Since 1950, reproductive efficiency has declined in mature cows but not in virgin heifers. Some have blamed this on the demands of high milk production, especially the need for energy. But, it must also be recognized that high producing cows who achieve good dry matter intake early in lactation and who are fed a diet with sufficient energy content, will achieve high peak milk, persist in milk production, and breed back well.
A summary of 1998-1999 DHI records of 1.2 million Holstein cows from 9,684 herds showed that high milk production is not necessarily linked to poor reproduction. In fact, herds with higher milk production generally have better reproductive efficiency. Higher producing herds are generally better at heat detection and begin breeding cows sooner. High producing herds do have more services per conception.
|
15-17,000# RHA |
19-21,000# RHA |
23-25,000# RHA |
| No. of Herds |
1285 |
2425 |
921 |
| Avg. Herd Size |
101 |
117 |
158 |
| Days Open |
170 |
156 |
151 |
| Days to 1st Service |
100 |
95 |
93 |
| Services Per Conception |
1.8 |
2.1 |
2.2 |
| Heat Detection Efficiency |
26 |
36 |
42 |
| Reproductive Culling |
17 |
17 |
20 | (Adapted from Stevenson, 1999)
Energy
Energy is generally the most-limiting factor in the diet of the early lactation cow. Repeat breeding, poor signs of heat, and cystic ovaries can all be caused by a lack of energy.
Normal activity of the ovary depends on good energy status of the cow. Cornell workers showed that a cow’s first ovulation after calving occurs about 10 days after the day of lowest energy status. They also showed that first ovulation was delayed 2.75 days for every Mcal of energy that the cow was short during the first 20 days after calving. A cow producing 90 pounds (41 kg) of milk requires about 40 Mcal of energy per day. The earlier ovulation begins, the more heat cycles a cow will have before breeding begins. This has been shown to increase the chances for conception.
Energy status impacts the production of hormones needed for good reproductive function. LH is a key factor needed for ovarian follicle development and initiation of ovarian cycling. Florida researchers found that poor energy status reduces the size of follicles. The number of 3-5 mm and 6-9 mm follicles was reduced as energy status improved and the number of 10-15 mm follicles increased. It was also found that the LH pulse increased with better energy status.
It is recommended that cows calve in at a body condition score (BCS) of 3.50-3.75 and then not lose more than 0.5 body condition score point during early lactation. Michigan workers found that the BCS at calving and the BCS at first service were not related to conception. Rather, it was the amount of body condition loss that was most important. Cows that lost one BCS point were 1.5 times less likely to conceive than cows that lost less than 1 point.
Body condition score rather than body weight should be used to assess the energy status of the cow because other tissues, such as the udder and the digestive tract, increase in weight during early lactation while the cow is mobilizing body fat from her back.
Thin cows (<2.75 BCS) at calving won’t have enough reserves to maintain high milk production in early lactation. Fat cows (> 4 BCS) will have poorer intakes and more metabolic problems after calving, causing them to loose more than 0.5 body condition score points during early lactation.
To limit excessive body condition loss, it is essential that cows have few calving problems, freshen with a good appetite, and are offered an appropriately energy-dense ration during early lactation. Research shows that cows with earlier first ovulation and fewer days open also eat more dry matter and make more milk than poorer breeders. A good pre-fresh ration and fresh cow ration can not only improve milk production and reduce vet visits, but can also improve reproductive efficiency.
Polyunsaturated Fatty Acids
Many studies have been conducted to determine the effect of supplementary fat on reproductive performance. In general, fat supplements have improved fertility. Much of this response has been attributed to a reduced period of negative energy balance. However, in some studies, milk production was improved with supplementary fat and cows did not experience lower body weight loss yet reproductive performance was still enhanced.
Fatty acids plus glycerol form fat. Polyunsaturated fatty acids contain more than one double bond. Individual polyunsaturated fatty acids include; linoleic acid, linolenic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Polyunsaturated fatty acids such as these are found in fishmeal and some rumen inert fats. They may help reproduction in more ways than just providing energy to the cow.
Dr. Charles Staples from the University of Florida conducted extensive literature reviews as well as his own studies to determine if there is an additional effect of polyunsaturated fatty acids on reproductive performance beyond their effect on the cow’s energy status. Staples and co-workers suggested that polyunsaturated fatty acids improve fertility by:
1. Sparing glucose to stimulate the release of LH from the anterior pituitary gland which stimulates the development of ovarian luteal cells,
2. Increasing circulating cholesterol concentrations and subsequently increasing progesterone levels to maintain pregnancy, or
3. Inhibiting the production of prostaglandin and estradiol, thus increasing the lifespan of the corpus luteum and improving embryo survival. Feeding small amounts of fishmeal (2.8% of diet dry matter) has improved conception rates in research studies.
