasma are negligible compared to that in blood plasma and, as a result, are unlikely to affect homeostasis and the daily requirement for these vitamins.

Under the commercial conditions of experiment 2, the results revealed an age effect but no dietary treatment effect for total sperm production, sperm concentration, volume and quality of motility score. The bottom line was that the vitamin supplement did not increase sperm production of boars.

Based on the results of the two experiments, the researchers concluded that dietary supplements of fat-soluble and water-soluble vitamins are effective in increasing the amount of vitamins available for the animal. In spite of this increased availability of circulating vitamins, there were no significant effects on sperm production or semen quality. Collection frequencies had no effect on vitamin status.

These results showed that the addition of dietary vitamins was not effective in helping boars cope with a hectic collection schedule. So, as far as vitamins go, these researchers are headed back to the drawing board.

Source: I. Audet, N. Bérubé, J. L. Bailey, J.-P. Laforest and J. J. Matte. 2009. Effects of dietary vitamin supplementation and semen collection frequency on reproductive performance and semen quality in boars. J Anim Sci 2009.87:1960-1970.

Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.