@conference {41361,
	title = {Total mixed rations versus pasture diets: Evidence for a genotype x diet on the concentration of amino acid-derived volatiles in milk},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {246-251},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {<p>The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy cows were compared on an all-pasture diet (Grass) or a total mixed ration (TMR). Dietary treatments had been imposed for two years prior to the 2000/2001 season for which these results are reported. The four treatments were NZ Grass (n=14); OS Grass (n=13); NZ TMR (n=14); and OS TMR (n=14). Genotype x diet interactions were observed for annual milk yield, milksolids yield, efficiency of milksolids production, liveweight gain during lactation, and the proportion of cows not in calf. Measurement of individual cow intake using alkane markers during early, mid, and late lactation identified when these genotype x diet interactions occurred. When fed TMR, OS HF performed better than NZ HF, but on grass NZ HF performed better than OS HF. This has implications for the selection of sires for the national herd, and for the use of different dairy cow genotypes in different dairying systems.</p>},
	issn = {1176-5283},
	author = {Kolver ES and Roche JR and de Veth MJ and Thorne PL and Napper AR}
}
@conference {41277,
	title = {Diet and genotype affect plasma calcium, magnesium and phosphorus concentrations in the periparturient cow},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {168-171},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The literature is inconsistent with regard to the effect of diet in the periparturient period on the health and production of dairy cows, and there is little or no data on the effect of genotype. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration pre- and post-calving. Cows receiving the total mixed ration pre-calving had a lower (P<0.05) plasma calcium concentration on the day of calving and the day following calving. Conversely, cows of both genotypes offered pasture had lower (P<0.01) plasma magnesium and phosphorus concentrations pre- and post-calving compared with cows fed a total mixed ration. OSHF cows had lower plasma calcium (P<0.05) and magnesium (P<0.001) concentrations post-calving. Plasma phosphorus concentrations were unaffected by genotype. Herds with a high proportion of OSHF genetics are at an increased risk of parturient hypocalcaemia and hypomagnesaemia. Recommended daily allowances for these minerals may need to be increased to allow for this predisposition.},
	issn = {1176-5283},
	author = {Roche JR and Kolver ES and de Veth MJ and Napper A}
}
@conference {41243,
	title = {Lipolytic response of New Zealand and overseas Holstein-Friesian dairy cows challenged with epinephrine},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {48-51},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Sixteen New Zealand Holstein-Friesians (NZ HF) and 15 overseas HF (OS HF) grazing pasture or fed a total mixed ration (TMR) were subjected to an epinephrine challenge during early lactation. A genotype x diet interaction trend (P=0.10) was observed; when grazing, OS HF displayed the greatest glycerol response, with the reverse occurring on TMR. No genotype or diet differences were observed for the glycerol or non-esterified fatty acid response. Dairy cows of both genotypes fed TMR produced a glucose response 31\% greater than both genotypes grazing pasture. These preliminary results suggest that genotype x diet-induced differences in the rate of lipolysis may occur in Holstein-Friesians during early lactation. These differences may be a function of small differences in energy balance. Feeding TMR was associated with a greater glucogenic response to epinephrine, which probably resulted from greater hepatic reserves of glycogen or simply a greater energy demand by the mammary gland. },
	issn = {1176-5283},
	author = {Kolver ES and Roche JR and de Veth MJ and Mackle TR}
}
@conference {41297,
	title = {Prediction of ruminal pH of dairy cows fed pasture},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {241-243},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Rumen pH as low as 5.6 has been reported in cows fed highly digestible pasture, however, incidences of sub-acute acidosis have not been well documented and there are no easy or reliable means for farmers to measure ruminal pH. This study collated animal and dietary parameters (81 treatment means), from 20 studies of lactating dairy cows fed pasture, to evaluate the relationship between ruminal pH and animal parameters, and identify suitable predictors of ruminal pH. Mean ruminal pH (5.6-6.7) was negatively correlated (P<0.05) with total volatile fatty acid concentration, milk yield, microbial N flow from the rumen, milk protein yield, milk fat yield, total non-structural carbohydrate content and acid detergent fibre content of the diet. No single dietary parameter, or group of parameters, was able to adequately predict ruminal pH. The increase in microbial nitrogen flow, milk, and milk fat production as ruminal pH decreased below 6.2 suggested that the performance of cows fed high quality pasture was not limited when mean ruminal pH decreased to 5.8. This implies that dairy cows fed pasture can tolerate a lower ruminal pH before sub-acute acidosis occurs than when forage-concentrate diets are fed. },
	issn = {1176-5283},
	author = {de Veth MJ and Kolver ES}
}
@conference {41114,
	title = {Amino acid supply to the small intestine of dairy cows fed pasture},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {180-183},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Two experiments measured the quantity and quality of amino acids available for absorption by four dairy cows fed pasture. Experiment 1 compared a diet of ryegrass/white clover pasture offered ad libitum or at 75\% of ad libitum intake during October. Experiment 2, conducted in December, compared an all-ryegrass diet with a diet comprising 100\% ryegrass, or 50\% ryegrass and 50\% white clover. Treatments were assigned according to a 2x2 crossover design. Restricted feeding (Experiment 1) significantly reduced the total supply of amino acids to the small intestine by 23\% (246 vs. 190g amino acid nitrogen/d). Compared to an all-ryegrass diet, a ryegrass diet which contained 50\% white clover (Experiment 2) significantly increased the total supply of amino acids by 10\% (284 vs. 259g amino acid nitrogen/d). For all four pasture diets, arginine, methionine, and histidine were identified, in that order, as being most limiting, supplying 67, 71, and 77\%, respectively, of the absorbable amino acid requirement. The supply of absorbable lysine from all four pasture diets was found to meet requirements of dairy cows in early to mid lactation. },
	issn = {1176-5283},
	author = {Kolver ES and Carruthers VR and Neil PG and de Veth MJ and Jansen EBL and Phipps DE}
}
@conference {41075,
	title = {Pasture digestion in response to changes in ruminal pH},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {66-69},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Four continuous culture fermenters were used to determine the ruminal pH required for the optimal digestion of pasture. Spring pasture was fermented at four controlled levels of ruminal pH (5.4, 5.8, 6.2 and 6.6) according to a 4x4 Latin square design. Decreasing pH from 6.6 to 5.4 reduced dry matter digestion by 14\%, neutral detergent fibre digestion by 11\%, total non-structural carbohydrate digestion by 5\% and microbial nitrogen flow by 18\%. A quadratic relationship was observed between ruminal pH and the true ruminal digestibility of dry matter (R{\texttwosuperior}=0.94, SE=2.06) and microbial nitrogen flow (R{\texttwosuperior}=0.66, SE=0.05). The ruminal digestibility of pasture dry matter was optimised at pH 6.35, and synthesis of microbial protein was optimised at pH 6.13. This experiment indicated that digestion was largely insensitive to pH across a broad range of pH (5.8 to 6.6), but that a large reduction in digestion occurred when mean pH was less than 5.8. },
	issn = {1176-5283},
	author = {de Veth MJ and Kolver ES}
}
