T. Smith

Bio: T. Smith is an academic researcher from University of Reading. The author has contributed to research in topics: Straw & Cattle feeding. The author has an hindex of 11, co-authored 13 publications receiving 420 citations.

Experiments on the nutrition of the dairy heifer: VIII. Effect on milk production of level of feeding at two stages of the lactation

Abstract: Eighty Friesian heifers were used to study the effect on milk production of two fixed levels of intake at two stages of the lactation. The rations were estimated to contain 7·9 and 6·2 kg starch equivalent per day, with adequate protein content. The heifers were allocated at random to these two levels of intake for weeks 1·9 of lactation and re-allocated at random to them for weeks 10–18 of lactation. Apart from minor variation the heifers were all fed alike for the remainder of the lactation.The higher level of feeding increased yields of milk and milk solids and solids-not-fat content in each period but had a smaller effect in mid- than in early lactation, a trend which was shown to continue further into later lactation. It also conserved body reserves.There was a residual effect in weeks 10–18 from the level of feeding in weeks 1–9 of lactation. This was directly additive to the effects of the current level of feeding. Those animals which had received the higher level of feeding in weeks 1–9 yielded more milk of higher solids-not-fat content than those which had had the lower level of feeding in weeks 1–9. The former group gained less live weight. The effect on milk production over the full lactation from additional feeding in early lactation was three times that observed in early lactation itself. Additional feeding in mid-lactation did not have a residual effect.The absolute output of milk per unit of food over the 18-week period was greatest for that group which had received the lower level of feeding throughout, followed by the group which received the higher level of feeding in weeks 1–9 only. This superiority was achieved at the expense of body reserves. There was a negative regression of live-weight change on milk production.Estimated intakes of metabolizable energy agreed closely with requirements for milk production as indicated by the Agricultural Research Council (1965).

Experiments on the nutrition of the dairy heifer:IX. Food utilization in lactation

Abstract: Food utilization by lactating dairy cows was studied in a randomized experiment covering the first 24 weeks of lactation, with further observations on performance over the remainder of the lactation under farm conditions. Over a 3-year period 90 firstcalf cows each took part in the experiment for one lactation, making six groups of 14–16 animals.For the experimental period a fixed basal diet was given of hay, concentrates, and wet brewer's grains. One group received only the basal ration. Four groups received in addition a fixed concentrates supplement for 4, 8, 12, 16 weeks from calving onwards respectively. The sixth group also had supplementary concentrates for 16 weeks but for weeks 5–12 inclusive the amount was doubled so that this group's diet simulated broadly ad libitum feeding in early lactation.Milk yield was increased by extra concentrates. The greater part of the effect was apparent in the first 2 weeks of different levels of intake, with a further build-up over the next 6–8 weeks. The size of the response fell as time from calving to initiation of different intakes increased. Additional food increased and delayed peak yield level. Persistency of milk yield was not affected by fixed differences in intake. Rate of liveweight change was improved by extra concentrates, less so in the third compared with the first month on treatment.A higher level of feeding in early lactation led to a greater partition of nutrients in mid-lactation to milk at the expense of gains in body reserves. This advantage to milk production extended to the end of lactation. In it the greatest response per unit concentrates was obtained from supplementation in the first 4 weeks of lactation but the total effect was increased by giving a double allowance of concentrates, and by extending the period of extra feeding to 8 weeks after calving.Solids-not-fat content and yield, and fat yield but not fat content, showed a similar response pattern to milk yield.Animal-to-animal variation in output on constant diets was characterized by negative regressions of live-weight change on milk yield. The regression coefficients were greater in early than in mid-lactation but they were constant in size at any one time for the various groups. A change in ration induced a change in output of the individual in which that production pathway favoured naturally by the animal was the more affected.

The influence of plane of nutrition and diet composition on the performance of dairy cows

Abstract: Summary Seventy-six first-calf cows (heifers), 32 second·calf cows and 39 adult cows participated in a trial in which three diets composed of 60:40, 75:25, 90:10 proportions of compound to hay (hay dry-matter digestibility 0·6) were given for the first 36 weeks of lactation in amounts to provide daily an estimated 125, 156 MJ and ad libitum digestible energy (DE) for heifers, and 156, 187 MJ and ad libitum DE for the other parities. The ad libitum intakes were 150 and 200 MJ DE daily for heifers and for older cows respectively. Greater compound content of the diet and larger daily allowance of DE were associated with increased occurrence of mastitis and lameness but not digestive upsets. Dry·matter (D.M.) digestibility was increased with a greater proportion of compound in the diet but was not affected by the amount consumed or stage of lactation. Milk yield and live·weight change were increased linearly and additively by a greater intake of digestible dry matter and by a greater proportion of compound in the diet, throughout the lactation save for no effect of diet composition on live·weight change in early lactation. On equal feed intakes older cows gave more milk and lost more live weight than heifers in early lactation but not thereafter; responses to additional feed were equal for all parities studied. Milk fat concentration was reduced both by increased allowance and by the high compound diet. Milk solids·not·fat (SNF) concentration was not affected by the treatments. Yield of milk fat was not affected by amount eaten and was reduced by the 90:10 diet. Yields of SNF and milk energy were increased by amount eaten and by increased compound in the diet. Thirty-two primiparous cows continued on their experimental treatments without interruption to the end of the second lactation. In the second lactation the effects on yields of milk, milk energy, and SNF were magnified indicating a cumulative effect from lactation to lactation. Little cumulative effect was observed on either milk fat yield, or concentrations of fat and SNF in milk. More generous feeding was associated with reduced milk output/unit D.M. consumed in the first but not the second lactation. More generous feeding improved live·weight change less in the second than in the first lactation. No cumulative effects over two lactations were observed consequent upon variation in diet composition.

