ONA REPORT

published in

THE FLORIDA CATTLEMAN AND LIVESTOCK JOURNAL


November 2016

Recent nutritional strategies to enhance reproductive performance of heifers – A summary of Range Cattle REC studies

by Philipe Moriel


For questions or comments regarding this publication contact: Dr. Philipe Moriel, University of Florida, IFAS

Replacement heifers are an important part of the cow-calf operation and represent genetic improvement of the cow herd. Heifers should calve by 24 months of age to achieve maximum lifetime productivity, and heifers that lose a pregnancy or conceive late in the breeding season are likely to not have enough time to rebreed during a defined breeding season. In addition, bos taurus heifers that calved during the first 21 days of calving season remained in those calving groups longer and weaned heavier calves in the subsequent 6 parturitions. In fact, early-calving heifers had an increase in weaning weight that amounted to the production of an extra calf during their lifetime compared to late-calving heifers. This represents a substantial financial benefit for cow-calf producers and reinforces the importance of having replacement heifers conceive as early as possible. Providing the correct nutrition that will allow the heifer to achieve these goals is crucial, and this topic has been the focus of multiple research studies at the RCREC. In this report, you will be provided with a summary of the most recent experiments evaluating growth and reproductive performance of beef heifers.

STUDY #1 – Frequency of energy supplementation. J. Anim. Sci. 90(2012):2371-2380.
Forage is the main component of cattle diets, but it is usually energy deficient. Consequently, energy supplementation is often required for growing animals. However, the expenses associated with energy supplementation can significantly increase production costs and become unattractive to cow-calf producers. A typical approach to decrease these expenses is to reduce the frequency of supplementation, such as 3 times weekly (Monday, Wednesday, and Friday) instead of daily to minimize costs associated with labor, fuel, and equipment.

Starting 60 days before breeding season, we compared the growth and reproductive performance of Brangus heifers that were supplemented with concentrate either daily or 3 times weekly. Supplements consisted of soybean hulls and wheat middlings, and were offered at weekly rates of 35 lb/heifer for 120 days. During the study, heifers receiving daily supplementation had similar average daily gain compared with heifers supplemented 3 times weekly (0.59 vs. 0.55 lb/day, respectively). However, the percentage of heifers reaching puberty at the start of breeding season (33 vs. 21%) and final pregnancy rate (21 vs. 12%) was greater for heifers supplemented daily compared to heifers supplemented 3 times weekly. Therefore, replacement beef heifers receiving diets based on low-quality forages should receive energy supplements daily to enhance their reproductive development.

STUDY #2 – Calf management systems for early-weaned heifers. J. Anim. Sci. 92(2014):3096-3107.
Calves from first-calf cows are early-weaned at 70 days of age at the Range Cattle REC. This practice improves the reproductive performance of first-calf beef cows. However, many beef producers are unwilling to adopt this management practice due to a lack of information on the nutritional management of early-weaned calves. Therefore, we evaluated different management systems for early-weaned beef calves and their long-term consequences on calf performance.

In January, heifers were assigned to be normally weaned at 8 to 9 months of age in July, or early weaned in January and: (1) limit fed a high-concentrate diet in drylot for 180 days; or (2) limit fed a high-concentrate diet in drylot for 90 days, then grazed on bahiagrass pastures until day 180. Then, heifers were managed similarly from July to end of the breeding season in early February. Early-weaned heifers limit-fed a high-concentrate diet for 90 days in drylot had similar growth performance than normally-weaned heifers. Interestingly, 80% of heifers that were limit-fed a high-concentrate diet in drylot for 90 days achieved puberty at the start of the breeding season, but only 40% of normally-weaned heifers achieved puberty at the start of the breeding season. This response indicates that early puberty attainment may be achieved if heifers are exposed to high-concentrate diets at young ages (approximately 70 days of age).

STUDY #3 – Should I mix cottonseed meal with Sugarcane molasses in a slurry form, or offer them separately to beef heifers? The Professional Animal Scientist 32(2016):302–308
Sugarcane molasses is a by-product of the sugarcane industry typically used as an energy source for grazing beef cattle in Florida. Commercially available molasses-based liquid supplements usually rely on urea to increase protein concentrations. However, adding cottonseed meal to a sugarcane molasses–urea mixture has been shown to improve growth performance of younger cows compared to those supplemented with molasses–urea supplement. Currently, the mixing of dry feeds with molasses in a beef cattle operation is performed manually or through relatively expensive equipment that is not widely available. Providing sugarcane molasses and natural protein feed sources separately could further decrease labor and feed costs. Recently, beef heifers were fed cottonseed meal manually mixed with sugarcane molasses in a slurry form (SLU) or fed cottonseed meal and molasses in separate bunks (SEP); 70 lb of sugarcane molasses and 14 lb of cottonseed meal were delivered twice weekly (Tuesdays and Fridays) for 70 days.

Average daily gain of heifers did not differ between feeding treatments (0.37 vs. 0.35 lb/day for SLU and SEP heifers respectively). However, 19% of heifers supplemented with molasses and cottonseed meal in a slurry form achieved puberty at the start of breeding season compared to only 8% of heifers fed molasses and cottonseed meal separately. This negative impact on puberty can likely be attributed to a faster consumption of cottonseed meal by heifers when fed cottonseed meal and molasses separately leading to different and more variable energy metabolism and impairing puberty achievement. However, overall pregnancy rates and calving distribution did not differ between treatments. This demonstrates that cottonseed meal and molasses could be offered separately rather than in a slurry form without affecting growth and reproductive performance of grazing replacement beef heifers. By providing cottonseed meal and molasses separately, cow-calf operations should be able to reduce labor and further lower feed costs, leading to greater profitability compared with providing cottonseed meal and molasses in a slurry form.

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You are invited to join us by webinar on November 28, at noon, when Philipe will present the information covered in this Ona Report and he will be available for questions. To participate this webinar you simply need to register online here: https://attendee.gotowebinar.com/register/7496424475530968324.  If you are nearby, you are also welcome to attend the presentation in person. Join us at the Center in the Grazinglands Education Building.
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