The objectives were to determine effects of graded levels of selenized yeast derived from a specific strain of Saccharomyces cerevisiae (CNCM I-3060) on animal performance and in selenium concentrations in the blood, milk, feces, and urine of dairy cows compared with sodium selenite; and to provide preliminary data on the proportion of selenium as selenomethionine in the milk and blood. Twenty Holstein cows were used in a 5 x 5 Latin square design study in which all cows received the same total mixed rations, which varied only in source or concentration of dietary selenium. There were 5 experimental treatments. Total dietary selenium of treatment 1, which received no added selenium, was 0.15 mg/kg of dry matter, whereas values for treatments 2, 3, and 4, derived from selenized yeast, were 0.27, 0.33, and 0.40 mg/kg of dry matter, respectively. Treatment 5 contained 0.25 mg of selenium obtained from sodium selenite/kg of dry matter. There were no significant treatment effects on animal performance, and blood chemistry and hematology showed few treatment effects. Regression analysis noted significant positive linear effects of increasing dietary selenium derived from selenized yeast on selenium concentrations in the milk, blood, urine, and feces. In addition, milk selenium results indicated improved bioavailability of selenium from selenized yeast, compared with sodium selenite. Preliminary analyses showed that compared with sodium selenite, the use of selenized yeast increased the concentration of selenomethionine in the milk and blood. There was no indication of adverse effects on cow health associated with the use of selenized yeast.

We examined the effects of monensin on feed intake and milk production in Holstein-Friesian cows receiving a total mixed rations in two experiments. In experiment 1, 60 individually fed cows consumed, during wk 7 to 26 of lactation, 1 kg/d of supplement containing either 0, 150,300, or 450 mg of monensin. In experiment 2, 98 group-fed cows also received 1 kg/d of a supplement with either 0 or 300 mg/d of monensin for two consecutive lactations. In lactations 1 and 2, treatment started at wk 8 and 3 wk prior to calving, and continued for 32 wk. In experiment 1, 150, 300, and 450 mg of monensin/d produced a small decrease in feed intake and milk yield responses of 2.8, 2.5 and 1.5 kg/d, respectively. In experiment 2, milk yield responses of 0.8 and 1.1 kg/d were recorded in lactations 1 and 2. Milk fat and milk protein content declined in experiments 1 and 2, lactations 1 and 2 by 0.46, 0.38 and 0.27%, and 0.16, 0.16 and 0.11%, respectively. Yield of milk constituents was unaffected. Efficiency of milk production was increased by 5% in experiment 1. In experiment 2, lactation 2, monensin decreased beta-hydroxybutyrate and acetoacetate but increased blood glucose concentration.

Recent studies have illustrated the effects of cis-9,trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9,trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9,trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg (on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18:0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsaturated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.

