Ministry of Agriculture, Food and Rural Affairs

The Importance of Optimal Nutrition Throughout Gestation

The most fundamental equation taught at University was P = G + E; Phenotype = Genetics + Environment. Phenotype is what is observed, which could be weaning weight, muscling, feet and legs, etc. What we observe is a combination of genetics and environment where E = feed and management. So even having the best genetics does not guarantee superior performance - the genes do not get a chance to express their superiority unless the cattle are fed and managed properly.

The past 2 winters have continuously had much colder temperatures than what is referred to as "normal". With colder temperatures, cows need additional nutrients for maintenance. Proper nutrition is also critical to the development of the fetus and can have long lasting impact throughout the lifetime of the calf.

With respect to calf development, many only think of nutrition and management from birth onwards. However, research would indicate that nutrition and management are important in a calf's life from conception. This can be referred to as "fetal programming" or "developmental programming". The concept of developmental programming is that a stimulus or insult at a critical period in fetal development has long term effects on the offspring. The insult can be such things as restricted nutrients, over nutrition and hypothermia. Maternal nutrition during pregnancy has been shown to program the growth and development of the fetus, both during pregnancy and later into adult life. Maternal diet also affects the mammary gland and colostrum yield.

It is well known that 75% of fetal growth occurs in the last 3 months of gestation, and consequently some beef farmers pay attention to the feeding of their cows in the last trimester. It is important to have beef cows in good shape at calving so the calf will be born easily with vigour, the cow will have good colostrum and she will breed back quickly. Corah (1975) reported that pregnant cows fed 70% of their calculated energy requirements during the last 90 days produced calves with increased mortality and morbidity. It appears that restricting nutrients during pregnancy can increase the susceptibility of cattle to respiratory disease later in life.

Inadequate nutrition during early gestation may appear to be unimportant because of the limited nutrient requirements of the fetus for growth and development during the first half of gestation. However, there is growing evidence that nutrition in early gestation is critical. This is the time of early fetal development, maximal placental growth, and differentiation. The first heartbeat occurs at about day 21, followed by development of other vital organs; testicles start development at day 45 and ovary development in heifers starts at day 80. Muscle development has a lower priority to organ development and is very vulnerable to nutrient deficiency, as the number of muscle fibres form during the 2nd to 8th month of gestation. Zhu (2006) found a reduction in muscle fibres as a result of nutrient restriction from early to mid-gestation. Du (2010) found that both muscle fibre number and the sites for marbling are influenced during fetal development. Greenwood (2004) showed that steers from cows nutritionally restricted during gestation had reduced carcass weights compared to those from cows fed adequately. Underwood (2010) reported increased tenderness in steers from dams grazed on improved pastures compared to steers whose dams grazed on native pasture during mid gestation.

Other studies have shown the impact of proper nutrition for a fetus on a number of factors important in beef production such as weaning weight, ADG and heifers' pregnancy rate.

Table 1. Effect of maternal nutrition on steer progeny performance*

	IP1	NR2
Weaning Weight	564	534
ADG	3.65	3.28
Carcass Weight	768	726
Marbling Score	455	420

*Underwood et al (2010)
¹IP = dams grazed improved pasture from day 120 to 180 of gestation
²NR = native range

Stalker (2006) found protein supplementation increased weaning weight and the percentage of calves weaned. Certainly, with the current price of feeder calves, the increase in weaning weights would easily justify the cost of supplement.

Martin (2007) also reported a 28% increase in the number of heifers calving within the first 21 days for heifers whose dams received supplement. Wu (2006) stated that maternal diet during pregnancy can influence neonatal mortalities, intestinal and respiratory dysfunction, slow postnatal growth, differing muscle fibre diameters, and reduced meat quality.

Table 2. Effect of maternal protein supplementation on heifer progeny performance*

	SUP1	NS2
205 day weight, lb	467	456
Age at puberty, days	339	334
Pregnant %	93	80

*Martin et al (2007)
¹SUP = dams were supplemented 3 times a week with 1 lb/day of 42% CP cube while grazing dormant Sandhills range during the last third of gestation.
²NS = dams did not receive protein supplement

Conclusion

Proper management of cow nutrition during gestation can improve progeny performance and health. Time should be spent with your nutritionist to ensure your cows are receiving optimal nutrition throughout the year.

References

Corah 1975 Influence of prepartum nutrition on the reproductive performance of beef females and the performance of their progen. J Anim Sci 41:819

Du 2010 Fetal programming of skeletal muscle development in ruminant animals. J Anim Sci 88 (E Suppl) E51

Greenwood 2004 Nutrition in utero and preweaning has long term consequences for growth and size of Piedmontese and Waygu sired steers. J Anim Sci 78:50

Martin 2007 Effects of dam nutrition on growth and reproductive performance of heifer calves J Anim Sci 85:841

Underwood 2010 Nutrition during mid to laate gestation affects growth, adipose tissue deposition and tenderness in cross-bred beef steers Meat Sci 86:588

Stalker et al 2006 Effects of pre and postpartum nutrition on reproduction in spring calving cows and calf performance J Anim Sci 84:2582

Wu et al 2006 Intrauterine growth retardation: implications for the animal sciences. J Anim Sci 84: 2316

Zhu 2006 Maternal nutrient restriction affects properties of skeletal muscle in offspring. J Physiol 575:241