A comparison of sources of supplementary nitrogen for young cattle receiving fibre-rich diets.

Abstract: Fishmeal, soya-bean meal and urea were compared as nitrogen sources in diets rich in fibre for yearling cattle, using feeding trials and digestibility and nitrogen retention studies. All animals were individually fed. Diets supplemented with fishmeal supported the highest rates of daily live-weight gain and nitrogen retention. There was no response in dry-matter intake and digestibility from extra nitrogen, either from fishmeal or urea, when the crude protein of the diet was 8·5% or over, and a small response in digestibility when soya-bean meal was used. Molar proportions of VFA, rumen NH 3 -N concentrations and blood urea nitrogen concentrations were all affected by both amount and source of nitrogen supplementation. Multiple regression analysis showed the undegradable protein supply to be more critical with high than with low fibre diets.

Experiments on the nutrition of the dairy heifer: VII. Observations on the effect of the energy intake on the utilization of protein in growth and in lactation

Abstract: Eight feeding trials on cattle showed that the response in live-weight gain was curvilinear when protein or energy level was varied independently in rations based on poor quality roughages to which cereals and groundnut were variously added to give a range of protein and energy intakes. Live-weight gain was increased by 0·12 lb/day for each 0·1 lb additional digestible crude protein/day at levels of intake below 0·7 lb/day and by 0·03 lb/day at higher levels. It was increased by 0·4 lb/day for each additional 0·1 lb starch equivalent daily/100 lb live weight at total intakes below 0·9 lb daily/ 100 lb and by 0·2 lb/day at higher levels. Over the range 0·5–2·0 lb digestible crude protein daily and 0·7–1·2 lb starch equivalent daily/100 lb live weight the effects of these nutrients were additive.A Latin square nitrogen balance trial demonstrated that a portion of the nitrogen from a protein supplement was retained in the body despite the excretion of the greater part of it in the urine and a further part in the faeces. Nitrogen retention was increased by a supplement of readily available energy through a decrease in urinary nitrogen loss. Nitrogen balance was not increased by a supplement of a fibrous energy source because this induced an increase in faecal nitrogen loss.In a further feeding trial milk yield was found to be affected in a similar manner to growth. At a yield of 30 lb/day the response per lb starch equivalent added to the diet was 0·5 lb milk including 0·05 lb solids not fat and to an increase of 0·1 lb digestible crude protein daily it was 0·25 lb milk including 0·025 lb solids not fat.

Changes in body components of autumn-calving Holstein-Friesian cows over the first 29 weeks of lactation

Abstract: Changes in body composition of 54, second to fourth parity, autumn-calving Holstein-Friesian dairy cows offered grass silage ad libitum and 3(L), 6(M) or 9(H) kg concentrate dry matter per day were measured by serial slaughter at 0, 2, 5, 8, 11, 14, 19, 24 and 29 weeks post partum.Concentrate level had a significant effect on the fresh weights of many of the body fractions with the differences generally being greater between L and M than between M and H. Increasing concentrate level generally reduced the extent of weight loss of body fractions in early lactation and enhanced subsequent repletion. Empty body weight decreased to week 8 and then increased steadily over the remaining 21 weeks, but within this pattern different organs were concomitantly increasing and decreasing. Carcass weight and the weights of the internal fat depots showed a decline over the first 8 weeks and a subsequent increase, udder weight declined throughout, weights of various sections of the digestive tract showed an initial increase then remained steady, whilst liver weight increased throughout.In week 0 the carcass accounted for proportionately 0-61 of the total energy in the body (6278 MJ), of which fat and crude protein (CP) comprised proportionately 0·67 and 0·33, respectively. In early lactation mobilization of fat and CP in the carcass was reduced with increasing level of concentrate. In the non-carcass fraction increasing concentrate level led to a higher weight of CP in the metabolically active organs such as the digestive tract and udder but had little effect on the weight of fat. Nevertheless, there was generally a positive effect of concentrate level on energy content. Total weights of fat, CP and water in the body declined to week 8 then increased over the following 21 weeks. Although weight of CP in the liver increased throughout lactation and weight of fat was elevated in weeks 0 and 2, the energy content of the liver remained fairly constant.Estimates of the change in net energy (NE) associated with live-weight loss and with live-weight gain showed a slight though non-significant difference between the two, despite evidence of a higher concentration of fat associated with gain than with loss, and CP concentration being the same in both cases. The mean value was 19·3 MJ/kg live-weight change.