The effect of a low-protein ration on milk yield and plasma metabolites in Friesian heifers during early lactation

Abstract

I. Sixteen first-calf Friesian heifers were used in a continuous treatment design experiment. For 2 weeks after calving they were given a 750 g concentrate, 250 g hay/kg ration with 169 g crude protein (nitrogen x 6.25; CP)/kg dry matter (DM). They were then divided into two groups of eight and given a high-protein (223 g CP/kg DM) or low-protein (107 g CP/kg DM) ration at the rate of 10.8 kg concentrates+ 3.6 kg hay for 8 weeks.2. Milk yield and composition, live weight and blood composition were monitored throughout. A digestibility trial was carried out with six animals on each treatment. 3.The low protein ration reduced DM, organic matter, energy and fibre digestibility significantly (P < 0.001) so that intakes of digestible energy were not equal and the low-protein group lost more weight than the highprotein group. 4.Milk yield and the fat content of milk were lower in heifers given the low-protein ration (P < 0.01). The lactose content of the milk was not affected and protein content only slightly reduced (P < 0.1) by lowprotein feeding. When the heifers were all changed onto an adequate protein (190 g CP/kg DM) ration in mid-lactation, those which had previously been under-fed protein appeared to recover in milk yield to the point they might have been expected to reach if given an adequate-protein ration throughout. 5.Concentrations of urea (P < o.001) and albumin (P < 0.05) were reduced by underfeeding protein, but albumin concentration was affected less by diet than by stage of lactation. Blood concentrations of total protein, glucose, sodium, potassium, calcium, inorganic phosphate, iron, copper, haemoglobin and packed cell volume were unaffected by treatment. Blood magnesium concentration was slightly lower (P < 0.1) with low-protein feeding.Few studies have been done, under UK feeding conditions, on the effects of low protein intakes on performance of cows early in lactation. This is a critical period in the lactation cycle when food intake often does not adequately match output of nutrients in milk, and body reserves of energy and possibly protein, are drawn on. Artificial manipulation (by abomasal infusion) of protein supply to cows in early lactation has prompted large responses i n milk nutrient output (0rskov et al. 1977) even to the extent that negative energy balance was increased.Only Treacher et al. (1976) have fed low-protein diets (down to ~2 0 g crude protein (nitrogen x 6.25; CP)/kg dry matter (DM)) to cows in early lactation in this country. They began low-protein feeding during gestation so that precalving and lactation effects were confounded.The effects of low-protein feeding in early lactation have received rather more attention in North America (Sparrow et al. We wished to study the gross effects of underfeeding of protein to heifers during the first 1 0 weeks of lactation by offering a ration containing less than I 10 g CP/kg DM. Where comparable levels of protein have been fed, the experiments have usually not been in early lactation and so may have been conducted in a less sensi...

Thyroid hormones, blood plasma metabolites and haematological parameters in relationship to milk yield in dairy cows

“…This is in agreement with Kitchenham and Rowlands (1976), who reported an increase of globulins with increasing age. In contrast to Little (1974), albumin level barely decreased at the onset of the first lactation and even increased during the first months of the ensuing lactation, as found by Oldham et al (1979). Albumin was the same in high-and low-yielding animals, except for a numerically small difference in the second half of lactation.…”

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“…Plasma urea concentrations also showed a typical response to parturition and lactation (Oldham et al, 1979). They were not significantly related to milk yield and there were no significant differences between high-and low-yielding cows.…”

Effects of different energy intakes before and after calving on food intake, performance and blood hormones and metabolites in dairy cows

“…Circulating albumin was comparable in all groups throughout the experiment, indicating that protein supply was adequate (Oldham, Broster, Napper and Siviter, 1979). The transient decrease of AAN at parturition may have been the consequence of amino acid uptake by the mammary gland.…”

Feeding frequency for lactating cows: effects on digestion, milk production and energy utilization

“…The diets, which were similar to those used in another experiment (Broster et al 1979), were designed to provide similar amounts of DE and total nitrogen. The 600 g concentrate/kg diet consisted of 6.0 kg hay and 9.0 kg concentrate A daily, and the 900 g concentrate/kg diet consisted of 1.4 kg hay and 12.6 kg concentrate C daily.…”