The effect of very low food intake on digestive physiology and forage digestibility in horses.

Equid digestion is often conceptualized as a high-throughput/low-efficiency system, in particular compared with ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies [initial body mass (BM) 288 ± 65 kg] in two subsequent trials with grass hay-only diets [in dry matter (DM): hay1, mid-early cut, crude protein (CP) 10.5%, neutral detergent fibre (NDF) 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%], each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g/kg(0.75) /day. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles <2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43% and 42/37%, respectively, on the ad libitum DMI to 35/35% and 30/28% on DMI30. Additional differences evident between the two hays included a higher estimated 'true' protein digestibility for hay1 and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds and might differ between ruminants and equids.

[Seasonal variations in the formation of virus-neutralizing antibodies in cattle after vaccination against foot-and-mouth disease]. / Jahreszeitliche Schwankungen der Bildung virusneutralisierender Antikörper nach Impfung gegen Maul- und Klauenseuche beim Rind.

The GDR in 1977 had been the first country to introduce a laboratory method for potency testing of FMD vaccines on the basis of secured correlations between titres of virus-neutralising serum antibodies of immunised cattle, on the one hand, and their probit-transformed protection against FMD, on the other. This is now the only state-registered method for potency testing. The method has ever since worked well all over the place. An evaluation of results obtained between 1982 and 1988 revealed seasonal variations of anti-FMD immunogenesis in cattle. FMD immunisations from February to July proved more effective than those performed in the rest of the year, in that higher antibody titres were built up within 14 days from vaccination. These results were confirmed by rates of protection of cattle recorded from direct potency testing of immunised animals, between 1969 and 1977.