Signal transducers and activators of transcription (STAT) genes are involved in signal mediation of various hormones and cytokines. STAT1 located on chromosome number 2 is involved in mammary gland development and is associated with milk composition traits in bovines. This study aimed to find any relationship and impact of STAT1/BspHI gene with milk fat and protein yields in a herd of Holstein Friesian (HF) crossbred cattle of sub-tropical climate of Northern India. Milk composition data of 535 adult HF crossbred cows for a period of 12 years was collected from the records maintained at Livestock Farm, Guru Angad Dev Veterinary and Animal Sciences University. First lactation data of 222 animals was chosen for further analysis. After data correction for non-genetic factors (season of calving, period of calving, interaction effect of season and period of calving and age at first calving) these animals were categorised into two groups based on corrected high and low milk fat and protein yields. Forty animals were then selected for blood collection and further laboratory analysis. Amplified using PCR-RFLP technique, the 314 bp STAT1 gene was digested using BspHI restriction enzyme. C-T polymorphism at nucleotide position 201 and 260 of the STAT1 amplicon was observed. At 201, for genotype AA and Aa, the genotypic frequencies were 0.80 and 0.20%. At 260, for genotype BB and Bb, the genotypic frequencies were 0.25 and 0.75%. Least square analysis showed a significant association of all genotypes with milk fat and protein yields. Hence, STAT1 can be used as a potential candidate gene to aid in better animal selection in breeding programmes.

Improving milk nitrogen efficiency through a reduction of CP supply without detrimental effect on productivity requires usage of feeding systems estimating both the flows of digestible protein, the exported true proteins and from these predict milk protein yield (MPY). Five feeding systems were compared in their ability to predict MPY v. observed MPY in two studies where either protein supply or protein and energy supply were changed. The five feedings systems were: Cornell Net Carbohydrate and Protein System (v6.5.5), Dutch protein evaluation system (1991 and 2007), Institut National de la Recherche Agronomique in France (INRA), National Research Council and NorFor. The key characteristic of the systems with the best predicted MPY was the inclusion of a variable efficiency of utilisation of protein supply taking into account the supply of both protein and energy. The systems still using a fixed efficiency had the highest slope bias in their prediction of MPY. Therefore, the development of new feeding systems or improvement of existing systems should include a variable efficiency of utilisation of the protein related to both the protein and energy supply. The limitation of the current comparison did not allow determining if additional factors, as used in INRA, were beneficial. This concept should also probably be transferred to essential amino acids.

To determine whether lactating cows select a nutritionally appropriate diet when given grass silage ad libitum and a choice of concentrates high or low in digestible undegradable protein (DUP), 24 mid-lactation Holstein-Friesian cows were given, in different 3-week periods, a concentrate high in DUP (HP), one low in DUP (LP), or a choice between the two (CHOICE), all at an allowance of 5·4 kg dry matter per day. Milk yield was significantly lower, and silage intake slightly but significantly higher, on LP than on either HP or CHOICE. The mean proportion of HP taken in the CHOICE period was 0·47 which was greater than the proportion required to satisfy the cows’ calculated requirements for effective rumen degradable protein, DUP or metabolizable protein but not significantly different from the ratio of 0·50 expected if no choice was made. Individual cows had a strong tendency initially to continue to eat from the feeder from which they had obtained concentrates in the period before CHOICE but this changed to eating significant amounts of both foods within about a week. The fact that the relationship between the proportion of HP in the concentrate intake and milk protein output was significant and positive, and became more so as the CHOICE period progressed, supports the hypothesis that protein demand was directing diet selection but must be viewed with caution as it was heavily influenced by the results of one animal: the highest-yielding cow which also chose to eat the greatest proportion of HP.

An animal model and an approximative method for calculating repeatabilities of estimated breeding values are used in Finnish dairy cow evaluation. Changes in estimated breeding values over time as daughters accumulate were studied. Special emphasis was given to the accuracy and potential bias in the pedigree indices of young sires. The data set used was the same as in the national evaluation and the traits investigated were protein yield and somatic cell count. The average repeatability in evaluation of bulls without daughters was 0·37. The empirical repeatability defined as a squared correlation between the pedigree index and the final sire proof was only 0·15. The reduction in the repeatability was attributed to the selection on pedigree index. The upward bias observed in pedigree indices was 5 kg (approx. 0·3 of genetic standard deviation). The bias was caused by the overestimation of bull dams' breeding value. Also the proofs of bull sires increased after the second crop of daughters. The correlation between the evaluations of the same sire calculated from two separate equal size daughter groups was 0·91 when the bull had 10 to 50 daughters and 0·87 with over 100 daughters. This illustrates how the relative weight of the pedigree decreases while more progeny information is accumulated in the evaluation.

The relationships between values for milk protein content (MP) and body condition score (BSC) were compared on a group of 30 farms in western Asturias, northern Spain during the autumn of1990. There was a marked positive relationship (P < 0·01) in between-farm variation in the two factors; a similar relationship has been reported from experiments in Scotland. It is suggested that an index based on the deviation of values for MP and BCS from normal or mean values might be useful, especially in advisory work, to indicate rapidly the dietary energy adequacy on individual frms. However, note would have to be taken of the known changes in MP and BCS with, for example, age of cow and stage of lactation