Urophagia in lactating cows associated with nitrogen deficiency in the diet - case reportsABSTRACT
This article describes two cases where adult dairy or beef cows, fed exclusively with corn or sorghum silage, began to ingest urine greedily. Providing 20 to 40g of urea/100kg of body weight was able to suppress urophagia in these two herds. In a situation where adult cows, not supplemented with protein concentrates, are ingesting urine, professionals should suspect a nitrogen deficiency in the diet. The diagnosis can be confirmed if urophagia stops after 15 to 21 days of supplying 20 to 40g of urea/100kg of body weight. Differential diagnoses of Na and Co deficiencies should be considered in episodes of urophagia.
Keywords:
corn and sorghum silage; nitrogen; urophagia
RESUMO
Este artigo descreve dois casos em que vacas adultas, de leite ou de corte, alimentadas exclusivamente com silagens de milho ou de sorgo, passaram a ingerir avidamente urina. O fornecimento de 20 a 40g de ureia/100kg de peso corporal foi capaz de suprimir a urofagia nesses dois rebanhos. Numa situação em que vacas adultas, confinadas ou semiconfinadas, não suplementadas com concentrados proteicos, estiverem ingerindo urina, os profissionais devem suspeitar de uma deficiência de nitrogênio na dieta. O diagnóstico pode ser confirmado se a interrupção da urofagia se verificar após 15 a 21 dias do fornecimento de 20 a 40g de ureia/100kg de peso corporal. Diagnósticos diferenciais das deficiências de Na e Co devem sempre ser levados em consideração nesses episódios de urofagia.
Palavras-chave:
nitrogênio; silagens; urofagia
INTRODUCTION
Ruminants have evolved for millions of years ingesting large amounts of forage feeds, which are rich in fiber (i.e., plant cell wall), and have a low to moderate nitrogen (N) content. In the rumen, the degradation of the plant cell wall by rumen microorganisms requires constant microbial growth; this process, in turn, requires adequate nitrogenous compounds intake and availability. Throughout the evolutionary process, ruminants have developed a complex and efficient system to maintain, via recycling, their body N. In this process, urea synthesized in the liver plays a central role, as this substance is recycled through saliva and by diffusion by the rumen epithelium. In the rumen, urea is the main source of ammonia for the growth of ruminal microorganisms that digest the fibrous carbohydrate present in plant cell wall (i.e., fiber). In the case of severe N intake restriction, which occurs in starving animals or those eating, for long periods, forage that is extremely low in protein, ruminants lose weight. This muscle catabolism increases hepatic ureagenesis to meet ruminal N demands. In this case, there is a proportional increase in the relevance of recycling events for maintaining N status in the rumen. One of the ways to slow down muscle catabolism is to provide urea and/or protein feedstuffs in the diet.
The present report describes two cases in which lactating cows, fed with more than 90% of their diet consisting of sorghum or corn silage and without any sources of supplementary nitrogen compounds, began to ingest urine (i.e., urophagia) profusely.
