Hypomagnesemic tetany is a disorder of magnesium metabolism in ruminants, affecting goats, sheep, beef, and dairy cattle. This disease exhibits a variety of clinical signs characterized by excitability, grinding of the teeth, salivation, ataxia, recumbency, and tetanic muscle spasms. This article summarizes recent knowledge of the pathogenesis of hypomagnesemia and the clinical consequences for the afflicted animals, primarily focusing on magnesium absorption from the gastrointestinal tract, pathogenesis of clinical signs, and renal magnesium excretion.

Pathophysiology of Grass Tetany and other Hypomagnesemias: Implications for Clinical Management

In recent years considerable information on ovine foetal growth has emanated from both medical research, in which the sheep has been used as a convenient experimental animal, and agricultural research, in which the main interest has been in improving the efficiency of the sheep as a meat and wool producer (Alexander, 1974). In the present paper an attempt is made to draw together some of the main findings, in particular those relating to the effects on foetal growth of underand over-nutrition at different stages of gestation. In reviewing the results of experiments made in early and mid pregnancy, nutritional treatments are described as either ‘high‘ or ‘low’, since in many early reports this is the only description of the treatments. In an attempt at more accurate definition, where possible body-weight changes are included in the present review.

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The influence of maternal nutrition on ovine foetal growth.

Nineteen feedstuffs were evaluated for total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME) using growing pigs. DE values, on a drymatter basis, ranged from 1570 kcal/kg D.M. (grassmeal) to 4890 kcal/kg D.M. (BP Grangemouth protein). ME averaged 97·4% of DE for cereal feeds and 81·9% of DE for protein feeds, the ratio of DE to ME being significantly affected by the crudeprotein content of the feedstuff:ME/DE × 100 = 99·7–0·18 × crude protein (%): r = –0·94; P < 0·01.TDN was more closely related to ME than DE:DE (kcal/kg D.M.) = 45 TDN + 156: r = 0·92; P < 0·01,ME (kcal/kg D.M.) = 43 TDN + 71: r = 0·98; P < 0·01.ME values were corrected to both 30% and 0% nitrogen retention. Correction to 30% retention caused a maximum change of 3% in ME value while correction to 0% retention had a variable effect related to protein content of the feedstuff:(ME(N0)/ME) × 100 = 98·3–0·113 × crude protein (%): r = –0·80; P < 0·01.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600071823

Energy values in pig nutrition:I. The relationship between digestible energy, metabolizable energy and total digestible nutrient values of a range of feedstuffs

Nitrogen and phosphorus nutrition of cattle: reducing the environmental impact of cattle operations.

The effects of pregnancy on haematological and some biochemical parameters were studied using 30 (25 pregnant of known gestational age, while fi ve animals remained as cycling non-pregnant control) Sahel does aged between 11⁄2 to 21⁄2 years and managed under controlled conditions. Their weights ranged between 14 to 25 kg. Red blood cell and the white blood cell counts were the only haematological parameters that showed a signifi cant (P<0.05) difference between the non pregnant and pregnant does during the 16 and 20 weeks of pregnancy. While cholesterol increased (53.9 mg/dL ± 1.59 to 82.08 mg/dL ± 1.58) signifi cantly (P<0.05), glucose decreased (68.33 mg/dL ± 1.21 to 45.74 mg/dL ± 1.58) signifi cantly (P<0.05) from 12 weeks of gestation. There were no signifi cant differences (P>0.05) in the other biochemical parameters determined, namely: Na, Ka, Ca, Total proteins, FFA, Urea, Creatinine, AST, ALT, and Alkaline phosphatase. The present study indicates that haematological and mineral imbalances are unlikely to occur during pregnancy in Sahel does when properly managed.

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Changes in the serum proteins, hematological and some serum biochemical prolife les in the gestation period in the sahel goats

Four young lambs fitted with cannulas at the pylorus and at the ileo-caecal junction were used to study the effects of weaning on digesta flow and mineral absorption. Prior to weaning when milk alone was fed the small intestine was the major site for dry matter disappearance and for the absorption of Ca, P, Na and K. Both the small and the large intestine were, however, important sites for Mg absorption at this time. After weaning, when the lambs were fed a concentrate diet, at least two-thirds of the digested dry matter disappeared within the reticulo-rumen. The small intestine, however, still remained the major site for the absorption of Ca, P, Na and K. Most Mg absorption, in contrast, now occurred anterior to the pylorus and it would appear that the move from hindgut to foregut as a site for Mg absorption was directly associated with the introduction of dry feed and the development of fermentative digestion within the reticulo-rumen. Both before and after weaning the faeces was the major route for the excretion of Ca surplus to requirement and the faeces also became increasingly important as a pathway for P and Mg excretion once dry feed was given. The urine, in contrast, was consistently the major pathway for the excretion of Na and K.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600062791

Digesta flow and mineral absorption in lambs before and after weaning

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments. In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes. In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change. A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Observations on the effect of protein intake and stage of gestation on the proportion of urinary nitrogen excreted as urea in sheep

SUMMARY Nine individually penned Finnish Landrace x Dorset Horn ewes with a mean litter size of 2·33 were offered a diet containing 63% digestible organic matter (DOM) and 13% crude protein in the dry matter at a daily intake of 0·82 kg DOM (1·3 x maternal maintenance) from 95 to 110 days of gestation. On day 111 DOMI was abruptly reduced to either 0·67 kg (T1, 0·54 kg (T2) or 0·36 kg (T3)/day and kept at these levels until a few days pre-partum. Daily N balance before food restriction was 4·9 ± 0·51 g/day. During the periods 3·9 (S1), 11·17 (S2) and 19·25 (S3) days after food restriction daily N balance was 2·8, 2·8 and 3·6 g for θwes on T1, 1·0,1·0 and 0·8 g for those on T2 and –4·1, -4·0and -4·0 g for those on T3. Total lamb birth weight was 8·0, 7·2 and 6·5 kg for treatments T1, T2 and T3 respectively. Using regression analysis it was calculated that plasma glucose concentration in late pregnancy for ewes with a total lamb birth weight of 8 kg fell below the pre-restriction value of 52 mg/100 ml when daily DOMI was reduced to 747 g. At this intake the plasma FFA concentration was 585/i-equiv./I compared with 288 before food restriction. Corresponding values for daily N balance were 5·1 and 4·9 g. A reduction in daily energy intake below 0·75 kg DOM resulted in a rapid decrease in plasma glucose and N balance, the latter being proportional to the increase in the concentration of plasma FFA. The mean daily loss of N from the maternal body was estimated to be 0·4, 1·6 and 6·1 g for treatments T1 to T3 respectively during the period of food restriction.

D. Scott

Papers

Digesta flow and mineral absorption in lambs before and after weaning

Observations on the effect of protein intake and stage of gestation on the proportion of urinary nitrogen excreted as urea in sheep

The effect of different degrees of food restriction in late pregnancy on nitrogen metabolism in ewes