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Context: There is little published information on how long it takes for the performance of phosphorus (P)-deficient mature cows to improve once they start receiving P supplements, or whether their long-term performance is impaired by P deficiency early in life. Aims: The performance of mature P-deficient and P-adequate Brahman cows was compared over 3 years to investigate the time it takes for the performance of P-deficient mature cows to improve once they are supplemented with P, and whether their long-term performance is compromised by P deficiency early in life. Methods: Cows that had been a part of a P-supplementation trial at Victoria River Research Station from weaning until they were 5.5 years old were used for this study. One treatment group had received continuous P supplement (P+) since weaning and the other treatment had never received any P supplement (P−). At the conclusion of the original trial, 42 cows were randomly selected from each treatment and then grazed together in the same paddock for 3 years, during which time they were given P supplement continuously. Performance attributes were measured and compared. Key results: This study found that P supplementation rapidly improved the liveweight, body condition, reproductive performance and survival rate of the P-deficient (P−) mature cows. Within a year of receiving P supplement, their performance improved to be similar to that of P+ cows. However, P deficiency early in life did have some residual stunting effects, resulting in lower mean hip height and liveweights of P− cows. Conclusions: The performance of P-deficient mature cows improved rapidly once they were given P supplements and matched that of cows that had always been supplemented. However, P deficiency early in life caused stunting, resulting in mature cows being shorter and lighter. Implications: Cattle producers in P-deficient country should see a rapid improvement in performance and return on investment once they start supplementing P-deficient cows. However, it is better to supplement cattle throughout their lives in P-deficient areas to avoid stunting. This study investigated how long it takes for the performance of phosphorus (P)-deficient mature cows to improve once they are supplemented with P, and whether their long-term performance is compromised by P deficiency early in life. The performance of P-deficient cows improved to be similar to that of P-adequate cows within a year of P supplementation commencing. However, P deficiency early in life did have some residual stunting effects, resulting in lower hip height and liveweight. [ABSTRACT FROM AUTHOR]

Context: There is a paucity of information on the responses to phosphorus (P) supplementation of breeder herds grazing P-deficient rangelands in northern Australia. Aims: A study examined the production and economic benefits of P supplementation of Brahman females grazing P-deficient pastures in the Northern Territory (NT) of Australia. Methods: Two treatment groups (initially n ~ 90) grazed two similar P-deficient paddocks for 5 years after weaning (at approximately 6 months of age). Management was the same except that the loose lick mineral supplement either contained P (+P) or did not contain P (−P). Performance attributes were measured from commencement until after the cows had the opportunity to calve during three successive annual cycles. Key results: The cows in the +P treatment were overall heavier (P < 0.001), taller (P < 0.001) and had higher plasma inorganic P (PiP) concentrations (P < 0.001) than did those in the −P treatment at every measurement date after the first wet season. Pregnancy rates in lactating cows were 25%, 39% and 63% units higher (P < 0.01) in +P in 2017, 2018 and 2019 respectively and overall average weaner weight was 33 kg heavier (P < 0.001) in +P. Due to higher weaning rates and heavier weaning weights, +P produced about AU$39 365 more value of weaners per 100 heifers allocated to each treatment than did −P over the first three calf crops. The cumulative mortality rate was 12% higher in the −P over the 5 years (14.8% vs 2.2%, P < 0.01), and would have been even higher if at-risk −P cows had not been fed additional supplements. Return on investment calculations indicated that each AU$1 spent on P supplement returned AU$4.98 in value of extra calves weaned and AU$7.88 in extra total liveweight increase over the 5 years of the study. Conclusions: The large production and financial benefits from P supplementation observed in this study are relevant to most northern Australian properties where soils are P deficient, although the magnitude of response is likely to vary depending on the level of P deficiency. Implications: The large production and economic benefits from P supplementation in this study demonstrated the importance of P supplementation for breeder herds grazing P-deficient pastures. A study was conducted over 5 years at Victoria River Research Station, Northern Territory, Australia, to determine the effects of phosphorus (P) supplementation on the growth and reproductive performance of Brahman females grazing P-deficient pastures and to evaluate the return on investment in P supplementation. P supplementation resulted in large improvements in growth, pregnancy rate, weaning rate, average weaner weight, weaner production, mortality rate and gave an excellent return on investment. [ABSTRACT FROM AUTHOR]