Trace minerals important for broiler breeders

Trace minerals important for broiler breeders

MORE than 130 specialists recently attended a broiler breeder seminar organized by Zinpro Corp. in Madrid, Spain.

This international program included speakers with backgrounds ranging from breeder fertility, hatchability and welfare to early embryo nutrition, as well as feeding and management recommendations to optimize broiler breeder performance.

The first speaker was Dr. Jeanna Wilson, professor at the University of Georgia, who noted that while there is much talk about female breeder management, what about males? Roosters play an equally important role in producing broiler chicks, she explained.

Rooster management requires more attention, Wilson said. Roosters must stay fit and interested in hens and be able to complete matings. Therefore, males should be discouraged from depositing breast meat by restricting their feed and providing a special diet.

Even then, fertility may drop. One of the main causes for such a drop in fertility can be found in aging and the natural relationship between bird behavior and physiology. Aging roosters may become less interested and not able to complete matings, while older hens physiologically need to be mated more often in order to sustain the same level of fertility, she said.

To get good fertility in broiler breeders, males should have excellent testicular growth. Their development should be maintained by consistent, daily, restricted feeding after getting to the hen house. If roosters lose weight, fleshing or general condition, the testes will regress in size and accelerate the natural decline. This regression will be accompanied by lower testosterone levels and semen production, as well as decreased mating behavior.

Mating behavior has to be encouraged without taking all energy from the bird. Bodyweight and fleshing have to be maintained while preventing excessive breast fleshing. As the flock ages, the number of roosters should be increased, and the aging flock should be spiked with young, mature roosters. The best time to spike, according to Wilson, is when the flock is 40-45 weeks of age.

Meanwhile, obvious culls and large, non-productive males should be removed. Removing "pretty boys" — the large, well-feathered males ruling the feeder and interrupting productive mating activity — also increases fertility. The spiked males must be 25-28 weeks old and should weigh 20-25% more than the average bodyweight of the hen flock.

In addition to this advice, Wilson listed a number of factors that broiler breeder managers should consider, including: nest selection, nesting behavior, feeding practice and providing water and feed to males at the floor (not at the slats), frequent egg collection, storing and cooling hatching eggs and removing cracked and dirty eggs.

Feeding minerals. Most broiler breeder managers understand broiler breeder nutrition but are less informed about the nutritional limitations and requirements of the broiler embryo before hatch.

Dr. Zehava Uni, professor in the animal science department of Hebrew University of Jerusalem, Israel, told attendees that the fertile egg has a defined-nutrient composition. However, the rate and mechanism of "eating" (digestion and absorption of these nutrients) by the embryo during incubation is not clear.

The embryo starts to consume yolk nutrients intensively only from mid-incubation on, while intensive consumption of fat from the yolk starts in the last week of incubation. Nonetheless, there is a differential uptake of yolk nutrients during incubation. This uptake is dramatically influenced by the hatchery conditions, Uni said.

Research has shown that during the last days of incubation, the levels of phosphorus, iron, zinc and copper in the yolk are low. These minerals are consumed from the yolk and leave the embryo, as of day 17, without an external source of minerals for at least six days. This may impair embryonic and hatchling development, which may lead to leg and skeletal problems and an immature immune system in rapidly growing strains.

These problems can, according to Uni's investigations, be prevented by supplementing the breeder hen diet with the lacking nutrients or by means of in ovo feeding at day 17 of incubation.

Energy maintenance. One of the major problems in broiler breeder nutrition today is energy, according to Pilgrim's Pride director of nutrition Dr. Michael Hellwig. Energy is a fundamental entity of nature that is transferred between parts of a system during the production of a physical change within the system. Lean meat birds have no fat to rely on when something goes wrong, he said.

"In the U.S., we have houses without heating. When the temperature is low, we rely on the birds' capability to maintain their own body temperature and support them by feeding energy (2% extra)," Hellwig said. "During hot weather, we cool the houses and want to keep feed energy low. Feed formulation, therefore, cannot be separated from feed management, but watch the bird, and take action a couple of days prior to weather changes, because responding later is asking for problems."

According to Hellwig, if the average house temperature is expected to drop below 63 degrees F/17 degrees C — hens are comfortable at 65 degrees F/18 degrees C — then provide 28 kcal of energy per bird per day beginning two to three days before the expected temperature drop and 46 kcal in case the temperature drops below 57 degrees F/14 degrees C.

Hellwig strongly advised breeder managers to maintain the birds' feather condition so they can better control their body temperature and protect their skin from damage during mating. It is his opinion that breeder managers should look at birds based on how they respond to the feed they are offered and try to get ahead of possible deficiencies or problems.

 

Phytase protocol

With the ever-widening variety among commercial phytases making direct comparisons almost impossible and making the end user's choice both difficult and confusing, AB Vista research director Dr. Mike Bedford is calling for a standardized protocol for on-farm phytase comparisons to help clarify buying decisions.

"The increasing differences now being seen between phytase enzyme characteristics, modes of action and activity levels make achieving a true comparison harder than ever," Bedford said. "As a result, highly valuable commercial decisions are being based almost entirely on data generated by on-farm trials that typically fail to produce valid, repeatable results.

"Simply comparing recommended doses against one another is no longer good enough. What's needed is a standardized trial protocol that will accurately and reliably evaluate different phytases on an equivalent basis," he added.

Current shortfalls include a failure to accurately assess the level of phosphorus deficiency in test diets, an insufficient phosphorus deficiency to allow full expression of each phytase on test and single dose rate trials that overlook differing phytase concentrations.

"The challenge is that these are commercial farms, not carefully controlled research facilities, so the protocol also needs to be robust and practical," Bedford noted.

"The starting point has to be to test diets (that are) sufficiently deficient in available phosphorus (avP) to ensure a marked reduction in feed intake and a clear impact from the test phytases, with that deficiency accurately determined by adding increments of 0.05% avP (in mineral form) until normal performance is restored," Bedford said. "Testing each phytase at rates calculated to release 0.05%, 0.10% and 0.15% avP, rather than at specific dose rates — while ensuring the top phytase dose rates do not restore performance to normal — will then establish directly comparable dose-response curves.

"Backed up by growth data and key bone measurements, such as bone ash weight, and related to recommended dose rates and cost per metric ton of feed treated, the result is a data set that can add real value when determining which phytase will deliver the best commercial return," he concluded.

Volume:86 Issue:22

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