DESCRIPTION OF CASES
Case 1 - Occurred on a property where dairy cattle (Jersey cows) are raised exclusively with forage. In spring/summer, the herd is raised on Tifton-85 pastures, supplemented only with mineral salt. In autumn/winter, the herd is kept practically confined and fed with sorghum silage (around 25kg/cow/day, as a natural basis), with mineral salt (containing, per kg, 75gNa, 200gCa, 60gP, 20gS, 20gMg, 35gK, 700mgCu, 15mgCo, 700mgFe, 40mgI, 1600mg Mn, 2500mgZn and 19mgSe) available in the salt troughs - no proteic or energetic supplement is given to the cows. After 4 pm, the herd is taken to pastures, with almost no forage available, to spend the night. Due to transport logistics and high costs, the use of concentrate feedstuffs in this specific region is almost always unfeasible. The owners reported that a few days after the lactating cows (20 to 25) start ingesting sorghum silage, they begin the consumption of urine on the concreted floor of the stockyard (Figures 1 - 3). They also reported that they had already tried several solutions to the problem and all were unsuccessful. As they do not detect any health issues or reduction in milk production, the ingestion of urine by the cows has always been treated as simply an “inelegant thing” to the eyes of owners and visitors. The owners requested a visit to the farm to investigate this phenomenon further. With this history-taking, the suspicion of sodium (Na) and cobalt (Co) deficiencies was initially investigated. Na deficiency was soon ruled out, as the cows had NaCl available to lick. To check for a possible Co deficiency, Vitamin B12 was intramuscularly given to four cows, and 100 mg of cobalt sulfate (21 mg of Co) was also supplied orally, in a single dose, to another four cows - after 14 days, these eight cows continued to lick/ingest urine profusely. A new suspicion, therefore, fell on a possible N deficiency in the diet, known to be restricted in protein. As urea is the main nitrogenous form present in urine, it was hypothesized that it would be possible to provide around 200 g/day of this compound to each cow and monitor the evolution of the urine intake behavior. This amount of urea was dispersed over the sorghum silage and meticulously mixed to avoid a great/rapid consumption and thus reduce the risk of poisoning. The amount of urea was equivalent to approximately 44g/100kg of body weight. The owners reported that five days after ingesting urea, some cows had already stopped ingesting urine; after fourteen days, practically all cows no longer performed urophagia. At thirty days, no cow was seen consuming urine. Another relevant finding was the slight improvement in the body condition score of some animals after thirty days of starting urea supply (Fig. 4).
On the left, cow before ingesting 200 g of urea per day. On the right, the same cow 37 days later.
Case 2 - It was described on a herd of about 170 Nellore cows. Similar to what happened in case 1, in spring/summer, the herd is raised exclusively on brachiaria (U. brizantha) pastures and supplemented only with mineral salt. In the autumn/winter of 2024, because the farm had 1.2 cows/ha and did not carry out good pasture management, the forage mass available was significantly reduced and the herd had to be kept in an area close to the stockyard, where it began to receive around 25 to 30 kg of corn silage, without any proteic or energetic supplement; the herd was supplemented only with mineral salt containing, per kg, 330gNa, 40gP, 750mgCu, and 85mgCo. As described in case 1, the owner reported that a few days after cows started to receive corn silage, they began ingesting urine, often directly from the vulva of other cows or the prepuce of calves (Figures 5 to 7). Faced with this problem, the owner requested support to investigate this phenomenon further. With the history-taking, the suspicion of sodium (Na) and cobalt (Co) deficiencies was initially investigated. Na deficiency was soon ruled out, as the cows had a mineral salt containing 310 g of Na/kg available to lick. Around 100mg of cobalt sulfate (21 mg of Co) was administered orally to ten cows to check for a possible Co deficiency; seven days later, this application was repeated. After fourteen days these ten cows continued to lick urine greedily. A new suspicion, therefore, fell on a possible N deficiency in the diet, known to be restricted in protein. As urea is the main nitrogenous form present in urine, it was hypothesized that it would be possible to provide around 100g/day of this compound to each cow and monitor the behavior of urine ingestion. This amount was dispersed over the corn silage and meticulously mixed to avoid a rapid/large consumption and thus reduce the risk of poisoning. This amount was equivalent to around 21g/100kg of body weight. The owners reported that five days after ingesting urea, some cows had already stopped ingesting urine; at fourteen days, practically all of them no longer performed urophagia. After thirty days, no cows were seen consuming urine.
DISCUSSION
Initially, it is necessary to make it clear that the cessation of urophagia through the ingestion of urea does not mean “urea deficiency” in the diet, as this substance a) does not exist in feeds of vegetable origin (i.e. roughages and concentrates) and b) there is no dietetic urea requirement. Therefore, it does not make any sense to talk about urea deficiency in a diet.
What resembles these two cases, although verified in cows with completely different purposes, is: a) the fact that the cows are ingesting practically their total daily dry matter requirement as silage, b) they have almost no forage mass on offer when maintained, at night, on pastures, c) do not receive any proteic or energetic concentrates and d) are producing milk; therefore, requiring more metabolizable protein when compared to what would be required for their maintenance only. The combination of these four aspects generated a daily deficit of nitrogenous compounds in both diets (Tables 1 and 2), which, in turn, must have increased the mobilization of muscle tissue and the recycling of endogenous urea produced from amino acid catabolism (Parker et al., 1995; Reynolds and Kristensen, 2008).