Protein
Protein is broken down to ammonia by the rumen microbes. Some of the ammonia is converted back into protein by the rumen microbes but some is not. When large amounts of protein are in the diet (>19% CP) especially soluble protein (>35% of the CP) (for example, from pasture or alfalfa silage) or degradable protein (DIP) (>70% of the CP), the microbes often cannot keep up with the ammonia production. The ability of the microbes to use rumen available protein will be partially dependent on the availability of carbohydrate. The carbohydrate must be available at the same time as the protein is available, not hours later in the day.
Excess ammonia is absorbed out of the rumen, converted to urea, and urea levels rise in all body fluids, including the reproductive tract. Blood Urea Nitrogen (BUN) levels over 18 mg/dl or Milk Urea Nitrogen (MUN) levels over 16 mg/dl have been associated with lower conception rates, more services/conception, and more days open. Increased concentrations of ammonia, urea, or other nitrogen compounds in the uterine fluids are toxic to sperm and to the embryo. Early embryonic death will show up in the cow as an irregular heat cycle.
It costs the cow energy to process the excess nitrogen into urea and to excrete it from her body. This adds to her overall energy requirement. Of course, as discussed above, shortage of energy can reduce reproductive performance.
Vitamin and Trace Mineral Supplementation
Vitamin E and selenium are antioxidants and they may impact prostaglandin synthesis. Their supplementation has increased conception rate and reduced the amount of retained placentas, abortions and cystic ovaries. Generally it is recommended that Vitamin E be at 15 IU/lb in the diet and selenium at 0.3 ppm or 0.14 mg/lb. Feeding more than the recommended levels has not been shown to be helpful.
Manganese is needed for making steroids. Its deficiency can cause irregular heats, silent heats, poor conception, and abortions. Diets should generally contain 44 ppm manganese.
Copper may affect the action of prostaglandin. Its deficiency will result in more early embryonic death. Deficiency of copper may be caused by too much dietary molybdenum or sulfur. Diets should normally contain 12 ppm of copper.
Phosphorus
Phosphorus deficiency has been blamed for breeding problems but there is no research that shows that feeding above the NRC requirements is beneficial. A survey of 11 high-producing herds over 3 years in Wisconsin found that rations averaged 0.57% phosphorus. Popular opinion says that the more phosphorus we feed, the better cows will breed back.
As with all nutrients, cows require a certain number of grams of phosphorus. But, we usually figure out the amount of dry matter that the cow is expected to eat and express the phosphorus requirement as a percentage of the diet. The National Research Council (NRC, 1989) requirements for Holstein cows producing 60 lbs (27 kg), 80 lbs (36 kg), or 100 lbs (45 kg) of milk are 68, 85, and 100 grams of phosphorus per day. At normal intakes, that would be equal to 0.36, 0.39, and 0.42% phosphorus in the ration. If intakes were 95% of that expected, ration phosphorus requirements would be 0.38, 0.41, and 0.44%.
Silent heats, irregular heats, and low conception rates can occur when phosphorus is lacking. But, many of the studies showing these problems fed less than 0.20% phosphorus. A Michigan State trial with first-calf heifers showed no differences in reproduction when they fed 98 or 138% of NRC requirements. Milk production was actually lower in the group that was fed more phosphorus. A German study used rations with 0.33 or 0.39% phosphorus for 2 lactations plus the dry period and found no differences in milk production (16,500 lbs (7500 kg)) or reproduction.
One reason that we have balanced for higher levels of phosphorus over the years has been to provide a margin of safety. First, with one-group TMR’s, we want to make sure that fresh cows who have lower intakes get enough phosphorus. The NRC recommends 0.49% phosphorus for the first 3 weeks of lactation. If we can make high-groups and fresh-cow groups on farms, we can reduce the total amount of phosphorus that we are feeding to the herd each day. Second, feeds are variable in their phosphorus content. We need to rely more on feed and forage analyses. Finally, we’ve been excessively concerned about the calcium:phosphorus ratio. If we meet the phosphorus requirement, we can do fine with ratios up to 3:1.
Increase in annual feed costs of a 100-cow herd
relative to phosphorus at 0.40% of dietary DM
| Milk Lb/d |
DMI Lb/d |
0.45% P |
0.50% P |
0.55% P |
|
60 |
45.6 |
$754 |
$1500 |
$2260 |
|
70 |
48.4 |
$798 |
$1603 |
$2402 |
|
80 |
51.2 |
$850 |
$1693 |
$2542 |
(Knowlton and Kohn, 1999)
Dry Period Nutrition
Dry period nutrition will affect dry matter intake, energy status and protein status after calving. If cows get a poor start, expect reproductive problems. Metabolic problems like milk fever, retained placenta, displaced abomasum, and ketosis usually interact and will increase the cow’s risk of other problems. Metabolic problems will decrease dry matter intake, energy status and protein status of the early lactation cow.
