Incremental effect of a calcium salt of cis-monounsaturated fatty acids supplement on milk fatty acid composition in cows fed maize silage-based diets.

In most Western countries, saturated fatty acid (SFA) intake exceeds recommended levels, which is considered a risk factor for cardiovascular disease (CVD). As milk and dairy products are major contributors to SFA intake in many countries, recent research has focused on sustainable methods of producing milk with a lower saturated fat concentration by altering dairy cow diets. Human intervention studies have shown that CVD risk can be reduced by consuming dairy products with reduced SFA and increased cis-monounsaturated fatty acid (MUFA) concentrations. This milk fatty acid profile can be achieved by supplementing dairy cow diets with cis-MUFA-rich unsaturated oils. However, rumen exposure of unsaturated oils also leads to enhanced milk trans fatty acid (TFA) concentrations. Because of concerns about the effects of TFA consumption on CVD, feeding strategies that increase MUFA concentrations in milk without concomitant increases in TFA concentration are preferred by milk processors. In an attempt to limit TFA production and increase the replacement of SFA by cis-MUFA, a preparation of rumen-protected unsaturated oils was developed using saponification with calcium salts. Four multiparous Holstein-Friesian cows in mid-late lactation were used in a 4 × 4 Latin square design with 21-d periods to investigate the effect of incremental dietary inclusion of a calcium salt of cis-MUFA product (Ca-MUFA; 20, 40, and 60 g/kg of dry matter of a maize silage-based diet), on milk production, composition, and fatty acid concentration. Increasing Ca-MUFA inclusion reduced dry matter intake linearly, but no change was observed in estimated ME intake. No change in milk yield was noted, but milk fat and protein concentrations were linearly reduced. Supplementation with Ca-MUFA resulted in a linear reduction in total SFA (from 71 to 52 g/100 g of fatty acids for control and 60 g/kg of dry matter diets, respectively). In addition, concentrations of both cis- and trans-MUFA were increased with Ca-MUFA inclusion, and increases in other biohydrogenation intermediates in milk fat were also observed. The Ca-MUFA supplement was very effective at reducing milk SFA concentration and increasing cis-MUFA concentrations without incurring any negative effects on milk and milk component yields. However, reduced milk fat and protein concentrations, together with increases in milk TFA concentrations, suggest partial dissociation of the calcium salts in the rumen.

Beef production potential of Norwegian Red and Holstein-Friesian bulls slaughtered at two ages.

There is a paucity of data on the beef production potential of Norwegian Red (NOR) compared with 'modern' Holstein-Friesian (HF) cattle. The present study used a total of 64 bulls in a 2 × 2 factorial design study encompassing two breeds (HF and NOR) and two slaughter ages (485; E, and 610; L, days). The mean initial age and live weight of the HF bulls were 179 (s.d. 47.1) days and 203 (s.d. 64.0) kg, while the corresponding data for the NOR bulls were 176 (s.d. 39.7) days and 185 (s.d. 63.6) kg, respectively. Bulls were offered a 50 : 50 mixture (dry matter (DM) basis) of grass silage and concentrates. No breed × slaughter group interactions were recorded for any parameters evaluated (P > 0.05). HF bulls had higher (P < 0.001) DM intake and poorer (P < 0.01) efficiency of conversion of food to carcass gain than NOR bulls. HF bulls tended (P = 0.07) to have a higher rate of live-weight gain and were heavier (P < 0.001) at slaughter than NOR bulls, though both carcass weight and rate of carcass gain did not differ between the breeds (P > 0.05). NOR bulls had higher (P < 0.001) dressing proportion and carcass conformation score than HF bulls, while breed of bull had no influence (P > 0.05) on carcass fat classification, depth of subcutaneous fat, marbling score or on the weight of fat in the internal depots. Daily food intakes did not differ (P > 0.05) across the two slaughter age groups, though efficiency of conversion of food to carcass gain was poorer (P < 0.05) in the L compared with E bulls. Rate of live-weight gain was lower (P < 0.01) for L bulls, although rate of carcass gain did not differ (P > 0.05) between the E and L bulls. Increasing age at slaughter increased (P < 0.01 or greater) dressing proportion, carcass fat class, depth of subcutaneous fat, marbling score and internal fat depots, but had no effect (P > 0.05) on the carcass conformation score. Instrumental measures of meat quality indicated that meat from NOR bulls was tougher (P < 0.01) than meat from HF bulls, while delaying slaughter increased (P < 0.001) a* and C*ab, and decreased (P < 0.01) h0, indicating improved redness. It is concluded that NOR bulls have higher food efficiency and produce more highly conformed carcasses than HF bulls, but HF bulls produce more tender meat.

The effects of milk yield and stage of lactation on the partitioning of nutrients in lactating dairy cows.

The objective of the experiment was to examine, using indirect calorimetry, the effects of milk yield and stage of lactation on the response in milk and body tissue energy, and heat production, to a reduction (decrement) in nutrient intake (assessed as metabolizable energy intake). Eight lactating dairy cows, four representing each of two stages of lactation [either mean initial days in milk (DIM) 158 (SD 6.1) or 414 (SD 51.1)] were used. Each cow underwent four 17-d periods incorporating two physiological states [number of mammary glands milked: either four (periods 1 and 2), or two (periods 3 and 4)], and two levels of metabolizable energy intake within each physiological state [either sufficient to meet requirements for zero tissue balance plus 10 MJ/d (periods 1 and 3)] or these allowances reduced by 20 MJ/d in the subsequent period (periods 2 and 4, respectively). Partitioning was calculated from the changes in metabolizable energy intake, milk energy, tissue energy, and heat production between DIM groups and between four and two gland milking (milk yield) components of the study. Partitioning of the changes in metabolizable energy intake was not influenced by DIM, but milk yield response was greater in the early lactation cows compared with the late group. Cows milked in four glands (higher milk yield) partitioned a significantly greater proportion of decremental changes in metabolizable energy intake to milk energy and less to tissue energy, than when milked in only two glands (lower milk yield).