An interesting aspect is that, as there is no “magic in nature”, the absolute recycling of N (g/d) does not increase, as the body's N pool is low in these situations. What increases is the share of recycled N in the total N available in the rumen. Therefore, the amount of N recycled is smaller, but the proportion in relation to what is synthesized in the liver and what enters the rumen becomes “proportionally greater”.
The calculations to estimate the amount of metabolizable protein (MP), resulting from urea ingestion are based on the following calculations: a) crude protein ingested via urea (CP) = amount of urea/day x 2.8; b) amount of crude protein of microbial origin from urea = 0.80 x CP ingested via urea and c) amount of microbial MP from urea = amount of crude protein of microbial origin from urea x 0.63 (Ruminant…, 1985).
Another interesting point is that the non-fibrous carbohydrates (i.e. especially starch) present in both silages probably further exacerbated the N deficiency in the rumen. Therefore, by providing urea in both diets, this deficit was corrected, and urophagia was interrupted. In the case of the Jersey herd, the diet without urea generated a deficit of - 316 g/day of metabolizable protein; when the cows began to ingest around 200 g of urea, the deficit fell to - 33 g/day (Table 1). A similar situation occurred in the Nellore herd, where the metabolizable protein deficit was - 113g/day in the diet without urea and, after being supplemented with 100 g of urea per day, there was a positive balance of 28 g of MP/day (Table 2).
When faced with cows ingesting urine, professionals should also suspect sodium (Na) and cobalt (Co) deficiencies. Both deficiencies must be investigated by obtaining a careful and detailed history, followed by a meticulous physical examination of the animals. Na deficiency is easily ruled out in cases where animals are correctly supplemented with a mineral mixture containing an adequate concentration of Na per kg. Clinical Co deficiency is easy to diagnose, as it produces marked cachexia in animals; on the other hand, subclinical Co deficiency requires the professional to choose some animals and apply Vitamin B12 or provide a dose of cobalt sulfate orally and reevaluate the animals approximately fourteen days later. If Na and Co deficiencies are ruled out, the professional must suspect nitrogen (N) deficiency in the diet; especially when cattle are being fed exclusively with roughage known to be low in protein, as in these two cases.
As the two herds were monitored daily and no dietary changes were made, except for the addition of urea to their diets, it was clear that the cessation of urophagia was likely a result of correcting the N deficiency through the consumption of urea, included in both diets.
CONCLUSIONS
In a situation where adult cows fed basically 100% of corn or sorghum silage and do not supplemented with protein concentrates, and are ingesting urine, professionals should suspect a nitrogen deficiency in the diet. This diagnosis can be confirmed if urophagia stops after 15 to 21 days of supplying 20 to 40g of urea per 100kg of body weight. Obviously, differential diagnoses of Na and Co deficiencies must always be considered in these episodes of urophagia.
ACKNOWLEDGEMENTS
We gratefully acknowledge Prof. Edenio Detmann (UFV-DZO) and Dr. Vinícius C. Souza (USP - FZEA) for their valuable suggestions in the manuscript.
REFERENCES
- PARKER, D.S.; LOMAX, M.A.; SEAL, C.J. et al. Metabolic implications of ammonia production in the ruminant. Proc. Nutr. Soc., v.54, p.549-563, 1995.
- REYNOLDS, C.K.; KRISTENSEN, N.B. Nitrogen recycling through the gut and the nitrogen economy of ruminants: an asynchronous symbiosis. J. Anim. Sci., v.86, Suppl.E293-305, 2008.
- RUMINANT nitrogen usage. Washington, DC. National Academic Press, 1985. 138p.
Publication Dates
-
Publication in this collection
14 July 2025 -
Date of issue
Jul-Aug 2025
History
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Received
03 Dec 2024 -
Accepted
21 Feb 2025
