Flush Feeding

Flush feeding the ram 

Released 29 May 2014

In the Angora ram as with most species several factors, including age, body weight, testis size, season and nutrition determine the quality and quantity of semen. Spermatogenesis (sperm formation) takes place over six weeks, so feeding during this period will influence sperm production. Rams seldom have fertility issues but younger rams are more susceptible to nutritional stress resulting in:

• Slower testicle development
• Delayed puberty (decreased endocrine activity)
• Decreased libido
• Decreased testosterone
• Decreased sperm quality

Sperm production can be improved by increasing energy and protein levels in the diet during times of nutritional stress, but the effects of increasing protein levels beyond maintenance requirements are unclear, with equivocal results in all breeding parameters. So while there is a clear benefit in flush feeding rams prior to mating when veld conditions are poor, there appears to be little benefit in doing so when there is already an adequate plain of nutrition.

Minerals and vitamins also play a role in ram fertility. Zinc is essential in the production of many of the sex hormones, including testosterone and gonadotrophin releasing hormone. Supplementation with zinc increases daily sperm production and reduces the proportion of abnormal spermatozoa. Selenium and Vitamin E play a biological role as cell antioxidant by preventing damage by oxygen and various peroxides formed from fatty acids. Selenium is also required for the accurate formation of the midpiece and flagella of the sperm. Vitamin A deficiency can cause degeneration of the seminiferous tubules and testicular atrophy. Vitamin A and iodine deficiency impair the ram’s libido.

Despite the physiological roles played by these vitamins and minerals, a study (Baca, Snyman and Kilian) showed there to be no consistent improvement in the rams’ breeding parameters following frequent supplementation of these vitamins and minerals. The high energy and protein diet provided was sufficient to ensure semen of good quality.

Flush feeding the ewes

The natural time for mating Angora goats (autumn) coincides with the time of the year when natural grazing is good and will normally satisfy the feeding needs of the non-pregnant ewe. For breeding ewes, however, there is sufficient proof that the practice of stimulatory (flush) feeding can raise conception figures and the eventual kidding percentage. The relative effect of flush feeding will increase with a decline in the state of the natural grazing. In the case of young two-tooth ewes mated for the first time, the effect of flush feeding will be most dramatic and in these animals  at least, should always be applied.

Flush feeding of ewes results in improved body mass and:

• Increased ovulation rate of individual ewes (see figure below)
• Increased number of ewes actually ovulating (see figure below)

Effect of ewe weight on ovulation rates   (Shelton and Groff)

• Improved ovum implantation
• Synchronises ewes- decrease kidding and mating period (uniform kid crop)
• Increased kidding percentage

It is well accepted that ewes under 27-28 kg have poorer kidding percentages (see figure below)

When flush feeding is implemented, it must be started two weeks before the mating season commences, and maintained for at least three weeks during the mating season. After this, the level of supplementation should be reduced gradually until it is discontinued. It is also important to note that flush feeding is more effective when a high level of supplementation is provided for a shorter period as opposed to low level supplementation level over a longer period.

Dr Mackie Hobson