Before calving, the cow has increased needs for protein and energy for the fetus. At the same time, dry matter intake is depressed to about 1.5% of body weight. The prefresh diet, therefore, needs to contain higher amounts of protein and energy than the far-off dry cow diet. Also, it is advantageous to adapt the rumen microbes and rumen papillae to higher dietary concentrations of grain before calving so that after calving the rumen will be able to adapt more quickly to a high-production diet. The prefresh diet also needs to be palatable and contain highly fermentable forage NDF to promote intake.
Dry period protein nutrition is important for reproduction. Cornell researchers decreased services per pregnancy by adding more UIP to the prefresh diet and increasing overall CP (12.3 to 15.3%) as well as UIP. The author has observed an increase in retained placentas on farms that don’t feed enough protein during the dry period. Protein is needed to maintain the muscle used to get rid of the placenta after calving. 12-13% CP is recommended during the far-off dry period and 14-15% CP (containing 35-40% UIP) during the pre-fresh period.
References:
Butler, W.R., R.W. Everett, and C.E. Coppack. 1981. The relationship between energy balance, milk production, and ovulation in postpartum dairy cows. J. Anim. Sci. 53:742.
Carstairs, J.A., D.A. Morrow, and R.S. Emery. 1980. Postpartum reproductive function of dairy cows as influenced by energy and phosphorus status. J. Anim. Sci 51:122.
Chandler, P.T. 1998. Body condition score, milk production potential, reproduction, and dietary fat. In: Proceedings of the Advanced Dairy Workshop, Syracuse, NY.
Chase, L.E. 1998. Phosphorus in dairy cattle nutrition. In: Proceedings of the 1998 Cornell Nutrition Conference for Feed Manufacturers, p. 212.
Domecq, J.J., A.L. Skidmore, J.W. Lloyd, and J.B. Kaneene. 1997. Relationship between body condition scores and conception at first artificial insemination in a large herd of high yielding Holstein cows. J. Dairy Sci. 80:113.
Ferguson, J.D., T. Blanchard, D.T. Galligan, D.C. Hoshall, and W. Chalupa. 1988. Infertility in dairy cattle fed a high percentage of protein degradable in the rumen. JAVMA 192:5:659.
Knowlton, K.F. and R. Kohn. 1999. Altering rations may reduce phosphorus losses. Feedstuffs. April 12, 1999, p. 12.
Lucy, M.R., C.R.Staples, F.M. Michel, and W.W. Thatcher. 1991. Energy balance and size and number of ovarian follicles detected by ultrasonography in early postpartum dairy cows. J. Dairy Sci. 74:473.
National Research Council. 1989. Nutrient Requirements for Dairy Cattle. 6th rev. ed. Update 1989. Natl. Acad. Sci., Washington, DC.
Oldick, B.S. and J.L. Firkins. 1996. Imbalanced, inadequate diets effect reproduction performance, bottom line. Feedstuffs. December 9, 1996, p. 12.
Spain, J. Reproductive Management – A Nutritionist’s Perspective. 1998. Western Canada Dairy Symposium.
Staples, C.R., R. Mattos, C.A. Risco, and W.W. Thatcher. 1998. Feeding fish meal may improve cow fertility rates. Feedstuffs. January 12, 1998, p, 12
Staples, C.R., W.W. Thatcher, C.M. Garcia-Bojalil, and M.C. Lucy. 1992. Nutritional influences on reproductive function. In: Large Dairy Herd Management. Edited by H.H. Van Horn and C.J. Wilcox, American Dairy Science Association.
Stevenson, J. 1999. Can you have good reproduction and high milk yield? Hoard’s Dairyman, August 10, 1999, p. 536.
Van Saun, R.J., S.C. Idleman, and C.J. Sniffen. 1993. Effect of undegradable protein amount fed prepartum on postpartum production in first lactation Holstein cows. J. Dairy Sci. 76:236.
Related Links:
Getting Problem Cows Pregnant
Heat Detection: Problems, Evaluation, and Solutions
David Marcinkowski, University of Maine Extension
Estrus (Heat) Detection Guidelines
J.F. Keown and D.N. Rice, University of Nebraska - Lincoln
Therapeutic Nutrition for Dairy Cattle
V. Ishler, M. O’Connor, and L. Hutchinson, Penn State University
Effect of Protein on Reproductive Performance
R.D. Smith, C.R. Holtz, and C.J. Sniffen, Cornell University
Neosporosis and Abortion in Dairy Cattle
M. Anderson, University of California
Go to Proceedings 1996, Table of Contents, Session V
|