Fresh grass in the cow diet improves the rheological and nutritional properties of butter. However, the relationship between the proportion of fresh grass in the diet and these properties is still unknown. The objective of the study was to determine the relationship between the proportion of fresh grass in the diet and the properties of milk and butter. Four groups of 2 cows were fed 4 isoenergetic diets characterized by increasing amounts of fresh grass (0, 30, 60, and 100% dry matter of forage) according to a Youden square design. Energy levels were similar among all diets. Thus, no effect of mobilization was observed and the results were only due to the proportion of fresh grass in the diet. Milk yield linearly increased with the proportion of fresh grass in the diet (+0.21 kg/d per 10% of grass). Fat yield remained unchanged. Thus, by effect of dilution, increasing the proportion of fresh grass in the diet induced a linear decrease in fat content. Milk fat globule size decreased by 0.29 mum when the proportion of grass reached 30% in the diet. Increasing the proportion of fresh grass in the diet induced a linear increase in unsaturated fatty acids percentages at the expense of saturated fatty acids. Relationships were +0.38, +0.12, +0.05 and -0.69 points/10% of fresh grass in the diet for C18:1 trans-11, C18:2 cis-9,trans-11, C18:3n-3, and C16:0, respectively. These modifications in fatty acid composition, and in particular in the spreadability index, C16:0/C18:1, were responsible for linear decreases in final melting temperature and solid fat content in butter fat, perceived in sensory analysis by a linear decrease in firmness in mouth. The nutritional value of butter was also linearly improved by the proportion of fresh grass in the diet by halving the atherogenicity index.

Interactions between genotype and environment are becoming increasingly important as cattle genotypes are being managed in a diverse range of environments worldwide. The objective of this study was to investigate if there is an interaction of strain of Holstein-Friesian cows (HF) by grass-based feed system that affects milk production, body weight, and body condition score. Three strains of HF were compared on 3 pasture-based feed systems over 3 consecutive years. The 3 strains of HF were: high production North American, high durability North American, and New Zealand. The 3 grass-based feeding systems (FS) were: a high grass allowance system (MPFS), a high concentrate system (HCFS), and a high stocking rate system (HSFS). There was a separate farmlet for each FS and a total of 99, 117, and 117 animals were used in yr 1, 2, and 3 respectively, divided equally between strains of HF and FS. The high production cows produced the highest yield of milk, the New Zealand the lowest, and the high durability animals were intermediate. Milk fat and protein content were higher for the New Zealand strain than for the high production and high durability strains. The New Zealand strain had the lowest body weight and the highest condition score, whereas the high durability strain had the highest body weight, and the high production strain had the lowest condition score. There was a strain x FS interaction for yield of milk, fat, and protein. The milk production response to increased concentrate supplementation (MPFS vs. HCFS) was greater with both the high production and high durability strains (1.10 kg of milk/kg of concentrate for high production; 1.00 kg of milk/kg of concentrate for high durability) than the New Zealand strain (0.55 kg of milk/kg of concentrate). The results indicate that the optimum strain of HF will vary with feed system.

No abstract

A total of 48 high genetic merit (HM) and 48 medium merit (MM) cows, each given a low (LC), medium (MC), or high (HC) level of concentrate supplementation, were used in a split-plot design experiment, which was run in three consecutive years, to evaluate animal production responses. Individual cow intakes were estimated twice each year while at pasture; measurement period 1 (MP1) was in May/June, and measurement period 2 (MP2) was in early September, corresponding on average to d 110 and 200 of lactation, respectively. In MP1, cows were offered 0 (LC), 3 (MC), and 6 kg (HC), whereas in MP2 the levels were 0 (LC), 0 (MC), and 4 kg (HC) of concentrate daily. Genotype had a significant effect on all milk production parameters in MP1 and MP2. The HM cows had the highest yield of milk, fat, protein, and lactose, whereas the MM cows had the highest milk fat, protein, and lactose concentrations. The HM cows had significantly higher grass dry matter intake (GDMI) estimates. In MP1, the average responses, per kg concentrate dry matter, was +1.10 kg of milk, +0.038 kg of protein, +0.032 kg of fat. The corresponding values in MP2 were +0.94 kg of milk, +0.037 kg of protein, and +0.025 kg of fat. The response to concentrate was linear and independent of preexperimental milk yield. In MP1, the partial regression coefficients relating daily GDMI to an increase in 1 kg of preexperimental milk yield (PMY), preexperimental BW (PBW), and concentrate intake (CI) were 0.123, 0.006, and -0.54, respectively, whereas the corresponding values in MP2 were 0.190,0.007, and-0.444, respectively. This study indicates that with high yielding dairy cows, on gras only GDMI of 17 kg of supporting milk yield of 30-kg/d is achievable. In this scenario, concentrate supplementation will result in lower substitution rates, and higher milk yield response than previously published with lower yielding cows.

The objective of this study was to determine the effect of daily herbage allowance (DHA) and concentrate level on milk production and dry matter intake of spring-calving dairy cows in early lactation. Seventy-two Holstein-Friesian dairy cows (mean calving date February 2) were randomly assigned across 6 treatments (n = 12) in a 2 x 3 factorial arrangement. The 6 treatments consisted of 2 DHA ( > 4 cm) and 3 concentrate levels: 13 kg of herbage dry matter/cow per d (low) or 17 kg of herbage dry matter/cow per d (high) DHA and unsupplemented, 3 kg, or 6 kg of dry matter concentrate/cow per d. The experimental period (period I) lasted 77 d and was followed by a carryover period (period II) during which animals were randomly reassigned across 2 grazing treatments offering 17 or 21 kg of herbage dry matter/cow per d. Increasing DHA significantly increased milk (+1.85 kg), solids-corrected milk, protein (+79.5 g), and lactose yields, protein concentration, and mean body weight (BW). Mean body condition score (BCS) and end-point BCS were also significantly higher with the high-DHA treatments. There was a linear response in milk yield, milk lactose concentration, and solids-corrected milk to concentrate supplementation. There was a significant difference in mean BW as concentrate increased from 0 to 3 kg (506 and 524 kg, respectively); there was no further increase in BW when 6 kg of concentrate was offered. Cows offered the low DHA had significantly lower grass dry matter intake (13.3 kg) and total dry matter intake (16.3 kg) than the high-DHA cows during period I. Concentrate supplementation significantly increased total dry matter intake. During period II, previous DHA continued to have a significant carryover effect on milk protein concentration, BW change, mean BCS, and end-point BCS. Concentrate supplementation during period I continued to have a significant carryover effect in period II on milk yield; milk fat, protein, and lactose yields; solids-corrected milk yield; BW; and mean BCS. Results from this study indicate that offering a medium level of DHA (17 kg of herbage dry matter) in early lactation will increase milk production. Offering concentrate will result in a linear increase in milk production. In an early spring feed-budgeting scenario, when grass supply is in deficit, offering 3 kg of dry matter concentrate with 17 kg of DHA has the additive effect of maintaining the grazing rotation at the target length as well as ensuring the herd is adequately fed.