Fifty-five multiparous Holstein-Friesian cows were used in a 20-week continuous design study to determine the effect of maize silage maturity on food intake and milk production. Forage maize (cv. Hudson) was harvested and ensiled at target dry matter (DM) contents of 230 (T23), 280 (T28), 330 (T33) and 380 (T38) g per kg fresh weight (FW). The mean values for volatile-corrected DM (VCDM), starch, neutral-detergent fibre (NDF), crude protein and predicted metabolizable energy (ME) content of the four maize silages were 226, 290, 302 and 390 g/kg FW, 114, 274, 309 and 354 g/kg VCDM, 574, 447, 431 and 448 g/kg VCDM, 96, 80, 74 and 75 g/kg VCDM and 10·3, 11·5, 11·6 and 11·2 MJ/kg DM, respectively. Grass silage containing 296 g VCDM per kg FW was produced from the primary growth of a perennial ryegrass sward. At week 3 of lactation cows were allocated to one of five forage treatments offered ad libitum. The forage treatments were either grass silage alone (TGS) or a 3 : 1 DM ratio of maize and grass silage designated as T23, T28, T33 and T38. All cows also received 8·7 kg DM per day of a dairy concentrate. Forage VCDM intake for TGS was lower (P < 0·001) than for T23 to T38. Increasing maize silage DM content from 226 (T23) to 290 (T28) g/kg increased (P < 0·05) forage VCDM intake from 10·9 to 13·3 kg/day but a further increase to 390 (T38) g/kg tended to reduce VCDM intake. When compared with TGS, the inclusion of maize silage increased milk yield from 28·0 kg/day to 29·4, 32·7, 33·0 and 30·8 kg/day for T23 to T38, respectively, the increases being significant for T28 to T38. However, milk yield was reduced (P < 0·05) when the DM content of the maize silage increased from 302 to 390 g/kg. Increasing maize silage DM content from T23 to T33 reduced (P < 0·05) milk fat content from 45·8 to 41·8 g/kg, which was also lower (P < 0·05) than for TGS. The inclusion of maize silage increased fat yield with a significant difference (P < 0·05) between TGS and T28. The inclusion of maize silage increased milk protein content (P < 0·05) and protein yield (P < 0·001) when compared with TGS. While increasing maize silage maturity did not affect (P > 0·05) milk protein content, protein yield was higher (P < 0·05) for the two intermediate DM contents. There were no treatment effects on body condition score. It is concluded that the changes in composition of maize silage with increasing maturity, which are associated with increased starch and reduced NDF content, resulted in large increases in food intake and yield of milk and protein as crops matured from T23 to T33. However, when crop maturity increased further to T38 there was a tendency for DM intake and yield of milk and protein to decline.

Forty multiparous Holstein cows were used in a 16-week continuous design study to determine the effects of either selenium (Se) source, selenised yeast (SY) (derived from a specific strain of Saccharomyces cerevisiae CNCM I-3060) or sodium selenite (SS), or Se inclusion rate in the form of SY in the diets of lactating dairy cows on the Se concentration and speciation in blood, milk and cheese. Cows received ad libitum a total mixed ration (TMR) with a 1 : 1 forage : concentrate ratio on a dry matter (DM) basis. There were four diets (T 1 to T 4 ), which differed only in either source or dose of Se additive. Estimated total dietary Se for T 1 (no supplement), T 2 (SS), T 3 (SY) and T 4 (SY) was 0.16, 0.30, 0.30 and 0.45 mg/kg DM, respectively. Blood and milk samples were taken at 28-day intervals and at each time point there were positive linear effects of Se in the form of SY on the Se concentration in blood and milk. At day 112, blood and milk Se values for T 1 to T 4 were 177, 208, 248 and 279 6 6.6 and 24, 38, 57 and 72 6 3.7 ng/g fresh material, respectively, and indicate improved uptake and incorporation of Se from SY. In whole blood, selenocysteine (SeCys) was the main selenised amino acid and the concentration of selenomethionine (SeMet) increased with the increasing inclusion rate of SY. In milk, there were no marked treatment effects on the SeCys content, but Se source had a marked effect on the concentration of SeMet. At day 112, replacing SS (T 2 ) with SY (T 3 ) increased the SeMet concentration of milk from 36 to 111 ng Se/g and its concentration increased further to 157 ng Se/g dried sample as the inclusion rate of SY increased further (T 4 ) to provide 0.45 mg Se/kg TMR. Neither Se source nor inclusion rate affected the keeping quality of milk. At day 112, milk from T 1 , T 2 and T 3 was made into a hard cheese and Se source had a marked effect on total Se and the concentration of total Se comprised as either SeMet or SeCys. Replacing SS (T 2 ) with SY (T 3 ) increased total Se, SeMet and SeCys content in cheese from 180 to 340 ng Se/g, 57 to 153 ng Se/g and 52 to 92 ng Se/g dried sample, respectively. The use of SY to produce food products with enhanced Se content as a means of meeting the Se requirements is discussed.